arch/powerpc/kernel/module_32.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*  Kernel module help for PPC.
   3     Copyright (C) 2001 Rusty Russell.
   4
   5 */
   6
   7 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
   8
   9 #include <linux/module.h>
  10 #include <linux/moduleloader.h>
  11 #include <linux/elf.h>
  12 #include <linux/vmalloc.h>
  13 #include <linux/fs.h>
  14 #include <linux/string.h>
  15 #include <linux/kernel.h>
  16 #include <linux/ftrace.h>
  17 #include <linux/cache.h>
  18 #include <linux/bug.h>
  19 #include <linux/sort.h>
  20 #include <asm/setup.h>
  21 #include <asm/code-patching.h>
  22
  23 /* Count how many different relocations (different symbol, different
  24    addend) */
  25 static unsigned int count_relocs(const Elf32_Rela *rela, unsigned int num)
  26 {
  27         unsigned int i, r_info, r_addend, _count_relocs;
  28
  29         _count_relocs = 0;
  30         r_info = 0;
  31         r_addend = 0;
  32         for (i = 0; i < num; i++)
  33                 /* Only count 24-bit relocs, others don't need stubs */
  34                 if (ELF32_R_TYPE(rela[i].r_info) == R_PPC_REL24 &&
  35                     (r_info != ELF32_R_SYM(rela[i].r_info) ||
  36                      r_addend != rela[i].r_addend)) {
  37                         _count_relocs++;
  38                         r_info = ELF32_R_SYM(rela[i].r_info);
  39                         r_addend = rela[i].r_addend;
  40                 }
  41
  42 #ifdef CONFIG_DYNAMIC_FTRACE
  43         _count_relocs++;        /* add one for ftrace_caller */
  44 #endif
  45         return _count_relocs;
  46 }
  47
  48 static int relacmp(const void *_x, const void *_y)
  49 {
  50         const Elf32_Rela *x, *y;
  51
  52         y = (Elf32_Rela *)_x;
  53         x = (Elf32_Rela *)_y;
  54
  55         /* Compare the entire r_info (as opposed to ELF32_R_SYM(r_info) only) to
  56          * make the comparison cheaper/faster. It won't affect the sorting or
  57          * the counting algorithms' performance
  58          */
  59         if (x->r_info < y->r_info)
  60                 return -1;
  61         else if (x->r_info > y->r_info)
  62                 return 1;
  63         else if (x->r_addend < y->r_addend)
  64                 return -1;
  65         else if (x->r_addend > y->r_addend)
  66                 return 1;
  67         else
  68                 return 0;
  69 }
  70
  71 /* Get the potential trampolines size required of the init and
  72    non-init sections */
  73 static unsigned long get_plt_size(const Elf32_Ehdr *hdr,
  74                                   const Elf32_Shdr *sechdrs,
  75                                   const char *secstrings,
  76                                   int is_init)
  77 {
  78         unsigned long ret = 0;
  79         unsigned i;
  80
  81         /* Everything marked ALLOC (this includes the exported
  82            symbols) */
  83         for (i = 1; i < hdr->e_shnum; i++) {
  84                 /* If it's called *.init*, and we're not init, we're
  85                    not interested */
  86                 if ((strstr(secstrings + sechdrs[i].sh_name, ".init") != NULL)
  87                     != is_init)
  88                         continue;
  89
  90                 /* We don't want to look at debug sections. */
  91                 if (strstr(secstrings + sechdrs[i].sh_name, ".debug"))
  92                         continue;
  93
  94                 if (sechdrs[i].sh_type == SHT_RELA) {
  95                         pr_debug("Found relocations in section %u\n", i);
  96                         pr_debug("Ptr: %p.  Number: %u\n",
  97                                (void *)hdr + sechdrs[i].sh_offset,
  98                                sechdrs[i].sh_size / sizeof(Elf32_Rela));
  99
 100                         /* Sort the relocation information based on a symbol and
 101                          * addend key. This is a stable O(n*log n) complexity
 102                          * algorithm but it will reduce the complexity of
 103                          * count_relocs() to linear complexity O(n)
 104                          */
 105                         sort((void *)hdr + sechdrs[i].sh_offset,
 106                              sechdrs[i].sh_size / sizeof(Elf32_Rela),
 107                              sizeof(Elf32_Rela), relacmp, NULL);
 108
 109                         ret += count_relocs((void *)hdr
 110                                              + sechdrs[i].sh_offset,
 111                                              sechdrs[i].sh_size
 112                                              / sizeof(Elf32_Rela))
 113                                 * sizeof(struct ppc_plt_entry);
 114                 }
 115         }
 116
 117         return ret;
 118 }
 119
 120 int module_frob_arch_sections(Elf32_Ehdr *hdr,
 121                               Elf32_Shdr *sechdrs,
