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
  22 /* Count how many different relocations (different symbol, different
  23    addend) */
  24 static unsigned int count_relocs(const Elf32_Rela *rela, unsigned int num)
  25 {
  26         unsigned int i, r_info, r_addend, _count_relocs;
  27
  28         _count_relocs = 0;
  29         r_info = 0;
  30         r_addend = 0;
  31         for (i = 0; i < num; i++)
  32                 /* Only count 24-bit relocs, others don't need stubs */
  33                 if (ELF32_R_TYPE(rela[i].r_info) == R_PPC_REL24 &&
  34                     (r_info != ELF32_R_SYM(rela[i].r_info) ||
  35                      r_addend != rela[i].r_addend)) {
  36                         _count_relocs++;
  37                         r_info = ELF32_R_SYM(rela[i].r_info);
  38                         r_addend = rela[i].r_addend;
  39                 }
  40
  41 #ifdef CONFIG_DYNAMIC_FTRACE
  42         _count_relocs++;        /* add one for ftrace_caller */
  43 #endif
  44         return _count_relocs;
  45 }
  46
  47 static int relacmp(const void *_x, const void *_y)
  48 {
  49         const Elf32_Rela *x, *y;
  50
  51         y = (Elf32_Rela *)_x;
  52         x = (Elf32_Rela *)_y;
  53
  54         /* Compare the entire r_info (as opposed to ELF32_R_SYM(r_info) only) to
  55          * make the comparison cheaper/faster. It won't affect the sorting or
  56          * the counting algorithms' performance
  57          */
  58         if (x->r_info < y->r_info)
  59                 return -1;
  60         else if (x->r_info > y->r_info)
  61                 return 1;
  62         else if (x->r_addend < y->r_addend)
  63                 return -1;
  64         else if (x->r_addend > y->r_addend)
  65                 return 1;
  66         else
  67                 return 0;
  68 }
  69
  70 /* Get the potential trampolines size required of the init and
  71    non-init sections */
  72 static unsigned long get_plt_size(const Elf32_Ehdr *hdr,
  73                                   const Elf32_Shdr *sechdrs,
  74                                   const char *secstrings,
  75                                   int is_init)
  76 {
  77         unsigned long ret = 0;
  78         unsigned i;
  79
  80         /* Everything marked ALLOC (this includes the exported
  81            symbols) */
  82         for (i = 1; i < hdr->e_shnum; i++) {
  83                 /* If it's called *.init*, and we're not init, we're
  84                    not interested */
  85                 if ((strstr(secstrings + sechdrs[i].sh_name, ".init") != NULL)
  86                     != is_init)
  87                         continue;
  88
  89                 /* We don't want to look at debug sections. */
  90                 if (strstr(secstrings + sechdrs[i].sh_name, ".debug"))
  91                         continue;
  92
  93                 if (sechdrs[i].sh_type == SHT_RELA) {
  94                         pr_debug("Found relocations in section %u\n", i);
  95                         pr_debug("Ptr: %p.  Number: %u\n",
  96                                (void *)hdr + sechdrs[i].sh_offset,
  97                                sechdrs[i].sh_size / sizeof(Elf32_Rela));
  98
  99                         /* Sort the relocation information based on a symbol and
 100                          * addend key. This is a stable O(n*log n) complexity
 101                          * alogrithm but it will reduce the complexity of
 102                          * count_relocs() to linear complexity O(n)
 103                          */
 104                         sort((void *)hdr + sechdrs[i].sh_offset,
 105                              sechdrs[i].sh_size / sizeof(Elf32_Rela),
 106                              sizeof(Elf32_Rela), relacmp, NULL);
 107
 108                         ret += count_relocs((void *)hdr
 109                                              + sechdrs[i].sh_offset,
 110                                              sechdrs[i].sh_size
 111                                              / sizeof(Elf32_Rela))
 112                                 * sizeof(struct ppc_plt_entry);
 113                 }
 114         }
 115
 116         return ret;
 117 }
 118
 119 int module_frob_arch_sections(Elf32_Ehdr *hdr,
 120                               Elf32_Shdr *sechdrs,
 121                               char *secstrings,
 122                               struct module *me)
 123 {
 124         unsigned int i;
 125
 126         /* Find .plt and .init.plt sections */
 127         for (i = 0; i < hdr->e_shnum; i++) {
 128                 if (strcmp(secstrings + sechdrs[i].sh_name, ".init.plt") == 0)
 129                         me->arch.init_plt_section = i;
 130                 else if (strcmp(secstrings + sechdrs[i].sh_name, ".plt") == 0)
 131                         me->arch.core_plt_section = i;
 132         }
 133         if (!me->arch.core_plt_section || !me->arch.init_plt_section) {
 134                 pr_err("Module doesn't contain .plt or .init.plt sections.\n");
 135                 return -ENOEXEC;
 136         }
 137
 138         /* Override their sizes */
 139         sechdrs[me->arch.core_plt_section].sh_size
 140                 = get_plt_size(hdr, sechdrs, secstrings, 0);
 141         sechdrs[me->arch.init_plt_section].sh_size
 142                 = get_plt_size(hdr, sechdrs, secstrings, 1);
 143         return 0;
 144 }
 145
 146 static inline int entry_matches(struct ppc_plt_entry *entry, Elf32_Addr val)
 147 {
 148         if (entry->jump[0] != PPC_RAW_LIS(_R12, PPC_HA(val)))
 149                 return 0;
 150         if (entry->jump[1] != PPC_RAW_ADDI(_R12, _R12, PPC_LO(val)))
 151                 return 0;
 152         return 1;
 153 }
 154
