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 static void relaswap(void *_x, void *_y, int size)
  71 {
  72         uint32_t *x, *y, tmp;
  73         int i;
  74
  75         y = (uint32_t *)_x;
  76         x = (uint32_t *)_y;
  77
  78         for (i = 0; i < sizeof(Elf32_Rela) / sizeof(uint32_t); i++) {
  79                 tmp = x[i];
  80                 x[i] = y[i];
  81                 y[i] = tmp;
  82         }
  83 }
  84
  85 /* Get the potential trampolines size required of the init and
  86    non-init sections */
  87 static unsigned long get_plt_size(const Elf32_Ehdr *hdr,
  88                                   const Elf32_Shdr *sechdrs,
  89                                   const char *secstrings,
  90                                   int is_init)
  91 {
  92         unsigned long ret = 0;
  93         unsigned i;
  94
  95         /* Everything marked ALLOC (this includes the exported
  96            symbols) */
  97         for (i = 1; i < hdr->e_shnum; i++) {
  98                 /* If it's called *.init*, and we're not init, we're
  99                    not interested */
 100                 if ((strstr(secstrings + sechdrs[i].sh_name, ".init") != NULL)
 101                     != is_init)
 102                         continue;
 103
 104                 /* We don't want to look at debug sections. */
 105                 if (strstr(secstrings + sechdrs[i].sh_name, ".debug"))
 106                         continue;
 107
 108                 if (sechdrs[i].sh_type == SHT_RELA) {
 109                         pr_debug("Found relocations in section %u\n", i);
 110                         pr_debug("Ptr: %p.  Number: %u\n",
 111                                (void *)hdr + sechdrs[i].sh_offset,
 112                                sechdrs[i].sh_size / sizeof(Elf32_Rela));
 113
 114                         /* Sort the relocation information based on a symbol and
 115                          * addend key. This is a stable O(n*log n) complexity
 116                          * alogrithm but it will reduce the complexity of
 117                          * count_relocs() to linear complexity O(n)
 118                          */
 119                         sort((void *)hdr + sechdrs[i].sh_offset,
 120                              sechdrs[i].sh_size / sizeof(Elf32_Rela),
 121                              sizeof(Elf32_Rela), relacmp, relaswap);
 122
 123                         ret += count_relocs((void *)hdr
 124                                              + sechdrs[i].sh_offset,
 125                                              sechdrs[i].sh_size
 126                                              / sizeof(Elf32_Rela))
 127                                 * sizeof(struct ppc_plt_entry);
 128                 }
 129         }
 130
 131         return ret;
 132 }
 133
 134 int module_frob_arch_sections(Elf32_Ehdr *hdr,
 135                               Elf32_Shdr *sechdrs,
 136                               char *secstrings,
 137                               struct module *me)
 138 {
 139         unsigned int i;
 140
 141         /* Find .plt and .init.plt sections */
 142         for (i = 0; i < hdr->e_shnum; i++) {
 143                 if (strcmp(secstrings + sechdrs[i].sh_name, ".init.plt") == 0)
 144                         me->arch.init_plt_section = i;
 145                 else if (strcmp(secstrings + sechdrs[i].sh_name, ".plt") == 0)
 146                         me->arch.core_plt_section = i;
 147         }
 148         if (!me->arch.core_plt_section || !me->arch.init_plt_section) {
 149                 pr_err("Module doesn't contain .plt or .init.plt sections.\n");
 150                 return -ENOEXEC;
 151         }
 152
 153         /* Override their sizes */
 154         sechdrs[me->arch.core_plt_section].sh_size
 155                 = get_plt_size(hdr, sechdrs, secstrings, 0);
 156         sechdrs[me->arch.init_plt_section].sh_size
 157                 = get_plt_size(hdr, sechdrs, secstrings, 1);
 158         return 0;
 159 }
 160
 161 static inline int entry_matches(struct ppc_plt_entry *entry, Elf32_Addr val)
 162 {
 163         if (entry->jump[0] != (PPC_INST_ADDIS | __PPC_RT(R12) | PPC_HA(val)))
 164                 return 0;
 165         if (entry->jump[1] != (PPC_INST_ADDI | __PPC_RT(R12) | __PPC_RA(R12) |
 166                                PPC_LO(val)))
 167                 return 0;
 168         return 1;
 169 }
 170
 171 /* Set up a trampoline in the PLT to bounce us to the distant function */
 172 static uint32_t do_plt_call(void *location,
 173                             Elf32_Addr val,
 174                             const Elf32_Shdr *sechdrs,
 175                             struct module *mod)
 176 {
 177         struct ppc_plt_entry *entry;
 178
 179         pr_debug("Doing plt for call to 0x%x at 0x%x\n", val, (unsigned int)location);
 180         /* Init, or core PLT? */
 181         if (location >= mod->core_layout.base
 182             && location < mod->core_layout.base + mod->core_layout.size)
 183                 entry = (void *)sechdrs[mod->arch.core_plt_section].sh_addr;
 184         else
 185                 entry = (void *)sechdrs[mod->arch.init_plt_section].sh_addr;
 186
 187         /* Find this entry, or if that fails, the next avail. entry */
 188         while (entry->jump[0]) {
 189                 if (entry_matches(entry, val)) return (uint32_t)entry;
