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

/*
 * Copyright (c) 2006 Apple Computer, Inc. All rights reserved.
 *
 * @APPLE_LICENSE_HEADER_START@
 * 
 * The contents of this file constitute Original Code as defined in and
 * are subject to the Apple Public Source License Version 1.1 (the
 * "License").  You may not use this file except in compliance with the
 * License.  Please obtain a copy of the License at
 * http://www.apple.com/publicsource and read it before using this file.
 * 
 * This 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 OR NON-INFRINGEMENT.  Please see the
 * License for the specific language governing rights and limitations
 * under the License.
 * 
 * @APPLE_LICENSE_HEADER_END@
 */

#include <sys/errno.h>

#include <mach/mach_types.h>
#include <mach/mach_traps.h>
#include <mach/host_priv.h>
#include <mach/kern_return.h>
#include <mach/memory_object_control.h>
#include <mach/memory_object_types.h>
#include <mach/port.h>
#include <mach/policy.h>
#include <mach/upl.h>
#include <mach/thread_act.h>
#include <mach/mach_vm.h>

#include <kern/host.h>
#include <kern/kalloc.h>
#include <kern/page_decrypt.h>
#include <kern/queue.h>
#include <kern/thread.h>

#include <ipc/ipc_port.h>
#include <ipc/ipc_space.h>

#include <default_pager/default_pager_types.h>
#include <default_pager/default_pager_object_server.h>

#include <vm/vm_map.h>
#include <vm/vm_pageout.h>
#include <vm/memory_object.h>
#include <vm/vm_pageout.h>
#include <vm/vm_protos.h>


/* 
 * APPLE PROTECT MEMORY PAGER 
 *
 * This external memory manager (EMM) handles memory from the encrypted
 * sections of some executables protected by the DSMOS kernel extension.
 * 
 * It mostly handles page-in requests (from memory_object_data_request()) by
 * getting the encrypted data from its backing VM object, itself backed by
 * the encrypted file, decrypting it and providing it to VM.
 *
 * The decrypted pages will never be dirtied, so the memory manager doesn't
 * need to handle page-out requests (from memory_object_data_return()).  The
 * pages need to be mapped copy-on-write, so that the originals stay clean.
 *
 * We don't expect to have to handle a large number of apple-protected
 * binaries, so the data structures are very simple (simple linked list)
 * for now.
 */

/* forward declarations */
void apple_protect_pager_reference(memory_object_t mem_obj);
void apple_protect_pager_deallocate(memory_object_t mem_obj);
kern_return_t apple_protect_pager_init(memory_object_t mem_obj,
                                       memory_object_control_t control,
                                       vm_size_t pg_size);
kern_return_t apple_protect_pager_terminate(memory_object_t mem_obj);
kern_return_t apple_protect_pager_data_request(memory_object_t mem_obj,
                                               memory_object_offset_t offset,
                                               vm_size_t length,
                                               vm_prot_t protection_required);
kern_return_t apple_protect_pager_data_return(memory_object_t mem_obj,
                                              memory_object_offset_t offset,
                                              vm_size_t data_cnt,
                                              memory_object_offset_t *resid_offset,
                                              int *io_error,
                                              boolean_t dirty,
                                              boolean_t kernel_copy,
                                              int upl_flags);
kern_return_t apple_protect_pager_data_initialize(memory_object_t mem_obj,
                                                  memory_object_offset_t offset,
                                                  vm_size_t data_cnt);
kern_return_t apple_protect_pager_data_unlock(memory_object_t mem_obj,
                                              memory_object_offset_t offset,
                                              vm_size_t size,
                                              vm_prot_t desired_access);
kern_return_t apple_protect_pager_synchronize(memory_object_t mem_obj,
                                              memory_object_offset_t offset,
                                              vm_size_t length,
                                              vm_sync_t sync_flags);
kern_return_t apple_protect_pager_unmap(memory_object_t mem_obj);

/*
 * Vector of VM operations for this EMM.
 * These routines are invoked by VM via the memory_object_*() interfaces.
 */
const struct memory_object_pager_ops apple_protect_pager_ops = {
        apple_protect_pager_reference,
        apple_protect_pager_deallocate,
        apple_protect_pager_init,
        apple_protect_pager_terminate,
        apple_protect_pager_data_request,
        apple_protect_pager_data_return,
        apple_protect_pager_data_initialize,
        apple_protect_pager_data_unlock,
        apple_protect_pager_synchronize,
        apple_protect_pager_unmap,
        "apple protect pager"
};

