arch/x86/kernel/module.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*  Kernel module help for x86.
   3     Copyright (C) 2001 Rusty Russell.
   4
   5 */
   6
   7 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
   8
   9 #include <linux/moduleloader.h>
  10 #include <linux/elf.h>
  11 #include <linux/vmalloc.h>
  12 #include <linux/fs.h>
  13 #include <linux/string.h>
  14 #include <linux/kernel.h>
  15 #include <linux/kasan.h>
  16 #include <linux/bug.h>
  17 #include <linux/mm.h>
  18 #include <linux/gfp.h>
  19 #include <linux/jump_label.h>
  20 #include <linux/random.h>
  21 #include <linux/memory.h>
  22
  23 #include <asm/text-patching.h>
  24 #include <asm/page.h>
  25 #include <asm/setup.h>
  26 #include <asm/unwind.h>
  27
  28 #if 0
  29 #define DEBUGP(fmt, ...)                                \
  30         printk(KERN_DEBUG fmt, ##__VA_ARGS__)
  31 #else
  32 #define DEBUGP(fmt, ...)                                \
  33 do {                                                    \
  34         if (0)                                          \
  35                 printk(KERN_DEBUG fmt, ##__VA_ARGS__);  \
  36 } while (0)
  37 #endif
  38
  39 #ifdef CONFIG_RANDOMIZE_BASE
  40 static unsigned long module_load_offset;
  41
  42 /* Mutex protects the module_load_offset. */
  43 static DEFINE_MUTEX(module_kaslr_mutex);
  44
  45 static unsigned long int get_module_load_offset(void)
  46 {
  47         if (kaslr_enabled()) {
  48                 mutex_lock(&module_kaslr_mutex);
  49                 /*
  50                  * Calculate the module_load_offset the first time this
  51                  * code is called. Once calculated it stays the same until
  52                  * reboot.
  53                  */
  54                 if (module_load_offset == 0)
  55                         module_load_offset =
  56                                 (get_random_int() % 1024 + 1) * PAGE_SIZE;
  57                 mutex_unlock(&module_kaslr_mutex);
  58         }
  59         return module_load_offset;
  60 }
  61 #else
  62 static unsigned long int get_module_load_offset(void)
  63 {
  64         return 0;
  65 }
  66 #endif
  67
  68 void *module_alloc(unsigned long size)
  69 {
  70         void *p;
  71
  72         if (PAGE_ALIGN(size) > MODULES_LEN)
  73                 return NULL;
  74
  75         p = __vmalloc_node_range(size, MODULE_ALIGN,
  76                                     MODULES_VADDR + get_module_load_offset(),
  77                                     MODULES_END, GFP_KERNEL,
  78                                     PAGE_KERNEL, 0, NUMA_NO_NODE,
  79                                     __builtin_return_address(0));
  80         if (p && (kasan_module_alloc(p, size) < 0)) {
  81                 vfree(p);
  82                 return NULL;
  83         }
  84
  85         return p;
  86 }
  87
  88 #ifdef CONFIG_X86_32
  89 int apply_relocate(Elf32_Shdr *sechdrs,
  90                    const char *strtab,
  91                    unsigned int symindex,
  92                    unsigned int relsec,
  93                    struct module *me)
  94 {
  95         unsigned int i;
  96         Elf32_Rel *rel = (void *)sechdrs[relsec].sh_addr;
  97         Elf32_Sym *sym;
  98         uint32_t *location;
  99
 100         DEBUGP("Applying relocate section %u to %u\n",
 101                relsec, sechdrs[relsec].sh_info);
 102         for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) {
 103                 /* This is where to make the change */
 104                 location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
 105                         + rel[i].r_offset;
 106                 /* This is the symbol it is referring to.  Note that all
 107                    undefined symbols have been resolved.  */
 108                 sym = (Elf32_Sym *)sechdrs[symindex].sh_addr
 109                         + ELF32_R_SYM(rel[i].r_info);
 110
 111                 switch (ELF32_R_TYPE(rel[i].r_info)) {
 112                 case R_386_32:
 113                         /* We add the value into the location given */
 114                         *location += sym->st_value;
 115                         break;
 116                 case R_386_PC32:
 117                 case R_386_PLT32:
 118                         /* Add the value, subtract its position */
 119                         *location += sym->st_value - (uint32_t)location;
 120                         break;
 121                 default:
 122                         pr_err("%s: Unknown relocation: %u\n",
 123                                me->name, ELF32_R_TYPE(rel[i].r_info));
 124                         return -ENOEXEC;
 125                 }
 126         }
 127         return 0;
 128 }
 129 #else /*X86_64*/
 130 static int __apply_relocate_add(Elf64_Shdr *sechdrs,
 131                    const char *strtab,
 132                    unsigned int symindex,
 133                    unsigned int relsec,
 134                    struct module *me,
 135                    void *(*write)(void *dest, const void *src, size_t len))
 136 {
 137         unsigned int i;
 138         Elf64_Rela *rel = (void *)sechdrs[relsec].sh_addr;
 139         Elf64_Sym *sym;
 140         void *loc;
 141         u64 val;
 142
 143         DEBUGP("Applying relocate section %u to %u\n",
 144                relsec, sechdrs[relsec].sh_info);
 145         for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) {
 146                 /* This is where to make the change */
 147                 loc = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
 148                         + rel[i].r_offset;
 149
 150                 /* This is the symbol it is referring to.  Note that all
 151                    undefined symbols have been resolved.  */
 152                 sym = (Elf64_Sym *)sechdrs[symindex].sh_addr
 153                         + ELF64_R_SYM(rel[i].r_info);
 154
 155                 DEBUGP("type %d st_value %Lx r_addend %Lx loc %Lx\n",
