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 #include <linux/module.h>
  19 #include <linux/moduleloader.h>
  20 #include <linux/elf.h>
  21 #include <linux/vmalloc.h>
  22 #include <linux/fs.h>
  23 #include <linux/string.h>
  24 #include <linux/kernel.h>
  25 #include <linux/cache.h>
  26
  27 #if 0
  28 #define DEBUGP printk
  29 #else
  30 #define DEBUGP(fmt , ...)
  31 #endif
  32
  33 LIST_HEAD(module_bug_list);
  34
  35 void *module_alloc(unsigned long size)
  36 {
  37         if (size == 0)
  38                 return NULL;
  39         return vmalloc(size);
  40 }
  41
  42 /* Free memory returned from module_alloc */
  43 void module_free(struct module *mod, void *module_region)
  44 {
  45         vfree(module_region);
  46         /* FIXME: If module_region == mod->init_region, trim exception
  47            table entries. */
  48 }
  49
  50 /* Count how many different relocations (different symbol, different
  51    addend) */
  52 static unsigned int count_relocs(const Elf32_Rela *rela, unsigned int num)
  53 {
  54         unsigned int i, j, ret = 0;
  55
  56         /* Sure, this is order(n^2), but it's usually short, and not
  57            time critical */
  58         for (i = 0; i < num; i++) {
  59                 for (j = 0; j < i; j++) {
  60                         /* If this addend appeared before, it's
  61                            already been counted */
  62                         if (ELF32_R_SYM(rela[i].r_info)
  63                             == ELF32_R_SYM(rela[j].r_info)
  64                             && rela[i].r_addend == rela[j].r_addend)
  65                                 break;
  66                 }
  67                 if (j == i) ret++;
  68         }
  69         return ret;
  70 }
  71
  72 /* Get the potential trampolines size required of the init and
  73    non-init sections */
  74 static unsigned long get_plt_size(const Elf32_Ehdr *hdr,
  75                                   const Elf32_Shdr *sechdrs,
  76                                   const char *secstrings,
  77                                   int is_init)
  78 {
  79         unsigned long ret = 0;
  80         unsigned i;
  81
  82         /* Everything marked ALLOC (this includes the exported
  83            symbols) */
  84         for (i = 1; i < hdr->e_shnum; i++) {
  85                 /* If it's called *.init*, and we're not init, we're
  86                    not interested */
  87                 if ((strstr(secstrings + sechdrs[i].sh_name, ".init") != 0)
  88                     != is_init)
  89                         continue;
  90
  91                 /* We don't want to look at debug sections. */
  92                 if (strstr(secstrings + sechdrs[i].sh_name, ".debug") != 0)
  93                         continue;
  94
  95                 if (sechdrs[i].sh_type == SHT_RELA) {
  96                         DEBUGP("Found relocations in section %u\n", i);
  97                         DEBUGP("Ptr: %p.  Number: %u\n",
  98                                (void *)hdr + sechdrs[i].sh_offset,
  99                                sechdrs[i].sh_size / sizeof(Elf32_Rela));
 100                         ret += count_relocs((void *)hdr
 101                                              + sechdrs[i].sh_offset,
 102                                              sechdrs[i].sh_size
 103                                              / sizeof(Elf32_Rela))
 104                                 * sizeof(struct ppc_plt_entry);
 105                 }
 106         }
 107
 108         return ret;
 109 }
 110
 111 int module_frob_arch_sections(Elf32_Ehdr *hdr,
 112                               Elf32_Shdr *sechdrs,
 113                               char *secstrings,
 114                               struct module *me)
 115 {
 116         unsigned int i;
 117
 118         /* Find .plt and .init.plt sections */
 119         for (i = 0; i < hdr->e_shnum; i++) {
 120                 if (strcmp(secstrings + sechdrs[i].sh_name, ".init.plt") == 0)
 121                         me->arch.init_plt_section = i;
 122                 else if (strcmp(secstrings + sechdrs[i].sh_name, ".plt") == 0)
 123                         me->arch.core_plt_section = i;
 124         }
 125         if (!me->arch.core_plt_section || !me->arch.init_plt_section) {
 126                 printk("Module doesn't contain .plt or .init.plt sections.\n");
