osfmk/kern/kext_alloc.c

   1 /*
   2  * Copyright (c) 2008 Apple Inc. All rights reserved.
   3  *
   4  * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. The rights granted to you under the License
  10  * may not be used to create, or enable the creation or redistribution of,
  11  * unlawful or unlicensed copies of an Apple operating system, or to
  12  * circumvent, violate, or enable the circumvention or violation of, any
  13  * terms of an Apple operating system software license agreement.
  14  *
  15  * Please obtain a copy of the License at
  16  * http://www.opensource.apple.com/apsl/ and read it before using this file.
  17  *
  18  * The Original Code and all software distributed under the License are
  19  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  20  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  21  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  22  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  23  * Please see the License for the specific language governing rights and
  24  * limitations under the License.
  25  *
  26  * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
  27  */
  28 #include <kern/assert.h>
  29 #include <kern/debug.h>
  30 #include <kern/kext_alloc.h>
  31 #include <kern/misc_protos.h>
  32
  33 #include <mach/host_priv_server.h>
  34 #include <mach/kern_return.h>
  35 #include <mach/mach_vm.h>
  36 #include <mach/vm_map.h>
  37 #include <mach/vm_types.h>
  38
  39 #include <mach-o/loader.h>
  40 #include <libkern/kernel_mach_header.h>
  41
  42 #define KEXT_ALLOC_MAX_OFFSET (2 * 1024 * 1024 * 1024UL)
  43
  44 vm_map_t g_kext_map = 0;
  45 static mach_vm_offset_t kext_alloc_base = 0;
  46 static mach_vm_offset_t kext_alloc_max = 0;
  47
  48 /*
  49  * On x86_64 systems, kernel extension text must remain within 2GB of the
  50  * kernel's text segment.  To ensure this happens, we snag 2GB of kernel VM
  51  * as early as possible for kext allocations.
  52  */
  53 void
  54 kext_alloc_init(void)
  55 {
  56 #if __x86_64__
  57     kern_return_t rval = 0;
  58     kernel_segment_command_t *text = NULL;
  59     mach_vm_offset_t text_end, text_start;
  60     mach_vm_size_t text_size;
  61     mach_vm_size_t kext_alloc_size;
  62
  63     /* Determine the start of the kernel's __TEXT segment and determine the
  64      * lower bound of the allocated submap for kext allocations.
  65      */
  66
  67     text = getsegbyname(SEG_TEXT);
  68     text_start = vm_map_trunc_page(text->vmaddr);
  69     text_start &= ~((512ULL * 1024 * 1024 * 1024) - 1);
  70     text_end = vm_map_round_page(text->vmaddr + text->vmsize);
  71     text_size = text_end - text_start;
  72
  73     kext_alloc_base = text_end - KEXT_ALLOC_MAX_OFFSET;
  74     kext_alloc_size = KEXT_ALLOC_MAX_OFFSET - text_size;
  75     kext_alloc_max = kext_alloc_base + kext_alloc_size;
  76
  77     /* Allocate the subblock of the kernel map */
  78
  79     rval = kmem_suballoc(kernel_map, (vm_offset_t *) &kext_alloc_base,
  80                          kext_alloc_size, /* pageable */ TRUE,
  81                          VM_FLAGS_FIXED|VM_FLAGS_OVERWRITE|VM_FLAGS_BELOW_MIN,
  82                          &g_kext_map);
  83     if (rval != KERN_SUCCESS) {
  84             panic("kext_alloc_init: kmem_suballoc failed 0x%x\n", rval);
  85     }
  86
  87     if ((kext_alloc_base + kext_alloc_size) > kext_alloc_max) {
  88         panic("kext_alloc_init: failed to get first 2GB\n");
  89     }
  90
  91     if (kernel_map->min_offset > kext_alloc_base) {
  92             kernel_map->min_offset = kext_alloc_base;
  93     }
  94
  95     printf("kext submap [0x%llx - 0x%llx], kernel text [0x%llx - 0x%llx]\n",
  96            kext_alloc_base, kext_alloc_max, text->vmaddr,
  97            text->vmaddr + text->vmsize);
  98 #else
  99     g_kext_map = kernel_map;
 100     kext_alloc_base = VM_MIN_KERNEL_ADDRESS;
 101     kext_alloc_max = VM_MAX_KERNEL_ADDRESS;
 102 #endif /* __x86_64__ */
 103 }
 104
 105 kern_return_t
 106 kext_alloc(vm_offset_t *_addr, vm_size_t size, boolean_t fixed)
 107 {
 108     kern_return_t rval = 0;
 109     mach_vm_offset_t addr = (fixed) ? *_addr : kext_alloc_base;
 110     int flags = (fixed) ? VM_FLAGS_FIXED : VM_FLAGS_ANYWHERE;
 111
 112     /* Allocate the kext virtual memory */
 113     rval = mach_vm_allocate(g_kext_map, &addr, size, flags);
 114     if (rval != KERN_SUCCESS) {
 115         printf("vm_allocate failed - %d\n", rval);
 116         goto finish;
 117     }
 118
 119     /* Check that the memory is reachable by kernel text */
 120     if ((addr + size) > kext_alloc_max) {
 121         kext_free((vm_offset_t)addr, size);
 122         goto finish;
 123     }
 124
 125     *_addr = (vm_offset_t)addr;
 126     rval = KERN_SUCCESS;
 127
 128 finish:
 129     return rval;
 130 }
 131
 132 void
 133 kext_free(vm_offset_t addr, vm_size_t size)
 134 {
 135     kern_return_t rval;
 136
 137     rval = mach_vm_deallocate(g_kext_map, addr, size);
 138     assert(rval == KERN_SUCCESS);
 139 }
 140