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         gfp_t gfp_mask = GFP_KERNEL;
  71         void *p;
  72
  73         if (PAGE_ALIGN(size) > MODULES_LEN)
  74                 return NULL;
  75
  76         p = __vmalloc_node_range(size, MODULE_ALIGN,
  77                                     MODULES_VADDR + get_module_load_offset(),
  78                                     MODULES_END, gfp_mask,
  79                                     PAGE_KERNEL, VM_DEFER_KMEMLEAK, NUMA_NO_NODE,
  80                                     __builtin_return_address(0));
  81         if (p && (kasan_module_alloc(p, size, gfp_mask) < 0)) {
  82                 vfree(p);
  83                 return NULL;
  84         }
  85
  86         return p;
  87 }
  88
  89 #ifdef CONFIG_X86_32
  90 int apply_relocate(Elf32_Shdr *sechdrs,
  91                    const char *strtab,
  92                    unsigned int symindex,
  93                    unsigned int relsec,
  94                    struct module *me)
  95 {
  96         unsigned int i;
  97         Elf32_Rel *rel = (void *)sechdrs[relsec].sh_addr;
  98         Elf32_Sym *sym;
  99         uint32_t *location;
 100
 101         DEBUGP("Applying relocate section %u to %u\n",
 102                relsec, sechdrs[relsec].sh_info);
 103         for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) {
 104                 /* This is where to make the change */
 105                 location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
 106                         + rel[i].r_offset;
 107                 /* This is the symbol it is referring to.  Note that all
 108                    undefined symbols have been resolved.  */
 109                 sym = (Elf32_Sym *)sechdrs[symindex].sh_addr
 110                         + ELF32_R_SYM(rel[i].r_info);
 111
 112                 switch (ELF32_R_TYPE(rel[i].r_info)) {
 113                 case R_386_32:
 114                         /* We add the value into the location given */
 115                         *location += sym->st_value;
 116                         break;
 117                 case R_386_PC32:
 118                 case R_386_PLT32:
 119                         /* Add the value, subtract its position */
 120                         *location += sym->st_value - (uint32_t)location;
 121                         break;
 122                 default:
 123                         pr_err("%s: Unknown relocation: %u\n",
 124                                me->name, ELF32_R_TYPE(rel[i].r_info));
 125                         return -ENOEXEC;
 126                 }
 127         }
 128         return 0;
 129 }
 130 #else /*X86_64*/
 131 static int __apply_relocate_add(Elf64_Shdr *sechdrs,
 132                    const char *strtab,
 133                    unsigned int symindex,
 134                    unsigned int relsec,
 135                    struct module *me,
 136                    void *(*write)(void *dest, const void *src, size_t len))
 137 {
 138         unsigned int i;
 139         Elf64_Rela *rel = (void *)sechdrs[relsec].sh_addr;
 140         Elf64_Sym *sym;
 141         void *loc;
 142         u64 val;
 143
 144         DEBUGP("Applying relocate section %u to %u\n",
 145                relsec, sechdrs[relsec].sh_info);
 146         for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) {
 147                 /* This is where to make the change */
 148                 loc = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
 149                         + rel[i].r_offset;
 150
 151                 /* This is the symbol it is referring to.  Note that all
 152                    undefined symbols have been resolved.  */
 153                 sym = (Elf64_Sym *)sechdrs[symindex].sh_addr
 154                         + ELF64_R_SYM(rel[i].r_info);
 155
 156                 DEBUGP("type %d st_value %Lx r_addend %Lx loc %Lx\n",
 157                        (int)ELF64_R_TYPE(rel[i].r_info),
 158                        sym->st_value, rel[i].r_addend, (u64)loc);
 159
 160                 val = sym->st_value + rel[i].r_addend;
 161
 162                 switch (ELF64_R_TYPE(rel[i].r_info)) {
 163                 case R_X86_64_NONE:
 164                         break;
 165                 case R_X86_64_64:
 166                         if (*(u64 *)loc != 0)
 167                                 goto invalid_relocation;
 168                         write(loc, &val, 8);
 169                         break;
 170                 case R_X86_64_32:
 171                         if (*(u32 *)loc != 0)
 172                                 goto invalid_relocation;
 173                         write(loc, &val, 4);
 174                         if (val != *(u32 *)loc)
 175                                 goto overflow;
 176                         break;
 177                 case R_X86_64_32S:
 178                         if (*(s32 *)loc != 0)
 179                                 goto invalid_relocation;
 180                         write(loc, &val, 4);
 181                         if ((s64)val != *(s32 *)loc)
 182                                 goto overflow;
 183                         break;
 184                 case R_X86_64_PC32:
 185                 case R_X86_64_PLT32:
 186                         if (*(u32 *)loc != 0)
 187                                 goto invalid_relocation;
