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 (location >= mod->core_layout.base
 167             && location < mod->core_layout.base + mod->core_layout.size)
 168                 entry = (void *)sechdrs[mod->arch.core_plt_section].sh_addr;
 169         else
 170                 entry = (void *)sechdrs[mod->arch.init_plt_section].sh_addr;
 171
 172         /* Find this entry, or if that fails, the next avail. entry */
 173         while (entry->jump[0]) {
 174                 if (entry_matches(entry, val)) return (uint32_t)entry;
 175                 entry++;
 176         }
 177
 178         if (patch_instruction(&entry->jump[0], ppc_inst(PPC_RAW_LIS(_R12, PPC_HA(val)))))
 179                 return 0;
 180         if (patch_instruction(&entry->jump[1], ppc_inst(PPC_RAW_ADDI(_R12, _R12, PPC_LO(val)))))
 181                 return 0;
 182         if (patch_instruction(&entry->jump[2], ppc_inst(PPC_RAW_MTCTR(_R12))))
 183                 return 0;
 184         if (patch_instruction(&entry->jump[3], ppc_inst(PPC_RAW_BCTR())))
 185                 return 0;
 186
 187         pr_debug("Initialized plt for 0x%x at %p\n", val, entry);
 188         return (uint32_t)entry;
 189 }
 190
 191 static int patch_location_16(uint32_t *loc, u16 value)
 192 {
 193         loc = PTR_ALIGN_DOWN(loc, sizeof(u32));
 194         return patch_instruction(loc, ppc_inst((*loc & 0xffff0000) | value));
 195 }
 196
 197 int apply_relocate_add(Elf32_Shdr *sechdrs,
 198                        const char *strtab,
 199                        unsigned int symindex,
 200                        unsigned int relsec,
 201                        struct module *module)
 202 {
 203         unsigned int i;
 204         Elf32_Rela *rela = (void *)sechdrs[relsec].sh_addr;
 205         Elf32_Sym *sym;
 206         uint32_t *location;
 207         uint32_t value;
 208
 209         pr_debug("Applying ADD relocate section %u to %u\n", relsec,
 210                sechdrs[relsec].sh_info);
 211         for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rela); i++) {
 212                 /* This is where to make the change */
 213                 location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
 214                         + rela[i].r_offset;
 215                 /* This is the symbol it is referring to.  Note that all
 216                    undefined symbols have been resolved.  */
 217                 sym = (Elf32_Sym *)sechdrs[symindex].sh_addr
 218                         + ELF32_R_SYM(rela[i].r_info);
 219                 /* `Everything is relative'. */
 220                 value = sym->st_value + rela[i].r_addend;
 221
 222                 switch (ELF32_R_TYPE(rela[i].r_info)) {
 223                 case R_PPC_ADDR32:
 224                         /* Simply set it */
 225                         *(uint32_t *)location = value;
 226                         break;
 227
 228                 case R_PPC_ADDR16_LO:
 229                         /* Low half of the symbol */
 230                         if (patch_location_16(location, PPC_LO(value)))
 231                                 return -EFAULT;
 232                         break;
 233
 234                 case R_PPC_ADDR16_HI:
 235                         /* Higher half of the symbol */
 236                         if (patch_location_16(location, PPC_HI(value)))
 237                                 return -EFAULT;
 238                         break;
 239
 240                 case R_PPC_ADDR16_HA:
 241                         if (patch_location_16(location, PPC_HA(value)))
 242                                 return -EFAULT;
 243                         break;
 244
 245                 case R_PPC_REL24:
 246                         if ((int)(value - (uint32_t)location) < -0x02000000
 247                             || (int)(value - (uint32_t)location) >= 0x02000000) {
 248                                 value = do_plt_call(location, value,
 249                                                     sechdrs, module);
 250                                 if (!value)
 251                                         return -EFAULT;
 252                         }
 253
 254                         /* Only replace bits 2 through 26 */
 255                         pr_debug("REL24 value = %08X. location = %08X\n",
 256                                value, (uint32_t)location);
 257                         pr_debug("Location before: %08X.\n",
 258                                *(uint32_t *)location);
 259                         value = (*(uint32_t *)location & ~PPC_LI_MASK) |
 260                                 PPC_LI(value - (uint32_t)location);
 261
 262                         if (patch_instruction(location, ppc_inst(value)))
 263                                 return -EFAULT;
 264
 265                         pr_debug("Location after: %08X.\n",
 266                                *(uint32_t *)location);
 267                         pr_debug("ie. jump to %08X+%08X = %08X\n",
 268                                  *(uint32_t *)PPC_LI((uint32_t)location), (uint32_t)location,
 269                                  (*(uint32_t *)PPC_LI((uint32_t)location)) + (uint32_t)location);
 270                         break;
 271
 272                 case R_PPC_REL32:
 273                         /* 32-bit relative jump. */
 274                         *(uint32_t *)location = value - (uint32_t)location;
 275                         break;
 276
 277                 default:
 278                         pr_err("%s: unknown ADD relocation: %u\n",
 279                                module->name,
 280                                ELF32_R_TYPE(rela[i].r_info));
 281                         return -ENOEXEC;
 282                 }
 283         }
 284
 285         return 0;
 286 }
 287
 288 #ifdef CONFIG_DYNAMIC_FTRACE
 289 notrace int module_trampoline_target(struct module *mod, unsigned long addr,
 290                                      unsigned long *target)
 291 {
 292         ppc_inst_t jmp[4];
 293
 294         /* Find where the trampoline jumps to */
 295         if (copy_inst_from_kernel_nofault(jmp, (void *)addr))
 296                 return -EFAULT;
 297         if (__copy_inst_from_kernel_nofault(jmp + 1, (void *)addr + 4))
 298                 return -EFAULT;
 299         if (__copy_inst_from_kernel_nofault(jmp + 2, (void *)addr + 8))
 300                 return -EFAULT;
 301         if (__copy_inst_from_kernel_nofault(jmp + 3, (void *)addr + 12))
 302                 return -EFAULT;
 303
 304         /* verify that this is what we expect it to be */
 305         if ((ppc_inst_val(jmp[0]) & 0xffff0000) != PPC_RAW_LIS(_R12, 0))
 306                 return -EINVAL;
 307         if ((ppc_inst_val(jmp[1]) & 0xffff0000) != PPC_RAW_ADDI(_R12, _R12, 0))
 308                 return -EINVAL;
 309         if (ppc_inst_val(jmp[2]) != PPC_RAW_MTCTR(_R12))
 310                 return -EINVAL;
 311         if (ppc_inst_val(jmp[3]) != PPC_RAW_BCTR())
 312                 return -EINVAL;
 313
 314         addr = (ppc_inst_val(jmp[1]) & 0xffff) | ((ppc_inst_val(jmp[0]) & 0xffff) << 16);
 315         if (addr & 0x8000)
 316                 addr -= 0x10000;
 317
 318         *target = addr;
 319
 320         return 0;
 321 }
 322
 323 int module_finalize_ftrace(struct module *module, const Elf_Shdr *sechdrs)
 324 {
 325         module->arch.tramp = do_plt_call(module->core_layout.base,
 326                                          (unsigned long)ftrace_caller,
 327                                          sechdrs, module);
 328         if (!module->arch.tramp)
 329                 return -ENOENT;
 330
 331 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
 332         module->arch.tramp_regs = do_plt_call(module->core_layout.base,
 333                                               (unsigned long)ftrace_regs_caller,
 334                                               sechdrs, module);
 335         if (!module->arch.tramp_regs)
 336                 return -ENOENT;
 337 #endif
 338
 339         return 0;
 340 }
 341 #endif