/*
 * The "apple_protect_pager" describes a memory object backed by
 * the "apple protect" EMM.
 */
typedef struct apple_protect_pager {
        memory_object_pager_ops_t pager_ops; /* == &apple_protect_pager_ops */
        unsigned int            pager_ikot;     /* JMM: fake ip_kotype() */
        queue_chain_t           pager_queue;    /* next & prev pagers */
        unsigned int            ref_count;      /* reference count */
        boolean_t               is_ready;       /* is this pager ready ? */
        boolean_t               is_mapped;      /* is this mem_obj mapped ? */
        memory_object_control_t pager_control;  /* mem object control handle */
        vm_object_t             backing_object; /* VM obj w/ encrypted data */
} *apple_protect_pager_t;
#define APPLE_PROTECT_PAGER_NULL        ((apple_protect_pager_t) NULL)

/*
 * List of memory objects managed by this EMM.
 * The list is protected by the "apple_protect_pager_lock" lock.
 */
int apple_protect_pager_count = 0;              /* number of pagers */
int apple_protect_pager_count_mapped = 0;       /* number of unmapped pagers */
queue_head_t apple_protect_pager_queue;
decl_mutex_data(,apple_protect_pager_lock)

/*
 * Maximum number of unmapped pagers we're willing to keep around.
 */
int apple_protect_pager_cache_limit = 10;

/*
 * Statistics & counters.
 */
int apple_protect_pager_count_max = 0;
int apple_protect_pager_count_unmapped_max = 0;
int apple_protect_pager_num_trim_max = 0;
int apple_protect_pager_num_trim_total = 0;

/* internal prototypes */
apple_protect_pager_t apple_protect_pager_create(vm_object_t backing_object);
apple_protect_pager_t apple_protect_pager_lookup(memory_object_t mem_obj);
void apple_protect_pager_dequeue(apple_protect_pager_t pager);
void apple_protect_pager_deallocate_internal(apple_protect_pager_t pager,
                                             boolean_t locked);
void apple_protect_pager_terminate_internal(apple_protect_pager_t pager);
void apple_protect_pager_trim(void);


#if DEBUG
int apple_protect_pagerdebug = 0;
#define PAGER_ALL               0xffffffff
#define PAGER_INIT              0x00000001
#define PAGER_PAGEIN            0x00000002

#define PAGER_DEBUG(LEVEL, A)                                           \
        MACRO_BEGIN                                                     \
        if ((apple_protect_pagerdebug & LEVEL)==LEVEL) {                \
                printf A;                                               \
        }                                                               \
        MACRO_END
#else
#define PAGER_DEBUG(LEVEL, A)
#endif


void
apple_protect_pager_bootstrap(void)
{
        mutex_init(&apple_protect_pager_lock, 0);
        queue_init(&apple_protect_pager_queue);
}

/*
 * apple_protect_pager_init()
 *
 * Initialize the memory object and makes it ready to be used and mapped.
 */
kern_return_t
apple_protect_pager_init(
        memory_object_t         mem_obj, 
        memory_object_control_t control, 
#if !DEBUG
        __unused
#endif
        vm_size_t pg_size)
{
        apple_protect_pager_t   pager;
        kern_return_t           kr;
        memory_object_attr_info_data_t  attributes;

        PAGER_DEBUG(PAGER_ALL,
                    ("apple_protect_pager_init: %p, %p, %x\n",
                     mem_obj, control, pg_size));

        if (control == MEMORY_OBJECT_CONTROL_NULL)
                return KERN_INVALID_ARGUMENT;

        pager = apple_protect_pager_lookup(mem_obj);

        memory_object_control_reference(control);

        pager->pager_control = control;

        attributes.copy_strategy = MEMORY_OBJECT_COPY_DELAY;
        /* attributes.cluster_size = (1 << (CLUSTER_SHIFT + PAGE_SHIFT));*/
        attributes.cluster_size = (1 << (PAGE_SHIFT));
        attributes.may_cache_object = FALSE;
        attributes.temporary = TRUE;

