xnu-4570.51.1.tar.gz

[apple/xnu.git] / osfmk / vm / vm_shared_region.c

/*
 * Copyright (c) 2007 Apple Inc. All rights reserved.
 *
 * @APPLE_LICENSE_HEADER_START@
 * 
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this
 * file.
 * 
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 * 
 * @APPLE_LICENSE_HEADER_END@
 */

/*
 * Shared region (... and comm page)
 *
 * This file handles the VM shared region and comm page.
 *
 */
/*
 * SHARED REGIONS
 * --------------
 *
 * A shared region is a submap that contains the most common system shared
 * libraries for a given environment.
 * An environment is defined by (cpu-type, 64-bitness, root directory).
 *
 * The point of a shared region is to reduce the setup overhead when exec'ing
 * a new process.
 * A shared region uses a shared VM submap that gets mapped automatically
 * at exec() time (see vm_map_exec()).  The first process of a given
 * environment sets up the shared region and all further processes in that
 * environment can re-use that shared region without having to re-create
 * the same mappings in their VM map.  All they need is contained in the shared
 * region.
 * It can also shared a pmap (mostly for read-only parts but also for the
 * initial version of some writable parts), which gets "nested" into the 
 * process's pmap.  This reduces the number of soft faults:  once one process
 * brings in a page in the shared region, all the other processes can access
 * it without having to enter it in their own pmap.
 *
 *
 * When a process is being exec'ed, vm_map_exec() calls vm_shared_region_enter()
 * to map the appropriate shared region in the process's address space.
 * We look up the appropriate shared region for the process's environment.
 * If we can't find one, we create a new (empty) one and add it to the list.
 * Otherwise, we just take an extra reference on the shared region we found.
 *
 * The "dyld" runtime (mapped into the process's address space at exec() time)
 * will then use the shared_region_check_np() and shared_region_map_np()
 * system call to validate and/or populate the shared region with the
 * appropriate dyld_shared_cache file.
 *
 * The shared region is inherited on fork() and the child simply takes an
 * extra reference on its parent's shared region.
 *
 * When the task terminates, we release a reference on its shared region.
 * When the last reference is released, we destroy the shared region.
 *
 * After a chroot(), the calling process keeps using its original shared region,
 * since that's what was mapped when it was started.  But its children
 * will use a different shared region, because they need to use the shared
 * cache that's relative to the new root directory.
 */
/*
 * COMM PAGE
 *
 * A "comm page" is an area of memory that is populated by the kernel with
 * the appropriate platform-specific version of some commonly used code.
 * There is one "comm page" per platform (cpu-type, 64-bitness) but only
 * for the native cpu-type.  No need to overly optimize translated code
 * for hardware that is not really there !
 *
 * The comm pages are created and populated at boot time.
 *
 * The appropriate comm page is mapped into a process's address space
 * at exec() time, in vm_map_exec().
 * It is then inherited on fork().
 *
 * The comm page is shared between the kernel and all applications of
 * a given platform.  Only the kernel can modify it.
 *
 * Applications just branch to fixed addresses in the comm page and find
 * the right version of the code for the platform.  There is also some
 * data provided and updated by the kernel for processes to retrieve easily
 * without having to do a system call.
 */

#include <debug.h>

#include <kern/ipc_tt.h>
#include <kern/kalloc.h>
#include <kern/thread_call.h>

#include <mach/mach_vm.h>

#include <vm/vm_map.h>
#include <vm/vm_shared_region.h>

#include <vm/vm_protos.h>

#include <machine/commpage.h>
#include <machine/cpu_capabilities.h>

/* "dyld" uses this to figure out what the kernel supports */
int shared_region_version = 3;

/* trace level, output is sent to the system log file */
int shared_region_trace_level = SHARED_REGION_TRACE_ERROR_LVL;

/* should local (non-chroot) shared regions persist when no task uses them ? */
int shared_region_persistence = 0;      /* no by default */

/* delay before reclaiming an unused shared region */
int shared_region_destroy_delay = 120; /* in seconds */

#ifndef CONFIG_EMBEDDED
/* 
 * Only one cache gets to slide on Desktop, since we can't
 * tear down slide info properly today and the desktop actually 
 * produces lots of shared caches.
 */
boolean_t shared_region_completed_slide = FALSE;
#endif

/* this lock protects all the shared region data structures */
lck_grp_t *vm_shared_region_lck_grp;
lck_mtx_t vm_shared_region_lock;

#define vm_shared_region_lock() lck_mtx_lock(&vm_shared_region_lock)
#define vm_shared_region_unlock() lck_mtx_unlock(&vm_shared_region_lock)
#define vm_shared_region_sleep(event, interruptible)                    \
        lck_mtx_sleep(&vm_shared_region_lock,                           \
                      LCK_SLEEP_DEFAULT,                                \
                      (event_t) (event),                                \
                      (interruptible))

/* the list of currently available shared regions (one per environment) */
queue_head_t    vm_shared_region_queue;

static void vm_shared_region_reference_locked(vm_shared_region_t shared_region);
static vm_shared_region_t vm_shared_region_create(
        void                    *root_dir,
        cpu_type_t              cputype,
        boolean_t               is_64bit);
static void vm_shared_region_destroy(vm_shared_region_t shared_region);

static void vm_shared_region_timeout(thread_call_param_t param0,
                                     thread_call_param_t param1);

static int __commpage_setup = 0;
#if defined(__i386__) || defined(__x86_64__)
static int __system_power_source = 1;   /* init to extrnal power source */
static void post_sys_powersource_internal(int i, int internal);
#endif /* __i386__ || __x86_64__ */


/*
 * Initialize the module...
 */
void
vm_shared_region_init(void)
{
        SHARED_REGION_TRACE_DEBUG(
                ("shared_region: -> init\n"));

        vm_shared_region_lck_grp = lck_grp_alloc_init("vm shared region",
                                                      LCK_GRP_ATTR_NULL);
        lck_mtx_init(&vm_shared_region_lock,
                     vm_shared_region_lck_grp,
                     LCK_ATTR_NULL);

        queue_init(&vm_shared_region_queue);

        SHARED_REGION_TRACE_DEBUG(
                ("shared_region: <- init\n"));
}

/*
 * Retrieve a task's shared region and grab an extra reference to 
 * make sure it doesn't disappear while the caller is using it. 
 * The caller is responsible for consuming that extra reference if
 * necessary.
 */
vm_shared_region_t
vm_shared_region_get(
        task_t          task)
{
        vm_shared_region_t      shared_region;

        SHARED_REGION_TRACE_DEBUG(
                ("shared_region: -> get(%p)\n",
                 (void *)VM_KERNEL_ADDRPERM(task)));

        task_lock(task);
        vm_shared_region_lock();
        shared_region = task->shared_region;
        if (shared_region) {
                assert(shared_region->sr_ref_count > 0);
                vm_shared_region_reference_locked(shared_region);
        }
        vm_shared_region_unlock();
        task_unlock(task);

        SHARED_REGION_TRACE_DEBUG(
                ("shared_region: get(%p) <- %p\n",
                 (void *)VM_KERNEL_ADDRPERM(task),
                 (void *)VM_KERNEL_ADDRPERM(shared_region)));

        return shared_region;
}

/*
 * Get the base address of the shared region.
 * That's the address at which it needs to be mapped in the process's address
 * space.
 * No need to lock since this data is set when the shared region is
 * created and is never modified after that.  The caller must hold an extra
 * reference on the shared region to prevent it from being destroyed.
 */
mach_vm_offset_t
vm_shared_region_base_address(
        vm_shared_region_t      shared_region)
{
        SHARED_REGION_TRACE_DEBUG(
                ("shared_region: -> base_address(%p)\n",
                 (void *)VM_KERNEL_ADDRPERM(shared_region)));
        assert(shared_region->sr_ref_count > 1);
        SHARED_REGION_TRACE_DEBUG(
                ("shared_region: base_address(%p) <- 0x%llx\n",
                 (void *)VM_KERNEL_ADDRPERM(shared_region),
                 (long long)shared_region->sr_base_address));
        return shared_region->sr_base_address;
}

/*
 * Get the size of the shared region.
 * That's the size that needs to be mapped in the process's address
 * space.
 * No need to lock since this data is set when the shared region is
 * created and is never modified after that.  The caller must hold an extra
 * reference on the shared region to prevent it from being destroyed.
 */
mach_vm_size_t
vm_shared_region_size(
        vm_shared_region_t      shared_region)
{
        SHARED_REGION_TRACE_DEBUG(
                ("shared_region: -> size(%p)\n",
                 (void *)VM_KERNEL_ADDRPERM(shared_region)));
        assert(shared_region->sr_ref_count > 1);
        SHARED_REGION_TRACE_DEBUG(
                ("shared_region: size(%p) <- 0x%llx\n",
                 (void *)VM_KERNEL_ADDRPERM(shared_region),
                 (long long)shared_region->sr_size));
        return shared_region->sr_size;
}

/*
 * Get the memory entry of the shared region.
 * That's the "memory object" that needs to be mapped in the process's address
 * space.
 * No need to lock since this data is set when the shared region is
 * created and is never modified after that.  The caller must hold an extra
 * reference on the shared region to prevent it from being destroyed.
 */
ipc_port_t
vm_shared_region_mem_entry(
        vm_shared_region_t      shared_region)
{
        SHARED_REGION_TRACE_DEBUG(
                ("shared_region: -> mem_entry(%p)\n",
                 (void *)VM_KERNEL_ADDRPERM(shared_region)));
        assert(shared_region->sr_ref_count > 1);
        SHARED_REGION_TRACE_DEBUG(
                ("shared_region: mem_entry(%p) <- %p\n",
                 (void *)VM_KERNEL_ADDRPERM(shared_region),
                 (void *)VM_KERNEL_ADDRPERM(shared_region->sr_mem_entry)));
        return shared_region->sr_mem_entry;
}

uint32_t
vm_shared_region_get_slide(
        vm_shared_region_t      shared_region)
{
        SHARED_REGION_TRACE_DEBUG(
                ("shared_region: -> vm_shared_region_get_slide(%p)\n",
                 (void *)VM_KERNEL_ADDRPERM(shared_region)));
        assert(shared_region->sr_ref_count > 1);
        SHARED_REGION_TRACE_DEBUG(
                ("shared_region: vm_shared_region_get_slide(%p) <- %u\n",
                 (void *)VM_KERNEL_ADDRPERM(shared_region),
                 shared_region->sr_slide_info.slide));

        /* 0 if we haven't slid */
        assert(shared_region->sr_slide_info.slide_object != NULL || 
                        shared_region->sr_slide_info.slide == 0);

        return shared_region->sr_slide_info.slide; 
}

vm_shared_region_slide_info_t
vm_shared_region_get_slide_info(
        vm_shared_region_t      shared_region)
{
        SHARED_REGION_TRACE_DEBUG(
                ("shared_region: -> vm_shared_region_get_slide_info(%p)\n",
                 (void *)VM_KERNEL_ADDRPERM(shared_region)));
        assert(shared_region->sr_ref_count > 1);
        SHARED_REGION_TRACE_DEBUG(
                ("shared_region: vm_shared_region_get_slide_info(%p) <- %p\n",
                 (void *)VM_KERNEL_ADDRPERM(shared_region),
                 (void *)VM_KERNEL_ADDRPERM(&shared_region->sr_slide_info)));
        return &shared_region->sr_slide_info;
}

/*
 * Set the shared region the process should use.
 * A NULL new shared region means that we just want to release the old
 * shared region.
 * The caller should already have an extra reference on the new shared region
 * (if any).  We release a reference on the old shared region (if any).
 */
void
vm_shared_region_set(
        task_t                  task,
        vm_shared_region_t      new_shared_region)
{
        vm_shared_region_t      old_shared_region;

