xnu-3247.10.11.tar.gz

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

/*
 * Copyright (c) 2014 Apple Computer, Inc. All rights reserved.
 *
 * @APPLE_OSREFERENCE_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. The rights granted to you under the License
 * may not be used to create, or enable the creation or redistribution of,
 * unlawful or unlicensed copies of an Apple operating system, or to
 * circumvent, violate, or enable the circumvention or violation of, any
 * terms of an Apple operating system software license agreement.
 * 
 * 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_OSREFERENCE_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_fault.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>


/* 
 * 4K MEMORY PAGER 
 *
 * This external memory manager (EMM) handles memory mappings that are
 * 4K-aligned but not page-aligned and can therefore not be mapped directly.
 * 
 * It mostly handles page-in requests (from memory_object_data_request()) by
 * getting the data needed to fill in each 4K-chunk.  That can require
 * getting data from one or two pages from its backing VM object
 * (a file or a "apple-protected" pager backed by an encrypted file), and
 * copies the data to another page so that it is aligned as expected by
 * the mapping.
 *
 * Returned pages can never be dirtied and must always be mapped copy-on-write,
 * so the memory manager does not need to handle page-out requests (from
 * memory_object_data_return()).
 *
 */

/* forward declarations */
void fourk_pager_reference(memory_object_t mem_obj);
void fourk_pager_deallocate(memory_object_t mem_obj);
kern_return_t fourk_pager_init(memory_object_t mem_obj,
                                 memory_object_control_t control,
                                 memory_object_cluster_size_t pg_size);
kern_return_t fourk_pager_terminate(memory_object_t mem_obj);
kern_return_t fourk_pager_data_request(memory_object_t mem_obj,
                                         memory_object_offset_t offset,
                                         memory_object_cluster_size_t length,
                                         vm_prot_t protection_required,
                                         memory_object_fault_info_t fault_info);
kern_return_t fourk_pager_data_return(memory_object_t mem_obj,
                                        memory_object_offset_t offset,
                                        memory_object_cluster_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 fourk_pager_data_initialize(memory_object_t mem_obj,
                                            memory_object_offset_t offset,
                                            memory_object_cluster_size_t data_cnt);
kern_return_t fourk_pager_data_unlock(memory_object_t mem_obj,
                                        memory_object_offset_t offset,
                                        memory_object_size_t size,
                                        vm_prot_t desired_access);
kern_return_t fourk_pager_synchronize(memory_object_t mem_obj,
                                        memory_object_offset_t offset,
                                        memory_object_size_t length,
                                        vm_sync_t sync_flags);
kern_return_t fourk_pager_map(memory_object_t mem_obj,
                                vm_prot_t prot);
kern_return_t fourk_pager_last_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 fourk_pager_ops = {
        fourk_pager_reference,
        fourk_pager_deallocate,
        fourk_pager_init,
        fourk_pager_terminate,
        fourk_pager_data_request,
        fourk_pager_data_return,
        fourk_pager_data_initialize,
        fourk_pager_data_unlock,
        fourk_pager_synchronize,
        fourk_pager_map,
        fourk_pager_last_unmap,
        NULL, /* data_reclaim */
        "fourk_pager"
};

/*
 * The "fourk_pager" describes a memory object backed by
 * the "4K" EMM.
 */
#define FOURK_PAGER_SLOTS 4     /* 16K / 4K */
typedef struct fourk_pager_backing {
        vm_object_t             backing_object;
        vm_object_offset_t      backing_offset;
} *fourk_pager_backing_t;
typedef struct fourk_pager {
        struct ipc_object_header        pager_header;   /* fake ip_kotype() */
        memory_object_pager_ops_t pager_ops; /* == &fourk_pager_ops */
        memory_object_control_t pager_control;  /* mem object control handle */
        queue_chain_t           pager_queue;    /* next & prev pagers */
        unsigned int            ref_count;      /* reference count */
        int     is_ready;       /* is this pager ready ? */
        int     is_mapped;      /* is this mem_obj mapped ? */
        struct fourk_pager_backing slots[FOURK_PAGER_SLOTS]; /* backing for each
                                                                4K-chunk */
} *fourk_pager_t;
#define FOURK_PAGER_NULL        ((fourk_pager_t) NULL)
#define pager_ikot pager_header.io_bits