        kr = memory_object_change_attributes(
                                        control,
                                        MEMORY_OBJECT_ATTRIBUTE_INFO,
                                        (memory_object_info_t) &attributes,
                                        MEMORY_OBJECT_ATTR_INFO_COUNT);
        if (kr != KERN_SUCCESS)
                panic("apple_protect_pager_init: "
                      "memory_object_change_attributes() failed");

        return KERN_SUCCESS;
}

/*
 * apple_protect_data_return()
 *
 * Handles page-out requests from VM.  This should never happen since
 * the pages provided by this EMM are not supposed to be dirty or dirtied
 * and VM should simply discard the contents and reclaim the pages if it
 * needs to.
 */
kern_return_t
apple_protect_pager_data_return(
        __unused memory_object_t        mem_obj,
        __unused memory_object_offset_t offset,
        __unused vm_size_t              data_cnt,
        __unused memory_object_offset_t *resid_offset,
        __unused int                    *io_error,
        __unused boolean_t              dirty,
        __unused boolean_t              kernel_copy,
        __unused int                    upl_flags)  
{
        panic("apple_protect_pager_data_return: should never get called");
        return KERN_FAILURE;
}

kern_return_t
apple_protect_pager_data_initialize(
        __unused memory_object_t        mem_obj,
        __unused memory_object_offset_t offset,
        __unused vm_size_t              data_cnt)
{
        panic("apple_protect_pager_data_initialize: should never get called");
        return KERN_FAILURE;
}

kern_return_t
apple_protect_pager_data_unlock(
        __unused memory_object_t        mem_obj,
        __unused memory_object_offset_t offset,
        __unused vm_size_t              size,
        __unused vm_prot_t              desired_access)
{
        return KERN_FAILURE;
}

/*
 * apple_protect_pager_data_request()
 *
 * Handles page-in requests from VM.
 */
kern_return_t   
apple_protect_pager_data_request(
        memory_object_t         mem_obj,
        memory_object_offset_t  offset,
        vm_size_t               length,
#if !DEBUG
        __unused
#endif
        vm_prot_t               protection_required)
{
        apple_protect_pager_t   pager;
        memory_object_control_t mo_control;
        upl_t                   upl = NULL;
        int                     upl_flags;
        upl_size_t              upl_size;
        upl_page_info_t         *upl_pl;
        vm_object_t             src_object, dst_object;
        kern_return_t           kr, retval;
        vm_map_offset_t         src_mapping = 0, dst_mapping = 0;
        vm_offset_t             src_vaddr, dst_vaddr;
        vm_offset_t             cur_offset;
        boolean_t               src_map_page_by_page;
        vm_map_entry_t          map_entry;

        PAGER_DEBUG(PAGER_ALL, ("apple_protect_pager_data_request: %x, %llx, %llxx, %x\n", mem_obj, offset, length, protection_required));

        pager = apple_protect_pager_lookup(mem_obj);
        assert(pager->is_ready);
        assert(pager->ref_count > 1); /* pager is alive and mapped */

        PAGER_DEBUG(PAGER_PAGEIN, ("apple_protect_pager_data_request: %x, %llx, %llx, %x, pager %x\n", mem_obj, offset, length, protection_required, pager));

        /*
         * Map the encrypted data in the kernel address space from the 
         * backing VM object (itself backed by the encrypted file via
         * the vnode pager).
         */
        src_object = pager->backing_object;
        assert(src_object != VM_OBJECT_NULL);
        vm_object_reference(src_object); /* ref. for the mapping */
        src_mapping = 0;
        kr = vm_map_enter(kernel_map,
                          &src_mapping,
                          length,
                          0,
                          VM_FLAGS_ANYWHERE,
                          src_object,
                          offset,
                          FALSE,
                          VM_PROT_READ,
                          VM_PROT_READ,
                          VM_INHERIT_NONE);
        switch (kr) {
        case KERN_SUCCESS:
                src_map_page_by_page = FALSE;
                src_vaddr = CAST_DOWN(vm_offset_t, src_mapping);
                break;
        case KERN_NO_SPACE:
                /* we can't map the entire section, so map it page by page */
                src_map_page_by_page = TRUE;
                vm_object_deallocate(src_object);
                break;
        default:
                vm_object_deallocate(src_object);
                retval = kr;
                goto done;
        }


