]> git.saurik.com Git - apple/xnu.git/blobdiff - osfmk/vm/vm_apple_protect.c
xnu-3247.1.106.tar.gz
[apple/xnu.git] / osfmk / vm / vm_apple_protect.c
index d57cfc71a74b8271ddf43918896ff525d6dcd21e..81301fd1102c610c5c2b9c655f841675f06e435f 100644 (file)
@@ -114,6 +114,10 @@ kern_return_t apple_protect_pager_map(memory_object_t mem_obj,
                                      vm_prot_t prot);
 kern_return_t apple_protect_pager_last_unmap(memory_object_t mem_obj);
 
+#define CRYPT_INFO_DEBUG 0
+void crypt_info_reference(struct pager_crypt_info *crypt_info);
+void crypt_info_deallocate(struct pager_crypt_info *crypt_info);
+
 /*
  * Vector of VM operations for this EMM.
  * These routines are invoked by VM via the memory_object_*() interfaces.
@@ -130,7 +134,8 @@ const struct memory_object_pager_ops apple_protect_pager_ops = {
        apple_protect_pager_synchronize,
        apple_protect_pager_map,
        apple_protect_pager_last_unmap,
-       "apple protect pager"
+       NULL, /* data_reclaim */
+       "apple_protect"
 };
 
 /*
@@ -138,7 +143,7 @@ const struct memory_object_pager_ops apple_protect_pager_ops = {
  * the "apple protect" EMM.
  */
 typedef struct apple_protect_pager {
-       struct ipc_object_header        pager_header;   /* fake ip_kotype() */
+       struct ipc_object_header pager_header;  /* fake ip_kotype() */
        memory_object_pager_ops_t pager_ops; /* == &apple_protect_pager_ops */
        queue_chain_t           pager_queue;    /* next & prev pagers */
        unsigned int            ref_count;      /* reference count */
@@ -146,7 +151,11 @@ typedef struct apple_protect_pager {
        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 */
-       struct pager_crypt_info crypt;
+       vm_object_offset_t      backing_offset;
+       vm_object_offset_t      crypto_backing_offset; /* for key... */
+       vm_object_offset_t      crypto_start;
+       vm_object_offset_t      crypto_end;
+       struct pager_crypt_info *crypt_info;
 } *apple_protect_pager_t;
 #define        APPLE_PROTECT_PAGER_NULL        ((apple_protect_pager_t) NULL)
 #define pager_ikot pager_header.io_bits
@@ -180,8 +189,13 @@ lck_attr_t         apple_protect_pager_lck_attr;
 
 
 /* internal prototypes */
-apple_protect_pager_t apple_protect_pager_create(vm_object_t backing_object,
-                                                struct pager_crypt_info *crypt_info);
+apple_protect_pager_t apple_protect_pager_create(
+       vm_object_t backing_object,
+       vm_object_offset_t backing_offset,
+       vm_object_offset_t crypto_backing_offset,
+       struct pager_crypt_info *crypt_info,
+       vm_object_offset_t crypto_start,
+       vm_object_offset_t crypto_end);
 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,
@@ -314,6 +328,7 @@ apple_protect_pager_data_unlock(
  *
  * Handles page-in requests from VM.
  */
+int apple_protect_pager_data_request_debug = 0;
 kern_return_t  
 apple_protect_pager_data_request(
        memory_object_t         mem_obj,
@@ -337,7 +352,7 @@ apple_protect_pager_data_request(
        vm_map_offset_t         kernel_mapping;
        vm_offset_t             src_vaddr, dst_vaddr;
        vm_offset_t             cur_offset;
-       vm_map_entry_t          map_entry;
+       vm_offset_t             offset_in_page;
        kern_return_t           error_code;
        vm_prot_t               prot;
        vm_page_t               src_page, top_page;
@@ -354,6 +369,9 @@ apple_protect_pager_data_request(
        upl_pl = NULL;
        fault_info = *((struct vm_object_fault_info *) 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;
 
        pager = apple_protect_pager_lookup(mem_obj);
@@ -386,11 +404,18 @@ apple_protect_pager_data_request(
        assert(dst_object != VM_OBJECT_NULL);
 