/*
 * List of memory objects managed by this EMM.
 * The list is protected by the "fourk_pager_lock" lock.
 */
int fourk_pager_count = 0;              /* number of pagers */
int fourk_pager_count_mapped = 0;       /* number of unmapped pagers */
queue_head_t fourk_pager_queue;
decl_lck_mtx_data(,fourk_pager_lock)

/*
 * Maximum number of unmapped pagers we're willing to keep around.
 */
int fourk_pager_cache_limit = 0;

/*
 * Statistics & counters.
 */
int fourk_pager_count_max = 0;
int fourk_pager_count_unmapped_max = 0;
int fourk_pager_num_trim_max = 0;
int fourk_pager_num_trim_total = 0;


lck_grp_t       fourk_pager_lck_grp;
lck_grp_attr_t  fourk_pager_lck_grp_attr;
lck_attr_t      fourk_pager_lck_attr;


/* internal prototypes */
fourk_pager_t fourk_pager_lookup(memory_object_t mem_obj);
void fourk_pager_dequeue(fourk_pager_t pager);
void fourk_pager_deallocate_internal(fourk_pager_t pager,
                                       boolean_t locked);
void fourk_pager_terminate_internal(fourk_pager_t pager);
void fourk_pager_trim(void);


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

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


void
fourk_pager_bootstrap(void)
{
        lck_grp_attr_setdefault(&fourk_pager_lck_grp_attr);
        lck_grp_init(&fourk_pager_lck_grp, "4K-pager", &fourk_pager_lck_grp_attr);
        lck_attr_setdefault(&fourk_pager_lck_attr);
        lck_mtx_init(&fourk_pager_lock, &fourk_pager_lck_grp, &fourk_pager_lck_attr);
        queue_init(&fourk_pager_queue);
}

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

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

        if (control == MEMORY_OBJECT_CONTROL_NULL)
                return KERN_INVALID_ARGUMENT;

        pager = fourk_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("fourk_pager_init: "
                      "memory_object_change_attributes() failed");

        return KERN_SUCCESS;
}

/*
 * fourk_pager_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
fourk_pager_data_return(
        __unused memory_object_t        mem_obj,
        __unused memory_object_offset_t offset,
        __unused memory_object_cluster_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("fourk_pager_data_return: should never get called");
        return KERN_FAILURE;
}

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

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

/*
 * fourk_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
fourk_pager_reference(
        memory_object_t         mem_obj)
{       
        fourk_pager_t   pager;

        pager = fourk_pager_lookup(mem_obj);

        lck_mtx_lock(&fourk_pager_lock);
        assert(pager->ref_count > 0);
        pager->ref_count++;
        lck_mtx_unlock(&fourk_pager_lock);
}


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

        queue_remove(&fourk_pager_queue,
                     pager,
                     fourk_pager_t,
                     pager_queue);
        pager->pager_queue.next = NULL;
        pager->pager_queue.prev = NULL;
        
        fourk_pager_count--;
}

/*
 * fourk_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. fourk_pager_deallocate())
 * to finish the clean up.
 *
 * "fourk_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
fourk_pager_terminate_internal(
        fourk_pager_t pager)
{
        int i;

        assert(pager->is_ready);
        assert(!pager->is_mapped);

        for (i = 0; i < FOURK_PAGER_SLOTS; i++) {
                if (pager->slots[i].backing_object != VM_OBJECT_NULL &&
                    pager->slots[i].backing_object != (vm_object_t) -1) {
                        vm_object_deallocate(pager->slots[i].backing_object);
                        pager->slots[i].backing_object = (vm_object_t) -1;
                        pager->slots[i].backing_offset = (vm_object_offset_t) -1;
                }
        }
        
        /* trigger the destruction of the memory object */
        memory_object_destroy(pager->pager_control, 0);
}

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

        if (! locked) {
                lck_mtx_lock(&fourk_pager_lock);
        }

        count_unmapped = (fourk_pager_count - 
                          fourk_pager_count_mapped);
        if (count_unmapped > fourk_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 really holding on to this pager anymore.
                 * Terminate it.
                 */
                fourk_pager_dequeue(pager);
                /* the pager is all ours: no need for the lock now */
                lck_mtx_unlock(&fourk_pager_lock);
                fourk_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.
                 */
                lck_mtx_unlock(&fourk_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 = FOURK_PAGER_NULL;
        } else {
                /* there are still plenty of references:  keep going... */
                lck_mtx_unlock(&fourk_pager_lock);
        }