        /*
         * Gather in a UPL all the VM pages requested by VM.
         */
        mo_control = pager->pager_control;

        upl_size = length;
        upl_flags =
                UPL_RET_ONLY_ABSENT |
                UPL_SET_LITE |
                UPL_NO_SYNC |
                UPL_CLEAN_IN_PLACE |    /* triggers UPL_CLEAR_DIRTY */
                UPL_SET_INTERNAL;
        kr = memory_object_upl_request(mo_control,
                                       offset, upl_size,
                                       &upl, NULL, NULL, upl_flags);
        if (kr != KERN_SUCCESS) {
                retval = kr;
                goto done;
        }

        /*
         * Reserve a virtual page in the kernel address space to map each
         * destination physical page when it's its turn to be filled.
         */
        dst_object = mo_control->moc_object;
        assert(dst_object != VM_OBJECT_NULL);
        dst_mapping = 0;
        vm_object_reference(kernel_object);     /* ref. for mapping */
        kr = vm_map_find_space(kernel_map,
                               &dst_mapping,
                               PAGE_SIZE_64,
                               0,
                               0,
                               &map_entry);
        if (kr != KERN_SUCCESS) {
                vm_object_deallocate(kernel_object);
                retval = kr;
                goto done;
        }
        map_entry->object.vm_object = kernel_object;
        map_entry->offset = dst_mapping - VM_MIN_KERNEL_ADDRESS;
        vm_map_unlock(kernel_map);
        dst_vaddr = CAST_DOWN(vm_offset_t, dst_mapping);

        /*
         * Fill in the contents of the pages requested by VM.
         */
        upl_pl = UPL_GET_INTERNAL_PAGE_LIST(upl);
        for (cur_offset = 0; cur_offset < length; cur_offset += PAGE_SIZE) {
                ppnum_t dst_pnum;

                /*
                 * Establish an explicit pmap mapping of the destination
                 * physical page.
                 * We can't do a regular VM mapping because the VM page
                 * is "busy".
                 */
                if (!upl_page_present(upl_pl, cur_offset / PAGE_SIZE)) {
                        /* this page is not in the UPL: skip it */
                        continue;
                }
                dst_pnum = (addr64_t)
                        upl_phys_page(upl_pl, cur_offset / PAGE_SIZE);
                assert (dst_pnum != 0);
                pmap_enter(kernel_pmap, dst_mapping, dst_pnum,
                           VM_PROT_READ | VM_PROT_WRITE,
                           dst_object->wimg_bits & VM_WIMG_MASK,
                           FALSE);

                /*
                 * Map the source (encrypted) page in the kernel's
                 * virtual address space.
                 */
                if (src_map_page_by_page) {
                        vm_object_reference(src_object); /* ref. for mapping */
                        kr = vm_map_enter(kernel_map,
                                          &src_mapping,
                                          PAGE_SIZE_64,
                                          0,
                                          VM_FLAGS_ANYWHERE,
                                          src_object,
                                          offset + cur_offset,
                                          FALSE,
                                          VM_PROT_READ,
                                          VM_PROT_READ,
                                          VM_INHERIT_NONE);
                        if (kr != KERN_SUCCESS) {
                                vm_object_deallocate(src_object);
                                retval = kr;
                                goto done;
                        }
                        src_vaddr = CAST_DOWN(vm_offset_t, src_mapping);
                } else {
                        src_vaddr = src_mapping + cur_offset;
                }

                /*
                 * Decrypt the encrypted contents of the source page
                 * into the destination page.
                 */
                dsmos_page_transform((const void *) src_vaddr,
                                     (void *) dst_vaddr);

