arch/powerpc/kernel/module_32.c

   1 /*  Kernel module help for PPC.
   2     Copyright (C) 2001 Rusty Russell.
   3
   4     This program is free software; you can redistribute it and/or modify
   5     it under the terms of the GNU General Public License as published by
   6     the Free Software Foundation; either version 2 of the License, or
   7     (at your option) any later version.
   8
   9     This program is distributed in the hope that it will be useful,
  10     but WITHOUT ANY WARRANTY; without even the implied warranty of
  11     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12     GNU General Public License for more details.
  13
  14     You should have received a copy of the GNU General Public License
  15     along with this program; if not, write to the Free Software
  16     Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  17 */
  18
  19 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  20
  21 #include <linux/module.h>
  22 #include <linux/moduleloader.h>
  23 #include <linux/elf.h>
  24 #include <linux/vmalloc.h>
  25 #include <linux/fs.h>
  26 #include <linux/string.h>
  27 #include <linux/kernel.h>
  28 #include <linux/ftrace.h>
  29 #include <linux/cache.h>
  30 #include <linux/bug.h>
  31 #include <linux/sort.h>
  32 #include <asm/setup.h>
  33
  34 /* Count how many different relocations (different symbol, different
  35    addend) */
  36 static unsigned int count_relocs(const Elf32_Rela *rela, unsigned int num)
  37 {
  38         unsigned int i, r_info, r_addend, _count_relocs;
  39
  40         _count_relocs = 0;
  41         r_info = 0;
  42         r_addend = 0;
  43         for (i = 0; i < num; i++)
  44                 /* Only count 24-bit relocs, others don't need stubs */
  45                 if (ELF32_R_TYPE(rela[i].r_info) == R_PPC_REL24 &&
  46                     (r_info != ELF32_R_SYM(rela[i].r_info) ||
  47                      r_addend != rela[i].r_addend)) {
  48                         _count_relocs++;
  49                         r_info = ELF32_R_SYM(rela[i].r_info);
  50                         r_addend = rela[i].r_addend;
  51                 }
  52
  53 #ifdef CONFIG_DYNAMIC_FTRACE
  54         _count_relocs++;        /* add one for ftrace_caller */
  55 #endif
  56         return _count_relocs;
  57 }
  58
  59 static int relacmp(const void *_x, const void *_y)
  60 {
  61         const Elf32_Rela *x, *y;
  62
  63         y = (Elf32_Rela *)_x;
  64         x = (Elf32_Rela *)_y;
  65
  66         /* Compare the entire r_info (as opposed to ELF32_R_SYM(r_info) only) to
  67          * make the comparison cheaper/faster. It won't affect the sorting or
  68          * the counting algorithms' performance
  69          */
  70         if (x->r_info < y->r_info)
  71                 return -1;
  72         else if (x->r_info > y->r_info)
  73                 return 1;
  74         else if (x->r_addend < y->r_addend)
  75                 return -1;
  76         else if (x->r_addend > y->r_addend)
  77                 return 1;
  78         else
  79                 return 0;
  80 }
  81
  82 static void relaswap(void *_x, void *_y, int size)
  83 {
  84         uint32_t *x, *y, tmp;
  85         int i;
  86
  87         y = (uint32_t *)_x;
  88         x = (uint32_t *)_y;
  89
  90         for (i = 0; i < sizeof(Elf32_Rela) / sizeof(uint32_t); i++) {
  91                 tmp = x[i];
  92                 x[i] = y[i];
  93                 y[i] = tmp;
  94         }
  95 }
  96
  97 /* Get the potential trampolines size required of the init and
  98    non-init sections */
  99 static unsigned long get_plt_size(const Elf32_Ehdr *hdr,
 100                                   const Elf32_Shdr *sechdrs,
 101                                   const char *secstrings,
 102                                   int is_init)
 103 {
 104         unsigned long ret = 0;
 105         unsigned i;
 106
 107         /* Everything marked ALLOC (this includes the exported
 108            symbols) */
 109         for (i = 1; i < hdr->e_shnum; i++) {
 110                 /* If it's called *.init*, and we're not init, we're
 111                    not interested */
 112                 if ((strstr(secstrings + sechdrs[i].sh_name, ".init") != NULL)
 113                     != is_init)
 114                         continue;
 115
 116                 /* We don't want to look at debug sections. */
 117                 if (strstr(secstrings + sechdrs[i].sh_name, ".debug"))
 118                         continue;
 119
 120                 if (sechdrs[i].sh_type == SHT_RELA) {