 188                         val -= (u64)loc;
 189                         write(loc, &val, 4);
 190 #if 0
 191                         if ((s64)val != *(s32 *)loc)
 192                                 goto overflow;
 193 #endif
 194                         break;
 195                 case R_X86_64_PC64:
 196                         if (*(u64 *)loc != 0)
 197                                 goto invalid_relocation;
 198                         val -= (u64)loc;
 199                         write(loc, &val, 8);
 200                         break;
 201                 default:
 202                         pr_err("%s: Unknown rela relocation: %llu\n",
 203                                me->name, ELF64_R_TYPE(rel[i].r_info));
 204                         return -ENOEXEC;
 205                 }
 206         }
 207         return 0;
 208
 209 invalid_relocation:
 210         pr_err("x86/modules: Skipping invalid relocation target, existing value is nonzero for type %d, loc %p, val %Lx\n",
 211                (int)ELF64_R_TYPE(rel[i].r_info), loc, val);
 212         return -ENOEXEC;
 213
 214 overflow:
 215         pr_err("overflow in relocation type %d val %Lx\n",
 216                (int)ELF64_R_TYPE(rel[i].r_info), val);
 217         pr_err("`%s' likely not compiled with -mcmodel=kernel\n",
 218                me->name);
 219         return -ENOEXEC;
 220 }
 221
 222 int apply_relocate_add(Elf64_Shdr *sechdrs,
 223                    const char *strtab,
 224                    unsigned int symindex,
 225                    unsigned int relsec,
 226                    struct module *me)
 227 {
 228         int ret;
 229         bool early = me->state == MODULE_STATE_UNFORMED;
 230         void *(*write)(void *, const void *, size_t) = memcpy;
 231
 232         if (!early) {
 233                 write = text_poke;
 234                 mutex_lock(&text_mutex);
 235         }
 236
 237         ret = __apply_relocate_add(sechdrs, strtab, symindex, relsec, me,
 238                                    write);
 239
 240         if (!early) {
 241                 text_poke_sync();
 242                 mutex_unlock(&text_mutex);
 243         }
 244
 245         return ret;
 246 }
 247
 248 #endif
 249
 250 int module_finalize(const Elf_Ehdr *hdr,
 251                     const Elf_Shdr *sechdrs,
 252                     struct module *me)
 253 {
 254         const Elf_Shdr *s, *text = NULL, *alt = NULL, *locks = NULL,
 255                 *para = NULL, *orc = NULL, *orc_ip = NULL,
 256                 *retpolines = NULL, *returns = NULL;
 257         char *secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
 258
 259         for (s = sechdrs; s < sechdrs + hdr->e_shnum; s++) {
 260                 if (!strcmp(".text", secstrings + s->sh_name))
 261                         text = s;
 262                 if (!strcmp(".altinstructions", secstrings + s->sh_name))
 263                         alt = s;
 264                 if (!strcmp(".smp_locks", secstrings + s->sh_name))
 265                         locks = s;
 266                 if (!strcmp(".parainstructions", secstrings + s->sh_name))
 267                         para = s;
 268                 if (!strcmp(".orc_unwind", secstrings + s->sh_name))
 269                         orc = s;
 270                 if (!strcmp(".orc_unwind_ip", secstrings + s->sh_name))
 271                         orc_ip = s;
 272                 if (!strcmp(".retpoline_sites", secstrings + s->sh_name))
 273                         retpolines = s;
 274                 if (!strcmp(".return_sites", secstrings + s->sh_name))
 275                         returns = s;
 276         }
 277
 278         /*
 279          * See alternative_instructions() for the ordering rules between the
 280          * various patching types.
 281          */
 282         if (para) {
 283                 void *pseg = (void *)para->sh_addr;
 284                 apply_paravirt(pseg, pseg + para->sh_size);
 285         }
 286         if (retpolines) {
 287                 void *rseg = (void *)retpolines->sh_addr;
 288                 apply_retpolines(rseg, rseg + retpolines->sh_size);
 289         }
 290         if (returns) {
 291                 void *rseg = (void *)returns->sh_addr;
 292                 apply_returns(rseg, rseg + returns->sh_size);
 293         }
 294         if (alt) {
 295                 /* patch .altinstructions */
 296                 void *aseg = (void *)alt->sh_addr;
 297                 apply_alternatives(aseg, aseg + alt->sh_size);
 298         }
 299         if (locks && text) {
 300                 void *lseg = (void *)locks->sh_addr;
 301                 void *tseg = (void *)text->sh_addr;
 302                 alternatives_smp_module_add(me, me->name,
 303                                             lseg, lseg + locks->sh_size,
 304                                             tseg, tseg + text->sh_size);
 305         }
 306
 307         /* make jump label nops */
 308         jump_label_apply_nops(me);
 309
 310         if (orc && orc_ip)
 311                 unwind_module_init(me, (void *)orc_ip->sh_addr, orc_ip->sh_size,
 312                                    (void *)orc->sh_addr, orc->sh_size);
 313
 314         return 0;
 315 }
 316
 317 void module_arch_cleanup(struct module *mod)
 318 {
 319         alternatives_smp_module_del(mod);
 320 }