                /*
                 * Remove the pmap mapping of the destination page
                 * in the kernel.
                 */
                pmap_remove(kernel_pmap,
                            (addr64_t) dst_mapping,
                            (addr64_t) (dst_mapping + PAGE_SIZE_64));
                if (src_map_page_by_page) {
                        /*
                         * Remove the kernel mapping of the source page.
                         * This releases the extra reference we took on
                         * src_object.
                         */
                        kr = vm_map_remove(kernel_map,
                                           src_mapping,
                                           src_mapping + PAGE_SIZE_64,
                                           VM_MAP_NO_FLAGS);
                        assert(kr == KERN_SUCCESS);
                        src_mapping = 0;
                }
        }

        retval = KERN_SUCCESS;
done:
        if (src_mapping != 0) {
                /* clean up the mapping of the source pages */
                kr = vm_map_remove(kernel_map,
                                   src_mapping,
                                   src_mapping + length,
                                   VM_MAP_NO_FLAGS);
                assert (kr == KERN_SUCCESS);
                src_mapping = 0;
                src_vaddr = 0;
        }
        if (upl != NULL) {
                /* clean up the UPL */

                /*
                 * The pages are currently dirty because we've just been
                 * writing on them, but as far as we're concerned, they're
                 * clean since they contain their "original" contents as
                 * provided by us, the pager.
                 * Tell the UPL to mark them "clean".
                 */
                upl_clear_dirty(upl, TRUE);

                /* abort or commit the UPL */
                if (retval != KERN_SUCCESS) {
                        upl_abort(upl, 0);
                } else {
                        upl_commit(upl, NULL, 0);
                }

                /* and deallocate the UPL */
                upl_deallocate(upl);
                upl = NULL;
        }
        if (dst_mapping != 0) {
                /* clean up the mapping of the destination pages */
                kr = vm_map_remove(kernel_map,
                                   dst_mapping,
                                   dst_mapping + PAGE_SIZE_64,
                                   VM_MAP_NO_FLAGS);
                assert(kr == KERN_SUCCESS);
                dst_mapping = 0;
                dst_vaddr = 0;
        }

        return retval;
}

/*
 * apple_protect_pager_reference()
 *
 * Get a reference on this memory object.
 * For external usage only.  Assumes that the initial reference count is not 0,
 * i.e one should not "revive" a dead pager this way.
 */
void
apple_protect_pager_reference(
        memory_object_t         mem_obj)
{       
        apple_protect_pager_t   pager;

        pager = apple_protect_pager_lookup(mem_obj);

        mutex_lock(&apple_protect_pager_lock);
        assert(pager->ref_count > 0);
        pager->ref_count++;
        mutex_unlock(&apple_protect_pager_lock);
}


/*
 * apple_protect_pager_dequeue:
 *
 * Removes a pager from the list of pagers.
 *
 * The caller must hold "apple_protect_pager_lock".
 */
void
apple_protect_pager_dequeue(
        apple_protect_pager_t pager)
{
        assert(!pager->is_mapped);

        queue_remove(&apple_protect_pager_queue,
                     pager,
                     apple_protect_pager_t,
                     pager_queue);
        pager->pager_queue.next = NULL;
        pager->pager_queue.prev = NULL;
        
        apple_protect_pager_count--;
}

/*
 * apple_protect_pager_terminate_internal:
 *
 * Trigger the asynchronous termination of the memory object associated
 * with this pager.
 * When the memory object is terminated, there will be one more call
 * to memory_object_deallocate() (i.e. apple_protect_pager_deallocate())
 * to finish the clean up.
 *
 * "apple_protect_pager_lock" should not be held by the caller.
 * We don't need the lock because the pager has already been removed from
 * the pagers' list and is now ours exclusively.
 */
void
apple_protect_pager_terminate_internal(
        apple_protect_pager_t pager)
{
        assert(pager->is_ready);
        assert(!pager->is_mapped);

        if (pager->backing_object != VM_OBJECT_NULL) {
                vm_object_deallocate(pager->backing_object);
                pager->backing_object = VM_OBJECT_NULL;
        }

        /* trigger the destruction of the memory object */
        memory_object_destroy(pager->pager_control, 0);
}

