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 #include "setup.h"
  28
  29 #if 0
  30 #define DEBUGP printk
  31 #else
  32 #define DEBUGP(fmt , ...)
  33 #endif
  34
  35 LIST_HEAD(module_bug_list);
  36
  37 void *module_alloc(unsigned long size)
  38 {
  39         if (size == 0)
  40                 return NULL;
  41         return vmalloc(size);
  42 }
  43
  44 /* Free memory returned from module_alloc */
  45 void module_free(struct module *mod, void *module_region)
  46 {
  47         vfree(module_region);
  48         /* FIXME: If module_region == mod->init_region, trim exception
  49            table entries. */
  50 }
  51
  52 /* Count how many different relocations (different symbol, different
  53    addend) */
  54 static unsigned int count_relocs(const Elf32_Rela *rela, unsigned int num)
  55 {
  56         unsigned int i, j, ret = 0;
  57
  58         /* Sure, this is order(n^2), but it's usually short, and not
  59            time critical */
  60         for (i = 0; i < num; i++) {
  61                 for (j = 0; j < i; j++) {
  62                         /* If this addend appeared before, it's
  63                            already been counted */
  64                         if (ELF32_R_SYM(rela[i].r_info)
  65                             == ELF32_R_SYM(rela[j].r_info)
  66                             && rela[i].r_addend == rela[j].r_addend)
  67                                 break;
  68                 }
  69                 if (j == i) ret++;
  70         }
  71         return ret;
  72 }
  73
  74 /* Get the potential trampolines size required of the init and
  75    non-init sections */
  76 static unsigned long get_plt_size(const Elf32_Ehdr *hdr,
  77                                   const Elf32_Shdr *sechdrs,
  78                                   const char *secstrings,
  79                                   int is_init)
  80 {
  81         unsigned long ret = 0;
  82         unsigned i;
  83
  84         /* Everything marked ALLOC (this includes the exported
  85            symbols) */
  86         for (i = 1; i < hdr->e_shnum; i++) {
  87                 /* If it's called *.init*, and we're not init, we're
  88                    not interested */
  89                 if ((strstr(secstrings + sechdrs[i].sh_name, ".init") != 0)
  90                     != is_init)
  91                         continue;
  92
  93                 /* We don't want to look at debug sections. */
  94                 if (strstr(secstrings + sechdrs[i].sh_name, ".debug") != 0)
  95                         continue;
  96
  97                 if (sechdrs[i].sh_type == SHT_RELA) {
  98                         DEBUGP("Found relocations in section %u\n", i);
  99                         DEBUGP("Ptr: %p.  Number: %u\n",
 100                                (void *)hdr + sechdrs[i].sh_offset,
 101                                sechdrs[i].sh_size / sizeof(Elf32_Rela));
 102                         ret += count_relocs((void *)hdr
 103                                              + sechdrs[i].sh_offset,
 104                                              sechdrs[i].sh_size
 105                                              / sizeof(Elf32_Rela))
 106                                 * sizeof(struct ppc_plt_entry);
 107                 }
 108         }
 109
 110         return ret;
 111 }
 112
 113 int module_frob_arch_sections(Elf32_Ehdr *hdr,
 114                               Elf32_Shdr *sechdrs,
 115                               char *secstrings,
 116                               struct module *me)
 117 {
 118         unsigned int i;
 119
 120         /* Find .plt and .init.plt sections */
 121         for (i = 0; i < hdr->e_shnum; i++) {
 122                 if (strcmp(secstrings + sechdrs[i].sh_name, ".init.plt") == 0)
 123                         me->arch.init_plt_section = i;
 124                 else if (strcmp(secstrings + sechdrs[i].sh_name, ".plt") == 0)
 125                         me->arch.core_plt_section = i;
 126         }
 127         if (!me->arch.core_plt_section || !me->arch.init_plt_section) {
 128                 printk("Module doesn't contain .plt or .init.plt sections.\n");
 129                 return -ENOEXEC;
 130         }
 131
 132         /* Override their sizes */
 133         sechdrs[me->arch.core_plt_section].sh_size
 134                 = get_plt_size(hdr, sechdrs, secstrings, 0);
 135         sechdrs[me->arch.init_plt_section].sh_size
 136                 = get_plt_size(hdr, sechdrs, secstrings, 1);
 137         return 0;
 138 }
 139
 140 int apply_relocate(Elf32_Shdr *sechdrs,
 141                    const char *strtab,
 142                    unsigned int symindex,
 143                    unsigned int relsec,
 144                    struct module *module)
 145 {
 146         printk(KERN_ERR "%s: Non-ADD RELOCATION unsupported\n",
 147                module->name);
 148         return -ENOEXEC;
 149 }
 150
 151 static inline int entry_matches(struct ppc_plt_entry *entry, Elf32_Addr val)
 152 {
 153         if (entry->jump[0] == 0x3d600000 + ((val + 0x8000) >> 16)
 154             && entry->jump[1] == 0x396b0000 + (val & 0xffff))
 155                 return 1;
 156         return 0;
 157 }
 158
 159 /* Set up a trampoline in the PLT to bounce us to the distant function */
 160 static uint32_t do_plt_call(void *location,
 161                             Elf32_Addr val,
 162                             Elf32_Shdr *sechdrs,
 163                             struct module *mod)
 164 {
 165         struct ppc_plt_entry *entry;
 166
 167         DEBUGP("Doing plt for call to 0x%x at 0x%x\n", val, (unsigned int)location);
 168         /* Init, or core PLT? */
 169         if (location >= mod->module_core
 170             && location < mod->module_core + mod->core_size)