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

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

        PAGER_DEBUG(PAGER_ALL, ("fourk_pager_deallocate: %p\n", mem_obj));
        pager = fourk_pager_lookup(mem_obj);
        fourk_pager_deallocate_internal(pager, FALSE);
}

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

        return KERN_SUCCESS;
}

/*
 *
 */
kern_return_t
fourk_pager_synchronize(
        memory_object_t         mem_obj,
        memory_object_offset_t  offset,
        memory_object_size_t            length,
        __unused vm_sync_t              sync_flags)
{
        fourk_pager_t   pager;

        PAGER_DEBUG(PAGER_ALL, ("fourk_pager_synchronize: %p\n", mem_obj));

        pager = fourk_pager_lookup(mem_obj);

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

        return KERN_SUCCESS;
}

/*
 * fourk_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 each time
 * the memory object gets mapped and we take one extra reference on the
 * memory object to account for all its mappings.
 */
kern_return_t
fourk_pager_map(
        memory_object_t         mem_obj,
        __unused vm_prot_t      prot)
{
        fourk_pager_t   pager;

        PAGER_DEBUG(PAGER_ALL, ("fourk_pager_map: %p\n", mem_obj));

        pager = fourk_pager_lookup(mem_obj);

        lck_mtx_lock(&fourk_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++;
                fourk_pager_count_mapped++;
        }
        lck_mtx_unlock(&fourk_pager_lock);

        return KERN_SUCCESS;
}

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

        PAGER_DEBUG(PAGER_ALL,
                    ("fourk_pager_last_unmap: %p\n", mem_obj));

        pager = fourk_pager_lookup(mem_obj);

        lck_mtx_lock(&fourk_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.
                 */
                fourk_pager_count_mapped--;
                count_unmapped = (fourk_pager_count -
                                  fourk_pager_count_mapped);
                if (count_unmapped > fourk_pager_count_unmapped_max) {
                        fourk_pager_count_unmapped_max = count_unmapped;
                }
                pager->is_mapped = FALSE;
                fourk_pager_deallocate_internal(pager, TRUE);
                /* caution: deallocate_internal() released the lock ! */
        } else {
                lck_mtx_unlock(&fourk_pager_lock);
        }
        
        return KERN_SUCCESS;
}


/*
 *
 */
fourk_pager_t
fourk_pager_lookup(
        memory_object_t  mem_obj)
{
        fourk_pager_t   pager;

        pager = (fourk_pager_t) mem_obj;
        assert(pager->pager_ops == &fourk_pager_ops);
        assert(pager->ref_count > 0);
        return pager;
}

void
fourk_pager_trim(void)
{
        fourk_pager_t   pager, prev_pager;
        queue_head_t            trim_queue;
        int                     num_trim;
        int                     count_unmapped;

        lck_mtx_lock(&fourk_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 = (fourk_pager_t)
                     queue_last(&fourk_pager_queue);
             !queue_end(&fourk_pager_queue,
                        (queue_entry_t) pager);
             pager = prev_pager) {
                /* get prev elt before we dequeue */
                prev_pager = (fourk_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 ... */
                        fourk_pager_dequeue(pager);
                        /* ... and add it to our trim queue */
                        queue_enter_first(&trim_queue,
                                          pager,
                                          fourk_pager_t,
                                          pager_queue);

                        count_unmapped = (fourk_pager_count -
                                          fourk_pager_count_mapped);
                        if (count_unmapped <= fourk_pager_cache_limit) {
                                /* we have enough pagers to trim */
                                break;
                        }
                }
        }
        if (num_trim > fourk_pager_num_trim_max) {
                fourk_pager_num_trim_max = num_trim;
        }
        fourk_pager_num_trim_total += num_trim;

        lck_mtx_unlock(&fourk_pager_lock);