        SHARED_REGION_TRACE_DEBUG(
                ("shared_region: -> set(%p, %p)\n",
                 (void *)VM_KERNEL_ADDRPERM(task),
                 (void *)VM_KERNEL_ADDRPERM(new_shared_region)));

        task_lock(task);
        vm_shared_region_lock();

        old_shared_region = task->shared_region;
        if (new_shared_region) {
                assert(new_shared_region->sr_ref_count > 0);
        }

        task->shared_region = new_shared_region;

        vm_shared_region_unlock();
        task_unlock(task);

        if (old_shared_region) {
                assert(old_shared_region->sr_ref_count > 0);
                vm_shared_region_deallocate(old_shared_region);
        }

        SHARED_REGION_TRACE_DEBUG(
                ("shared_region: set(%p) <- old=%p new=%p\n",
                 (void *)VM_KERNEL_ADDRPERM(task),
                 (void *)VM_KERNEL_ADDRPERM(old_shared_region),
                 (void *)VM_KERNEL_ADDRPERM(new_shared_region)));
}

/*
 * Lookup up the shared region for the desired environment.
 * If none is found, create a new (empty) one.
 * Grab an extra reference on the returned shared region, to make sure
 * it doesn't get destroyed before the caller is done with it.  The caller
 * is responsible for consuming that extra reference if necessary.
 */
vm_shared_region_t
vm_shared_region_lookup(
        void            *root_dir,
        cpu_type_t      cputype,
        boolean_t       is_64bit)
{
        vm_shared_region_t      shared_region;
        vm_shared_region_t      new_shared_region;

        SHARED_REGION_TRACE_DEBUG(
                ("shared_region: -> lookup(root=%p,cpu=%d,64bit=%d)\n",

                 (void *)VM_KERNEL_ADDRPERM(root_dir), cputype, is_64bit));

        shared_region = NULL;
        new_shared_region = NULL;

        vm_shared_region_lock();
        for (;;) {
                queue_iterate(&vm_shared_region_queue,
                              shared_region,
                              vm_shared_region_t,
                              sr_q) {
                        assert(shared_region->sr_ref_count > 0);
                        if (shared_region->sr_cpu_type == cputype &&
                            shared_region->sr_root_dir == root_dir &&
                            shared_region->sr_64bit == is_64bit) {
                                /* found a match ! */
                                vm_shared_region_reference_locked(shared_region);
                                goto done;
                        }
                }
                if (new_shared_region == NULL) {
                        /* no match: create a new one */
                        vm_shared_region_unlock();
                        new_shared_region = vm_shared_region_create(root_dir,
                                                                    cputype,
                                                                    is_64bit);
                        /* do the lookup again, in case we lost a race */
                        vm_shared_region_lock();
                        continue;
                }
                /* still no match: use our new one */
                shared_region = new_shared_region;
                new_shared_region = NULL;
                queue_enter(&vm_shared_region_queue,
                            shared_region,
                            vm_shared_region_t,
                            sr_q);
                break;
        }

done:
        vm_shared_region_unlock();

        if (new_shared_region) {
                /*
                 * We lost a race with someone else to create a new shared
                 * region for that environment.  Get rid of our unused one.
                 */
                assert(new_shared_region->sr_ref_count == 1);
                new_shared_region->sr_ref_count--;
                vm_shared_region_destroy(new_shared_region);
                new_shared_region = NULL;
        }

        SHARED_REGION_TRACE_DEBUG(
                ("shared_region: lookup(root=%p,cpu=%d,64bit=%d) <- %p\n",
                 (void *)VM_KERNEL_ADDRPERM(root_dir),
                 cputype, is_64bit,
                 (void *)VM_KERNEL_ADDRPERM(shared_region)));

        assert(shared_region->sr_ref_count > 0);
        return shared_region;
}

/*
 * Take an extra reference on a shared region.
 * The vm_shared_region_lock should already be held by the caller.
 */
static void
vm_shared_region_reference_locked(
        vm_shared_region_t      shared_region)
{
        LCK_MTX_ASSERT(&vm_shared_region_lock, LCK_MTX_ASSERT_OWNED);

        SHARED_REGION_TRACE_DEBUG(
                ("shared_region: -> reference_locked(%p)\n",
                 (void *)VM_KERNEL_ADDRPERM(shared_region)));
        assert(shared_region->sr_ref_count > 0);
        shared_region->sr_ref_count++;

        if (shared_region->sr_timer_call != NULL) {
                boolean_t cancelled;

                /* cancel and free any pending timeout */
                cancelled = thread_call_cancel(shared_region->sr_timer_call);
                if (cancelled) {
                        thread_call_free(shared_region->sr_timer_call);
                        shared_region->sr_timer_call = NULL;
                        /* release the reference held by the cancelled timer */
                        shared_region->sr_ref_count--;
                } else {
                        /* the timer will drop the reference and free itself */
                }
        }

        SHARED_REGION_TRACE_DEBUG(
                ("shared_region: reference_locked(%p) <- %d\n",
                 (void *)VM_KERNEL_ADDRPERM(shared_region),
                 shared_region->sr_ref_count));
}

/*
 * Release a reference on the shared region.
 * Destroy it if there are no references left.
 */
void
vm_shared_region_deallocate(
        vm_shared_region_t      shared_region)
{
        SHARED_REGION_TRACE_DEBUG(
                ("shared_region: -> deallocate(%p)\n",
                 (void *)VM_KERNEL_ADDRPERM(shared_region)));

        vm_shared_region_lock();
        
        assert(shared_region->sr_ref_count > 0);

        if (shared_region->sr_root_dir == NULL) {
                /*
                 * Local (i.e. based on the boot volume) shared regions
                 * can persist or not based on the "shared_region_persistence"
                 * sysctl.
                 * Make sure that this one complies.
                 *
                 * See comments in vm_shared_region_slide() for notes about
                 * shared regions we have slid (which are not torn down currently).
                 */
                if (shared_region_persistence &&
                    !shared_region->sr_persists) {
                        /* make this one persistent */
                        shared_region->sr_ref_count++;
                        shared_region->sr_persists = TRUE;
                } else if (!shared_region_persistence &&
                           shared_region->sr_persists) {
                        /* make this one no longer persistent */
                        assert(shared_region->sr_ref_count > 1);
                        shared_region->sr_ref_count--;
                        shared_region->sr_persists = FALSE;
                }
        }

        assert(shared_region->sr_ref_count > 0);
        shared_region->sr_ref_count--;
        SHARED_REGION_TRACE_DEBUG(
                ("shared_region: deallocate(%p): ref now %d\n",
                 (void *)VM_KERNEL_ADDRPERM(shared_region),
                 shared_region->sr_ref_count));

        if (shared_region->sr_ref_count == 0) {
                uint64_t deadline;

                assert(!shared_region->sr_slid);

                if (shared_region->sr_timer_call == NULL) {
                        /* hold one reference for the timer */
                        assert(! shared_region->sr_mapping_in_progress);
                        shared_region->sr_ref_count++;

                        /* set up the timer */
                        shared_region->sr_timer_call = thread_call_allocate(
                                (thread_call_func_t) vm_shared_region_timeout,
                                (thread_call_param_t) shared_region);

                        /* schedule the timer */
                        clock_interval_to_deadline(shared_region_destroy_delay,
                                                   1000 * 1000 * 1000,
                                                   &deadline);
                        thread_call_enter_delayed(shared_region->sr_timer_call,
                                                  deadline);

                        SHARED_REGION_TRACE_DEBUG(
                                ("shared_region: deallocate(%p): armed timer\n",
                                 (void *)VM_KERNEL_ADDRPERM(shared_region)));

                        vm_shared_region_unlock();
                } else {
                        /* timer expired: let go of this shared region */

                        /* 
                         * We can't properly handle teardown of a slid object today.
                         */
                        assert(!shared_region->sr_slid);

                        /*
                         * Remove it from the queue first, so no one can find
                         * it...
                         */
                        queue_remove(&vm_shared_region_queue,
                                     shared_region,
                                     vm_shared_region_t,
                                     sr_q);
                        vm_shared_region_unlock();

                        /* ... and destroy it */
                        vm_shared_region_destroy(shared_region);
                        shared_region = NULL;
                }
        } else {
                vm_shared_region_unlock();
        }

        SHARED_REGION_TRACE_DEBUG(
                ("shared_region: deallocate(%p) <-\n",
                 (void *)VM_KERNEL_ADDRPERM(shared_region)));
}

void
vm_shared_region_timeout(
        thread_call_param_t     param0,
        __unused thread_call_param_t    param1)
{
        vm_shared_region_t      shared_region;

        shared_region = (vm_shared_region_t) param0;

        vm_shared_region_deallocate(shared_region);
}

/*
 * Create a new (empty) shared region for a new environment.
 */
static vm_shared_region_t
vm_shared_region_create(
        void                    *root_dir,
        cpu_type_t              cputype,
        boolean_t               is_64bit)
{
        kern_return_t           kr;
        vm_named_entry_t        mem_entry;
        ipc_port_t              mem_entry_port;
        vm_shared_region_t      shared_region;
        vm_shared_region_slide_info_t si;
        vm_map_t                sub_map;
        mach_vm_offset_t        base_address, pmap_nesting_start;
        mach_vm_size_t          size, pmap_nesting_size;

        SHARED_REGION_TRACE_DEBUG(
                ("shared_region: -> create(root=%p,cpu=%d,64bit=%d)\n",
                 (void *)VM_KERNEL_ADDRPERM(root_dir), cputype, is_64bit));

        base_address = 0;
        size = 0;
        mem_entry = NULL;
        mem_entry_port = IPC_PORT_NULL;
        sub_map = VM_MAP_NULL;

        /* create a new shared region structure... */
        shared_region = kalloc(sizeof (*shared_region));
        if (shared_region == NULL) {
                SHARED_REGION_TRACE_ERROR(
                        ("shared_region: create: couldn't allocate\n"));
                goto done;
        }

        /* figure out the correct settings for the desired environment */
        if (is_64bit) {
                switch (cputype) {
#if defined(__arm64__)
                case CPU_TYPE_ARM64:
                        base_address = SHARED_REGION_BASE_ARM64;
                        size = SHARED_REGION_SIZE_ARM64;
                        pmap_nesting_start = SHARED_REGION_NESTING_BASE_ARM64;
                        pmap_nesting_size = SHARED_REGION_NESTING_SIZE_ARM64;
                        break;
#elif !defined(__arm__)
                case CPU_TYPE_I386:
                        base_address = SHARED_REGION_BASE_X86_64;
                        size = SHARED_REGION_SIZE_X86_64;
                        pmap_nesting_start = SHARED_REGION_NESTING_BASE_X86_64;
                        pmap_nesting_size = SHARED_REGION_NESTING_SIZE_X86_64;
                        break;
                case CPU_TYPE_POWERPC:
                        base_address = SHARED_REGION_BASE_PPC64;
                        size = SHARED_REGION_SIZE_PPC64;
                        pmap_nesting_start = SHARED_REGION_NESTING_BASE_PPC64;
                        pmap_nesting_size = SHARED_REGION_NESTING_SIZE_PPC64;
                        break;
#endif
                default:
                        SHARED_REGION_TRACE_ERROR(
                                ("shared_region: create: unknown cpu type %d\n",
                                 cputype));
                        kfree(shared_region, sizeof (*shared_region));
                        shared_region = NULL;
                        goto done;
                }
        } else {
                switch (cputype) {
#if defined(__arm__) || defined(__arm64__)
                case CPU_TYPE_ARM:
                case CPU_TYPE_ARM64:
                        base_address = SHARED_REGION_BASE_ARM;
                        size = SHARED_REGION_SIZE_ARM;
                        pmap_nesting_start = SHARED_REGION_NESTING_BASE_ARM;
                        pmap_nesting_size = SHARED_REGION_NESTING_SIZE_ARM;
                        break;
#else
                case CPU_TYPE_I386:
                        base_address = SHARED_REGION_BASE_I386;
                        size = SHARED_REGION_SIZE_I386;
                        pmap_nesting_start = SHARED_REGION_NESTING_BASE_I386;
                        pmap_nesting_size = SHARED_REGION_NESTING_SIZE_I386;
                        break;
                case CPU_TYPE_POWERPC:
                        base_address = SHARED_REGION_BASE_PPC;
                        size = SHARED_REGION_SIZE_PPC;
                        pmap_nesting_start = SHARED_REGION_NESTING_BASE_PPC;
                        pmap_nesting_size = SHARED_REGION_NESTING_SIZE_PPC;
                        break;
#endif
                default:
                        SHARED_REGION_TRACE_ERROR(
                                ("shared_region: create: unknown cpu type %d\n",
                                 cputype));
                        kfree(shared_region, sizeof (*shared_region));
                        shared_region = NULL;
                        goto done;
                }
        }