 171                 entry = (void *)sechdrs[mod->arch.core_plt_section].sh_addr;
 172         else
 173                 entry = (void *)sechdrs[mod->arch.init_plt_section].sh_addr;
 174
 175         /* Find this entry, or if that fails, the next avail. entry */
 176         while (entry->jump[0]) {
 177                 if (entry_matches(entry, val)) return (uint32_t)entry;
 178                 entry++;
 179         }
 180
 181         /* Stolen from Paul Mackerras as well... */
 182         entry->jump[0] = 0x3d600000+((val+0x8000)>>16); /* lis r11,sym@ha */
 183         entry->jump[1] = 0x396b0000 + (val&0xffff);     /* addi r11,r11,sym@l*/
 184         entry->jump[2] = 0x7d6903a6;                    /* mtctr r11 */
 185         entry->jump[3] = 0x4e800420;                    /* bctr */
 186
 187         DEBUGP("Initialized plt for 0x%x at %p\n", val, entry);
 188         return (uint32_t)entry;
 189 }
 190
 191 int apply_relocate_add(Elf32_Shdr *sechdrs,
 192                        const char *strtab,
 193                        unsigned int symindex,
 194                        unsigned int relsec,
 195                        struct module *module)
 196 {
 197         unsigned int i;
 198         Elf32_Rela *rela = (void *)sechdrs[relsec].sh_addr;
 199         Elf32_Sym *sym;
 200         uint32_t *location;
 201         uint32_t value;
 202
 203         DEBUGP("Applying ADD relocate section %u to %u\n", relsec,
 204                sechdrs[relsec].sh_info);
 205         for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rela); i++) {
 206                 /* This is where to make the change */
 207                 location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
 208                         + rela[i].r_offset;
 209                 /* This is the symbol it is referring to.  Note that all
 210                    undefined symbols have been resolved.  */
 211                 sym = (Elf32_Sym *)sechdrs[symindex].sh_addr
 212                         + ELF32_R_SYM(rela[i].r_info);
 213                 /* `Everything is relative'. */
 214                 value = sym->st_value + rela[i].r_addend;
 215
 216                 switch (ELF32_R_TYPE(rela[i].r_info)) {
 217                 case R_PPC_ADDR32:
 218                         /* Simply set it */
 219                         *(uint32_t *)location = value;
 220                         break;
 221
 222                 case R_PPC_ADDR16_LO:
 223                         /* Low half of the symbol */
 224                         *(uint16_t *)location = value;
 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                         DEBUGP("REL24 value = %08X. location = %08X\n",
 243                                value, (uint32_t)location);
 244                         DEBUGP("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                         DEBUGP("Location after: %08X.\n",
 251                                *(uint32_t *)location);
 252                         DEBUGP("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                         printk("%s: unknown ADD relocation: %u\n",
 266                                module->name,
 267                                ELF32_R_TYPE(rela[i].r_info));
 268                         return -ENOEXEC;
 269                 }
 270         }
 271         return 0;
 272 }
 273
 274 static const Elf_Shdr *find_section(const Elf_Ehdr *hdr,
 275                                     const Elf_Shdr *sechdrs,
 276                                     const char *name)
 277 {
 278         char *secstrings;
 279         unsigned int i;
 280
 281         secstrings = (char *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
 282         for (i = 1; i < hdr->e_shnum; i++)
 283                 if (strcmp(secstrings+sechdrs[i].sh_name, name) == 0)
 284                         return &sechdrs[i];
 285         return NULL;
 286 }
 287
 288 int module_finalize(const Elf_Ehdr *hdr,
 289                     const Elf_Shdr *sechdrs,
 290                     struct module *me)
 291 {
 292         const Elf_Shdr *sect;
 293
 294         me->arch.bug_table = NULL;
 295         me->arch.num_bugs = 0;
 296
 297         /* Find the __bug_table section, if present */
 298         sect = find_section(hdr, sechdrs, "__bug_table");
 299         if (sect != NULL) {
 300                 me->arch.bug_table = (void *) sect->sh_addr;
 301                 me->arch.num_bugs = sect->sh_size / sizeof(struct bug_entry);
 302         }
 303
 304         /*
 305          * Strictly speaking this should have a spinlock to protect against
 306          * traversals, but since we only traverse on BUG()s, a spinlock
 307          * could potentially lead to deadlock and thus be counter-productive.
 308          */
 309         list_add(&me->arch.bug_list, &module_bug_list);
 310
 311         /* Apply feature fixups */
 312         sect = find_section(hdr, sechdrs, "__ftr_fixup");
 313         if (sect != NULL)
 314                 do_feature_fixups(cur_cpu_spec->cpu_features,
 315                                   (void *)sect->sh_addr,
 316                                   (void *)sect->sh_addr + sect->sh_size);
 317
 318         return 0;
 319 }
 320
 321 void module_arch_cleanup(struct module *mod)
 322 {
 323         list_del(&mod->arch.bug_list);
 324 }
 325
 326 struct bug_entry *module_find_bug(unsigned long bugaddr)
 327 {
 328         struct mod_arch_specific *mod;
 329         unsigned int i;
 330         struct bug_entry *bug;
 331
 332         list_for_each_entry(mod, &module_bug_list, bug_list) {
 333                 bug = mod->bug_table;
 334                 for (i = 0; i < mod->num_bugs; ++i, ++bug)
 335                         if (bugaddr == bug->bug_addr)
 336                                 return bug;
 337         }
 338         return NULL;
 339 }