 127                 return -ENOEXEC;
 128         }
 129
 130         /* Override their sizes */
 131         sechdrs[me->arch.core_plt_section].sh_size
 132                 = get_plt_size(hdr, sechdrs, secstrings, 0);
 133         sechdrs[me->arch.init_plt_section].sh_size
 134                 = get_plt_size(hdr, sechdrs, secstrings, 1);
 135         return 0;
 136 }
 137
 138 int apply_relocate(Elf32_Shdr *sechdrs,
 139                    const char *strtab,
 140                    unsigned int symindex,
 141                    unsigned int relsec,
 142                    struct module *module)
 143 {
 144         printk(KERN_ERR "%s: Non-ADD RELOCATION unsupported\n",
 145                module->name);
 146         return -ENOEXEC;
 147 }
 148
 149 static inline int entry_matches(struct ppc_plt_entry *entry, Elf32_Addr val)
 150 {
 151         if (entry->jump[0] == 0x3d600000 + ((val + 0x8000) >> 16)
 152             && entry->jump[1] == 0x396b0000 + (val & 0xffff))
 153                 return 1;
 154         return 0;
 155 }
 156
 157 /* Set up a trampoline in the PLT to bounce us to the distant function */
 158 static uint32_t do_plt_call(void *location,
 159                             Elf32_Addr val,
 160                             Elf32_Shdr *sechdrs,
 161                             struct module *mod)
 162 {
 163         struct ppc_plt_entry *entry;
 164
 165         DEBUGP("Doing plt for call to 0x%x at 0x%x\n", val, (unsigned int)location);
 166         /* Init, or core PLT? */
 167         if (location >= mod->module_core
 168             && location < mod->module_core + mod->core_size)
 169                 entry = (void *)sechdrs[mod->arch.core_plt_section].sh_addr;
 170         else
 171                 entry = (void *)sechdrs[mod->arch.init_plt_section].sh_addr;
 172
 173         /* Find this entry, or if that fails, the next avail. entry */
 174         while (entry->jump[0]) {
 175                 if (entry_matches(entry, val)) return (uint32_t)entry;
 176                 entry++;
 177         }
 178
 179         /* Stolen from Paul Mackerras as well... */
 180         entry->jump[0] = 0x3d600000+((val+0x8000)>>16); /* lis r11,sym@ha */
 181         entry->jump[1] = 0x396b0000 + (val&0xffff);     /* addi r11,r11,sym@l*/
 182         entry->jump[2] = 0x7d6903a6;                    /* mtctr r11 */
 183         entry->jump[3] = 0x4e800420;                    /* bctr */
 184
 185         DEBUGP("Initialized plt for 0x%x at %p\n", val, entry);
 186         return (uint32_t)entry;
 187 }
 188
 189 int apply_relocate_add(Elf32_Shdr *sechdrs,
 190                        const char *strtab,
 191                        unsigned int symindex,
 192                        unsigned int relsec,
 193                        struct module *module)
 194 {
 195         unsigned int i;
 196         Elf32_Rela *rela = (void *)sechdrs[relsec].sh_addr;
 197         Elf32_Sym *sym;
 198         uint32_t *location;
 199         uint32_t value;
 200
 201         DEBUGP("Applying ADD relocate section %u to %u\n", relsec,
 202                sechdrs[relsec].sh_info);
 203         for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rela); i++) {
 204                 /* This is where to make the change */
 205                 location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
 206                         + rela[i].r_offset;
 207                 /* This is the symbol it is referring to.  Note that all
 208                    undefined symbols have been resolved.  */
 209                 sym = (Elf32_Sym *)sechdrs[symindex].sh_addr
 210                         + ELF32_R_SYM(rela[i].r_info);
 211                 /* `Everything is relative'. */
 212                 value = sym->st_value + rela[i].r_addend;
 213
 214                 switch (ELF32_R_TYPE(rela[i].r_info)) {
 215                 case R_PPC_ADDR32:
 216                         /* Simply set it */
 217                         *(uint32_t *)location = value;
 218                         break;
 219
 220                 case R_PPC_ADDR16_LO:
 221                         /* Low half of the symbol */
 222                         *(uint16_t *)location = value;
 223                         break;
 224
 225                 case R_PPC_ADDR16_HA:
 226                         /* Sign-adjusted lower 16 bits: PPC ELF ABI says:
 227                            (((x >> 16) + ((x & 0x8000) ? 1 : 0))) & 0xFFFF.