        /* create a memory entry structure and a Mach port handle */
        kr = mach_memory_entry_allocate(&mem_entry,
                                        &mem_entry_port);
        if (kr != KERN_SUCCESS) {
                kfree(shared_region, sizeof (*shared_region));
                shared_region = NULL;
                SHARED_REGION_TRACE_ERROR(
                        ("shared_region: create: "
                         "couldn't allocate mem_entry\n"));
                goto done;
        }

#if     defined(__arm__) || defined(__arm64__)
        {
                struct pmap *pmap_nested;

                pmap_nested = pmap_create(NULL, 0, is_64bit);
                if (pmap_nested != PMAP_NULL) {
                        pmap_set_nested(pmap_nested);
                        sub_map = vm_map_create(pmap_nested, 0, size, TRUE);
#if defined(__arm64__)
                        if (is_64bit ||
                            page_shift_user32 == SIXTEENK_PAGE_SHIFT) {
                                /* enforce 16KB alignment of VM map entries */
                                vm_map_set_page_shift(sub_map,
                                                      SIXTEENK_PAGE_SHIFT);
                        }
#elif (__ARM_ARCH_7K__ >= 2) && defined(PLATFORM_WatchOS)
                        /* enforce 16KB alignment for watch targets with new ABI */
                        vm_map_set_page_shift(sub_map, SIXTEENK_PAGE_SHIFT);
#endif /* __arm64__ */
                } else {
                        sub_map = VM_MAP_NULL;
                }
        }
#else
        /* create a VM sub map and its pmap */
        sub_map = vm_map_create(pmap_create(NULL, 0, is_64bit),
                                0, size,
                                TRUE);
#endif
        if (sub_map == VM_MAP_NULL) {
                ipc_port_release_send(mem_entry_port);
                kfree(shared_region, sizeof (*shared_region));
                shared_region = NULL;
                SHARED_REGION_TRACE_ERROR(
                        ("shared_region: create: "
                         "couldn't allocate map\n"));
                goto done;
        }

        assert(!sub_map->disable_vmentry_reuse);
        sub_map->is_nested_map = TRUE;

        /* make the memory entry point to the VM sub map */
        mem_entry->is_sub_map = TRUE;
        mem_entry->backing.map = sub_map;
        mem_entry->size = size;
        mem_entry->protection = VM_PROT_ALL;

        /* make the shared region point at the memory entry */
        shared_region->sr_mem_entry = mem_entry_port;

        /* fill in the shared region's environment and settings */
        shared_region->sr_base_address = base_address;
        shared_region->sr_size = size;
        shared_region->sr_pmap_nesting_start = pmap_nesting_start;
        shared_region->sr_pmap_nesting_size = pmap_nesting_size;
        shared_region->sr_cpu_type = cputype;
        shared_region->sr_64bit = is_64bit;
        shared_region->sr_root_dir = root_dir;

        queue_init(&shared_region->sr_q);
        shared_region->sr_mapping_in_progress = FALSE;
        shared_region->sr_slide_in_progress = FALSE;
        shared_region->sr_persists = FALSE;
        shared_region->sr_slid = FALSE;
        shared_region->sr_timer_call = NULL;
        shared_region->sr_first_mapping = (mach_vm_offset_t) -1;

        /* grab a reference for the caller */
        shared_region->sr_ref_count = 1;

        /* And set up slide info */
        si = &shared_region->sr_slide_info;
        si->start = 0;
        si->end = 0;
        si->slide = 0;
        si->slide_object = NULL;
        si->slide_info_size = 0;
        si->slide_info_entry = NULL;

        /* Initialize UUID */
        memset(&shared_region->sr_uuid, '\0', sizeof(shared_region->sr_uuid));
        shared_region->sr_uuid_copied = FALSE;
done:
        if (shared_region) {
                SHARED_REGION_TRACE_INFO(
                        ("shared_region: create(root=%p,cpu=%d,64bit=%d,"
                         "base=0x%llx,size=0x%llx) <- "
                         "%p mem=(%p,%p) map=%p pmap=%p\n",
                         (void *)VM_KERNEL_ADDRPERM(root_dir),
                         cputype, is_64bit, (long long)base_address,
                         (long long)size,
                         (void *)VM_KERNEL_ADDRPERM(shared_region),
                         (void *)VM_KERNEL_ADDRPERM(mem_entry_port),
                         (void *)VM_KERNEL_ADDRPERM(mem_entry),
                         (void *)VM_KERNEL_ADDRPERM(sub_map),
                         (void *)VM_KERNEL_ADDRPERM(sub_map->pmap)));
        } else {
                SHARED_REGION_TRACE_INFO(
                        ("shared_region: create(root=%p,cpu=%d,64bit=%d,"
                         "base=0x%llx,size=0x%llx) <- NULL",
                         (void *)VM_KERNEL_ADDRPERM(root_dir),
                         cputype, is_64bit, (long long)base_address,
                         (long long)size));
        }
        return shared_region;
}

/*
 * Destroy a now-unused shared region.
 * The shared region is no longer in the queue and can not be looked up.
 */
static void
vm_shared_region_destroy(
        vm_shared_region_t      shared_region)
{
        vm_named_entry_t        mem_entry;
        vm_map_t                map;

        SHARED_REGION_TRACE_INFO(
                ("shared_region: -> destroy(%p) (root=%p,cpu=%d,64bit=%d)\n",
                 (void *)VM_KERNEL_ADDRPERM(shared_region),
                 (void *)VM_KERNEL_ADDRPERM(shared_region->sr_root_dir),
                 shared_region->sr_cpu_type,
                 shared_region->sr_64bit));

        assert(shared_region->sr_ref_count == 0);
        assert(!shared_region->sr_persists);
        assert(!shared_region->sr_slid);

        mem_entry = (vm_named_entry_t) shared_region->sr_mem_entry->ip_kobject;
        assert(mem_entry->is_sub_map);
        assert(!mem_entry->internal);
        assert(!mem_entry->is_copy);
        map = mem_entry->backing.map;

        /*
         * Clean up the pmap first.  The virtual addresses that were
         * entered in this possibly "nested" pmap may have different values
         * than the VM map's min and max offsets, if the VM sub map was
         * mapped at a non-zero offset in the processes' main VM maps, which
         * is usually the case, so the clean-up we do in vm_map_destroy() would
         * not be enough.
         */
        if (map->pmap) {
                pmap_remove(map->pmap,
                            shared_region->sr_base_address,
                            (shared_region->sr_base_address +
                             shared_region->sr_size));
        }

        /*
         * Release our (one and only) handle on the memory entry.
         * This will generate a no-senders notification, which will be processed
         * by ipc_kobject_notify(), which will release the one and only
         * reference on the memory entry and cause it to be destroyed, along
         * with the VM sub map and its pmap.
         */
        mach_memory_entry_port_release(shared_region->sr_mem_entry);
        mem_entry = NULL;
        shared_region->sr_mem_entry = IPC_PORT_NULL;

        if (shared_region->sr_timer_call) {
                thread_call_free(shared_region->sr_timer_call);
        }

#if 0
        /* 
         * If slid, free those resources.  We'll want this eventually,
         * but can't handle it properly today.
         */
        si = &shared_region->sr_slide_info;
        if (si->slide_info_entry) {
                kmem_free(kernel_map,
                          (vm_offset_t) si->slide_info_entry,
                          (vm_size_t) si->slide_info_size);
                vm_object_deallocate(si->slide_object);
        }
#endif 

        /* release the shared region structure... */
        kfree(shared_region, sizeof (*shared_region));

        SHARED_REGION_TRACE_DEBUG(
                ("shared_region: destroy(%p) <-\n",
                 (void *)VM_KERNEL_ADDRPERM(shared_region)));
        shared_region = NULL;

}

/*
 * Gets the address of the first (in time) mapping in the shared region.
 */
kern_return_t
vm_shared_region_start_address(
        vm_shared_region_t      shared_region,
        mach_vm_offset_t        *start_address)
{
        kern_return_t           kr;
        mach_vm_offset_t        sr_base_address;
        mach_vm_offset_t        sr_first_mapping;

        SHARED_REGION_TRACE_DEBUG(
                ("shared_region: -> start_address(%p)\n",
                 (void *)VM_KERNEL_ADDRPERM(shared_region)));
        assert(shared_region->sr_ref_count > 1);

        vm_shared_region_lock();

        /*
         * Wait if there's another thread establishing a mapping
         * in this shared region right when we're looking at it.
         * We want a consistent view of the map...
         */
        while (shared_region->sr_mapping_in_progress) {
                /* wait for our turn... */
                assert(shared_region->sr_ref_count > 1);
                vm_shared_region_sleep(&shared_region->sr_mapping_in_progress,
                                       THREAD_UNINT);
        }
        assert(! shared_region->sr_mapping_in_progress);
        assert(shared_region->sr_ref_count > 1);
        
        sr_base_address = shared_region->sr_base_address;
        sr_first_mapping = shared_region->sr_first_mapping;

        if (sr_first_mapping == (mach_vm_offset_t) -1) {
                /* shared region is empty */
                kr = KERN_INVALID_ADDRESS;
        } else {
                kr = KERN_SUCCESS;
                *start_address = sr_base_address + sr_first_mapping;
        }

        vm_shared_region_unlock();
        
        SHARED_REGION_TRACE_DEBUG(
                ("shared_region: start_address(%p) <- 0x%llx\n",
                 (void *)VM_KERNEL_ADDRPERM(shared_region),
                 (long long)shared_region->sr_base_address));

        return kr;
}

void
vm_shared_region_undo_mappings(
        vm_map_t sr_map,
        mach_vm_offset_t sr_base_address,
        struct shared_file_mapping_np *mappings,
        unsigned int mappings_count)
{
        unsigned int            j = 0;
        vm_shared_region_t      shared_region = NULL;
        boolean_t               reset_shared_region_state = FALSE;

        shared_region = vm_shared_region_get(current_task());
        if (shared_region == NULL) {
                printf("Failed to undo mappings because of NULL shared region.\n");
                return;
        }
        

        if (sr_map == NULL) {
                ipc_port_t              sr_handle;
                vm_named_entry_t        sr_mem_entry;

                vm_shared_region_lock();
                assert(shared_region->sr_ref_count > 1);

                while (shared_region->sr_mapping_in_progress) {
                        /* wait for our turn... */
                        vm_shared_region_sleep(&shared_region->sr_mapping_in_progress,
                                               THREAD_UNINT);
                }
                assert(! shared_region->sr_mapping_in_progress);
                assert(shared_region->sr_ref_count > 1);
                /* let others know we're working in this shared region */
                shared_region->sr_mapping_in_progress = TRUE;

                vm_shared_region_unlock();

                reset_shared_region_state = TRUE;

