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     text_start &= ~((512ULL * 1024 * 1024 * 1024) - 1);
  80     text_end = vm_map_round_page(text->vmaddr + text->vmsize);
  81     text_size = text_end - text_start;
  82
  83     kext_alloc_base = KEXT_ALLOC_BASE(text_end);
  84     kext_alloc_size = KEXT_ALLOC_SIZE(text_size);
  85     kext_alloc_max = kext_alloc_base + kext_alloc_size;
  86
  87     /* Post boot kext allocation will start after the prelinked kexts */
  88     prelinkTextSegment = getsegbyname("__PRELINK_TEXT");
  89     if (prelinkTextSegment) {
  90         /* use kext_post_boot_base to start allocations past all the prelinked
  91          * kexts
  92          */
  93         kext_post_boot_base =
  94             vm_map_round_page(kext_alloc_base + prelinkTextSegment->vmsize);
  95     }
  96     else {
  97         kext_post_boot_base = kext_alloc_base;
  98     }
  99
 100     /* Allocate the sub block of the kernel map */
 101     rval = kmem_suballoc(kernel_map, (vm_offset_t *) &kext_alloc_base,
 102                          kext_alloc_size, /* pageable */ TRUE,
 103                          VM_FLAGS_FIXED|VM_FLAGS_OVERWRITE,
 104                          &g_kext_map);
 105     if (rval != KERN_SUCCESS) {
 106             panic("kext_alloc_init: kmem_suballoc failed 0x%x\n", rval);
 107     }
 108
 109     if ((kext_alloc_base + kext_alloc_size) > kext_alloc_max) {
 110         panic("kext_alloc_init: failed to get first 2GB\n");
 111     }
 112
 113     if (kernel_map->min_offset > kext_alloc_base) {
 114             kernel_map->min_offset = kext_alloc_base;
 115     }
 116
 117     printf("kext submap [0x%lx - 0x%lx], kernel text [0x%lx - 0x%lx]\n",
 118            VM_KERNEL_UNSLIDE(kext_alloc_base),
 119            VM_KERNEL_UNSLIDE(kext_alloc_max),
 120            VM_KERNEL_UNSLIDE(text->vmaddr),
 121            VM_KERNEL_UNSLIDE(text->vmaddr + text->vmsize));
 122
 123 #else
 124     g_kext_map = kernel_map;
 125     kext_alloc_base = VM_MIN_KERNEL_ADDRESS;
 126     kext_alloc_max = VM_MAX_KERNEL_ADDRESS;
 127 #endif /* CONFIG_KEXT_BASEMENT */
 128 }
 129
 130 kern_return_t
 131 kext_alloc(vm_offset_t *_addr, vm_size_t size, boolean_t fixed)
 132 {
 133     kern_return_t rval = 0;
 134 #if CONFIG_KEXT_BASEMENT
 135     mach_vm_offset_t addr = (fixed) ? *_addr : kext_post_boot_base;
 136 #else
 137     mach_vm_offset_t addr = (fixed) ? *_addr : kext_alloc_base;
 138 #endif
 139     int flags = (fixed) ? VM_FLAGS_FIXED : VM_FLAGS_ANYWHERE;
 140
 141 #if CONFIG_KEXT_BASEMENT
 142     /* Allocate the kext virtual memory
 143      * 10608884 - use mach_vm_map since we want VM_FLAGS_ANYWHERE allocated past
 144      * kext_post_boot_base (when possible).  mach_vm_allocate will always
 145      * start at 0 into the map no matter what you pass in addr.  We want non
 146      * fixed (post boot) kext allocations to start looking for free space
 147      * just past where prelinked kexts have loaded.
 148      */
 149     rval = mach_vm_map(g_kext_map,
 150                        &addr,
 151                        size,
 152                        0,
 153                        flags,
 154                        MACH_PORT_NULL,
 155                        0,
 156                        TRUE,
 157                        VM_PROT_DEFAULT,
 158                        VM_PROT_ALL,
 159                        VM_INHERIT_DEFAULT);
 160     if (rval != KERN_SUCCESS) {
 161         printf("mach_vm_map failed - %d\n", rval);
 162         goto finish;
 163     }
 164 #else
 165     rval = mach_vm_allocate(g_kext_map, &addr, size, flags);
 166     if (rval != KERN_SUCCESS) {
 167         printf("vm_allocate failed - %d\n", rval);
 168         goto finish;
 169     }
 170 #endif
 171
 172     /* Check that the memory is reachable by kernel text */
 173     if ((addr + size) > kext_alloc_max) {
 174         kext_free((vm_offset_t)addr, size);
 175         rval = KERN_INVALID_ADDRESS;
 176         goto finish;
 177     }
 178
 179     *_addr = (vm_offset_t)addr;
 180     rval = KERN_SUCCESS;
 181
 182 finish:
 183     return rval;
 184 }
 185
 186 void
 187 kext_free(vm_offset_t addr, vm_size_t size)
 188 {
 189     kern_return_t rval;
 190
 191     rval = mach_vm_deallocate(g_kext_map, addr, size);
 192     assert(rval == KERN_SUCCESS);
 193 }
 194