 
+#if __x86_64__ || __arm__ || __arm64__
+       /* we'll use the 1-to-1 mapping of physical memory */
+       src_vaddr = 0;
+       dst_vaddr = 0;
+#else /* __x86_64__ || __arm__ || __arm64__ */
        /*
         * Reserve 2 virtual pages in the kernel address space to map each
         * 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,
@@ -408,6 +433,7 @@ apple_protect_pager_data_request(
        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__ */
 
        /*
         * We'll map the encrypted data in the kernel address space from the 
@@ -443,10 +469,12 @@ apple_protect_pager_data_request(
                vm_object_paging_begin(src_object);
                error_code = 0;
                prot = VM_PROT_READ;
+               src_page = VM_PAGE_NULL;
                kr = vm_fault_page(src_object,
-                                  offset + cur_offset,
+                                  pager->backing_offset + offset + cur_offset,
                                   VM_PROT_READ,
                                   FALSE,
+                                  FALSE, /* src_page not looked up */
                                   &prot,
                                   &src_page,
                                   &top_page,
@@ -500,17 +528,24 @@ apple_protect_pager_data_request(
                        }
                        vm_page_unlock_queues();
                }
-               
+
                /*
                 * Establish an explicit mapping of the source
                 * physical page.
                 */
+#if __x86_64__
+               src_vaddr = (vm_map_offset_t)
+                       PHYSMAP_PTOV((pmap_paddr_t)src_page->phys_page
+                                    << PAGE_SHIFT);
+#else
                pmap_enter(kernel_pmap,
-                          kernel_mapping,
+                          src_vaddr,
                           src_page->phys_page,
                           VM_PROT_READ,
-                          src_object->wimg_bits & VM_WIMG_MASK,
+                          VM_PROT_NONE,
+                          0,
                           TRUE);
+#endif
                /*
                 * Establish an explicit pmap mapping of the destination
                 * physical page.
@@ -520,44 +555,156 @@ apple_protect_pager_data_request(
                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,
-                          kernel_mapping + PAGE_SIZE_64,
+                          dst_vaddr,
                           dst_pnum,
                           VM_PROT_READ | VM_PROT_WRITE,
-                          dst_object->wimg_bits & VM_WIMG_MASK,
+                          VM_PROT_NONE,
+                          0,
                           TRUE);
+#endif
+
+               /*
+                * Validate the original page...
+                */
+               if (src_page->object->code_signed) {
+                       vm_page_validate_cs_mapped(
+                               src_page,
+                               (const void *) src_vaddr);
+               }
+               /*
+                * ... and transfer the results to the destination page.
+                */
+               UPL_SET_CS_VALIDATED(upl_pl, cur_offset / PAGE_SIZE,
+                                    src_page->cs_validated);
+               UPL_SET_CS_TAINTED(upl_pl, cur_offset / PAGE_SIZE,
+                                  src_page->cs_tainted);
+               UPL_SET_CS_NX(upl_pl, cur_offset / PAGE_SIZE,
+                                  src_page->cs_nx);
+
+               /*
+                * page_decrypt() might access a mapped file, so let's release
+                * the object lock for the source page to avoid a potential
+                * deadlock.  The source page is kept busy and we have a
+                * "paging_in_progress" reference on its object, so it's safe
+                * to unlock the object here.
+                */
+               assert(src_page->busy);
+               assert(src_page->object->paging_in_progress > 0);
+               vm_object_unlock(src_page->object);
 