                /* no need to lock because this data is never modified... */
                sr_handle = shared_region->sr_mem_entry;
                sr_mem_entry = (vm_named_entry_t) sr_handle->ip_kobject;
                sr_map = sr_mem_entry->backing.map;
                sr_base_address = shared_region->sr_base_address;
        }
        /*
         * Undo the mappings we've established so far.
         */
        for (j = 0; j < mappings_count; j++) {
                kern_return_t kr2;

                if (mappings[j].sfm_size == 0) {
                        /*
                         * We didn't establish this
                         * mapping, so nothing to undo.
                         */
                        continue;
                }
                SHARED_REGION_TRACE_INFO(
                        ("shared_region: mapping[%d]: "
                         "address:0x%016llx "
                         "size:0x%016llx "
                         "offset:0x%016llx "
                         "maxprot:0x%x prot:0x%x: "
                         "undoing...\n",
                         j,
                         (long long)mappings[j].sfm_address,
                         (long long)mappings[j].sfm_size,
                         (long long)mappings[j].sfm_file_offset,
                         mappings[j].sfm_max_prot,
                         mappings[j].sfm_init_prot));
                kr2 = mach_vm_deallocate(
                        sr_map,
                        (mappings[j].sfm_address -
                         sr_base_address),
                        mappings[j].sfm_size);
                assert(kr2 == KERN_SUCCESS);
        }

        if (reset_shared_region_state) {
                vm_shared_region_lock();
                assert(shared_region->sr_ref_count > 1);
                assert(shared_region->sr_mapping_in_progress);
                /* we're done working on that shared region */
                shared_region->sr_mapping_in_progress = FALSE;
                thread_wakeup((event_t) &shared_region->sr_mapping_in_progress);
                vm_shared_region_unlock();
                reset_shared_region_state = FALSE;
        }

        vm_shared_region_deallocate(shared_region);
}

/*
 * Establish some mappings of a file in the shared region.
 * This is used by "dyld" via the shared_region_map_np() system call
 * to populate the shared region with the appropriate shared cache.
 *
 * One could also call it several times to incrementally load several
 * libraries, as long as they do not overlap.  
 * It will return KERN_SUCCESS if the mappings were successfully established
 * or if they were already established identically by another process.
 */
kern_return_t
vm_shared_region_map_file(
        vm_shared_region_t              shared_region,
        unsigned int                    mappings_count,
        struct shared_file_mapping_np   *mappings,
        memory_object_control_t         file_control,
        memory_object_size_t            file_size,
        void                            *root_dir,
        uint32_t                        slide,
        user_addr_t                     slide_start,
        user_addr_t                     slide_size)
{
        kern_return_t           kr;
        vm_object_t             file_object;
        ipc_port_t              sr_handle;
        vm_named_entry_t        sr_mem_entry;
        vm_map_t                sr_map;
        mach_vm_offset_t        sr_base_address;
        unsigned int            i;
        mach_port_t             map_port;
        vm_map_offset_t         target_address;
        vm_object_t             object;
        vm_object_size_t        obj_size;
        struct shared_file_mapping_np   *mapping_to_slide = NULL;
        mach_vm_offset_t        first_mapping = (mach_vm_offset_t) -1;
        vm_map_offset_t         lowest_unnestable_addr = 0;
        vm_map_kernel_flags_t   vmk_flags;


#if __arm64__
        if ((shared_region->sr_64bit ||
             page_shift_user32 == SIXTEENK_PAGE_SHIFT) &&
            ((slide & SIXTEENK_PAGE_MASK) != 0)) {
                printf("FOURK_COMPAT: %s: rejecting mis-aligned slide 0x%x\n",
                       __FUNCTION__, slide);
                kr = KERN_INVALID_ARGUMENT;
                goto done;
        }
#endif /* __arm64__ */

        kr = KERN_SUCCESS;

        vm_shared_region_lock();
        assert(shared_region->sr_ref_count > 1);

        if (shared_region->sr_root_dir != root_dir) {
                /*
                 * This shared region doesn't match the current root
                 * directory of this process.  Deny the mapping to
                 * avoid tainting the shared region with something that 
                 * doesn't quite belong into it.
                 */
                vm_shared_region_unlock();
                kr = KERN_PROTECTION_FAILURE;
                goto done;
        }

        /*
         * Make sure we handle only one mapping at a time in a given
         * shared region, to avoid race conditions.  This should not
         * happen frequently...
         */
        while (shared_region->sr_mapping_in_progress) {
                /* wait for our turn... */
                vm_shared_region_sleep(&shared_region->sr_mapping_in_progress,
                                       THREAD_UNINT);
        }
        assert(! shared_region->sr_mapping_in_progress);
        assert(shared_region->sr_ref_count > 1);
        /* let others know we're working in this shared region */
        shared_region->sr_mapping_in_progress = TRUE;

        vm_shared_region_unlock();

        /* no need to lock because this data is never modified... */
        sr_handle = shared_region->sr_mem_entry;
        sr_mem_entry = (vm_named_entry_t) sr_handle->ip_kobject;
        sr_map = sr_mem_entry->backing.map;
        sr_base_address = shared_region->sr_base_address;

        SHARED_REGION_TRACE_DEBUG(
                ("shared_region: -> map(%p,%d,%p,%p,0x%llx)\n",
                 (void *)VM_KERNEL_ADDRPERM(shared_region), mappings_count,
                 (void *)VM_KERNEL_ADDRPERM(mappings),
                 (void *)VM_KERNEL_ADDRPERM(file_control), file_size));

        /* get the VM object associated with the file to be mapped */
        file_object = memory_object_control_to_vm_object(file_control);

        assert(file_object);

        /* establish the mappings */
        for (i = 0; i < mappings_count; i++) {
                SHARED_REGION_TRACE_INFO(
                        ("shared_region: mapping[%d]: "
                         "address:0x%016llx size:0x%016llx offset:0x%016llx "
                         "maxprot:0x%x prot:0x%x\n",
                         i,
                         (long long)mappings[i].sfm_address,
                         (long long)mappings[i].sfm_size,
                         (long long)mappings[i].sfm_file_offset,
                         mappings[i].sfm_max_prot,
                         mappings[i].sfm_init_prot));

                if (mappings[i].sfm_init_prot & VM_PROT_ZF) {
                        /* zero-filled memory */
                        map_port = MACH_PORT_NULL;
                } else {
                        /* file-backed memory */
                        __IGNORE_WCASTALIGN(map_port = (ipc_port_t) file_object->pager);
                }
                
                if (mappings[i].sfm_init_prot & VM_PROT_SLIDE) {
                        /*
                         * This is the mapping that needs to be slid.
                         */
                        if (mapping_to_slide != NULL) {
                                SHARED_REGION_TRACE_INFO(
                                        ("shared_region: mapping[%d]: "
                                         "address:0x%016llx size:0x%016llx "
                                         "offset:0x%016llx "
                                         "maxprot:0x%x prot:0x%x "
                                         "will not be slid as only one such mapping is allowed...\n",
                                         i,
                                         (long long)mappings[i].sfm_address,
                                         (long long)mappings[i].sfm_size,
                                         (long long)mappings[i].sfm_file_offset,
                                         mappings[i].sfm_max_prot,
                                         mappings[i].sfm_init_prot));
                        } else {
                                mapping_to_slide = &mappings[i];
                        }
                }

                /* mapping's address is relative to the shared region base */
                target_address =
                        mappings[i].sfm_address - sr_base_address;

                vmk_flags = VM_MAP_KERNEL_FLAGS_NONE;
                vmk_flags.vmkf_already = TRUE;

                /* establish that mapping, OK if it's "already" there */
                if (map_port == MACH_PORT_NULL) {
                        /*
                         * We want to map some anonymous memory in a
                         * shared region.
                         * We have to create the VM object now, so that it
                         * can be mapped "copy-on-write".
                         */
                        obj_size = vm_map_round_page(mappings[i].sfm_size,
                                                     VM_MAP_PAGE_MASK(sr_map));
                        object = vm_object_allocate(obj_size);
                        if (object == VM_OBJECT_NULL) {
                                kr = KERN_RESOURCE_SHORTAGE;
                        } else {
                                kr = vm_map_enter(
                                        sr_map,
                                        &target_address,
                                        vm_map_round_page(mappings[i].sfm_size,
                                                          VM_MAP_PAGE_MASK(sr_map)),
                                        0,
                                        VM_FLAGS_FIXED,
                                        vmk_flags,
                                        VM_KERN_MEMORY_NONE,
                                        object,
                                        0,
                                        TRUE,
                                        mappings[i].sfm_init_prot & VM_PROT_ALL,
                                        mappings[i].sfm_max_prot & VM_PROT_ALL,
                                        VM_INHERIT_DEFAULT);
                        }
                } else {
                        object = VM_OBJECT_NULL; /* no anonymous memory here */
                        kr = vm_map_enter_mem_object(
                                sr_map,
                                &target_address,
                                vm_map_round_page(mappings[i].sfm_size,
                                                  VM_MAP_PAGE_MASK(sr_map)),
                                0,
                                VM_FLAGS_FIXED,
                                vmk_flags,
                                VM_KERN_MEMORY_NONE,
                                map_port,
                                mappings[i].sfm_file_offset,
                                TRUE,
                                mappings[i].sfm_init_prot & VM_PROT_ALL,
                                mappings[i].sfm_max_prot & VM_PROT_ALL,
                                VM_INHERIT_DEFAULT);

                }

                if (kr == KERN_SUCCESS) {
                        /*
                         * Record the first (chronologically) successful
                         * mapping in this shared region.
                         * We're protected by "sr_mapping_in_progress" here,
                         * so no need to lock "shared_region".
                         */
                        if (first_mapping == (mach_vm_offset_t) -1) {
                                first_mapping = target_address;
                        }

                        /*
                         * Record the lowest writable address in this
                         * sub map, to log any unexpected unnesting below
                         * that address (see log_unnest_badness()).
                         */
                        if ((mappings[i].sfm_init_prot & VM_PROT_WRITE) &&
                            sr_map->is_nested_map &&
                            (lowest_unnestable_addr == 0 ||
                             (target_address < lowest_unnestable_addr))) {
                                lowest_unnestable_addr = target_address;
                        }
                } else {
                        if (map_port == MACH_PORT_NULL) {
                                /*
                                 * Get rid of the VM object we just created
                                 * but failed to map.
                                 */
                                vm_object_deallocate(object);
                                object = VM_OBJECT_NULL;
                        }
                        if (kr == KERN_MEMORY_PRESENT) {
                                /*
                                 * This exact mapping was already there:
                                 * that's fine.
                                 */
                                SHARED_REGION_TRACE_INFO(
                                        ("shared_region: mapping[%d]: "
                                         "address:0x%016llx size:0x%016llx "
                                         "offset:0x%016llx "
                                         "maxprot:0x%x prot:0x%x "
                                         "already mapped...\n",
                                         i,
                                         (long long)mappings[i].sfm_address,
                                         (long long)mappings[i].sfm_size,
                                         (long long)mappings[i].sfm_file_offset,
                                         mappings[i].sfm_max_prot,
                                         mappings[i].sfm_init_prot));
                                /*
                                 * We didn't establish this mapping ourselves;
                                 * let's reset its size, so that we do not
                                 * attempt to undo it if an error occurs later.
                                 */
                                mappings[i].sfm_size = 0;
                                kr = KERN_SUCCESS;
                        } else {
                                /* this mapping failed ! */
                                SHARED_REGION_TRACE_ERROR(
                                        ("shared_region: mapping[%d]: "
                                         "address:0x%016llx size:0x%016llx "
                                         "offset:0x%016llx "
                                         "maxprot:0x%x prot:0x%x failed 0x%x\n",
                                         i,
                                         (long long)mappings[i].sfm_address,
                                         (long long)mappings[i].sfm_size,
                                         (long long)mappings[i].sfm_file_offset,
                                         mappings[i].sfm_max_prot,
                                         mappings[i].sfm_init_prot,
                                         kr));

                                vm_shared_region_undo_mappings(sr_map, sr_base_address, mappings, i);
                                break;
                        }