 121                         pr_debug("Found relocations in section %u\n", i);
 122                         pr_debug("Ptr: %p.  Number: %u\n",
 123                                (void *)hdr + sechdrs[i].sh_offset,
 124                                sechdrs[i].sh_size / sizeof(Elf32_Rela));
 125
 126                         /* Sort the relocation information based on a symbol and
 127                          * addend key. This is a stable O(n*log n) complexity
 128                          * alogrithm but it will reduce the complexity of
 129                          * count_relocs() to linear complexity O(n)
 130                          */
 131                         sort((void *)hdr + sechdrs[i].sh_offset,
 132                              sechdrs[i].sh_size / sizeof(Elf32_Rela),
 133                              sizeof(Elf32_Rela), relacmp, relaswap);
 134
 135                         ret += count_relocs((void *)hdr
 136                                              + sechdrs[i].sh_offset,
 137                                              sechdrs[i].sh_size
 138                                              / sizeof(Elf32_Rela))
 139                                 * sizeof(struct ppc_plt_entry);
 140                 }
 141         }
 142
 143         return ret;
 144 }
 145
 146 int module_frob_arch_sections(Elf32_Ehdr *hdr,
 147                               Elf32_Shdr *sechdrs,
 148                               char *secstrings,
 149                               struct module *me)
 150 {
 151         unsigned int i;
 152
 153         /* Find .plt and .init.plt sections */
 154         for (i = 0; i < hdr->e_shnum; i++) {
 155                 if (strcmp(secstrings + sechdrs[i].sh_name, ".init.plt") == 0)
 156                         me->arch.init_plt_section = i;
 157                 else if (strcmp(secstrings + sechdrs[i].sh_name, ".plt") == 0)
 158                         me->arch.core_plt_section = i;
 159         }
 160         if (!me->arch.core_plt_section || !me->arch.init_plt_section) {
 161                 pr_err("Module doesn't contain .plt or .init.plt sections.\n");
 162                 return -ENOEXEC;
 163         }
 164
 165         /* Override their sizes */
 166         sechdrs[me->arch.core_plt_section].sh_size
 167                 = get_plt_size(hdr, sechdrs, secstrings, 0);
 168         sechdrs[me->arch.init_plt_section].sh_size
 169                 = get_plt_size(hdr, sechdrs, secstrings, 1);
 170         return 0;
 171 }
 172
 173 static inline int entry_matches(struct ppc_plt_entry *entry, Elf32_Addr val)
 174 {
 175         if (entry->jump[0] != (PPC_INST_ADDIS | __PPC_RT(R12) | PPC_HA(val)))
 176                 return 0;
 177         if (entry->jump[1] != (PPC_INST_ADDI | __PPC_RT(R12) | __PPC_RA(R12) |
 178                                PPC_LO(val)))
 179                 return 0;
 180         return 1;
 181 }
 182
 183 /* Set up a trampoline in the PLT to bounce us to the distant function */
 184 static uint32_t do_plt_call(void *location,
 185                             Elf32_Addr val,
 186                             const Elf32_Shdr *sechdrs,
 187                             struct module *mod)
 188 {
 189         struct ppc_plt_entry *entry;
 190
 191         pr_debug("Doing plt for call to 0x%x at 0x%x\n", val, (unsigned int)location);
 192         /* Init, or core PLT? */
 193         if (location >= mod->core_layout.base
 194             && location < mod->core_layout.base + mod->core_layout.size)
 195                 entry = (void *)sechdrs[mod->arch.core_plt_section].sh_addr;
 196         else
 197                 entry = (void *)sechdrs[mod->arch.init_plt_section].sh_addr;
 198
 199         /* Find this entry, or if that fails, the next avail. entry */
 200         while (entry->jump[0]) {
 201                 if (entry_matches(entry, val)) return (uint32_t)entry;
 202                 entry++;
 203         }
 204
 205         /*
 206          * lis r12, sym@ha
 207          * addi r12, r12, sym@l
 208          * mtctr r12
 209          * bctr
 210          */
 211         entry->jump[0] = PPC_INST_ADDIS | __PPC_RT(R12) | PPC_HA(val);
 212         entry->jump[1] = PPC_INST_ADDI | __PPC_RT(R12) | __PPC_RA(R12) | PPC_LO(val);
 213         entry->jump[2] = PPC_INST_MTCTR | __PPC_RS(R12);
 214         entry->jump[3] = PPC_INST_BCTR;
 215
 216         pr_debug("Initialized plt for 0x%x at %p\n", val, entry);
 217         return (uint32_t)entry;
 218 }
 219
 220 int apply_relocate_add(Elf32_Shdr *sechdrs,
 221                        const char *strtab,
 222                        unsigned int symindex,