                /*
                 * Decrypt the encrypted contents of the source page
                 * into the destination page.
                 */
-               ret = pager->crypt.page_decrypt((const void *) src_vaddr,
-                                               (void *) dst_vaddr,
-                                               offset+cur_offset,
-                                               pager->crypt.crypt_ops);
+               for (offset_in_page = 0;
+                    offset_in_page < PAGE_SIZE;
+                    offset_in_page += 4096) {
+                       if (offset + cur_offset + offset_in_page <
+                           pager->crypto_start ||
+                           offset + cur_offset + offset_in_page >=
+                           pager->crypto_end) {
+                               /* not encrypted: just copy */
+                               bcopy((const char *)(src_vaddr +
+                                                    offset_in_page),
+                                     (char *)(dst_vaddr + offset_in_page),
+                                     4096);
+                               if (apple_protect_pager_data_request_debug) {
+                                       printf("apple_protect_data_request"
+                                              "(%p,0x%llx+0x%llx+0x%04llx): "
+                                              "out of crypto range "
+                                              "[0x%llx:0x%llx]: "
+                                              "COPY [0x%016llx 0x%016llx] "
+                                              "code_signed=%d "
+                                              "cs_validated=%d "
+                                              "cs_tainted=%d "
+                                              "cs_nx=%d\n",
+                                              pager,
+                                              offset,
+                                              (uint64_t) cur_offset,
+                                              (uint64_t) offset_in_page,
+                                              pager->crypto_start,
+                                              pager->crypto_end,
+                                              *(uint64_t *)(dst_vaddr+
+                                                            offset_in_page),
+                                              *(uint64_t *)(dst_vaddr+
+                                                            offset_in_page+8),
+                                              src_page->object->code_signed,
+                                              src_page->cs_validated,
+                                              src_page->cs_tainted,
+                                              src_page->cs_nx);
+                               }
+                               ret = 0;
+                               continue;
+                       }
+                       ret = pager->crypt_info->page_decrypt(
+                               (const void *)(src_vaddr + offset_in_page),
+                               (void *)(dst_vaddr + offset_in_page),
+                               ((pager->crypto_backing_offset -
+                                 pager->crypto_start) + /* XXX ? */
+                                offset +
+                                cur_offset +
+                                offset_in_page),
+                               pager->crypt_info->crypt_ops);
+                       if (apple_protect_pager_data_request_debug) {
+                               printf("apple_protect_data_request"
+                                      "(%p,0x%llx+0x%llx+0x%04llx): "
+                                      "in crypto range [0x%llx:0x%llx]: "
+                                      "DECRYPT offset 0x%llx="
+                                      "(0x%llx-0x%llx+0x%llx+0x%llx+0x%04llx)"
+                                      "[0x%016llx 0x%016llx] "
+                                      "code_signed=%d "
+                                      "cs_validated=%d "
+                                      "cs_tainted=%d "
+                                      "cs_nx=%d "
+                                      "ret=0x%x\n",
+                                      pager,
+                                      offset,
+                                      (uint64_t) cur_offset,
+                                      (uint64_t) offset_in_page,
+                                      pager->crypto_start, pager->crypto_end,
+                                      ((pager->crypto_backing_offset -
+                                        pager->crypto_start) +
+                                       offset +
+                                       cur_offset +
+                                       offset_in_page),
+                                      pager->crypto_backing_offset,
+                                      pager->crypto_start,
+                                      offset,
+                                      (uint64_t) cur_offset,
+                                      (uint64_t) offset_in_page,
+                                      *(uint64_t *)(dst_vaddr+offset_in_page),
+                                      *(uint64_t *)(dst_vaddr+offset_in_page+8),
+                                      src_page->object->code_signed,
+                                      src_page->cs_validated,
+                                      src_page->cs_tainted,
+                                      src_page->cs_nx,
+                                      ret);
+                       }
+                       if (ret) {
+                               break;
+                       }
+               }
                if (ret) {
                        /*
                         * Decryption failed.  Abort the fault.
                         */
                        retval = KERN_ABORTED;
-               } else {
-                       /*
-                        * Validate the original page...
-                        */
-                       if (src_page->object->code_signed) {
-                               vm_page_validate_cs_mapped(
-                                       src_page,
-                                       (const void *) src_vaddr);
-                       }
-                       /*
-                        * ... and transfer the results to the destination page.
-                        */
-                       UPL_SET_CS_VALIDATED(upl_pl, cur_offset / PAGE_SIZE,
-                                            src_page->cs_validated);
-                       UPL_SET_CS_TAINTED(upl_pl, cur_offset / PAGE_SIZE,
-                                          src_page->cs_tainted);
                }
-               
+
+               assert(src_page->busy);
+               assert(src_page->object->paging_in_progress > 0);
+               vm_object_lock(src_page->object);
+
+#if __x86_64__ || __arm__ || __arm64__
+               /* we used the 1-to-1 mapping of physical memory */
+               src_vaddr = 0;
+               dst_vaddr = 0;
+#else /* __x86_64__ || __arm__ || __arm64__ */
                /*
                 * Remove the pmap mapping of the source and destination pages
                 * in the kernel.
@@ -565,6 +712,7 @@ apple_protect_pager_data_request(
                pmap_remove(kernel_pmap,
                            (addr64_t) kernel_mapping,
                            (addr64_t) (kernel_mapping + (2 * PAGE_SIZE_64)));
+#endif /* __x86_64__ || __arm__ || __arm64__ */
 