        /* terminate the trimmed pagers */
        while (!queue_empty(&trim_queue)) {
                queue_remove_first(&trim_queue,
                                   pager,
                                   fourk_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--;
                fourk_pager_terminate_internal(pager);
        }
}






vm_object_t
fourk_pager_to_vm_object(
        memory_object_t mem_obj)
{
        fourk_pager_t   pager;
        vm_object_t     object;

        pager = fourk_pager_lookup(mem_obj);
        if (pager == NULL) {
                return VM_OBJECT_NULL;
        }

        assert(pager->ref_count > 0);
        assert(pager->pager_control != MEMORY_OBJECT_CONTROL_NULL);
        object = memory_object_control_to_vm_object(pager->pager_control);
        assert(object != VM_OBJECT_NULL);
        return object;
}

memory_object_t
fourk_pager_create(void)
{
        fourk_pager_t           pager;
        memory_object_control_t control;
        kern_return_t           kr;
        int                     i;

#if 00
        if (PAGE_SIZE_64 == FOURK_PAGE_SIZE) {
                panic("fourk_pager_create: page size is 4K !?");
        }
#endif

        pager = (fourk_pager_t) kalloc(sizeof (*pager));
        if (pager == FOURK_PAGER_NULL) {
                return MEMORY_OBJECT_NULL;
        }
        bzero(pager, sizeof (*pager));

        /*
         * 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 first 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 = &fourk_pager_ops;
        pager->pager_ikot = IKOT_MEMORY_OBJECT;
        pager->pager_control = MEMORY_OBJECT_CONTROL_NULL;
        pager->ref_count = 2;   /* existence + setup reference */
        pager->is_ready = FALSE;/* not ready until it has a "name" */
        pager->is_mapped = FALSE;

        for (i = 0; i < FOURK_PAGER_SLOTS; i++) {
                pager->slots[i].backing_object = (vm_object_t) -1;
                pager->slots[i].backing_offset = (vm_object_offset_t) -1;
        }
        
        lck_mtx_lock(&fourk_pager_lock);

        /* enter new pager at the head of our list of pagers */
        queue_enter_first(&fourk_pager_queue,
                          pager,
                          fourk_pager_t,
                          pager_queue);
        fourk_pager_count++;
        if (fourk_pager_count > fourk_pager_count_max) {
                fourk_pager_count_max = fourk_pager_count;
        }
        lck_mtx_unlock(&fourk_pager_lock);

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

        lck_mtx_lock(&fourk_pager_lock);
        /* the new pager is now ready to be used */
        pager->is_ready = TRUE;
        lck_mtx_unlock(&fourk_pager_lock);

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

        return (memory_object_t) pager;
}

/*
 * fourk_pager_data_request()
 *
 * Handles page-in requests from VM.
 */
int fourk_pager_data_request_debug = 0;
kern_return_t   
fourk_pager_data_request(
        memory_object_t         mem_obj,
        memory_object_offset_t  offset,
        memory_object_cluster_size_t            length,
#if !DEBUG
        __unused
#endif
        vm_prot_t               protection_required,
        memory_object_fault_info_t mo_fault_info)
{
        fourk_pager_t           pager;
        memory_object_control_t mo_control;
        upl_t                   upl;
        int                     upl_flags;
        upl_size_t              upl_size;
        upl_page_info_t         *upl_pl;
        unsigned int            pl_count;
        vm_object_t             dst_object;
        kern_return_t           kr, retval;
        vm_map_offset_t         kernel_mapping;
        vm_offset_t             src_vaddr, dst_vaddr;
        vm_offset_t             cur_offset;
        int                     sub_page;
        int                     sub_page_idx, sub_page_cnt;

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

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

        retval = KERN_SUCCESS;
        kernel_mapping = 0;

        offset = memory_object_trunc_page(offset);

        /*
         * 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;
        pl_count = 0;
        kr = memory_object_upl_request(mo_control,
                                       offset, upl_size,
                                       &upl, NULL, NULL, upl_flags);
        if (kr != KERN_SUCCESS) {
                retval = kr;
                goto done;
        }
        dst_object = mo_control->moc_object;
        assert(dst_object != VM_OBJECT_NULL);