/*
 * apple_protect_pager_deallocate_internal()
 *
 * Release a reference on this pager and free it when the last
 * reference goes away.
 * Can be called with apple_protect_pager_lock held or not but always returns
 * with it unlocked.
 */
void
apple_protect_pager_deallocate_internal(
        apple_protect_pager_t   pager,
        boolean_t               locked)
{
        boolean_t       needs_trimming;
        int             count_unmapped;

        if (! locked) {
                mutex_lock(&apple_protect_pager_lock);
        }

        count_unmapped = (apple_protect_pager_count - 
                          apple_protect_pager_count_mapped);
        if (count_unmapped > apple_protect_pager_cache_limit) {
                /* we have too many unmapped pagers:  trim some */
                needs_trimming = TRUE;
        } else {
                needs_trimming = FALSE;
        }

        /* drop a reference on this pager */
        pager->ref_count--;

        if (pager->ref_count == 1) {
                /*
                 * Only the "named" reference is left, which means that
                 * no one is realy holding on to this pager anymore.
                 * Terminate it.
                 */
                apple_protect_pager_dequeue(pager);
                /* the pager is all ours: no need for the lock now */
                mutex_unlock(&apple_protect_pager_lock);
                apple_protect_pager_terminate_internal(pager);
        } else if (pager->ref_count == 0) {
                /*
                 * Dropped the existence reference;  the memory object has
                 * been terminated.  Do some final cleanup and release the
                 * pager structure.
                 */
                mutex_unlock(&apple_protect_pager_lock);
                if (pager->pager_control != MEMORY_OBJECT_CONTROL_NULL) {
                        memory_object_control_deallocate(pager->pager_control);
                        pager->pager_control = MEMORY_OBJECT_CONTROL_NULL;
                }
                kfree(pager, sizeof (*pager));
                pager = APPLE_PROTECT_PAGER_NULL;
        } else {
                /* there are still plenty of references:  keep going... */
                mutex_unlock(&apple_protect_pager_lock);
        }

        if (needs_trimming) {
                apple_protect_pager_trim();
        }
        /* caution: lock is not held on return... */
}

/*
 * apple_protect_pager_deallocate()
 *
 * Release a reference on this pager and free it when the last
 * reference goes away.
 */
void
apple_protect_pager_deallocate(
        memory_object_t         mem_obj)
{
        apple_protect_pager_t   pager;

        PAGER_DEBUG(PAGER_ALL, ("apple_protect_pager_deallocate: %x\n", mem_obj));
        pager = apple_protect_pager_lookup(mem_obj);
        apple_protect_pager_deallocate_internal(pager, FALSE);
}

/*
 *
 */
kern_return_t
apple_protect_pager_terminate(
#if !DEBUG
        __unused
#endif
        memory_object_t mem_obj)
{
        PAGER_DEBUG(PAGER_ALL, ("apple_protect_pager_terminate: %x\n", mem_obj));

        return KERN_SUCCESS;
}

/*
 *
 */
kern_return_t
apple_protect_pager_synchronize(
        memory_object_t         mem_obj,
        memory_object_offset_t  offset,
        vm_size_t               length,
        __unused vm_sync_t              sync_flags)
{
        apple_protect_pager_t   pager;

        PAGER_DEBUG(PAGER_ALL, ("apple_protect_pager_synchronize: %x\n", mem_obj));

        pager = apple_protect_pager_lookup(mem_obj);

        memory_object_synchronize_completed(pager->pager_control,
                                            offset, length);

        return KERN_SUCCESS;
}

/*
 * apple_protect_pager_map()
 *
 * This allows VM to let us, the EMM, know that this memory object
 * is currently mapped one or more times.  This is called by VM only the first
 * time the memory object gets mapped and we take one extra reference on the
 * memory object to account for all its mappings.
 */
void
apple_protect_pager_map(
        memory_object_t         mem_obj)
{
        apple_protect_pager_t   pager;

        PAGER_DEBUG(PAGER_ALL, ("apple_protect_pager_map: %x\n", mem_obj));

        pager = apple_protect_pager_lookup(mem_obj);

        mutex_lock(&apple_protect_pager_lock);
        assert(pager->is_ready);
        assert(pager->ref_count > 0); /* pager is alive */
        if (pager->is_mapped == FALSE) {
                /*
                 * First mapping of this pager:  take an extra reference
                 * that will remain until all the mappings of this pager
                 * are removed.
                 */
                pager->is_mapped = TRUE;
                pager->ref_count++;
                apple_protect_pager_count_mapped++;
        }
        mutex_unlock(&apple_protect_pager_lock);
}