                /*
                 * Cleanup the result of vm_fault_page() of the source page.
@@ -629,7 +777,7 @@ done:
                } else {
                        boolean_t empty;
                        upl_commit_range(upl, 0, upl->size, 
-                                        UPL_COMMIT_CS_VALIDATED,
+                                        UPL_COMMIT_CS_VALIDATED | UPL_COMMIT_WRITTEN_BY_KERNEL,
                                         upl_pl, pl_count, &empty);
                }
 
@@ -725,12 +873,18 @@ apple_protect_pager_terminate_internal(
                pager->backing_object = VM_OBJECT_NULL;
        }
 
+       /* one less pager using this "pager_crypt_info" */
+#if CRYPT_INFO_DEBUG
+       printf("CRYPT_INFO %s: deallocate %p ref %d\n",
+              __FUNCTION__,
+              pager->crypt_info,
+              pager->crypt_info->crypt_refcnt);
+#endif /* CRYPT_INFO_DEBUG */
+       crypt_info_deallocate(pager->crypt_info);
+       pager->crypt_info = NULL;
+
        /* trigger the destruction of the memory object */
        memory_object_destroy(pager->pager_control, 0);
-       
-       /* deallocate any crypt module data */
-       if(pager->crypt.crypt_end)
-               pager->crypt.crypt_end(pager->crypt.crypt_ops);
 }
 
 /*
@@ -947,12 +1101,17 @@ apple_protect_pager_lookup(
 
 apple_protect_pager_t
 apple_protect_pager_create(
-       vm_object_t     backing_object,
-       struct pager_crypt_info *crypt_info)
+       vm_object_t             backing_object,
+       vm_object_offset_t      backing_offset,
+       vm_object_offset_t      crypto_backing_offset,
+       struct pager_crypt_info *crypt_info,
+       vm_object_offset_t      crypto_start,
+       vm_object_offset_t      crypto_end)
 {
        apple_protect_pager_t   pager, pager2;
        memory_object_control_t control;
        kern_return_t           kr;
+       struct pager_crypt_info *old_crypt_info;
 
        pager = (apple_protect_pager_t) kalloc(sizeof (*pager));
        if (pager == APPLE_PROTECT_PAGER_NULL) {
@@ -969,32 +1128,88 @@ apple_protect_pager_create(
        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->ref_count = 1;   /* existence reference (for the cache) */
+       pager->ref_count++;     /* for the caller */
        pager->is_mapped = FALSE;
        pager->pager_control = MEMORY_OBJECT_CONTROL_NULL;
        pager->backing_object = backing_object;
-       pager->crypt = *crypt_info;
+       pager->backing_offset = backing_offset;
+       pager->crypto_backing_offset = crypto_backing_offset;
+       pager->crypto_start = crypto_start;
+       pager->crypto_end = crypto_end;
+       pager->crypt_info = crypt_info; /* allocated by caller */
+
+#if CRYPT_INFO_DEBUG
+       printf("CRYPT_INFO %s: crypt_info %p [%p,%p,%p,%d]\n",
+              __FUNCTION__,
+              crypt_info,
+              crypt_info->page_decrypt,
+              crypt_info->crypt_end,
+              crypt_info->crypt_ops,
+              crypt_info->crypt_refcnt);
+#endif /* CRYPT_INFO_DEBUG */
        
        vm_object_reference(backing_object);
 