 228                            This is the same, only sane.
 229                          */
 230                         *(uint16_t *)location = (value + 0x8000) >> 16;
 231                         break;
 232
 233                 case R_PPC_REL24:
 234                         if ((int)(value - (uint32_t)location) < -0x02000000
 235                             || (int)(value - (uint32_t)location) >= 0x02000000)
 236                                 value = do_plt_call(location, value,
 237                                                     sechdrs, module);
 238
 239                         /* Only replace bits 2 through 26 */
 240                         DEBUGP("REL24 value = %08X. location = %08X\n",
 241                                value, (uint32_t)location);
 242                         DEBUGP("Location before: %08X.\n",
 243                                *(uint32_t *)location);
 244                         *(uint32_t *)location
 245                                 = (*(uint32_t *)location & ~0x03fffffc)
 246                                 | ((value - (uint32_t)location)
 247                                    & 0x03fffffc);
 248                         DEBUGP("Location after: %08X.\n",
 249                                *(uint32_t *)location);
 250                         DEBUGP("ie. jump to %08X+%08X = %08X\n",
 251                                *(uint32_t *)location & 0x03fffffc,
 252                                (uint32_t)location,
 253                                (*(uint32_t *)location & 0x03fffffc)
 254                                + (uint32_t)location);
 255                         break;
 256
 257                 case R_PPC_REL32:
 258                         /* 32-bit relative jump. */
 259                         *(uint32_t *)location = value - (uint32_t)location;
 260                         break;
 261
 262                 default:
 263                         printk("%s: unknown ADD relocation: %u\n",
 264                                module->name,
 265                                ELF32_R_TYPE(rela[i].r_info));
 266                         return -ENOEXEC;
 267                 }
 268         }
 269         return 0;
 270 }
 271
 272 int module_finalize(const Elf_Ehdr *hdr,
 273                     const Elf_Shdr *sechdrs,
 274                     struct module *me)
 275 {
 276         char *secstrings;
 277         unsigned int i;
 278
 279         me->arch.bug_table = NULL;
 280         me->arch.num_bugs = 0;
 281
 282         /* Find the __bug_table section, if present */
 283         secstrings = (char *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
 284         for (i = 1; i < hdr->e_shnum; i++) {
 285                 if (strcmp(secstrings+sechdrs[i].sh_name, "__bug_table"))
 286                         continue;
 287                 me->arch.bug_table = (void *) sechdrs[i].sh_addr;
 288                 me->arch.num_bugs = sechdrs[i].sh_size / sizeof(struct bug_entry);
 289                 break;
 290         }
 291
 292         /*
 293          * Strictly speaking this should have a spinlock to protect against
 294          * traversals, but since we only traverse on BUG()s, a spinlock
 295          * could potentially lead to deadlock and thus be counter-productive.
 296          */
 297         list_add(&me->arch.bug_list, &module_bug_list);
 298
 299         return 0;
 300 }
 301
 302 void module_arch_cleanup(struct module *mod)
 303 {
 304         list_del(&mod->arch.bug_list);
 305 }
 306
 307 struct bug_entry *module_find_bug(unsigned long bugaddr)
 308 {
 309         struct mod_arch_specific *mod;
 310         unsigned int i;
 311         struct bug_entry *bug;
 312
 313         list_for_each_entry(mod, &module_bug_list, bug_list) {
 314                 bug = mod->bug_table;
 315                 for (i = 0; i < mod->num_bugs; ++i, ++bug)
 316                         if (bugaddr == bug->bug_addr)
 317                                 return bug;
 318         }
 319         return NULL;
 320 }