                }

        }

        if (kr == KERN_SUCCESS &&
            slide_size != 0 &&
            mapping_to_slide != NULL) {
                kr = vm_shared_region_slide(slide, 
                                            mapping_to_slide->sfm_file_offset, 
                                            mapping_to_slide->sfm_size, 
                                            slide_start, 
                                            slide_size, 
                                            file_control);
                if (kr  != KERN_SUCCESS) {
                        SHARED_REGION_TRACE_ERROR(
                                ("shared_region: region_slide("
                                 "slide:0x%x start:0x%016llx "
                                 "size:0x%016llx) failed 0x%x\n",
                                 slide,
                                 (long long)slide_start,
                                 (long long)slide_size,
                                 kr));
                        vm_shared_region_undo_mappings(sr_map,
                                                       sr_base_address,
                                                       mappings,
                                                       mappings_count);
                }
        }

        if (kr == KERN_SUCCESS) {
                /* adjust the map's "lowest_unnestable_start" */
                lowest_unnestable_addr &= ~(pmap_nesting_size_min-1);
                if (lowest_unnestable_addr !=
                    sr_map->lowest_unnestable_start) {
                        vm_map_lock(sr_map);
                        sr_map->lowest_unnestable_start =
                                lowest_unnestable_addr;
                        vm_map_unlock(sr_map);
                }
        }

        vm_shared_region_lock();
        assert(shared_region->sr_ref_count > 1);
        assert(shared_region->sr_mapping_in_progress);
        /* set "sr_first_mapping"; dyld uses it to validate the shared cache */ 
        if (kr == KERN_SUCCESS &&
            shared_region->sr_first_mapping == (mach_vm_offset_t) -1) {
                shared_region->sr_first_mapping = first_mapping;
        }


        /* copy in the shared region UUID to the shared region structure */
        if (kr == KERN_SUCCESS && !shared_region->sr_uuid_copied) {
                 int error = copyin((shared_region->sr_base_address + shared_region->sr_first_mapping +
                                         offsetof(struct _dyld_cache_header, uuid)),
                                 (char *)&shared_region->sr_uuid,
                                 sizeof(shared_region->sr_uuid));
                 if (error == 0) {
                        shared_region->sr_uuid_copied = TRUE;
                 } else {
#if DEVELOPMENT || DEBUG
                        panic("shared_region: copyin_UUID(sr_base_addr:0x%016llx sr_first_mapping:0x%016llx "
                                "offset:0x%016llx size:0x%016llx) failed with %d\n",
                                 (long long)shared_region->sr_base_address,
                                 (long long)shared_region->sr_first_mapping,
                                 (long long)offsetof(struct _dyld_cache_header, uuid),
                                 (long long)sizeof(shared_region->sr_uuid),
                                 error);
#endif /* DEVELOPMENT || DEBUG */
                        shared_region->sr_uuid_copied = FALSE;
                 }
        }

        /* we're done working on that shared region */
        shared_region->sr_mapping_in_progress = FALSE;
        thread_wakeup((event_t) &shared_region->sr_mapping_in_progress);
        vm_shared_region_unlock();

done:
        SHARED_REGION_TRACE_DEBUG(
                ("shared_region: map(%p,%d,%p,%p,0x%llx) <- 0x%x \n",
                 (void *)VM_KERNEL_ADDRPERM(shared_region), mappings_count,
                 (void *)VM_KERNEL_ADDRPERM(mappings),
                 (void *)VM_KERNEL_ADDRPERM(file_control), file_size, kr));
        return kr;
}

/*
 * Enter the appropriate shared region into "map" for "task".
 * This involves looking up the shared region (and possibly creating a new
 * one) for the desired environment, then mapping the VM sub map into the
 * task's VM "map", with the appropriate level of pmap-nesting.
 */
kern_return_t
vm_shared_region_enter(
        struct _vm_map          *map,
        struct task             *task,
        boolean_t               is_64bit,
        void                    *fsroot,
        cpu_type_t              cpu)
{
        kern_return_t           kr;
        vm_shared_region_t      shared_region;
        vm_map_offset_t         sr_address, sr_offset, target_address;
        vm_map_size_t           sr_size, mapping_size;
        vm_map_offset_t         sr_pmap_nesting_start;
        vm_map_size_t           sr_pmap_nesting_size;
        ipc_port_t              sr_handle;
        vm_prot_t               cur_prot, max_prot;

        SHARED_REGION_TRACE_DEBUG(
                ("shared_region: -> "
                 "enter(map=%p,task=%p,root=%p,cpu=%d,64bit=%d)\n",
                 (void *)VM_KERNEL_ADDRPERM(map),
                 (void *)VM_KERNEL_ADDRPERM(task),
                 (void *)VM_KERNEL_ADDRPERM(fsroot), cpu, is_64bit));

        /* lookup (create if needed) the shared region for this environment */
        shared_region = vm_shared_region_lookup(fsroot, cpu, is_64bit);
        if (shared_region == NULL) {
                /* this should not happen ! */
                SHARED_REGION_TRACE_ERROR(
                        ("shared_region: -> "
                         "enter(map=%p,task=%p,root=%p,cpu=%d,64bit=%d): "
                         "lookup failed !\n",
                         (void *)VM_KERNEL_ADDRPERM(map),
                         (void *)VM_KERNEL_ADDRPERM(task),
                         (void *)VM_KERNEL_ADDRPERM(fsroot), cpu, is_64bit));
                //panic("shared_region_enter: lookup failed\n");
                return KERN_FAILURE;
        }
        
        /* let the task use that shared region */
        vm_shared_region_set(task, shared_region);

        kr = KERN_SUCCESS;
        /* no need to lock since this data is never modified */
        sr_address = shared_region->sr_base_address;
        sr_size = shared_region->sr_size;
        sr_handle = shared_region->sr_mem_entry;
        sr_pmap_nesting_start = shared_region->sr_pmap_nesting_start;
        sr_pmap_nesting_size = shared_region->sr_pmap_nesting_size;

        cur_prot = VM_PROT_READ;
#if __x86_64__
        /*
         * XXX BINARY COMPATIBILITY
         * java6 apparently needs to modify some code in the
         * dyld shared cache and needs to be allowed to add
         * write access...
         */
        max_prot = VM_PROT_ALL;
#else /* __x86_64__ */
        max_prot = VM_PROT_READ;
#endif /* __x86_64__ */
        /*
         * Start mapping the shared region's VM sub map into the task's VM map.
         */
        sr_offset = 0;

        if (sr_pmap_nesting_start > sr_address) {
                /* we need to map a range without pmap-nesting first */
                target_address = sr_address;
                mapping_size = sr_pmap_nesting_start - sr_address;
                kr = vm_map_enter_mem_object(
                        map,
                        &target_address,
                        mapping_size,
                        0,
                        VM_FLAGS_FIXED,
                        VM_MAP_KERNEL_FLAGS_NONE,
                        VM_KERN_MEMORY_NONE,
                        sr_handle,
                        sr_offset,
                        TRUE,
                        cur_prot,
                        max_prot,
                        VM_INHERIT_SHARE);
                if (kr != KERN_SUCCESS) {
                        SHARED_REGION_TRACE_ERROR(
                                ("shared_region: enter(%p,%p,%p,%d,%d): "
                                 "vm_map_enter(0x%llx,0x%llx,%p) error 0x%x\n",
                                 (void *)VM_KERNEL_ADDRPERM(map),
                                 (void *)VM_KERNEL_ADDRPERM(task),
                                 (void *)VM_KERNEL_ADDRPERM(fsroot),
                                 cpu, is_64bit,
                                 (long long)target_address,
                                 (long long)mapping_size,
                                 (void *)VM_KERNEL_ADDRPERM(sr_handle), kr));
                        goto done;
                }
                SHARED_REGION_TRACE_DEBUG(
                        ("shared_region: enter(%p,%p,%p,%d,%d): "
                         "vm_map_enter(0x%llx,0x%llx,%p) error 0x%x\n",
                         (void *)VM_KERNEL_ADDRPERM(map),
                         (void *)VM_KERNEL_ADDRPERM(task),
                         (void *)VM_KERNEL_ADDRPERM(fsroot), cpu, is_64bit,
                         (long long)target_address, (long long)mapping_size,
                         (void *)VM_KERNEL_ADDRPERM(sr_handle), kr));
                sr_offset += mapping_size;
                sr_size -= mapping_size;
        }
        /*
         * We may need to map several pmap-nested portions, due to platform
         * specific restrictions on pmap nesting.
         * The pmap-nesting is triggered by the "VM_MEMORY_SHARED_PMAP" alias...
         */
        for (;
             sr_pmap_nesting_size > 0;
             sr_offset += mapping_size,
                     sr_size -= mapping_size,
                     sr_pmap_nesting_size -= mapping_size) {
                target_address = sr_address + sr_offset;
                mapping_size = sr_pmap_nesting_size;
                if (mapping_size > pmap_nesting_size_max) {
                        mapping_size = (vm_map_offset_t) pmap_nesting_size_max;
                }
                kr = vm_map_enter_mem_object(
                        map,
                        &target_address,
                        mapping_size,
                        0,
                        VM_FLAGS_FIXED,
                        VM_MAP_KERNEL_FLAGS_NONE,
                        VM_MEMORY_SHARED_PMAP,
                        sr_handle,
                        sr_offset,
                        TRUE,
                        cur_prot,
                        max_prot,
                        VM_INHERIT_SHARE);
                if (kr != KERN_SUCCESS) {
                        SHARED_REGION_TRACE_ERROR(
                                ("shared_region: enter(%p,%p,%p,%d,%d): "
                                 "vm_map_enter(0x%llx,0x%llx,%p) error 0x%x\n",
                                 (void *)VM_KERNEL_ADDRPERM(map),
                                 (void *)VM_KERNEL_ADDRPERM(task),
                                 (void *)VM_KERNEL_ADDRPERM(fsroot),
                                 cpu, is_64bit,
                                 (long long)target_address,
                                 (long long)mapping_size,
                                 (void *)VM_KERNEL_ADDRPERM(sr_handle), kr));
                        goto done;
                }
                SHARED_REGION_TRACE_DEBUG(
                        ("shared_region: enter(%p,%p,%p,%d,%d): "
                         "nested vm_map_enter(0x%llx,0x%llx,%p) error 0x%x\n",
                         (void *)VM_KERNEL_ADDRPERM(map),
                         (void *)VM_KERNEL_ADDRPERM(task),
                         (void *)VM_KERNEL_ADDRPERM(fsroot), cpu, is_64bit,
                         (long long)target_address, (long long)mapping_size,
                         (void *)VM_KERNEL_ADDRPERM(sr_handle), kr));
        }
        if (sr_size > 0) {
                /* and there's some left to be mapped without pmap-nesting */
                target_address = sr_address + sr_offset;
                mapping_size = sr_size;
                kr = vm_map_enter_mem_object(
                        map,
                        &target_address,
                        mapping_size,
                        0,
                        VM_FLAGS_FIXED,
                        VM_MAP_KERNEL_FLAGS_NONE,
                        VM_KERN_MEMORY_NONE,
                        sr_handle,
                        sr_offset,
                        TRUE,
                        cur_prot,
                        max_prot,
                        VM_INHERIT_SHARE);
                if (kr != KERN_SUCCESS) {
                        SHARED_REGION_TRACE_ERROR(
                                ("shared_region: enter(%p,%p,%p,%d,%d): "
                                 "vm_map_enter(0x%llx,0x%llx,%p) error 0x%x\n",
                                 (void *)VM_KERNEL_ADDRPERM(map),
                                 (void *)VM_KERNEL_ADDRPERM(task),
                                 (void *)VM_KERNEL_ADDRPERM(fsroot),
                                 cpu, is_64bit,
                                 (long long)target_address,
                                 (long long)mapping_size,
                                 (void *)VM_KERNEL_ADDRPERM(sr_handle), kr));
                        goto done;
                }
                SHARED_REGION_TRACE_DEBUG(
                        ("shared_region: enter(%p,%p,%p,%d,%d): "
                         "vm_map_enter(0x%llx,0x%llx,%p) error 0x%x\n",
                         (void *)VM_KERNEL_ADDRPERM(map),
                         (void *)VM_KERNEL_ADDRPERM(task),
                         (void *)VM_KERNEL_ADDRPERM(fsroot), cpu, is_64bit,
                         (long long)target_address, (long long)mapping_size,
                         (void *)VM_KERNEL_ADDRPERM(sr_handle), kr));
                sr_offset += mapping_size;
                sr_size -= mapping_size;
        }
        assert(sr_size == 0);

done:
        SHARED_REGION_TRACE_DEBUG(
                ("shared_region: enter(%p,%p,%p,%d,%d) <- 0x%x\n",
                 (void *)VM_KERNEL_ADDRPERM(map),
                 (void *)VM_KERNEL_ADDRPERM(task),
                 (void *)VM_KERNEL_ADDRPERM(fsroot), cpu, is_64bit, kr));
        return kr;
}