+       old_crypt_info = NULL;
+
        lck_mtx_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) {
+               if ((pager2->crypt_info->page_decrypt !=
+                    crypt_info->page_decrypt) ||
+                   (pager2->crypt_info->crypt_end !=
+                    crypt_info->crypt_end) ||
+                   (pager2->crypt_info->crypt_ops !=
+                    crypt_info->crypt_ops)) {
+                       /* crypt_info contents do not match: next pager */
+                       continue;
+               }
+
+               /* found a match for crypt_info ... */
+               if (old_crypt_info) {
+                       /* ... already switched to that crypt_info */
+                       assert(old_crypt_info == pager2->crypt_info);
+               } else if (pager2->crypt_info != crypt_info) {
+                       /* ... switch to that pager's crypt_info */
+#if CRYPT_INFO_DEBUG
+                       printf("CRYPT_INFO %s: reference %p ref %d "
+                              "(create match)\n",
+                              __FUNCTION__,
+                              pager2->crypt_info,
+                              pager2->crypt_info->crypt_refcnt);
+#endif /* CRYPT_INFO_DEBUG */
+                       old_crypt_info = pager2->crypt_info;
+                       crypt_info_reference(old_crypt_info);
+                       pager->crypt_info = old_crypt_info;
+               }
+               
+               if (pager2->backing_object == backing_object &&
+                   pager2->backing_offset == backing_offset &&
+                   pager2->crypto_backing_offset == crypto_backing_offset &&
+                   pager2->crypto_start == crypto_start &&
+                   pager2->crypto_end == crypto_end) {
+                       /* full match: use that pager */
                        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... */
                lck_mtx_unlock(&apple_protect_pager_lock);
                vm_object_deallocate(pager->backing_object);
                pager->backing_object = VM_OBJECT_NULL;
+#if CRYPT_INFO_DEBUG
+               printf("CRYPT_INFO %s: %p ref %d (create pager match)\n",
+                      __FUNCTION__,
+                      pager->crypt_info,
+                      pager->crypt_info->crypt_refcnt);
+#endif /* CRYPT_INFO_DEBUG */
+               crypt_info_deallocate(pager->crypt_info);
+               pager->crypt_info = NULL;
                kfree(pager, sizeof (*pager));
                /* ... and go with the winner */
                pager = pager2;
@@ -1026,6 +1241,20 @@ apple_protect_pager_create(
        /* wakeup anyone waiting for this pager to be ready */
        thread_wakeup(&pager->is_ready);
 
+       if (old_crypt_info != NULL &&
+           old_crypt_info != crypt_info) {
+               /* we re-used an old crypt_info instead of using our new one */
+#if CRYPT_INFO_DEBUG
+               printf("CRYPT_INFO %s: deallocate %p ref %d "
+                      "(create used old)\n",
+                      __FUNCTION__,
+                      crypt_info,
+                      crypt_info->crypt_refcnt);
+#endif /* CRYPT_INFO_DEBUG */
+               crypt_info_deallocate(crypt_info);
+               crypt_info = NULL;
+       }
+
        return pager;
 }
 
@@ -1038,10 +1267,27 @@ apple_protect_pager_create(
  */
 memory_object_t
 apple_protect_pager_setup(
-                         vm_object_t   backing_object,
-                         struct pager_crypt_info *crypt_info)
+       vm_object_t             backing_object,
+       vm_object_offset_t      backing_offset,
+       vm_object_offset_t      crypto_backing_offset,
+       struct pager_crypt_info *crypt_info,
+       vm_object_offset_t      crypto_start,
+       vm_object_offset_t      crypto_end)
 {
        apple_protect_pager_t   pager;
+       struct pager_crypt_info *old_crypt_info, *new_crypt_info;
+
+#if CRYPT_INFO_DEBUG
+       printf("CRYPT_INFO %s: crypt_info=%p [%p,%p,%p,%d]\n",
+              __FUNCTION__,
+              crypt_info,
+              crypt_info->page_decrypt,
+              crypt_info->crypt_end,
+              crypt_info->crypt_ops,
+              crypt_info->crypt_refcnt);
+#endif /* CRYPT_INFO_DEBUG */
+
+       old_crypt_info = NULL;
 
        lck_mtx_lock(&apple_protect_pager_lock);
 
