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
  43 vm_map_t g_kext_map = 0;
  44 static mach_vm_offset_t kext_alloc_base = 0;
  45 static mach_vm_offset_t kext_alloc_max = 0;
  46
  47 /*
  48  * On x86_64 systems, kernel extension text must remain within 2GB of the
  49  * kernel's text segment.  To ensure this happens, we snag 2GB of kernel VM
  50  * as early as possible for kext allocations.
  51  */
  52 void
  53 kext_alloc_init(void)
  54 {
  55 #if __x86_64__
  56     kern_return_t rval = 0;
  57     kernel_segment_command_t *text = NULL;
  58     mach_vm_offset_t text_end, text_start;
  59     mach_vm_size_t text_size;
  60     mach_vm_size_t kext_alloc_size;
  61
  62     /* Determine the start of the kernel's __TEXT segment and determine the
  63      * lower bound of the allocated submap for kext allocations.
  64      */
  65
  66     text = getsegbyname(SEG_TEXT);
  67     text_start = vm_map_trunc_page(text->vmaddr);
  68     text_start &= ~((512ULL * 1024 * 1024 * 1024) - 1);
  69     text_end = vm_map_round_page(text->vmaddr + text->vmsize);
  70     text_size = text_end - text_start;
  71
  72     kext_alloc_base = KEXT_ALLOC_BASE(text_end);
  73     kext_alloc_size = KEXT_ALLOC_SIZE(text_size);
  74     kext_alloc_max = kext_alloc_base + kext_alloc_size;
  75
  76     /* Allocate the subblock of the kernel map */
  77
  78     rval = kmem_suballoc(kernel_map, (vm_offset_t *) &kext_alloc_base,
  79                          kext_alloc_size, /* pageable */ TRUE,
  80                          VM_FLAGS_FIXED|VM_FLAGS_OVERWRITE,
  81                          &g_kext_map);
  82     if (rval != KERN_SUCCESS) {
  83             panic("kext_alloc_init: kmem_suballoc failed 0x%x\n", rval);
  84     }
  85
  86     if ((kext_alloc_base + kext_alloc_size) > kext_alloc_max) {
  87         panic("kext_alloc_init: failed to get first 2GB\n");
  88     }
  89
  90     if (kernel_map->min_offset > kext_alloc_base) {
  91             kernel_map->min_offset = kext_alloc_base;
  92     }
  93
  94     printf("kext submap [0x%llx - 0x%llx], kernel text [0x%llx - 0x%llx]\n",
  95            kext_alloc_base, kext_alloc_max, text->vmaddr,
  96            text->vmaddr + text->vmsize);
  97 #else
  98     g_kext_map = kernel_map;
  99     kext_alloc_base = VM_MIN_KERNEL_ADDRESS;
 100     kext_alloc_max = VM_MAX_KERNEL_ADDRESS;
 101 #endif /* __x86_64__ */
 102 }
 103
 104 kern_return_t
 105 kext_alloc(vm_offset_t *_addr, vm_size_t size, boolean_t fixed)
 106 {
 107     kern_return_t rval = 0;
 108     mach_vm_offset_t addr = (fixed) ? *_addr : kext_alloc_base;
 109     int flags = (fixed) ? VM_FLAGS_FIXED : VM_FLAGS_ANYWHERE;
 110
 111     /* Allocate the kext virtual memory */
 112     rval = mach_vm_allocate(g_kext_map, &addr, size, flags);
 113     if (rval != KERN_SUCCESS) {
 114         printf("vm_allocate failed - %d\n", rval);
 115         goto finish;
 116     }
 117
 118     /* Check that the memory is reachable by kernel text */
 119     if ((addr + size) > kext_alloc_max) {
 120         kext_free((vm_offset_t)addr, size);
 121         goto finish;
 122     }
 123
 124     *_addr = (vm_offset_t)addr;
 125     rval = KERN_SUCCESS;
 126
 127 finish:
 128     return rval;
 129 }
 130
 131 void
 132 kext_free(vm_offset_t addr, vm_size_t size)
 133 {
 134     kern_return_t rval;
 135
 136     rval = mach_vm_deallocate(g_kext_map, addr, size);
 137     assert(rval == KERN_SUCCESS);
 138 }
 139