#if __x86_64__ || __arm__ || __arm64__
        /* use the 1-to-1 mapping of physical memory */
#else /* __x86_64__ || __arm__ || __arm64__ */
        /*
         * Reserve 2 virtual pages in the kernel address space to map the
         * source and destination physical pages when it's their turn to
         * be processed.
         */
        vm_map_entry_t          map_entry;

        vm_object_reference(kernel_object);     /* ref. for mapping */
        kr = vm_map_find_space(kernel_map,
                               &kernel_mapping,
                               2 * 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 = kernel_mapping;
        vm_map_unlock(kernel_map);
        src_vaddr = CAST_DOWN(vm_offset_t, kernel_mapping);
        dst_vaddr = CAST_DOWN(vm_offset_t, kernel_mapping + PAGE_SIZE_64);
#endif /* __x86_64__ || __arm__ || __arm64__ */

        /*
         * Fill in the contents of the pages requested by VM.
         */
        upl_pl = UPL_GET_INTERNAL_PAGE_LIST(upl);
        pl_count = length / PAGE_SIZE;
        for (cur_offset = 0;
             retval == KERN_SUCCESS && cur_offset < length;
             cur_offset += PAGE_SIZE) {
                ppnum_t dst_pnum;
                int num_subpg_signed, num_subpg_validated;
                int num_subpg_tainted, num_subpg_nx;

                if (!upl_page_present(upl_pl, (int)(cur_offset / PAGE_SIZE))) {
                        /* this page is not in the UPL: skip it */
                        continue;
                }

                /*
                 * Establish an explicit pmap mapping of the destination
                 * physical page.
                 * We can't do a regular VM mapping because the VM page
                 * is "busy".
                 */
                dst_pnum = (ppnum_t)
                        upl_phys_page(upl_pl, (int)(cur_offset / PAGE_SIZE));
                assert(dst_pnum != 0);
#if __x86_64__
                dst_vaddr = (vm_map_offset_t)
                        PHYSMAP_PTOV((pmap_paddr_t)dst_pnum << PAGE_SHIFT);
#else
                pmap_enter(kernel_pmap,
                           dst_vaddr,
                           dst_pnum,
                           VM_PROT_READ | VM_PROT_WRITE,
                           VM_PROT_NONE,
                           0,
                           TRUE);
#endif

                /* retrieve appropriate data for each 4K-page in this page */
                if (PAGE_SHIFT == FOURK_PAGE_SHIFT &&
                    page_shift_user32 == SIXTEENK_PAGE_SHIFT) {
                        /*
                         * Find the slot for the requested 4KB page in
                         * the 16K page...
                         */
                        assert(PAGE_SHIFT == FOURK_PAGE_SHIFT);
                        assert(page_shift_user32 == SIXTEENK_PAGE_SHIFT);
                        sub_page_idx = ((offset & SIXTEENK_PAGE_MASK) /
                                        PAGE_SIZE);
                        /*
                         * ... and provide only that one 4KB page.
                         */
                        sub_page_cnt = 1;
                } else {
                        /*
                         * Iterate over all slots, i.e. retrieve all four 4KB
                         * pages in the requested 16KB page.
                         */
                        assert(PAGE_SHIFT == SIXTEENK_PAGE_SHIFT);
                        sub_page_idx = 0;
                        sub_page_cnt = FOURK_PAGER_SLOTS;
                }

                num_subpg_signed = 0;
                num_subpg_validated = 0;
                num_subpg_tainted = 0;
                num_subpg_nx = 0;

                /* retrieve appropriate data for each 4K-page in this page */
                for (sub_page = sub_page_idx;
                     sub_page < sub_page_idx + sub_page_cnt;
                     sub_page++) {
                        vm_object_t             src_object;
                        memory_object_offset_t  src_offset;
                        vm_offset_t             offset_in_src_page;
                        kern_return_t           error_code;
                        vm_page_t               src_page;
                        vm_page_t               top_page;
                        vm_prot_t               prot;
                        int                     interruptible;
                        struct vm_object_fault_info     fault_info;
                        boolean_t       subpg_validated;
                        unsigned        subpg_tainted;


                        if (offset < SIXTEENK_PAGE_SIZE) {
                                /*
                                 * The 1st 16K-page can cover multiple
                                 * sub-mappings, as described in the 
                                 * pager->slots[] array.
                                 */
                                src_object =
                                        pager->slots[sub_page].backing_object;
                                src_offset =
                                        pager->slots[sub_page].backing_offset;
                        } else {
                                fourk_pager_backing_t slot;