 223                        unsigned int relsec,
 224                        struct module *module)
 225 {
 226         unsigned int i;
 227         Elf32_Rela *rela = (void *)sechdrs[relsec].sh_addr;
 228         Elf32_Sym *sym;
 229         uint32_t *location;
 230         uint32_t value;
 231
 232         pr_debug("Applying ADD relocate section %u to %u\n", relsec,
 233                sechdrs[relsec].sh_info);
 234         for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rela); i++) {
 235                 /* This is where to make the change */
 236                 location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
 237                         + rela[i].r_offset;
 238                 /* This is the symbol it is referring to.  Note that all
 239                    undefined symbols have been resolved.  */
 240                 sym = (Elf32_Sym *)sechdrs[symindex].sh_addr
 241                         + ELF32_R_SYM(rela[i].r_info);
 242                 /* `Everything is relative'. */
 243                 value = sym->st_value + rela[i].r_addend;
 244
 245                 switch (ELF32_R_TYPE(rela[i].r_info)) {
 246                 case R_PPC_ADDR32:
 247                         /* Simply set it */
 248                         *(uint32_t *)location = value;
 249                         break;
 250
 251                 case R_PPC_ADDR16_LO:
 252                         /* Low half of the symbol */
 253                         *(uint16_t *)location = value;
 254                         break;
 255
 256                 case R_PPC_ADDR16_HI:
 257                         /* Higher half of the symbol */
 258                         *(uint16_t *)location = (value >> 16);
 259                         break;
 260
 261                 case R_PPC_ADDR16_HA:
 262                         /* Sign-adjusted lower 16 bits: PPC ELF ABI says:
 263                            (((x >> 16) + ((x & 0x8000) ? 1 : 0))) & 0xFFFF.
 264                            This is the same, only sane.
 265                          */
 266                         *(uint16_t *)location = (value + 0x8000) >> 16;
 267                         break;
 268
 269                 case R_PPC_REL24:
 270                         if ((int)(value - (uint32_t)location) < -0x02000000
 271                             || (int)(value - (uint32_t)location) >= 0x02000000)
 272                                 value = do_plt_call(location, value,
 273                                                     sechdrs, module);
 274
 275                         /* Only replace bits 2 through 26 */
 276                         pr_debug("REL24 value = %08X. location = %08X\n",
 277                                value, (uint32_t)location);
 278                         pr_debug("Location before: %08X.\n",
 279                                *(uint32_t *)location);
 280                         *(uint32_t *)location
 281                                 = (*(uint32_t *)location & ~0x03fffffc)
 282                                 | ((value - (uint32_t)location)
 283                                    & 0x03fffffc);
 284                         pr_debug("Location after: %08X.\n",
 285                                *(uint32_t *)location);
 286                         pr_debug("ie. jump to %08X+%08X = %08X\n",
 287                                *(uint32_t *)location & 0x03fffffc,
 288                                (uint32_t)location,
 289                                (*(uint32_t *)location & 0x03fffffc)
 290                                + (uint32_t)location);
 291                         break;
 292
 293                 case R_PPC_REL32:
 294                         /* 32-bit relative jump. */
 295                         *(uint32_t *)location = value - (uint32_t)location;
 296                         break;
 297
 298                 default:
 299                         pr_err("%s: unknown ADD relocation: %u\n",
 300                                module->name,
 301                                ELF32_R_TYPE(rela[i].r_info));
 302                         return -ENOEXEC;
 303                 }
 304         }
 305
 306         return 0;
 307 }
 308
 309 #ifdef CONFIG_DYNAMIC_FTRACE
 310 int module_finalize_ftrace(struct module *module, const Elf_Shdr *sechdrs)
 311 {
 312         module->arch.tramp = do_plt_call(module->core_layout.base,
 313                                          (unsigned long)ftrace_caller,
 314                                          sechdrs, module);
 315         if (!module->arch.tramp)
 316                 return -ENOENT;
 317
 318         return 0;
 319 }
 320 #endif