arch/x86/kernel/module.c

   1 /*  Kernel module help for x86.
   2     Copyright (C) 2001 Rusty Russell.
   3
   4     This program is free software; you can redistribute it and/or modify
   5     it under the terms of the GNU General Public License as published by
   6     the Free Software Foundation; either version 2 of the License, or
   7     (at your option) any later version.
   8
   9     This program is distributed in the hope that it will be useful,
  10     but WITHOUT ANY WARRANTY; without even the implied warranty of
  11     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12     GNU General Public License for more details.
  13
  14     You should have received a copy of the GNU General Public License
  15     along with this program; if not, write to the Free Software
  16     Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  17 */
  18
  19 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  20
  21 #include <linux/moduleloader.h>
  22 #include <linux/elf.h>
  23 #include <linux/vmalloc.h>
  24 #include <linux/fs.h>
  25 #include <linux/string.h>
  26 #include <linux/kernel.h>
  27 #include <linux/bug.h>
  28 #include <linux/mm.h>
  29 #include <linux/gfp.h>
  30 #include <linux/jump_label.h>
  31 #include <linux/random.h>
  32
  33 #include <asm/page.h>
  34 #include <asm/pgtable.h>
  35
  36 #if 0
  37 #define DEBUGP(fmt, ...)                                \
  38         printk(KERN_DEBUG fmt, ##__VA_ARGS__)
  39 #else
  40 #define DEBUGP(fmt, ...)                                \
  41 do {                                                    \
  42         if (0)                                          \
  43                 printk(KERN_DEBUG fmt, ##__VA_ARGS__);  \
  44 } while (0)
  45 #endif
  46
  47 #ifdef CONFIG_RANDOMIZE_BASE
  48 static unsigned long module_load_offset;
  49
  50 /* Mutex protects the module_load_offset. */
  51 static DEFINE_MUTEX(module_kaslr_mutex);
  52
  53 static unsigned long int get_module_load_offset(void)
  54 {
  55         if (kaslr_enabled) {
  56                 mutex_lock(&module_kaslr_mutex);
  57                 /*
  58                  * Calculate the module_load_offset the first time this
  59                  * code is called. Once calculated it stays the same until
  60                  * reboot.
  61                  */
  62                 if (module_load_offset == 0)
  63                         module_load_offset =
  64                                 (get_random_int() % 1024 + 1) * PAGE_SIZE;
  65                 mutex_unlock(&module_kaslr_mutex);
  66         }
  67         return module_load_offset;
  68 }
  69 #else
  70 static unsigned long int get_module_load_offset(void)
  71 {
  72         return 0;
  73 }
  74 #endif
  75
  76 void *module_alloc(unsigned long size)
  77 {
  78         if (PAGE_ALIGN(size) > MODULES_LEN)
  79                 return NULL;
  80         return __vmalloc_node_range(size, 1,
  81                                     MODULES_VADDR + get_module_load_offset(),
  82                                     MODULES_END, GFP_KERNEL | __GFP_HIGHMEM,
  83                                     PAGE_KERNEL_EXEC, NUMA_NO_NODE,
  84                                     __builtin_return_address(0));
  85 }
  86
  87 #ifdef CONFIG_X86_32
  88 int apply_relocate(Elf32_Shdr *sechdrs,
  89                    const char *strtab,
  90                    unsigned int symindex,
  91                    unsigned int relsec,
  92                    struct module *me)
  93 {
  94         unsigned int i;
  95         Elf32_Rel *rel = (void *)sechdrs[relsec].sh_addr;
  96         Elf32_Sym *sym;
  97         uint32_t *location;
  98
  99         DEBUGP("Applying relocate section %u to %u\n",
 100                relsec, sechdrs[relsec].sh_info);
 101         for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) {
 102                 /* This is where to make the change */
 103                 location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
 104                         + rel[i].r_offset;
 105                 /* This is the symbol it is referring to.  Note that all
 106                    undefined symbols have been resolved.  */
 107                 sym = (Elf32_Sym *)sechdrs[symindex].sh_addr
 108                         + ELF32_R_SYM(rel[i].r_info);
 109
 110                 switch (ELF32_R_TYPE(rel[i].r_info)) {
 111                 case R_386_32:
 112                         /* We add the value into the location given */
 113                         *location += sym->st_value;
 114                         break;
 115                 case R_386_PC32:
 116                         /* Add the value, subtract its position */
 117                         *location += sym->st_value - (uint32_t)location;
 118                         break;
 119                 default:
 120                         pr_err("%s: Unknown relocation: %u\n",
 121                                me->name, ELF32_R_TYPE(rel[i].r_info));