@@ -1049,35 +1295,146 @@ apple_protect_pager_setup(
                      pager,
                      apple_protect_pager_t,
                      pager_queue) {
-               if (pager->backing_object == backing_object) {
-                       /* For the same object we must always use the same protection options */
-                       if (!((pager->crypt.page_decrypt == crypt_info->page_decrypt) &&
-                             (pager->crypt.crypt_ops == crypt_info->crypt_ops) )) {
-                               lck_mtx_unlock(&apple_protect_pager_lock);
-                               return MEMORY_OBJECT_NULL;
-                       }
+               if ((pager->crypt_info->page_decrypt !=
+                    crypt_info->page_decrypt) ||
+                   (pager->crypt_info->crypt_end !=
+                    crypt_info->crypt_end) ||
+                   (pager->crypt_info->crypt_ops !=
+                    crypt_info->crypt_ops)) {
+                       /* no match for "crypt_info": next pager */
+                       continue;
+               }
+               /* found a match for crypt_info ... */
+               if (old_crypt_info) {
+                       /* ... already switched to that crypt_info */
+                       assert(old_crypt_info == pager->crypt_info);
+               } else {
+                       /* ... switch to that pager's crypt_info */
+                       old_crypt_info = pager->crypt_info;
+#if CRYPT_INFO_DEBUG
+                       printf("CRYPT_INFO %s: "
+                              "switching crypt_info from %p [%p,%p,%p,%d] "
+                              "to %p [%p,%p,%p,%d] from pager %p\n",
+                              __FUNCTION__,
+                              crypt_info,
+                              crypt_info->page_decrypt,
+                              crypt_info->crypt_end,
+                              crypt_info->crypt_ops,
+                              crypt_info->crypt_refcnt,
+                              old_crypt_info,
+                              old_crypt_info->page_decrypt,
+                              old_crypt_info->crypt_end,
+                              old_crypt_info->crypt_ops,
+                              old_crypt_info->crypt_refcnt,
+                              pager);
+                       printf("CRYPT_INFO %s: %p ref %d (setup match)\n",
+                              __FUNCTION__,
+                              pager->crypt_info,
+                              pager->crypt_info->crypt_refcnt);
+#endif /* CRYPT_INFO_DEBUG */
+                       crypt_info_reference(pager->crypt_info);
+               }
+               
+               if (pager->backing_object == backing_object &&
+                   pager->backing_offset == backing_offset &&
+                   pager->crypto_backing_offset == crypto_backing_offset &&
+                   pager->crypto_start == crypto_start &&
+                   pager->crypto_end == crypto_end) {
+                       /* full match: use that pager! */
+                       assert(old_crypt_info == pager->crypt_info);
+                       assert(old_crypt_info->crypt_refcnt > 1);
+#if CRYPT_INFO_DEBUG
+                       printf("CRYPT_INFO %s: "
+                              "pager match with %p crypt_info %p\n",
+                              __FUNCTION__,
+                              pager,
+                              pager->crypt_info);
+                       printf("CRYPT_INFO %s: deallocate %p ref %d "
+                              "(pager match)\n",
+                              __FUNCTION__,
+                              old_crypt_info,
+                              old_crypt_info->crypt_refcnt);
+#endif /* CRYPT_INFO_DEBUG */
+                       /* release the extra ref on crypt_info we got above */
+                       crypt_info_deallocate(old_crypt_info);
+                       assert(old_crypt_info->crypt_refcnt > 0);
+                       /* give extra reference on pager to the caller */
+                       assert(pager->ref_count > 0);
+                       pager->ref_count++;
                        break;
                }
        }
        if (queue_end(&apple_protect_pager_queue,
                      (queue_entry_t) pager)) {
+               lck_mtx_unlock(&apple_protect_pager_lock);
                /* no existing pager for this backing object */
                pager = APPLE_PROTECT_PAGER_NULL;
-       } else {
-               /* make sure pager doesn't disappear */
-               pager->ref_count++;
-       }
-
-       lck_mtx_unlock(&apple_protect_pager_lock);
-
-       if (pager == APPLE_PROTECT_PAGER_NULL) {
-               pager = apple_protect_pager_create(backing_object, crypt_info);
+               if (old_crypt_info) {
+                       /* use this old crypt_info for new pager */
+                       new_crypt_info = old_crypt_info;
+#if CRYPT_INFO_DEBUG
+                       printf("CRYPT_INFO %s: "
+                              "will use old_crypt_info %p for new pager\n",
+                              __FUNCTION__,
+                              old_crypt_info);
+#endif /* CRYPT_INFO_DEBUG */
+               } else {
+                       /* allocate a new crypt_info for new pager */
+                       new_crypt_info = kalloc(sizeof (*new_crypt_info));
+                       *new_crypt_info = *crypt_info;
+                       new_crypt_info->crypt_refcnt = 1;
+#if CRYPT_INFO_DEBUG
+                       printf("CRYPT_INFO %s: "
+                              "will use new_crypt_info %p for new pager\n",
+                              __FUNCTION__,
+                              new_crypt_info);
+#endif /* CRYPT_INFO_DEBUG */
+               }
+               if (new_crypt_info == NULL) {
+                       /* can't create new pager without a crypt_info */
+               } else {
+                       /* create new pager */
+                       pager = apple_protect_pager_create(
+                               backing_object,
+                               backing_offset,
+                               crypto_backing_offset,
+                               new_crypt_info,
+                               crypto_start,
+                               crypto_end);
+               }
                if (pager == APPLE_PROTECT_PAGER_NULL) {
+                       /* could not create a new pager */
+                       if (new_crypt_info == old_crypt_info) {
+                               /* release extra reference on old_crypt_info */
+#if CRYPT_INFO_DEBUG
+                               printf("CRYPT_INFO %s: deallocate %p ref %d "
+                                      "(create fail old_crypt_info)\n",
+                                      __FUNCTION__,
+                                      old_crypt_info, 
+                                      old_crypt_info->crypt_refcnt);
+#endif /* CRYPT_INFO_DEBUG */
+                               crypt_info_deallocate(old_crypt_info);
+                               old_crypt_info = NULL;
+                       } else {
+                               /* release unused new_crypt_info */
+                               assert(new_crypt_info->crypt_refcnt == 1);
+#if CRYPT_INFO_DEBUG
+                               printf("CRYPT_INFO %s: deallocate %p ref %d "
+                                      "(create fail new_crypt_info)\n",
+                                      __FUNCTION__,
+                                      new_crypt_info,
+                                      new_crypt_info->crypt_refcnt);
+#endif /* CRYPT_INFO_DEBUG */
+                               crypt_info_deallocate(new_crypt_info);
+                               new_crypt_info = NULL;
+                       }
                        return MEMORY_OBJECT_NULL;
                }
+               lck_mtx_lock(&apple_protect_pager_lock);
+       } else {
+               assert(old_crypt_info == pager->crypt_info);
        }
 