                                /*
                                 * Beyond the 1st 16K-page in the pager is
                                 * an extension of the last "sub page" in
                                 * the pager->slots[] array.
                                 */
                                slot = &pager->slots[FOURK_PAGER_SLOTS-1];
                                src_object = slot->backing_object;
                                src_offset = slot->backing_offset;
                                src_offset += FOURK_PAGE_SIZE;
                                src_offset +=
                                        (vm_map_trunc_page(offset,
                                                           SIXTEENK_PAGE_MASK)
                                         - SIXTEENK_PAGE_SIZE);
                                src_offset += sub_page * FOURK_PAGE_SIZE;
                        }
                        offset_in_src_page = src_offset & PAGE_MASK_64;
                        src_offset = vm_object_trunc_page(src_offset);
                                
                        if (src_object == VM_OBJECT_NULL ||
                            src_object == (vm_object_t) -1) {
                                /* zero-fill */
                                bzero((char *)(dst_vaddr +
                                               ((sub_page-sub_page_idx)
                                                * FOURK_PAGE_SIZE)),
                                      FOURK_PAGE_SIZE);
                                if (fourk_pager_data_request_debug) {
                                        printf("fourk_pager_data_request"
                                               "(%p,0x%llx+0x%lx+0x%04x): "
                                               "ZERO\n",
                                               pager,
                                               offset,
                                               cur_offset,
                                               ((sub_page - sub_page_idx)
                                                * FOURK_PAGE_SIZE));
                                }
                                continue;
                        }

                        /* fault in the source page from src_object */
                retry_src_fault:
                        src_page = VM_PAGE_NULL;
                        top_page = VM_PAGE_NULL;
                        fault_info = *((struct vm_object_fault_info *)
                                       (uintptr_t)mo_fault_info);
                        fault_info.stealth = TRUE;
                        fault_info.io_sync = FALSE;
                        fault_info.mark_zf_absent = FALSE;
                        fault_info.batch_pmap_op = FALSE;
                        interruptible = fault_info.interruptible;
                        prot = VM_PROT_READ;
                        error_code = 0;

                        vm_object_lock(src_object);
                        vm_object_paging_begin(src_object);
                        kr = vm_fault_page(src_object,
                                           src_offset,
                                           VM_PROT_READ,
                                           FALSE,
                                           FALSE, /* src_page not looked up */
                                           &prot,
                                           &src_page,
                                           &top_page,
                                           NULL,
                                           &error_code,
                                           FALSE,
                                           FALSE,
                                           &fault_info);
                        switch (kr) {
                        case VM_FAULT_SUCCESS:
                                break;
                        case VM_FAULT_RETRY:
                                goto retry_src_fault;
                        case VM_FAULT_MEMORY_SHORTAGE:
                                if (vm_page_wait(interruptible)) {
                                        goto retry_src_fault;
                                }
                                /* fall thru */
                        case VM_FAULT_INTERRUPTED:
                                retval = MACH_SEND_INTERRUPTED;
                                goto src_fault_done;
                        case VM_FAULT_SUCCESS_NO_VM_PAGE:
                                /* success but no VM page: fail */
                                vm_object_paging_end(src_object);
                                vm_object_unlock(src_object);
                                /*FALLTHROUGH*/
                        case VM_FAULT_MEMORY_ERROR:
                                /* the page is not there! */
                                if (error_code) {
                                        retval = error_code;
                                } else {
                                        retval = KERN_MEMORY_ERROR;
                                }
                                goto src_fault_done;
                        default:
                                panic("fourk_pager_data_request: "
                                      "vm_fault_page() unexpected error 0x%x\n",
                                      kr);
                        }
                        assert(src_page != VM_PAGE_NULL);
                        assert(src_page->busy);

                        if (!src_page->active &&
                            !src_page->inactive &&
                            !src_page->speculative &&
                            !src_page->throttled &&
                            !VM_PAGE_WIRED(src_page)) {
                                vm_page_lockspin_queues();
                                if (!src_page->active &&
                                    !src_page->inactive &&
                                    !src_page->speculative &&
                                    !src_page->throttled &&
                                    !VM_PAGE_WIRED(src_page)) {
                                        vm_page_deactivate(src_page);
                                }
                                vm_page_unlock_queues();
                        }