 190                 entry++;
 191         }
 192
 193         /*
 194          * lis r12, sym@ha
 195          * addi r12, r12, sym@l
 196          * mtctr r12
 197          * bctr
 198          */
 199         entry->jump[0] = PPC_INST_ADDIS | __PPC_RT(R12) | PPC_HA(val);
 200         entry->jump[1] = PPC_INST_ADDI | __PPC_RT(R12) | __PPC_RA(R12) | PPC_LO(val);
 201         entry->jump[2] = PPC_INST_MTCTR | __PPC_RS(R12);
 202         entry->jump[3] = PPC_INST_BCTR;
 203
 204         pr_debug("Initialized plt for 0x%x at %p\n", val, entry);
 205         return (uint32_t)entry;
 206 }
 207
 208 int apply_relocate_add(Elf32_Shdr *sechdrs,
 209                        const char *strtab,
 210                        unsigned int symindex,
 211                        unsigned int relsec,
 212                        struct module *module)
 213 {
 214         unsigned int i;
 215         Elf32_Rela *rela = (void *)sechdrs[relsec].sh_addr;
 216         Elf32_Sym *sym;
 217         uint32_t *location;
 218         uint32_t value;
 219
 220         pr_debug("Applying ADD relocate section %u to %u\n", relsec,
 221                sechdrs[relsec].sh_info);
 222         for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rela); i++) {
 223                 /* This is where to make the change */
 224                 location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
 225                         + rela[i].r_offset;
 226                 /* This is the symbol it is referring to.  Note that all
 227                    undefined symbols have been resolved.  */
 228                 sym = (Elf32_Sym *)sechdrs[symindex].sh_addr
 229                         + ELF32_R_SYM(rela[i].r_info);
 230                 /* `Everything is relative'. */
 231                 value = sym->st_value + rela[i].r_addend;
 232
 233                 switch (ELF32_R_TYPE(rela[i].r_info)) {
 234                 case R_PPC_ADDR32:
 235                         /* Simply set it */
 236                         *(uint32_t *)location = value;
 237                         break;
 238
 239                 case R_PPC_ADDR16_LO:
 240                         /* Low half of the symbol */
 241                         *(uint16_t *)location = value;
 242                         break;
 243
 244                 case R_PPC_ADDR16_HI:
 245                         /* Higher half of the symbol */
 246                         *(uint16_t *)location = (value >> 16);
 247                         break;
 248
 249                 case R_PPC_ADDR16_HA:
 250                         /* Sign-adjusted lower 16 bits: PPC ELF ABI says:
 251                            (((x >> 16) + ((x & 0x8000) ? 1 : 0))) & 0xFFFF.
 252                            This is the same, only sane.
 253                          */
 254                         *(uint16_t *)location = (value + 0x8000) >> 16;
 255                         break;
 256
 257                 case R_PPC_REL24:
 258                         if ((int)(value - (uint32_t)location) < -0x02000000
 259                             || (int)(value - (uint32_t)location) >= 0x02000000)
 260                                 value = do_plt_call(location, value,
 261                                                     sechdrs, module);
 262
 263                         /* Only replace bits 2 through 26 */
 264                         pr_debug("REL24 value = %08X. location = %08X\n",
 265                                value, (uint32_t)location);
 266                         pr_debug("Location before: %08X.\n",
 267                                *(uint32_t *)location);
 268                         *(uint32_t *)location
 269                                 = (*(uint32_t *)location & ~0x03fffffc)
 270                                 | ((value - (uint32_t)location)
 271                                    & 0x03fffffc);
 272                         pr_debug("Location after: %08X.\n",
 273                                *(uint32_t *)location);
 274                         pr_debug("ie. jump to %08X+%08X = %08X\n",
 275                                *(uint32_t *)location & 0x03fffffc,
 276                                (uint32_t)location,
 277                                (*(uint32_t *)location & 0x03fffffc)
 278                                + (uint32_t)location);
 279                         break;
 280
 281                 case R_PPC_REL32:
 282                         /* 32-bit relative jump. */
 283                         *(uint32_t *)location = value - (uint32_t)location;
 284                         break;
 285
 286                 default:
 287                         pr_err("%s: unknown ADD relocation: %u\n",
 288                                module->name,
 289                                ELF32_R_TYPE(rela[i].r_info));
 290                         return -ENOEXEC;
 291                 }
 292         }
 293
 294         return 0;
 295 }
 296
 297 #ifdef CONFIG_DYNAMIC_FTRACE
 298 int module_finalize_ftrace(struct module *module, const Elf_Shdr *sechdrs)
 299 {
 300         module->arch.tramp = do_plt_call(module->core_layout.base,
 301                                          (unsigned long)ftrace_caller,
 302                                          sechdrs, module);
 303         if (!module->arch.tramp)
 304                 return -ENOENT;
 305
 306         return 0;
 307 }
 308 #endif