#define SANE_SLIDE_INFO_SIZE            (2560*1024) /*Can be changed if needed*/
struct vm_shared_region_slide_info      slide_info;

kern_return_t
vm_shared_region_sliding_valid(uint32_t slide) 
{
        kern_return_t kr = KERN_SUCCESS;
        vm_shared_region_t sr = vm_shared_region_get(current_task());

        /* No region yet? we're fine. */
        if (sr == NULL) {
                return kr;
        }

        if ((sr->sr_slid == TRUE) && slide) {
                if (slide != vm_shared_region_get_slide_info(sr)->slide) {
                        printf("Only one shared region can be slid\n");
                        kr = KERN_FAILURE;      
                } else {
                        /*
                         * Request for sliding when we've
                         * already done it with exactly the
                         * same slide value before.
                         * This isn't wrong technically but
                         * we don't want to slide again and
                         * so we return this value.
                         */
                        kr = KERN_INVALID_ARGUMENT; 
                }
        }
        vm_shared_region_deallocate(sr);
        return kr;
}

kern_return_t
vm_shared_region_slide_init(
                vm_shared_region_t sr,
                mach_vm_size_t  slide_info_size,
                mach_vm_offset_t start,
                mach_vm_size_t size,
                uint32_t slide,
                memory_object_control_t sr_file_control)
{
        kern_return_t kr = KERN_SUCCESS;
        vm_object_t object = VM_OBJECT_NULL;
        vm_object_offset_t offset = 0;
        vm_shared_region_slide_info_t si = vm_shared_region_get_slide_info(sr);
        vm_offset_t slide_info_entry;
        
        vm_map_t map = NULL, cur_map = NULL;
        boolean_t       is_map_locked = FALSE;

        assert(sr->sr_slide_in_progress);
        assert(!sr->sr_slid);
        assert(si->slide_object == NULL);
        assert(si->slide_info_entry == NULL);

        if (slide_info_size > SANE_SLIDE_INFO_SIZE) {
                printf("Slide_info_size too large: %lx\n", (uintptr_t)slide_info_size);
                kr = KERN_FAILURE;
                return kr;
        }

        kr = kmem_alloc(kernel_map,
                        (vm_offset_t *) &slide_info_entry,
                        (vm_size_t) slide_info_size, VM_KERN_MEMORY_OSFMK);
        if (kr != KERN_SUCCESS) {
                return kr;
        }

        if (sr_file_control != MEMORY_OBJECT_CONTROL_NULL) {

                object = memory_object_control_to_vm_object(sr_file_control);
                vm_object_reference(object);
                offset = start;

                vm_object_lock(object);
        } else {
                /*
                 * Remove this entire "else" block and all "map" references
                 * once we get rid of the shared_region_slide_np()
                 * system call. 
                 */ 
                vm_map_entry_t entry = VM_MAP_ENTRY_NULL;
                map = current_map();
                vm_map_lock_read(map);
                is_map_locked = TRUE;
        Retry:
                cur_map = map;
                if(!vm_map_lookup_entry(map, start, &entry)) {
                        kr = KERN_INVALID_ARGUMENT;
                } else {
                        vm_object_t shadow_obj = VM_OBJECT_NULL;
         
                        if (entry->is_sub_map == TRUE) { 
                                map = VME_SUBMAP(entry);
                                start -= entry->vme_start;
                                start += VME_OFFSET(entry);
                                vm_map_lock_read(map);
                                vm_map_unlock_read(cur_map);
                                goto Retry;
                        } else {
                                object = VME_OBJECT(entry);
                                offset = ((start - entry->vme_start) +
                                          VME_OFFSET(entry));
                        }
         
                        vm_object_lock(object);
                        while (object->shadow != VM_OBJECT_NULL) {
                                shadow_obj = object->shadow;
                                vm_object_lock(shadow_obj);
                                vm_object_unlock(object);
                                object = shadow_obj;            
                        }
                }
        }
                
        if (object->internal == TRUE) {
                kr = KERN_INVALID_ADDRESS;
        } else if (object->object_slid) {
                /* Can only be slid once */
                printf("%s: found vm_object %p already slid?\n", __FUNCTION__, object);
                kr = KERN_FAILURE;
        } else {

                si->slide_info_entry = (vm_shared_region_slide_info_entry_t)slide_info_entry;
                si->slide_info_size = slide_info_size;
                si->slide_object = object;
                si->start = offset;
                si->end = si->start + size;     
                si->slide = slide;

                /*
                 * If we want to have this region get deallocated/freed
                 * then we will have to make sure that we msync(..MS_INVALIDATE..)
                 * the pages associated with this shared region. Those pages would
                 * have been slid with an older slide value.
                 */

                /* 
                 * Pointers in object are held without references; they
                 * are disconnected at the time that we destroy the
                 * shared region, and since the shared region holds 
                 * a reference on the object, no references in the other
                 * direction are required.
                 */
                object->object_slid = TRUE;
                object->vo_slide_info = si;
        }

        vm_object_unlock(object);
        if (is_map_locked == TRUE) {
                vm_map_unlock_read(map);
        }

        if (kr != KERN_SUCCESS) {
                kmem_free(kernel_map, slide_info_entry, slide_info_size);
        }
        return kr;
}

void* 
vm_shared_region_get_slide_info_entry(vm_shared_region_t sr) {
        return (void*)sr->sr_slide_info.slide_info_entry;
}

static kern_return_t
vm_shared_region_slide_sanity_check_v1(vm_shared_region_slide_info_entry_v1_t s_info)
{
        uint32_t pageIndex=0;
        uint16_t entryIndex=0;
        uint16_t *toc = NULL;

        toc = (uint16_t*)((uintptr_t)s_info + s_info->toc_offset);
        for (;pageIndex < s_info->toc_count; pageIndex++) {

                entryIndex =  (uint16_t)(toc[pageIndex]);

                if (entryIndex >= s_info->entry_count) {
                        printf("No sliding bitmap entry for pageIndex: %d at entryIndex: %d amongst %d entries\n", pageIndex, entryIndex, s_info->entry_count);
                        return KERN_FAILURE;
                }

        }
        return KERN_SUCCESS;
}

static kern_return_t
vm_shared_region_slide_sanity_check_v2(vm_shared_region_slide_info_entry_v2_t s_info, mach_vm_size_t slide_info_size)
{
        if (s_info->page_size != PAGE_SIZE_FOR_SR_SLIDE) {
                return KERN_FAILURE;
        }

        /* Ensure that the slide info doesn't reference any data outside of its bounds. */

        uint32_t page_starts_count = s_info->page_starts_count;
        uint32_t page_extras_count = s_info->page_extras_count;
        mach_vm_size_t num_trailing_entries = page_starts_count + page_extras_count;
        if (num_trailing_entries < page_starts_count) {
                return KERN_FAILURE;
        }

        /* Scale by sizeof(uint16_t). Hard-coding the size simplifies the overflow check. */
        mach_vm_size_t trailing_size = num_trailing_entries << 1;
        if (trailing_size >> 1 != num_trailing_entries) {
                return KERN_FAILURE;
        }

        mach_vm_size_t required_size = sizeof(*s_info) + trailing_size;
        if (required_size < sizeof(*s_info)) {
                return KERN_FAILURE;
        }

        if (required_size > slide_info_size) {
                return KERN_FAILURE;
        }

        return KERN_SUCCESS;
}

kern_return_t
vm_shared_region_slide_sanity_check(vm_shared_region_t sr)
{
        vm_shared_region_slide_info_t si;
        vm_shared_region_slide_info_entry_t s_info;
        kern_return_t kr;

        si = vm_shared_region_get_slide_info(sr);
        s_info = si->slide_info_entry;

        kr = mach_vm_protect(kernel_map,
                             (mach_vm_offset_t)(vm_offset_t)s_info,
                             (mach_vm_size_t) si->slide_info_size,
                             TRUE, VM_PROT_READ);
        if (kr != KERN_SUCCESS) {
                panic("vm_shared_region_slide_sanity_check: vm_protect() error 0x%x\n", kr);
        }

        if (s_info->version == 1) {
                kr = vm_shared_region_slide_sanity_check_v1(&s_info->v1);
        } else if (s_info->version == 2) {
                kr = vm_shared_region_slide_sanity_check_v2(&s_info->v2, si->slide_info_size);
        } else {
                goto fail;
        }
        if (kr != KERN_SUCCESS) {
                goto fail;
        }

        return KERN_SUCCESS;
fail:
        if (si->slide_info_entry != NULL) {
                kmem_free(kernel_map,
                          (vm_offset_t) si->slide_info_entry,
                          (vm_size_t) si->slide_info_size);
                
                vm_object_lock(si->slide_object);
                si->slide_object->object_slid = FALSE;
                si->slide_object->vo_slide_info = NULL;
                vm_object_unlock(si->slide_object);
                
                vm_object_deallocate(si->slide_object);
                si->slide_object        = NULL;
                si->start = 0;
                si->end = 0;    
                si->slide = 0;
                si->slide_info_entry = NULL;
                si->slide_info_size = 0;
        }
        return KERN_FAILURE;
}

static kern_return_t
vm_shared_region_slide_page_v1(vm_shared_region_slide_info_t si, vm_offset_t vaddr, uint32_t pageIndex)
{
        uint16_t *toc = NULL;
        slide_info_entry_toc_t bitmap = NULL;
        uint32_t i=0, j=0;
        uint8_t b = 0;
        uint32_t slide = si->slide;
        int is_64 = task_has_64BitAddr(current_task());

        vm_shared_region_slide_info_entry_v1_t s_info = &si->slide_info_entry->v1;
        toc = (uint16_t*)((uintptr_t)s_info + s_info->toc_offset);
        
        if (pageIndex >= s_info->toc_count) {
                printf("No slide entry for this page in toc. PageIndex: %d Toc Count: %d\n", pageIndex, s_info->toc_count);
        } else {
                uint16_t entryIndex =  (uint16_t)(toc[pageIndex]);
                slide_info_entry_toc_t slide_info_entries = (slide_info_entry_toc_t)((uintptr_t)s_info + s_info->entry_offset);
                
                if (entryIndex >= s_info->entry_count) {
                        printf("No sliding bitmap entry for entryIndex: %d amongst %d entries\n", entryIndex, s_info->entry_count);
                } else {
                        bitmap = &slide_info_entries[entryIndex];

                        for(i=0; i < NUM_SLIDING_BITMAPS_PER_PAGE; ++i) {
                                b = bitmap->entry[i];
                                if (b!=0) {
                                        for (j=0; j <8; ++j) {
                                                if (b & (1 <<j)){
                                                        uint32_t *ptr_to_slide;
                                                        uint32_t old_value;