#if __x86_64__
                        src_vaddr = (vm_map_offset_t)
                                PHYSMAP_PTOV((pmap_paddr_t)src_page->phys_page
                                             << PAGE_SHIFT);
#else
                        /*
                         * Establish an explicit mapping of the source
                         * physical page.
                         */
                        pmap_enter(kernel_pmap,
                                   src_vaddr,
                                   src_page->phys_page,
                                   VM_PROT_READ,
                                   VM_PROT_NONE,
                                   0,
                                   TRUE);
#endif

                        /*
                         * Validate the 4K page we want from
                         * this source page...
                         */
                        subpg_validated = FALSE;
                        subpg_tainted = 0;
                        if (src_page->object->code_signed) {
                                vm_page_validate_cs_mapped_chunk(
                                        src_page,
                                        (const void *) src_vaddr,
                                        offset_in_src_page,
                                        &subpg_validated,
                                        &subpg_tainted);
                                num_subpg_signed++;
                                if (subpg_validated) {
                                        num_subpg_validated++;
                                }
                                if (subpg_tainted & CS_VALIDATE_TAINTED) {
                                        num_subpg_tainted++;
                                }
                                if (subpg_tainted & CS_VALIDATE_NX) {
                                        /* subpg should not be executable */
                                        if (sub_page_cnt > 1) {
                                                /*
                                                 * The destination page has
                                                 * more than 1 subpage and its
                                                 * other subpages might need
                                                 * EXEC, so we do not propagate
                                                 * CS_VALIDATE_NX to the
                                                 * destination page...
                                                 */
                                        } else {
                                                num_subpg_nx++;
                                        }
                                }
                        }

                        /*
                         * Copy the relevant portion of the source page
                         * into the appropriate part of the destination page.
                         */
                        bcopy((const char *)(src_vaddr + offset_in_src_page),
                              (char *)(dst_vaddr +
                                       ((sub_page - sub_page_idx) *
                                        FOURK_PAGE_SIZE)),
                              FOURK_PAGE_SIZE);
                        if (fourk_pager_data_request_debug) {
                                printf("fourk_data_request"
                                       "(%p,0x%llx+0x%lx+0x%04x): "
                                       "backed by [%p:0x%llx]: "
                                       "[0x%016llx 0x%016llx] "
                                       "code_signed=%d "
                                       "cs_valid=%d cs_tainted=%d cs_nx=%d\n",
                                       pager,
                                       offset, cur_offset,
                                       (sub_page-sub_page_idx)*FOURK_PAGE_SIZE,
                                       src_page->object,
                                       src_page->offset + offset_in_src_page,
                                       *(uint64_t *)(dst_vaddr +
                                                     ((sub_page-sub_page_idx) *
                                                      FOURK_PAGE_SIZE)),
                                       *(uint64_t *)(dst_vaddr +
                                                     ((sub_page-sub_page_idx) *
                                                      FOURK_PAGE_SIZE) +
                                                     8),
                                       src_page->object->code_signed,
                                       subpg_validated,
                                       !!(subpg_tainted & CS_VALIDATE_TAINTED),
                                       !!(subpg_tainted & CS_VALIDATE_NX));
                        }

#if __x86_64__ || __arm__ || __arm64__
                        /* we used the 1-to-1 mapping of physical memory */
                        src_vaddr = 0;
#else /* __x86_64__ || __arm__ || __arm64__ */
                        /*
                         * Remove the pmap mapping of the source page 
                         * in the kernel.
                         */
                        pmap_remove(kernel_pmap,
                                    (addr64_t) src_vaddr,
                                    (addr64_t) src_vaddr + PAGE_SIZE_64);
#endif /* __x86_64__ || __arm__ || __arm64__ */

                src_fault_done:
                        /*
                         * Cleanup the result of vm_fault_page().
                         */
                        if (src_page) {
                                vm_object_t     src_page_object;

                                src_page_object = src_page->object;
                                PAGE_WAKEUP_DONE(src_page);
                                src_page = VM_PAGE_NULL;
                                vm_object_paging_end(src_page_object);
                                vm_object_unlock(src_page_object);
                                if (top_page) {
                                        vm_object_t     top_object;