/*
 * apple_protect_pager_unmap()
 *
 * This is called by VM when this memory object is no longer mapped anywhere.
 */
kern_return_t
apple_protect_pager_unmap(
        memory_object_t         mem_obj)
{
        apple_protect_pager_t   pager;
        int                     count_unmapped;

        PAGER_DEBUG(PAGER_ALL, ("apple_protect_pager_unmap: %x\n", mem_obj));

        pager = apple_protect_pager_lookup(mem_obj);

        mutex_lock(&apple_protect_pager_lock);
        if (pager->is_mapped) {
                /*
                 * All the mappings are gone, so let go of the one extra
                 * reference that represents all the mappings of this pager.
                 */
                apple_protect_pager_count_mapped--;
                count_unmapped = (apple_protect_pager_count -
                                  apple_protect_pager_count_mapped);
                if (count_unmapped > apple_protect_pager_count_unmapped_max) {
                        apple_protect_pager_count_unmapped_max = count_unmapped;
                }
                pager->is_mapped = FALSE;
                apple_protect_pager_deallocate_internal(pager, TRUE);
                /* caution: deallocate_internal() released the lock ! */
        } else {
                mutex_unlock(&apple_protect_pager_lock);
        }
        
        return KERN_SUCCESS;
}


/*
 *
 */
apple_protect_pager_t
apple_protect_pager_lookup(
        memory_object_t  mem_obj)
{
        apple_protect_pager_t   pager;

        pager = (apple_protect_pager_t) mem_obj;
        assert(pager->pager_ops == &apple_protect_pager_ops);
        assert(pager->ref_count > 0);
        return pager;
}

apple_protect_pager_t
apple_protect_pager_create(
        vm_object_t     backing_object)
{
        apple_protect_pager_t   pager, pager2;
        memory_object_control_t control;
        kern_return_t           kr;

        pager = (apple_protect_pager_t) kalloc(sizeof (*pager));
        if (pager == APPLE_PROTECT_PAGER_NULL) {
                return APPLE_PROTECT_PAGER_NULL;
        }

        /*
         * The vm_map call takes both named entry ports and raw memory
         * objects in the same parameter.  We need to make sure that
         * vm_map does not see this object as a named entry port.  So,
         * we reserve the second word in the object for a fake ip_kotype
         * setting - that will tell vm_map to use it as a memory object.
         */
        pager->pager_ops = &apple_protect_pager_ops;
        pager->pager_ikot = IKOT_MEMORY_OBJECT;
        pager->is_ready = FALSE;/* not ready until it has a "name" */
        pager->ref_count = 2;   /* existence + setup reference */
        pager->is_mapped = FALSE;
        pager->pager_control = MEMORY_OBJECT_CONTROL_NULL;
        pager->backing_object = backing_object;
        vm_object_reference(backing_object);

        mutex_lock(&apple_protect_pager_lock);
        /* see if anyone raced us to create a pager for the same object */
        queue_iterate(&apple_protect_pager_queue,
                      pager2,
                      apple_protect_pager_t,
                      pager_queue) {
                if (pager2->backing_object == backing_object) {
                        break;
                }
        }
        if (! queue_end(&apple_protect_pager_queue,
                        (queue_entry_t) pager2)) {
                /* while we hold the lock, transfer our setup ref to winner */
                pager2->ref_count++;
                /* we lost the race, down with the loser... */
                mutex_unlock(&apple_protect_pager_lock);
                vm_object_deallocate(pager->backing_object);
                pager->backing_object = VM_OBJECT_NULL;
                kfree(pager, sizeof (*pager));
                /* ... and go with the winner */
                pager = pager2;
                /* let the winner make sure the pager gets ready */
                return pager;
        }

        /* enter new pager at the head of our list of pagers */
        queue_enter_first(&apple_protect_pager_queue,
                          pager,
                          apple_protect_pager_t,
                          pager_queue);
        apple_protect_pager_count++;
        if (apple_protect_pager_count > apple_protect_pager_count_max) {
                apple_protect_pager_count_max = apple_protect_pager_count;
        }
        mutex_unlock(&apple_protect_pager_lock);

        kr = memory_object_create_named((memory_object_t) pager,
                                        0,
                                        &control);
        assert(kr == KERN_SUCCESS);

        mutex_lock(&apple_protect_pager_lock);
        /* the new pager is now ready to be used */
        pager->is_ready = TRUE;
        mutex_unlock(&apple_protect_pager_lock);