                                                        ptr_to_slide = (uint32_t*)((uintptr_t)(vaddr)+(sizeof(uint32_t)*(i*8 +j)));
                                                        old_value = *ptr_to_slide;
                                                        *ptr_to_slide += slide;
                                                        if (is_64 && *ptr_to_slide < old_value) {
                                                                /*
                                                                 * We just slid the low 32 bits of a 64-bit pointer
                                                                 * and it looks like there should have been a carry-over
                                                                 * to the upper 32 bits.
                                                                 * The sliding failed...
                                                                 */
                                                                printf("vm_shared_region_slide() carry over: i=%d j=%d b=0x%x slide=0x%x old=0x%x new=0x%x\n",
                                                                       i, j, b, slide, old_value, *ptr_to_slide);
                                                                return KERN_FAILURE;
                                                        }
                                                }
                                        }
                                }
                        }
                }
        }

        return KERN_SUCCESS;
}

static kern_return_t
rebase_chain_32(
        uint8_t *page_content,
        uint16_t start_offset,
        uint32_t slide_amount,
        vm_shared_region_slide_info_entry_v2_t s_info)
{
        const uint32_t last_page_offset = PAGE_SIZE_FOR_SR_SLIDE - sizeof(uint32_t);

        const uint32_t delta_mask = (uint32_t)(s_info->delta_mask);
        const uint32_t value_mask = ~delta_mask;
        const uint32_t value_add = (uint32_t)(s_info->value_add);
        const uint32_t delta_shift = __builtin_ctzll(delta_mask) - 2;

        uint32_t page_offset = start_offset;
        uint32_t delta = 1;

        while (delta != 0 && page_offset <= last_page_offset) {
                uint8_t *loc;
                uint32_t value;

                loc = page_content + page_offset;
                memcpy(&value, loc, sizeof(value));
                delta = (value & delta_mask) >> delta_shift;
                value &= value_mask;

                if (value != 0) {
                        value += value_add;
                        value += slide_amount;
                }
                memcpy(loc, &value, sizeof(value));
                page_offset += delta;
        }

        /* If the offset went past the end of the page, then the slide data is invalid. */
        if (page_offset > last_page_offset) {
                return KERN_FAILURE;
        }
        return KERN_SUCCESS;
}

static kern_return_t
rebase_chain_64(
        uint8_t *page_content,
        uint16_t start_offset,
        uint32_t slide_amount,
        vm_shared_region_slide_info_entry_v2_t s_info)
{
        const uint32_t last_page_offset = PAGE_SIZE_FOR_SR_SLIDE - sizeof(uint64_t);

        const uint64_t delta_mask = s_info->delta_mask;
        const uint64_t value_mask = ~delta_mask;
        const uint64_t value_add = s_info->value_add;
        const uint64_t delta_shift = __builtin_ctzll(delta_mask) - 2;

        uint32_t page_offset = start_offset;
        uint32_t delta = 1;

        while (delta != 0 && page_offset <= last_page_offset) {
                uint8_t *loc;
                uint64_t value;

                loc = page_content + page_offset;
                memcpy(&value, loc, sizeof(value));
                delta = (uint32_t)((value & delta_mask) >> delta_shift);
                value &= value_mask;

                if (value != 0) {
                        value += value_add;
                        value += slide_amount;
                }
                memcpy(loc, &value, sizeof(value));
                page_offset += delta;
        }

        if (page_offset + sizeof(uint32_t) == PAGE_SIZE_FOR_SR_SLIDE) {
                /* If a pointer straddling the page boundary needs to be adjusted, then
                 * add the slide to the lower half. The encoding guarantees that the upper
                 * half on the next page will need no masking.
                 *
                 * This assumes a little-endian machine and that the region being slid
                 * never crosses a 4 GB boundary. */

                uint8_t *loc = page_content + page_offset;
                uint32_t value;

                memcpy(&value, loc, sizeof(value));
                value += slide_amount;
                memcpy(loc, &value, sizeof(value));
        } else if (page_offset > last_page_offset) {
                return KERN_FAILURE;
        }

        return KERN_SUCCESS;
}

static kern_return_t
rebase_chain(
        boolean_t is_64,
        uint32_t pageIndex,
        uint8_t *page_content,
        uint16_t start_offset,
        uint32_t slide_amount,
        vm_shared_region_slide_info_entry_v2_t s_info)
{
        kern_return_t kr;
        if (is_64) {
                kr = rebase_chain_64(page_content, start_offset, slide_amount, s_info);
        } else {
                kr = rebase_chain_32(page_content, start_offset, slide_amount, s_info);
        }

        if (kr != KERN_SUCCESS) {
                printf("vm_shared_region_slide_page() offset overflow: pageIndex=%u, start_offset=%u, slide_amount=%u\n",
                       pageIndex, start_offset, slide_amount);
        }
        return kr;
}

static kern_return_t
vm_shared_region_slide_page_v2(vm_shared_region_slide_info_t si, vm_offset_t vaddr, uint32_t pageIndex)
{
        vm_shared_region_slide_info_entry_v2_t s_info = &si->slide_info_entry->v2;
        const uint32_t slide_amount = si->slide;

        /* The high bits of the delta_mask field are nonzero precisely when the shared
         * cache is 64-bit. */
        const boolean_t is_64 = (s_info->delta_mask >> 32) != 0;

        const uint16_t *page_starts = (uint16_t *)((uintptr_t)s_info + s_info->page_starts_offset);
        const uint16_t *page_extras = (uint16_t *)((uintptr_t)s_info + s_info->page_extras_offset);

        uint8_t *page_content = (uint8_t *)vaddr;
        uint16_t page_entry;

        if (pageIndex >= s_info->page_starts_count) {
                printf("vm_shared_region_slide_page() did not find page start in slide info: pageIndex=%u, count=%u\n",
                       pageIndex, s_info->page_starts_count);
                return KERN_FAILURE;
        }
        page_entry = page_starts[pageIndex];

        if (page_entry == DYLD_CACHE_SLIDE_PAGE_ATTR_NO_REBASE) {
                return KERN_SUCCESS;
        }

        if (page_entry & DYLD_CACHE_SLIDE_PAGE_ATTR_EXTRA) {
                uint16_t chain_index = page_entry & DYLD_CACHE_SLIDE_PAGE_VALUE;
                uint16_t info;

                do {
                        uint16_t page_start_offset;
                        kern_return_t kr;

                        if (chain_index >= s_info->page_extras_count) {
                                printf("vm_shared_region_slide_page() out-of-bounds extras index: index=%u, count=%u\n",
                                       chain_index, s_info->page_extras_count);
                                return KERN_FAILURE;
                        }
                        info = page_extras[chain_index];
                        page_start_offset = (info & DYLD_CACHE_SLIDE_PAGE_VALUE) << DYLD_CACHE_SLIDE_PAGE_OFFSET_SHIFT;

                        kr = rebase_chain(is_64, pageIndex, page_content, page_start_offset, slide_amount, s_info);
                        if (kr != KERN_SUCCESS) {
                                return KERN_FAILURE;
                        }

                        chain_index++;
                } while (!(info & DYLD_CACHE_SLIDE_PAGE_ATTR_END));
        } else {
                const uint32_t page_start_offset = page_entry << DYLD_CACHE_SLIDE_PAGE_OFFSET_SHIFT;
                kern_return_t kr;

                kr = rebase_chain(is_64, pageIndex, page_content, page_start_offset, slide_amount, s_info);
                if (kr != KERN_SUCCESS) {
                        return KERN_FAILURE;
                }
        }

        return KERN_SUCCESS;
}

kern_return_t
vm_shared_region_slide_page(vm_shared_region_slide_info_t si, vm_offset_t vaddr, uint32_t pageIndex)
{
        if (si->slide_info_entry->version == 1) {
                return vm_shared_region_slide_page_v1(si, vaddr, pageIndex);
        } else {
                return vm_shared_region_slide_page_v2(si, vaddr, pageIndex);
        }
}

/******************************************************************************/
/* Comm page support                                                          */
/******************************************************************************/

ipc_port_t commpage32_handle = IPC_PORT_NULL;
ipc_port_t commpage64_handle = IPC_PORT_NULL;
vm_named_entry_t commpage32_entry = NULL;
vm_named_entry_t commpage64_entry = NULL;
vm_map_t commpage32_map = VM_MAP_NULL;
vm_map_t commpage64_map = VM_MAP_NULL;

ipc_port_t commpage_text32_handle = IPC_PORT_NULL;
ipc_port_t commpage_text64_handle = IPC_PORT_NULL;
vm_named_entry_t commpage_text32_entry = NULL;
vm_named_entry_t commpage_text64_entry = NULL;
vm_map_t commpage_text32_map = VM_MAP_NULL;
vm_map_t commpage_text64_map = VM_MAP_NULL;

user32_addr_t commpage_text32_location = (user32_addr_t) _COMM_PAGE32_TEXT_START;
user64_addr_t commpage_text64_location = (user64_addr_t) _COMM_PAGE64_TEXT_START;

#if defined(__i386__) || defined(__x86_64__)
/*
 * Create a memory entry, VM submap and pmap for one commpage.
 */
static void
_vm_commpage_init(
        ipc_port_t      *handlep,
        vm_map_size_t   size)
{
        kern_return_t           kr;
        vm_named_entry_t        mem_entry;
        vm_map_t                new_map;

        SHARED_REGION_TRACE_DEBUG(
                ("commpage: -> _init(0x%llx)\n",
                 (long long)size));

        kr = mach_memory_entry_allocate(&mem_entry,
                                        handlep);
        if (kr != KERN_SUCCESS) {
                panic("_vm_commpage_init: could not allocate mem_entry");
        }
        new_map = vm_map_create(pmap_create(NULL, 0, 0), 0, size, TRUE);
        if (new_map == VM_MAP_NULL) {
                panic("_vm_commpage_init: could not allocate VM map");
        }
        mem_entry->backing.map = new_map;
        mem_entry->internal = TRUE;
        mem_entry->is_sub_map = TRUE;
        mem_entry->offset = 0;
        mem_entry->protection = VM_PROT_ALL;
        mem_entry->size = size;

        SHARED_REGION_TRACE_DEBUG(
                ("commpage: _init(0x%llx) <- %p\n",
                 (long long)size, (void *)VM_KERNEL_ADDRPERM(*handlep)));
}
#endif


/*
 *Initialize the comm text pages at boot time
 */
 extern u_int32_t random(void);
 void
vm_commpage_text_init(void)
{
        SHARED_REGION_TRACE_DEBUG(
                ("commpage text: ->init()\n"));
#if defined(__i386__) || defined(__x86_64__)
        /* create the 32 bit comm text page */
        unsigned int offset = (random() % _PFZ32_SLIDE_RANGE) << PAGE_SHIFT; /* restricting to 32bMAX-2PAGE */
        _vm_commpage_init(&commpage_text32_handle, _COMM_PAGE_TEXT_AREA_LENGTH);
        commpage_text32_entry = (vm_named_entry_t) commpage_text32_handle->ip_kobject;
        commpage_text32_map = commpage_text32_entry->backing.map;
        commpage_text32_location = (user32_addr_t) (_COMM_PAGE32_TEXT_START + offset);
        /* XXX if (cpu_is_64bit_capable()) ? */
        /* create the 64-bit comm page */
        offset = (random() % _PFZ64_SLIDE_RANGE) << PAGE_SHIFT; /* restricting sliding upto 2Mb range */
        _vm_commpage_init(&commpage_text64_handle, _COMM_PAGE_TEXT_AREA_LENGTH);
        commpage_text64_entry = (vm_named_entry_t) commpage_text64_handle->ip_kobject;
        commpage_text64_map = commpage_text64_entry->backing.map;
        commpage_text64_location = (user64_addr_t) (_COMM_PAGE64_TEXT_START + offset);

        commpage_text_populate();
#elif defined(__arm64__) || defined(__arm__)
#else
#error Unknown architecture.
#endif /* __i386__ || __x86_64__ */
        /* populate the routines in here */
        SHARED_REGION_TRACE_DEBUG(
                ("commpage text: init() <-\n"));

}

/*
 * Initialize the comm pages at boot time.
 */
void
vm_commpage_init(void)
{
        SHARED_REGION_TRACE_DEBUG(
                ("commpage: -> init()\n"));

