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 KASLR_IOREG_DEBUG 0
  43
  44
  45 vm_map_t g_kext_map = 0;
  46 #if KASLR_IOREG_DEBUG
  47 mach_vm_offset_t kext_alloc_base = 0;
  48 mach_vm_offset_t kext_alloc_max = 0;
  49 #else
  50 static mach_vm_offset_t kext_alloc_base = 0;
  51 static mach_vm_offset_t kext_alloc_max = 0;
  52 #if CONFIG_KEXT_BASEMENT
  53 static mach_vm_offset_t kext_post_boot_base = 0;
  54 #endif
  55 #endif
  56
  57 /*
  58  * On x86_64 systems, kernel extension text must remain within 2GB of the
  59  * kernel's text segment.  To ensure this happens, we snag 2GB of kernel VM
  60  * as early as possible for kext allocations.
  61  */
  62 void
  63 kext_alloc_init(void)
  64 {
  65 #if CONFIG_KEXT_BASEMENT
  66     kern_return_t rval = 0;
  67     kernel_segment_command_t *text = NULL;
  68     kernel_segment_command_t *prelinkTextSegment = NULL;
  69     mach_vm_offset_t text_end, text_start;
  70     mach_vm_size_t text_size;
  71     mach_vm_size_t kext_alloc_size;
  72
  73     /* Determine the start of the kernel's __TEXT segment and determine the
  74      * lower bound of the allocated submap for kext allocations.
  75      */
  76
  77     text = getsegbyname(SEG_TEXT);
  78     text_start = vm_map_trunc_page(text->vmaddr,
  79                                    VM_MAP_PAGE_MASK(kernel_map));
  80     text_start &= ~((512ULL * 1024 * 1024 * 1024) - 1);
  81     text_end = vm_map_round_page(text->vmaddr + text->vmsize,
  82                                  VM_MAP_PAGE_MASK(kernel_map));
  83     text_size = text_end - text_start;
  84
  85     kext_alloc_base = KEXT_ALLOC_BASE(text_end);
  86     kext_alloc_size = KEXT_ALLOC_SIZE(text_size);
  87     kext_alloc_max = kext_alloc_base + kext_alloc_size;
  88
  89     /* Post boot kext allocation will start after the prelinked kexts */
  90     prelinkTextSegment = getsegbyname("__PRELINK_TEXT");
  91     if (prelinkTextSegment) {
  92         /* use kext_post_boot_base to start allocations past all the prelinked
  93          * kexts
  94          */
  95         kext_post_boot_base =
  96                 vm_map_round_page(kext_alloc_base + prelinkTextSegment->vmsize,
  97                                   VM_MAP_PAGE_MASK(kernel_map));
  98     }
  99     else {
 100         kext_post_boot_base = kext_alloc_base;
 101     }
 102
 103     /* Allocate the sub block of the kernel map */
 104     rval = kmem_suballoc(kernel_map, (vm_offset_t *) &kext_alloc_base,
 105                          kext_alloc_size, /* pageable */ TRUE,
 106                          VM_FLAGS_FIXED|VM_FLAGS_OVERWRITE | VM_MAKE_TAG(VM_KERN_MEMORY_KEXT),
 107                          &g_kext_map);
 108     if (rval != KERN_SUCCESS) {
 109             panic("kext_alloc_init: kmem_suballoc failed 0x%x\n", rval);
 110     }
 111
 112     if ((kext_alloc_base + kext_alloc_size) > kext_alloc_max) {
 113         panic("kext_alloc_init: failed to get first 2GB\n");
 114     }
 115
 116     if (kernel_map->min_offset > kext_alloc_base) {
 117             kernel_map->min_offset = kext_alloc_base;
 118     }
 119
 120     printf("kext submap [0x%lx - 0x%lx], kernel text [0x%lx - 0x%lx]\n",
 121            VM_KERNEL_UNSLIDE(kext_alloc_base),
 122            VM_KERNEL_UNSLIDE(kext_alloc_max),
 123            VM_KERNEL_UNSLIDE(text->vmaddr),
 124            VM_KERNEL_UNSLIDE(text->vmaddr + text->vmsize));
 125
 126 #else
 127     g_kext_map = kernel_map;
 128     kext_alloc_base = VM_MIN_KERNEL_ADDRESS;
 129     kext_alloc_max = VM_MAX_KERNEL_ADDRESS;
 130 #endif /* CONFIG_KEXT_BASEMENT */
 131 }
 132
 133 kern_return_t
 134 kext_alloc(vm_offset_t *_addr, vm_size_t size, boolean_t fixed)
 135 {
 136     kern_return_t rval = 0;
 137 #if CONFIG_KEXT_BASEMENT
 138     mach_vm_offset_t addr = (fixed) ? *_addr : kext_post_boot_base;
 139 #else
 140     mach_vm_offset_t addr = (fixed) ? *_addr : kext_alloc_base;
 141 #endif
 142     int flags = (fixed) ? VM_FLAGS_FIXED : VM_FLAGS_ANYWHERE;
 143
 144     flags |= VM_MAKE_TAG(VM_KERN_MEMORY_KEXT);
 145
 146 #if CONFIG_KEXT_BASEMENT
 147     /* Allocate the kext virtual memory
 148      * 10608884 - use mach_vm_map since we want VM_FLAGS_ANYWHERE allocated past
 149      * kext_post_boot_base (when possible).  mach_vm_allocate will always
 150      * start at 0 into the map no matter what you pass in addr.  We want non
 151      * fixed (post boot) kext allocations to start looking for free space
 152      * just past where prelinked kexts have loaded.
 153      */
 154     rval = mach_vm_map(g_kext_map,
 155                        &addr,
 156                        size,
 157                        0,
 158                        flags,
 159                        MACH_PORT_NULL,
 160                        0,
 161                        TRUE,
 162                        VM_PROT_DEFAULT,
 163                        VM_PROT_ALL,
 164                        VM_INHERIT_DEFAULT);
 165     if (rval != KERN_SUCCESS) {
 166         printf("mach_vm_map failed - %d\n", rval);
 167         goto finish;
 168     }
 169 #else
 170     rval = mach_vm_allocate(g_kext_map, &addr, size, flags);
 171     if (rval != KERN_SUCCESS) {
 172         printf("vm_allocate failed - %d\n", rval);
 173         goto finish;
 174     }
 175 #endif
 176
 177     /* Check that the memory is reachable by kernel text */
 178     if ((addr + size) > kext_alloc_max) {
 179         kext_free((vm_offset_t)addr, size);
 180         rval = KERN_INVALID_ADDRESS;
 181         goto finish;
 182     }
 183
 184     *_addr = (vm_offset_t)addr;
 185     rval = KERN_SUCCESS;
 186
 187 finish:
 188     return rval;
 189 }
 190
 191 void
 192 kext_free(vm_offset_t addr, vm_size_t size)
 193 {
 194     kern_return_t rval;
 195
 196     rval = mach_vm_deallocate(g_kext_map, addr, size);
 197     assert(rval == KERN_SUCCESS);
 198 }
 199