 122                               char *secstrings,
 123                               struct module *me)
 124 {
 125         unsigned int i;
 126
 127         /* Find .plt and .init.plt sections */
 128         for (i = 0; i < hdr->e_shnum; i++) {
 129                 if (strcmp(secstrings + sechdrs[i].sh_name, ".init.plt") == 0)
 130                         me->arch.init_plt_section = i;
 131                 else if (strcmp(secstrings + sechdrs[i].sh_name, ".plt") == 0)
 132                         me->arch.core_plt_section = i;
 133         }
 134         if (!me->arch.core_plt_section || !me->arch.init_plt_section) {
 135                 pr_err("Module doesn't contain .plt or .init.plt sections.\n");
 136                 return -ENOEXEC;
 137         }
 138
 139         /* Override their sizes */
 140         sechdrs[me->arch.core_plt_section].sh_size
 141                 = get_plt_size(hdr, sechdrs, secstrings, 0);
 142         sechdrs[me->arch.init_plt_section].sh_size
 143                 = get_plt_size(hdr, sechdrs, secstrings, 1);
 144         return 0;
 145 }
 146
 147 static inline int entry_matches(struct ppc_plt_entry *entry, Elf32_Addr val)
 148 {
 149         if (entry->jump[0] != PPC_RAW_LIS(_R12, PPC_HA(val)))
 150                 return 0;
 151         if (entry->jump[1] != PPC_RAW_ADDI(_R12, _R12, PPC_LO(val)))
 152                 return 0;
 153         return 1;
 154 }
 155
 156 /* Set up a trampoline in the PLT to bounce us to the distant function */
 157 static uint32_t do_plt_call(void *location,
 158                             Elf32_Addr val,
 159                             const Elf32_Shdr *sechdrs,
 160                             struct module *mod)
 161 {
 162         struct ppc_plt_entry *entry;
 163
 164         pr_debug("Doing plt for call to 0x%x at 0x%x\n", val, (unsigned int)location);
 165         /* Init, or core PLT? */
 166         if (within_module_core((unsigned long)location, mod))
 167                 entry = (void *)sechdrs[mod->arch.core_plt_section].sh_addr;
 168         else
 169                 entry = (void *)sechdrs[mod->arch.init_plt_section].sh_addr;
 170
 171         /* Find this entry, or if that fails, the next avail. entry */
 172         while (entry->jump[0]) {
 173                 if (entry_matches(entry, val)) return (uint32_t)entry;
 174                 entry++;
 175         }
 176
 177         if (patch_instruction(&entry->jump[0], ppc_inst(PPC_RAW_LIS(_R12, PPC_HA(val)))))
 178                 return 0;
 179         if (patch_instruction(&entry->jump[1], ppc_inst(PPC_RAW_ADDI(_R12, _R12, PPC_LO(val)))))
 180                 return 0;
 181         if (patch_instruction(&entry->jump[2], ppc_inst(PPC_RAW_MTCTR(_R12))))
 182                 return 0;
 183         if (patch_instruction(&entry->jump[3], ppc_inst(PPC_RAW_BCTR())))
 184                 return 0;
 185
 186         pr_debug("Initialized plt for 0x%x at %p\n", val, entry);
 187         return (uint32_t)entry;
 188 }
 189
 190 static int patch_location_16(uint32_t *loc, u16 value)
 191 {
 192         loc = PTR_ALIGN_DOWN(loc, sizeof(u32));
 193         return patch_instruction(loc, ppc_inst((*loc & 0xffff0000) | value));
 194 }
 195
 196 int apply_relocate_add(Elf32_Shdr *sechdrs,
 197                        const char *strtab,
 198                        unsigned int symindex,
 199                        unsigned int relsec,
 200                        struct module *module)
 201 {
 202         unsigned int i;
 203         Elf32_Rela *rela = (void *)sechdrs[relsec].sh_addr;
 204         Elf32_Sym *sym;
 205         uint32_t *location;
 206         uint32_t value;
 207
 208         pr_debug("Applying ADD relocate section %u to %u\n", relsec,
 209                sechdrs[relsec].sh_info);
 210         for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rela); i++) {
 211                 /* This is where to make the change */
 212                 location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
 213                         + rela[i].r_offset;
 214                 /* This is the symbol it is referring to.  Note that all
 215                    undefined symbols have been resolved.  */
 216                 sym = (Elf32_Sym *)sechdrs[symindex].sh_addr
 217                         + ELF32_R_SYM(rela[i].r_info);
 218                 /* `Everything is relative'. */
 219                 value = sym->st_value + rela[i].r_addend;
 220
 221                 switch (ELF32_R_TYPE(rela[i].r_info)) {
 222                 case R_PPC_ADDR32:
 223                         /* Simply set it */
 224                         *(uint32_t *)location = value;
 225                         break;
 226
 227                 case R_PPC_ADDR16_LO:
 228                         /* Low half of the symbol */
 229                         if (patch_location_16(location, PPC_LO(value)))
 230                                 return -EFAULT;