#if defined(__i386__) || defined(__x86_64__)
        /* create the 32-bit comm page */
        _vm_commpage_init(&commpage32_handle, _COMM_PAGE32_AREA_LENGTH);
        commpage32_entry = (vm_named_entry_t) commpage32_handle->ip_kobject;
        commpage32_map = commpage32_entry->backing.map;

        /* XXX if (cpu_is_64bit_capable()) ? */
        /* create the 64-bit comm page */
        _vm_commpage_init(&commpage64_handle, _COMM_PAGE64_AREA_LENGTH);
        commpage64_entry = (vm_named_entry_t) commpage64_handle->ip_kobject;
        commpage64_map = commpage64_entry->backing.map;

#endif /* __i386__ || __x86_64__ */

        /* populate them according to this specific platform */
        commpage_populate();
        __commpage_setup = 1;
#if defined(__i386__) || defined(__x86_64__)
        if (__system_power_source == 0) {
                post_sys_powersource_internal(0, 1);
        }
#endif /* __i386__ || __x86_64__ */

        SHARED_REGION_TRACE_DEBUG(
                ("commpage: init() <-\n"));
}

/*
 * Enter the appropriate comm page into the task's address space.
 * This is called at exec() time via vm_map_exec().
 */
kern_return_t
vm_commpage_enter(
        vm_map_t        map,
        task_t          task,
        boolean_t       is64bit)
{
#if     defined(__arm__)
#pragma unused(is64bit)
        (void)task;
        (void)map;
        return KERN_SUCCESS;
#elif   defined(__arm64__)
#pragma unused(is64bit)
        (void)task;
        (void)map;
        pmap_insert_sharedpage(vm_map_pmap(map));
        return KERN_SUCCESS;
#else
        ipc_port_t              commpage_handle, commpage_text_handle;
        vm_map_offset_t         commpage_address, objc_address, commpage_text_address;
        vm_map_size_t           commpage_size, objc_size, commpage_text_size;
        int                     vm_flags;
        vm_map_kernel_flags_t   vmk_flags;
        kern_return_t           kr;

        SHARED_REGION_TRACE_DEBUG(
                ("commpage: -> enter(%p,%p)\n",
                 (void *)VM_KERNEL_ADDRPERM(map),
                 (void *)VM_KERNEL_ADDRPERM(task)));

        commpage_text_size = _COMM_PAGE_TEXT_AREA_LENGTH;
        /* the comm page is likely to be beyond the actual end of the VM map */
        vm_flags = VM_FLAGS_FIXED;
        vmk_flags = VM_MAP_KERNEL_FLAGS_NONE;
        vmk_flags.vmkf_beyond_max = TRUE;

        /* select the appropriate comm page for this task */
        assert(! (is64bit ^ vm_map_is_64bit(map)));
        if (is64bit) {
                commpage_handle = commpage64_handle;
                commpage_address = (vm_map_offset_t) _COMM_PAGE64_BASE_ADDRESS;
                commpage_size = _COMM_PAGE64_AREA_LENGTH;
                objc_size = _COMM_PAGE64_OBJC_SIZE;
                objc_address = _COMM_PAGE64_OBJC_BASE;
                commpage_text_handle = commpage_text64_handle;
                commpage_text_address = (vm_map_offset_t) commpage_text64_location;
        } else {
                commpage_handle = commpage32_handle;
                commpage_address =
                        (vm_map_offset_t)(unsigned) _COMM_PAGE32_BASE_ADDRESS;
                commpage_size = _COMM_PAGE32_AREA_LENGTH;
                objc_size = _COMM_PAGE32_OBJC_SIZE;
                objc_address = _COMM_PAGE32_OBJC_BASE;
                commpage_text_handle = commpage_text32_handle;
                commpage_text_address = (vm_map_offset_t) commpage_text32_location;
        }

    vm_tag_t tag = VM_KERN_MEMORY_NONE;
        if ((commpage_address & (pmap_nesting_size_min - 1)) == 0 &&
            (commpage_size & (pmap_nesting_size_min - 1)) == 0) {
                /* the commpage is properly aligned or sized for pmap-nesting */
                tag = VM_MEMORY_SHARED_PMAP;
        }
        /* map the comm page in the task's address space */
        assert(commpage_handle != IPC_PORT_NULL);
        kr = vm_map_enter_mem_object(
                map,
                &commpage_address,
                commpage_size,
                0,
                vm_flags,
                vmk_flags,
                tag,
                commpage_handle,
                0,
                FALSE,
                VM_PROT_READ,
                VM_PROT_READ,
                VM_INHERIT_SHARE);
        if (kr != KERN_SUCCESS) {
                SHARED_REGION_TRACE_ERROR(
                        ("commpage: enter(%p,0x%llx,0x%llx) "
                         "commpage %p mapping failed 0x%x\n",
                         (void *)VM_KERNEL_ADDRPERM(map),
                         (long long)commpage_address,
                         (long long)commpage_size,
                         (void *)VM_KERNEL_ADDRPERM(commpage_handle), kr));
        }

        /* map the comm text page in the task's address space */
        assert(commpage_text_handle != IPC_PORT_NULL);
        kr = vm_map_enter_mem_object(
                map,
                &commpage_text_address,
                commpage_text_size,
                0,
                vm_flags,
                vmk_flags,
                tag,
                commpage_text_handle,
                0,
                FALSE,
                VM_PROT_READ|VM_PROT_EXECUTE,
                VM_PROT_READ|VM_PROT_EXECUTE,
                VM_INHERIT_SHARE);
        if (kr != KERN_SUCCESS) {
                SHARED_REGION_TRACE_ERROR(
                        ("commpage text: enter(%p,0x%llx,0x%llx) "
                         "commpage text %p mapping failed 0x%x\n",
                         (void *)VM_KERNEL_ADDRPERM(map),
                         (long long)commpage_text_address,
                         (long long)commpage_text_size,
                         (void *)VM_KERNEL_ADDRPERM(commpage_text_handle), kr));
        }

        /*
         * Since we're here, we also pre-allocate some virtual space for the
         * Objective-C run-time, if needed...
         */
        if (objc_size != 0) {
                kr = vm_map_enter_mem_object(
                        map,
                        &objc_address,
                        objc_size,
                        0,
                        VM_FLAGS_FIXED,
                        vmk_flags,
                        tag,
                        IPC_PORT_NULL,
                        0,
                        FALSE,
                        VM_PROT_ALL,
                        VM_PROT_ALL,
                        VM_INHERIT_DEFAULT);
                if (kr != KERN_SUCCESS) {
                        SHARED_REGION_TRACE_ERROR(
                                ("commpage: enter(%p,0x%llx,0x%llx) "
                                 "objc mapping failed 0x%x\n",
                                 (void *)VM_KERNEL_ADDRPERM(map),
                                 (long long)objc_address,
                                 (long long)objc_size, kr));
                }
        }

        SHARED_REGION_TRACE_DEBUG(
                ("commpage: enter(%p,%p) <- 0x%x\n",
                 (void *)VM_KERNEL_ADDRPERM(map),
                 (void *)VM_KERNEL_ADDRPERM(task), kr));
        return kr;
#endif
}

int
vm_shared_region_slide(uint32_t slide,
                        mach_vm_offset_t        entry_start_address,
                        mach_vm_size_t          entry_size,
                        mach_vm_offset_t        slide_start,
                        mach_vm_size_t          slide_size,
                        memory_object_control_t sr_file_control)
{
        void *slide_info_entry = NULL;
        int                     error;
        vm_shared_region_t      sr;

        SHARED_REGION_TRACE_DEBUG(
                ("vm_shared_region_slide: -> slide %#x, entry_start %#llx, entry_size %#llx, slide_start %#llx, slide_size %#llx\n",
                 slide, entry_start_address, entry_size, slide_start, slide_size));

        sr = vm_shared_region_get(current_task());
        if (sr == NULL) {
                printf("%s: no shared region?\n", __FUNCTION__);
                SHARED_REGION_TRACE_DEBUG(
                        ("vm_shared_region_slide: <- %d (no shared region)\n",
                         KERN_FAILURE));
                return KERN_FAILURE;
        }

        /*
         * Protect from concurrent access.
         */
        vm_shared_region_lock();
        while(sr->sr_slide_in_progress) {
                vm_shared_region_sleep(&sr->sr_slide_in_progress, THREAD_UNINT);
        }
        if (sr->sr_slid
#ifndef CONFIG_EMBEDDED
                        || shared_region_completed_slide
#endif
                        ) {
                vm_shared_region_unlock();

                vm_shared_region_deallocate(sr);
                printf("%s: shared region already slid?\n", __FUNCTION__);
                SHARED_REGION_TRACE_DEBUG(
                        ("vm_shared_region_slide: <- %d (already slid)\n",
                         KERN_FAILURE));
                return KERN_FAILURE;
        }

        sr->sr_slide_in_progress = TRUE;
        vm_shared_region_unlock();

        if((error = vm_shared_region_slide_init(sr, slide_size, entry_start_address, entry_size, slide, sr_file_control))) {
                printf("slide_info initialization failed with kr=%d\n", error);
                goto done;
        }

        slide_info_entry = vm_shared_region_get_slide_info_entry(sr);
        if (slide_info_entry == NULL){
                error = KERN_FAILURE;
        } else {        
                error = copyin((user_addr_t)slide_start,
                               slide_info_entry,
                               (vm_size_t)slide_size);
                if (error) { 
                        error = KERN_INVALID_ADDRESS;
                }
        }
        if (error) {
                goto done;
        }
 
        if (vm_shared_region_slide_sanity_check(sr) != KERN_SUCCESS) {
                error = KERN_INVALID_ARGUMENT; 
                printf("Sanity Check failed for slide_info\n");
        } else {
#if DEBUG
                printf("Succesfully init slide_info with start_address: %p region_size: %ld slide_header_size: %ld\n",
                                (void*)(uintptr_t)entry_start_address, 
                                (unsigned long)entry_size, 
                                (unsigned long)slide_size);
#endif
        }
done:
        vm_shared_region_lock();

        assert(sr->sr_slide_in_progress);
        assert(sr->sr_slid == FALSE);
        sr->sr_slide_in_progress = FALSE;
        thread_wakeup(&sr->sr_slide_in_progress);

        if (error == KERN_SUCCESS) {
                sr->sr_slid = TRUE;

                /*
                 * We don't know how to tear down a slid shared region today, because
                 * we would have to invalidate all the pages that have been slid
                 * atomically with respect to anyone mapping the shared region afresh.  
                 * Therefore, take a dangling reference to prevent teardown.  
                 */
                sr->sr_ref_count++; 
#ifndef CONFIG_EMBEDDED
                shared_region_completed_slide = TRUE;
#endif
        }
        vm_shared_region_unlock();

        vm_shared_region_deallocate(sr);

        SHARED_REGION_TRACE_DEBUG(
                ("vm_shared_region_slide: <- %d\n",
                 error));

        return error;
}

/* 
 * This is called from powermanagement code to let kernel know the current source of power.
 * 0 if it is external source (connected to power )
 * 1 if it is internal power source ie battery
 */
void
#if defined(__i386__) || defined(__x86_64__)
post_sys_powersource(int i)
#else
post_sys_powersource(__unused int i)
#endif
{
#if defined(__i386__) || defined(__x86_64__)
        post_sys_powersource_internal(i, 0);
#endif /* __i386__ || __x86_64__ */
}


#if defined(__i386__) || defined(__x86_64__)
static void
post_sys_powersource_internal(int i, int internal)
{
        if (internal == 0)
                __system_power_source = i;

        if (__commpage_setup != 0) {
                if (__system_power_source != 0)
                        commpage_set_spin_count(0);
                else
                        commpage_set_spin_count(MP_SPIN_TRIES);
        }
}
#endif /* __i386__ || __x86_64__ */