        /* wakeup anyone waiting for this pager to be ready */
        thread_wakeup(&pager->is_ready);

        return pager;
}

/*
 * apple_protect_pager_setup()
 *
 * Provide the caller with a memory object backed by the provided
 * "backing_object" VM object.  If such a memory object already exists,
 * re-use it, otherwise create a new memory object.
 */
memory_object_t
apple_protect_pager_setup(
        vm_object_t     backing_object)
{
        apple_protect_pager_t   pager;

        mutex_lock(&apple_protect_pager_lock);

        queue_iterate(&apple_protect_pager_queue,
                      pager,
                      apple_protect_pager_t,
                      pager_queue) {
                if (pager->backing_object == backing_object) {
                        break;
                }
        }
        if (queue_end(&apple_protect_pager_queue,
                      (queue_entry_t) pager)) {
                /* no existing pager for this backing object */
                pager = APPLE_PROTECT_PAGER_NULL;
        } else {
                /* make sure pager doesn't disappear */
                pager->ref_count++;
        }

        mutex_unlock(&apple_protect_pager_lock);

        if (pager == APPLE_PROTECT_PAGER_NULL) {
                pager = apple_protect_pager_create(backing_object);
                if (pager == APPLE_PROTECT_PAGER_NULL) {
                        return MEMORY_OBJECT_NULL;
                }
        }

        mutex_lock(&apple_protect_pager_lock);
        while (!pager->is_ready) {
                thread_sleep_mutex(&pager->is_ready,
                                   &apple_protect_pager_lock,
                                   THREAD_UNINT);
        }
        mutex_unlock(&apple_protect_pager_lock);

        return (memory_object_t) pager;
}       

void
apple_protect_pager_trim(void)
{
        apple_protect_pager_t   pager, prev_pager;
        queue_head_t            trim_queue;
        int                     num_trim;
        int                     count_unmapped;

        mutex_lock(&apple_protect_pager_lock);

        /*
         * We have too many pagers, try and trim some unused ones,
         * starting with the oldest pager at the end of the queue.
         */
        queue_init(&trim_queue);
        num_trim = 0;

        for (pager = (apple_protect_pager_t)
                     queue_last(&apple_protect_pager_queue);
             !queue_end(&apple_protect_pager_queue,
                        (queue_entry_t) pager);
             pager = prev_pager) {
                /* get prev elt before we dequeue */
                prev_pager = (apple_protect_pager_t)
                        queue_prev(&pager->pager_queue);

                if (pager->ref_count == 2 &&
                    pager->is_ready &&
                    !pager->is_mapped) {
                        /* this pager can be trimmed */
                        num_trim++;
                        /* remove this pager from the main list ... */
                        apple_protect_pager_dequeue(pager);
                        /* ... and add it to our trim queue */
                        queue_enter_first(&trim_queue,
                                          pager,
                                          apple_protect_pager_t,
                                          pager_queue);

                        count_unmapped = (apple_protect_pager_count -
                                          apple_protect_pager_count_mapped);
                        if (count_unmapped <= apple_protect_pager_cache_limit) {
                                /* we have enough pagers to trim */
                                break;
                        }
                }
        }
        if (num_trim > apple_protect_pager_num_trim_max) {
                apple_protect_pager_num_trim_max = num_trim;
        }
        apple_protect_pager_num_trim_total += num_trim;

        mutex_unlock(&apple_protect_pager_lock);

        /* terminate the trimmed pagers */
        while (!queue_empty(&trim_queue)) {
                queue_remove_first(&trim_queue,
                                   pager,
                                   apple_protect_pager_t,
                                   pager_queue);
                pager->pager_queue.next = NULL;
                pager->pager_queue.prev = NULL;
                assert(pager->ref_count == 2);
                /*
                 * We can't call deallocate_internal() because the pager
                 * has already been dequeued, but we still need to remove
                 * a reference.
                 */
                pager->ref_count--;
                apple_protect_pager_terminate_internal(pager);
        }
}