-       lck_mtx_lock(&apple_protect_pager_lock);
        while (!pager->is_ready) {
                lck_mtx_sleep(&apple_protect_pager_lock,
                        LCK_SLEEP_DEFAULT,
@@ -1161,3 +1518,47 @@ apple_protect_pager_trim(void)
                apple_protect_pager_terminate_internal(pager);
        }
 }
+
+
+void
+crypt_info_reference(
+       struct pager_crypt_info *crypt_info)
+{
+       assert(crypt_info->crypt_refcnt != 0);
+#if CRYPT_INFO_DEBUG
+       printf("CRYPT_INFO %s: %p ref %d -> %d\n",
+              __FUNCTION__,
+              crypt_info,
+              crypt_info->crypt_refcnt,
+              crypt_info->crypt_refcnt + 1);
+#endif /* CRYPT_INFO_DEBUG */
+       OSAddAtomic(+1, &crypt_info->crypt_refcnt);
+}
+
+void
+crypt_info_deallocate(
+       struct pager_crypt_info *crypt_info)
+{
+#if CRYPT_INFO_DEBUG
+       printf("CRYPT_INFO %s: %p ref %d -> %d\n",
+              __FUNCTION__,
+              crypt_info,
+              crypt_info->crypt_refcnt,
+              crypt_info->crypt_refcnt - 1);
+#endif /* CRYPT_INFO_DEBUG */
+       OSAddAtomic(-1, &crypt_info->crypt_refcnt);
+       if (crypt_info->crypt_refcnt == 0) {
+               /* deallocate any crypt module data */
+               if (crypt_info->crypt_end) {
+                       crypt_info->crypt_end(crypt_info->crypt_ops);
+                       crypt_info->crypt_end = NULL;
+               }
+#if CRYPT_INFO_DEBUG
+               printf("CRYPT_INFO %s: freeing %p\n",
+                      __FUNCTION__,
+                      crypt_info);
+#endif /* CRYPT_INFO_DEBUG */
+               kfree(crypt_info, sizeof (*crypt_info));
+               crypt_info = NULL;
+       }
+}