 231                         break;
 232
 233                 case R_PPC_ADDR16_HI:
 234                         /* Higher half of the symbol */
 235                         if (patch_location_16(location, PPC_HI(value)))
 236                                 return -EFAULT;
 237                         break;
 238
 239                 case R_PPC_ADDR16_HA:
 240                         if (patch_location_16(location, PPC_HA(value)))
 241                                 return -EFAULT;
 242                         break;
 243
 244                 case R_PPC_REL24:
 245                         if ((int)(value - (uint32_t)location) < -0x02000000
 246                             || (int)(value - (uint32_t)location) >= 0x02000000) {
 247                                 value = do_plt_call(location, value,
 248                                                     sechdrs, module);
 249                                 if (!value)
 250                                         return -EFAULT;
 251                         }
 252
 253                         /* Only replace bits 2 through 26 */
 254                         pr_debug("REL24 value = %08X. location = %08X\n",
 255                                value, (uint32_t)location);
 256                         pr_debug("Location before: %08X.\n",
 257                                *(uint32_t *)location);
 258                         value = (*(uint32_t *)location & ~PPC_LI_MASK) |
 259                                 PPC_LI(value - (uint32_t)location);
 260
 261                         if (patch_instruction(location, ppc_inst(value)))
 262                                 return -EFAULT;
 263
 264                         pr_debug("Location after: %08X.\n",
 265                                *(uint32_t *)location);
 266                         pr_debug("ie. jump to %08X+%08X = %08X\n",
 267                                  *(uint32_t *)PPC_LI((uint32_t)location), (uint32_t)location,
 268                                  (*(uint32_t *)PPC_LI((uint32_t)location)) + (uint32_t)location);
 269                         break;
 270
 271                 case R_PPC_REL32:
 272                         /* 32-bit relative jump. */
 273                         *(uint32_t *)location = value - (uint32_t)location;
 274                         break;
 275
 276                 default:
 277                         pr_err("%s: unknown ADD relocation: %u\n",
 278                                module->name,
 279                                ELF32_R_TYPE(rela[i].r_info));
 280                         return -ENOEXEC;
 281                 }
 282         }
 283
 284         return 0;
 285 }
 286
 287 #ifdef CONFIG_DYNAMIC_FTRACE
 288 notrace int module_trampoline_target(struct module *mod, unsigned long addr,
 289                                      unsigned long *target)
 290 {
 291         ppc_inst_t jmp[4];
 292
 293         /* Find where the trampoline jumps to */
 294         if (copy_inst_from_kernel_nofault(jmp, (void *)addr))
 295                 return -EFAULT;
 296         if (__copy_inst_from_kernel_nofault(jmp + 1, (void *)addr + 4))
 297                 return -EFAULT;
 298         if (__copy_inst_from_kernel_nofault(jmp + 2, (void *)addr + 8))
 299                 return -EFAULT;
 300         if (__copy_inst_from_kernel_nofault(jmp + 3, (void *)addr + 12))
 301                 return -EFAULT;
 302
 303         /* verify that this is what we expect it to be */
 304         if ((ppc_inst_val(jmp[0]) & 0xffff0000) != PPC_RAW_LIS(_R12, 0))
 305                 return -EINVAL;
 306         if ((ppc_inst_val(jmp[1]) & 0xffff0000) != PPC_RAW_ADDI(_R12, _R12, 0))
 307                 return -EINVAL;
 308         if (ppc_inst_val(jmp[2]) != PPC_RAW_MTCTR(_R12))
 309                 return -EINVAL;
 310         if (ppc_inst_val(jmp[3]) != PPC_RAW_BCTR())
 311                 return -EINVAL;
 312
 313         addr = (ppc_inst_val(jmp[1]) & 0xffff) | ((ppc_inst_val(jmp[0]) & 0xffff) << 16);
 314         if (addr & 0x8000)
 315                 addr -= 0x10000;
 316
 317         *target = addr;
 318
 319         return 0;
 320 }
 321
 322 int module_finalize_ftrace(struct module *module, const Elf_Shdr *sechdrs)
 323 {
 324         module->arch.tramp = do_plt_call(module->mem[MOD_TEXT].base,
 325                                          (unsigned long)ftrace_caller,
 326                                          sechdrs, module);
 327         if (!module->arch.tramp)
 328                 return -ENOENT;
 329
 330 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
 331         module->arch.tramp_regs = do_plt_call(module->mem[MOD_TEXT].base,
 332                                               (unsigned long)ftrace_regs_caller,
 333                                               sechdrs, module);
 334         if (!module->arch.tramp_regs)
 335                 return -ENOENT;
 336 #endif
 337
 338         return 0;
 339 }
 340 #endif