 156                        (int)ELF64_R_TYPE(rel[i].r_info),
 157                        sym->st_value, rel[i].r_addend, (u64)loc);
 158
 159                 val = sym->st_value + rel[i].r_addend;
 160
 161                 switch (ELF64_R_TYPE(rel[i].r_info)) {
 162                 case R_X86_64_NONE:
 163                         break;
 164                 case R_X86_64_64:
 165                         if (*(u64 *)loc != 0)
 166                                 goto invalid_relocation;
 167                         write(loc, &val, 8);
 168                         break;
 169                 case R_X86_64_32:
 170                         if (*(u32 *)loc != 0)
 171                                 goto invalid_relocation;
 172                         write(loc, &val, 4);
 173                         if (val != *(u32 *)loc)
 174                                 goto overflow;
 175                         break;
 176                 case R_X86_64_32S:
 177                         if (*(s32 *)loc != 0)
 178                                 goto invalid_relocation;
 179                         write(loc, &val, 4);
 180                         if ((s64)val != *(s32 *)loc)
 181                                 goto overflow;
 182                         break;
 183                 case R_X86_64_PC32:
 184                 case R_X86_64_PLT32:
 185                         if (*(u32 *)loc != 0)
 186                                 goto invalid_relocation;
 187                         val -= (u64)loc;
 188                         write(loc, &val, 4);
 189 #if 0
 190                         if ((s64)val != *(s32 *)loc)
 191                                 goto overflow;
 192 #endif
 193                         break;
 194                 case R_X86_64_PC64:
 195                         if (*(u64 *)loc != 0)
 196                                 goto invalid_relocation;
 197                         val -= (u64)loc;
 198                         write(loc, &val, 8);
 199                         break;
 200                 default:
 201                         pr_err("%s: Unknown rela relocation: %llu\n",
 202                                me->name, ELF64_R_TYPE(rel[i].r_info));
 203                         return -ENOEXEC;
 204                 }
 205         }
 206         return 0;
 207
 208 invalid_relocation:
 209         pr_err("x86/modules: Skipping invalid relocation target, existing value is nonzero for type %d, loc %p, val %Lx\n",
 210                (int)ELF64_R_TYPE(rel[i].r_info), loc, val);
 211         return -ENOEXEC;
 212
 213 overflow:
 214         pr_err("overflow in relocation type %d val %Lx\n",
 215                (int)ELF64_R_TYPE(rel[i].r_info), val);
 216         pr_err("`%s' likely not compiled with -mcmodel=kernel\n",
 217                me->name);
 218         return -ENOEXEC;
 219 }
 220
 221 int apply_relocate_add(Elf64_Shdr *sechdrs,
 222                    const char *strtab,
 223                    unsigned int symindex,
 224                    unsigned int relsec,
 225                    struct module *me)
 226 {
 227         int ret;
 228         bool early = me->state == MODULE_STATE_UNFORMED;
 229         void *(*write)(void *, const void *, size_t) = memcpy;
 230
 231         if (!early) {
 232                 write = text_poke;
 233                 mutex_lock(&text_mutex);
 234         }
 235
 236         ret = __apply_relocate_add(sechdrs, strtab, symindex, relsec, me,
 237                                    write);
 238
 239         if (!early) {
 240                 text_poke_sync();
 241                 mutex_unlock(&text_mutex);
 242         }
 243
 244         return ret;
 245 }
 246
 247 #endif
 248
 249 int module_finalize(const Elf_Ehdr *hdr,
 250                     const Elf_Shdr *sechdrs,
 251                     struct module *me)
 252 {
 253         const Elf_Shdr *s, *text = NULL, *alt = NULL, *locks = NULL,
 254                 *para = NULL, *orc = NULL, *orc_ip = NULL;
 255         char *secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
 256
 257         for (s = sechdrs; s < sechdrs + hdr->e_shnum; s++) {
 258                 if (!strcmp(".text", secstrings + s->sh_name))
 259                         text = s;
 260                 if (!strcmp(".altinstructions", secstrings + s->sh_name))
 261                         alt = s;
 262                 if (!strcmp(".smp_locks", secstrings + s->sh_name))
 263                         locks = s;
 264                 if (!strcmp(".parainstructions", secstrings + s->sh_name))
 265                         para = s;
 266                 if (!strcmp(".orc_unwind", secstrings + s->sh_name))
 267                         orc = s;
 268                 if (!strcmp(".orc_unwind_ip", secstrings + s->sh_name))
 269                         orc_ip = s;
 270         }
 271
 272         if (alt) {
 273                 /* patch .altinstructions */
 274                 void *aseg = (void *)alt->sh_addr;
 275                 apply_alternatives(aseg, aseg + alt->sh_size);
 276         }
 277         if (locks && text) {
 278                 void *lseg = (void *)locks->sh_addr;
 279                 void *tseg = (void *)text->sh_addr;
 280                 alternatives_smp_module_add(me, me->name,
 281                                             lseg, lseg + locks->sh_size,
 282                                             tseg, tseg + text->sh_size);
 283         }
 284
 285         if (para) {
 286                 void *pseg = (void *)para->sh_addr;
 287                 apply_paravirt(pseg, pseg + para->sh_size);
 288         }
 289
 290         /* make jump label nops */
 291         jump_label_apply_nops(me);
 292
 293         if (orc && orc_ip)
 294                 unwind_module_init(me, (void *)orc_ip->sh_addr, orc_ip->sh_size,
 295                                    (void *)orc->sh_addr, orc->sh_size);
 296
 297         return 0;
 298 }
 299
 300 void module_arch_cleanup(struct module *mod)
 301 {
 302         alternatives_smp_module_del(mod);
 303 }