 155 /* Set up a trampoline in the PLT to bounce us to the distant function */
 156 static uint32_t do_plt_call(void *location,
 157                             Elf32_Addr val,
 158                             const Elf32_Shdr *sechdrs,
 159                             struct module *mod)
 160 {
 161         struct ppc_plt_entry *entry;
 162
 163         pr_debug("Doing plt for call to 0x%x at 0x%x\n", val, (unsigned int)location);
 164         /* Init, or core PLT? */
 165         if (location >= mod->core_layout.base
 166             && location < mod->core_layout.base + mod->core_layout.size)
 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         entry->jump[0] = PPC_RAW_LIS(_R12, PPC_HA(val));
 178         entry->jump[1] = PPC_RAW_ADDI(_R12, _R12, PPC_LO(val));
 179         entry->jump[2] = PPC_RAW_MTCTR(_R12);
 180         entry->jump[3] = PPC_RAW_BCTR();
 181
 182         pr_debug("Initialized plt for 0x%x at %p\n", val, entry);
 183         return (uint32_t)entry;
 184 }
 185
 186 int apply_relocate_add(Elf32_Shdr *sechdrs,
 187                        const char *strtab,
 188                        unsigned int symindex,
 189                        unsigned int relsec,
 190                        struct module *module)
 191 {
 192         unsigned int i;
 193         Elf32_Rela *rela = (void *)sechdrs[relsec].sh_addr;
 194         Elf32_Sym *sym;
 195         uint32_t *location;
 196         uint32_t value;
 197
 198         pr_debug("Applying ADD relocate section %u to %u\n", relsec,
 199                sechdrs[relsec].sh_info);
 200         for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rela); i++) {
 201                 /* This is where to make the change */
 202                 location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
 203                         + rela[i].r_offset;
 204                 /* This is the symbol it is referring to.  Note that all
 205                    undefined symbols have been resolved.  */
 206                 sym = (Elf32_Sym *)sechdrs[symindex].sh_addr
 207                         + ELF32_R_SYM(rela[i].r_info);
 208                 /* `Everything is relative'. */
 209                 value = sym->st_value + rela[i].r_addend;
 210
 211                 switch (ELF32_R_TYPE(rela[i].r_info)) {
 212                 case R_PPC_ADDR32:
 213                         /* Simply set it */
 214                         *(uint32_t *)location = value;
 215                         break;
 216
 217                 case R_PPC_ADDR16_LO:
 218                         /* Low half of the symbol */
 219                         *(uint16_t *)location = value;
 220                         break;
 221
 222                 case R_PPC_ADDR16_HI:
 223                         /* Higher half of the symbol */
 224                         *(uint16_t *)location = (value >> 16);
 225                         break;
 226
 227                 case R_PPC_ADDR16_HA:
 228                         /* Sign-adjusted lower 16 bits: PPC ELF ABI says:
 229                            (((x >> 16) + ((x & 0x8000) ? 1 : 0))) & 0xFFFF.
 230                            This is the same, only sane.
 231                          */
 232                         *(uint16_t *)location = (value + 0x8000) >> 16;
 233                         break;
 234
 235                 case R_PPC_REL24:
 236                         if ((int)(value - (uint32_t)location) < -0x02000000
 237                             || (int)(value - (uint32_t)location) >= 0x02000000)
 238                                 value = do_plt_call(location, value,
 239                                                     sechdrs, module);
 240
 241                         /* Only replace bits 2 through 26 */
 242                         pr_debug("REL24 value = %08X. location = %08X\n",
 243                                value, (uint32_t)location);
 244                         pr_debug("Location before: %08X.\n",
 245                                *(uint32_t *)location);
 246                         *(uint32_t *)location
 247                                 = (*(uint32_t *)location & ~0x03fffffc)
 248                                 | ((value - (uint32_t)location)
 249                                    & 0x03fffffc);
 250                         pr_debug("Location after: %08X.\n",
 251                                *(uint32_t *)location);
 252                         pr_debug("ie. jump to %08X+%08X = %08X\n",
 253                                *(uint32_t *)location & 0x03fffffc,
 254                                (uint32_t)location,
 255                                (*(uint32_t *)location & 0x03fffffc)
 256                                + (uint32_t)location);
 257                         break;
 258
 259                 case R_PPC_REL32:
 260                         /* 32-bit relative jump. */
 261                         *(uint32_t *)location = value - (uint32_t)location;
 262                         break;
 263
 264                 default:
 265                         pr_err("%s: unknown ADD relocation: %u\n",
 266                                module->name,
 267                                ELF32_R_TYPE(rela[i].r_info));
 268                         return -ENOEXEC;
 269                 }
 270         }
 271
 272         return 0;
 273 }
 274
 275 #ifdef CONFIG_DYNAMIC_FTRACE
 276 int module_finalize_ftrace(struct module *module, const Elf_Shdr *sechdrs)
 277 {
 278         module->arch.tramp = do_plt_call(module->core_layout.base,
 279                                          (unsigned long)ftrace_caller,
 280                                          sechdrs, module);
 281         if (!module->arch.tramp)
 282                 return -ENOENT;
 283
 284         return 0;
 285 }
 286 #endif