 122                         return -ENOEXEC;
 123                 }
 124         }
 125         return 0;
 126 }
 127 #else /*X86_64*/
 128 int apply_relocate_add(Elf64_Shdr *sechdrs,
 129                    const char *strtab,
 130                    unsigned int symindex,
 131                    unsigned int relsec,
 132                    struct module *me)
 133 {
 134         unsigned int i;
 135         Elf64_Rela *rel = (void *)sechdrs[relsec].sh_addr;
 136         Elf64_Sym *sym;
 137         void *loc;
 138         u64 val;
 139
 140         DEBUGP("Applying relocate section %u to %u\n",
 141                relsec, sechdrs[relsec].sh_info);
 142         for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) {
 143                 /* This is where to make the change */
 144                 loc = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
 145                         + rel[i].r_offset;
 146
 147                 /* This is the symbol it is referring to.  Note that all
 148                    undefined symbols have been resolved.  */
 149                 sym = (Elf64_Sym *)sechdrs[symindex].sh_addr
 150                         + ELF64_R_SYM(rel[i].r_info);
 151
 152                 DEBUGP("type %d st_value %Lx r_addend %Lx loc %Lx\n",
 153                        (int)ELF64_R_TYPE(rel[i].r_info),
 154                        sym->st_value, rel[i].r_addend, (u64)loc);
 155
 156                 val = sym->st_value + rel[i].r_addend;
 157
 158                 switch (ELF64_R_TYPE(rel[i].r_info)) {
 159                 case R_X86_64_NONE:
 160                         break;
 161                 case R_X86_64_64:
 162                         *(u64 *)loc = val;
 163                         break;
 164                 case R_X86_64_32:
 165                         *(u32 *)loc = val;
 166                         if (val != *(u32 *)loc)
 167                                 goto overflow;
 168                         break;
 169                 case R_X86_64_32S:
 170                         *(s32 *)loc = val;
 171                         if ((s64)val != *(s32 *)loc)
 172                                 goto overflow;
 173                         break;
 174                 case R_X86_64_PC32:
 175                         val -= (u64)loc;
 176                         *(u32 *)loc = val;
 177 #if 0
 178                         if ((s64)val != *(s32 *)loc)
 179                                 goto overflow;
 180 #endif
 181                         break;
 182                 default:
 183                         pr_err("%s: Unknown rela relocation: %llu\n",
 184                                me->name, ELF64_R_TYPE(rel[i].r_info));
 185                         return -ENOEXEC;
 186                 }
 187         }
 188         return 0;
 189
 190 overflow:
 191         pr_err("overflow in relocation type %d val %Lx\n",
 192                (int)ELF64_R_TYPE(rel[i].r_info), val);
 193         pr_err("`%s' likely not compiled with -mcmodel=kernel\n",
 194                me->name);
 195         return -ENOEXEC;
 196 }
 197 #endif
 198
 199 int module_finalize(const Elf_Ehdr *hdr,
 200                     const Elf_Shdr *sechdrs,
 201                     struct module *me)
 202 {
 203         const Elf_Shdr *s, *text = NULL, *alt = NULL, *locks = NULL,
 204                 *para = NULL;
 205         char *secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
 206
 207         for (s = sechdrs; s < sechdrs + hdr->e_shnum; s++) {
 208                 if (!strcmp(".text", secstrings + s->sh_name))
 209                         text = s;
 210                 if (!strcmp(".altinstructions", secstrings + s->sh_name))
 211                         alt = s;
 212                 if (!strcmp(".smp_locks", secstrings + s->sh_name))
 213                         locks = s;
 214                 if (!strcmp(".parainstructions", secstrings + s->sh_name))
 215                         para = s;
 216         }
 217
 218         if (alt) {
 219                 /* patch .altinstructions */
 220                 void *aseg = (void *)alt->sh_addr;
 221                 apply_alternatives(aseg, aseg + alt->sh_size);
 222         }
 223         if (locks && text) {
 224                 void *lseg = (void *)locks->sh_addr;
 225                 void *tseg = (void *)text->sh_addr;
 226                 alternatives_smp_module_add(me, me->name,
 227                                             lseg, lseg + locks->sh_size,
 228                                             tseg, tseg + text->sh_size);
 229         }
 230
 231         if (para) {
 232                 void *pseg = (void *)para->sh_addr;
 233                 apply_paravirt(pseg, pseg + para->sh_size);
 234         }
 235
 236         /* make jump label nops */
 237         jump_label_apply_nops(me);
 238
 239         return 0;
 240 }
 241
 242 void module_arch_cleanup(struct module *mod)
 243 {
 244         alternatives_smp_module_del(mod);
 245 }