                                        top_object = top_page->object;
                                        vm_object_lock(top_object);
                                        VM_PAGE_FREE(top_page);
                                        top_page = VM_PAGE_NULL;
                                        vm_object_paging_end(top_object);
                                        vm_object_unlock(top_object);
                                }
                        }
                }
                if (num_subpg_signed > 0) {
                        /* some code-signing involved with this 16K page */
                        if (num_subpg_tainted > 0) {
                                /* a tainted subpage taints entire 16K page */
                                UPL_SET_CS_TAINTED(upl_pl,
                                                   cur_offset / PAGE_SIZE,
                                                   TRUE);
                                /* also mark as "validated" for consisteny */
                                UPL_SET_CS_VALIDATED(upl_pl,
                                                     cur_offset / PAGE_SIZE,
                                                     TRUE);
                        } else if (num_subpg_validated == num_subpg_signed) {
                                /*
                                 * All the code-signed 4K subpages of this
                                 * 16K page are validated:  our 16K page is
                                 * considered validated.
                                 */
                                UPL_SET_CS_VALIDATED(upl_pl,
                                                     cur_offset / PAGE_SIZE,
                                                     TRUE);
                        }
                        if (num_subpg_nx > 0) {
                                UPL_SET_CS_NX(upl_pl,
                                              cur_offset / PAGE_SIZE,
                                              TRUE);
                        }
                }
        }

done:
        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);
                        if (retval == KERN_ABORTED) {
                                wait_result_t   wait_result;

                                /*
                                 * We aborted the fault and did not provide
                                 * any contents for the requested pages but
                                 * the pages themselves are not invalid, so
                                 * let's return success and let the caller
                                 * retry the fault, in case it might succeed
                                 * later (when the decryption code is up and
                                 * running in the kernel, for example).
                                 */
                                retval = KERN_SUCCESS;
                                /*
                                 * Wait a little bit first to avoid using
                                 * too much CPU time retrying and failing
                                 * the same fault over and over again.
                                 */
                                wait_result = assert_wait_timeout(
                                        (event_t) fourk_pager_data_request,
                                        THREAD_UNINT,
                                        10000,  /* 10ms */
                                        NSEC_PER_USEC);
                                assert(wait_result == THREAD_WAITING);
                                wait_result = thread_block(THREAD_CONTINUE_NULL);
                                assert(wait_result == THREAD_TIMED_OUT);
                        }
                } else {
                        boolean_t empty;
                        upl_commit_range(upl, 0, upl->size, 
                                         UPL_COMMIT_CS_VALIDATED | UPL_COMMIT_WRITTEN_BY_KERNEL,
                                         upl_pl, pl_count, &empty);
                }

                /* and deallocate the UPL */
                upl_deallocate(upl);
                upl = NULL;
        }
        if (kernel_mapping != 0) {
                /* clean up the mapping of the source and destination pages */
                kr = vm_map_remove(kernel_map,
                                   kernel_mapping,
                                   kernel_mapping + (2 * PAGE_SIZE_64),
                                   VM_MAP_NO_FLAGS);
                assert(kr == KERN_SUCCESS);
                kernel_mapping = 0;
                src_vaddr = 0;
                dst_vaddr = 0;
        }

        return retval;
}



kern_return_t
fourk_pager_populate(
        memory_object_t         mem_obj,
        boolean_t               overwrite,
        int                     index,
        vm_object_t             new_backing_object,
        vm_object_offset_t      new_backing_offset,
        vm_object_t             *old_backing_object,
        vm_object_offset_t      *old_backing_offset)
{
        fourk_pager_t   pager;

        pager = fourk_pager_lookup(mem_obj);
        if (pager == NULL) {
                return KERN_INVALID_ARGUMENT;
        }

        assert(pager->ref_count > 0);
        assert(pager->pager_control != MEMORY_OBJECT_CONTROL_NULL);

        if (index < 0 || index > FOURK_PAGER_SLOTS) {
                return KERN_INVALID_ARGUMENT;
        }

        if (!overwrite &&
            (pager->slots[index].backing_object != (vm_object_t) -1 ||
             pager->slots[index].backing_offset != (vm_object_offset_t) -1)) {
                return KERN_INVALID_ADDRESS;
        }

        *old_backing_object = pager->slots[index].backing_object;
        *old_backing_offset = pager->slots[index].backing_offset;

        pager->slots[index].backing_object = new_backing_object;
        pager->slots[index].backing_offset = new_backing_offset;

        return KERN_SUCCESS;
}