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 #include <linux/bug.h>
  27
  28 #include "setup.h"
  29
  30 #if 0
  31 #define DEBUGP printk
  32 #else
  33 #define DEBUGP(fmt , ...)
  34 #endif
  35
  36 LIST_HEAD(module_bug_list);
  37
  38 void *module_alloc(unsigned long size)
  39 {
  40         if (size == 0)
  41                 return NULL;
  42         return vmalloc(size);
  43 }
  44
  45 /* Free memory returned from module_alloc */
  46 void module_free(struct module *mod, void *module_region)
  47 {
  48         vfree(module_region);
  49         /* FIXME: If module_region == mod->init_region, trim exception
  50            table entries. */
  51 }
  52
  53 /* Count how many different relocations (different symbol, different
  54    addend) */
  55 static unsigned int count_relocs(const Elf32_Rela *rela, unsigned int num)
  56 {
  57         unsigned int i, j, ret = 0;
  58
  59         /* Sure, this is order(n^2), but it's usually short, and not
  60            time critical */
  61         for (i = 0; i < num; i++) {
  62                 for (j = 0; j < i; j++) {
  63                         /* If this addend appeared before, it's
  64                            already been counted */
  65                         if (ELF32_R_SYM(rela[i].r_info)
  66                             == ELF32_R_SYM(rela[j].r_info)
  67                             && rela[i].r_addend == rela[j].r_addend)
  68                                 break;
  69                 }
  70                 if (j == i) ret++;
  71         }
  72         return ret;
  73 }
  74
  75 /* Get the potential trampolines size required of the init and
  76    non-init sections */
  77 static unsigned long get_plt_size(const Elf32_Ehdr *hdr,
  78                                   const Elf32_Shdr *sechdrs,
  79                                   const char *secstrings,
  80                                   int is_init)
  81 {
  82         unsigned long ret = 0;
  83         unsigned i;
  84
  85         /* Everything marked ALLOC (this includes the exported
  86            symbols) */
  87         for (i = 1; i < hdr->e_shnum; i++) {
  88                 /* If it's called *.init*, and we're not init, we're
  89                    not interested */
  90                 if ((strstr(secstrings + sechdrs[i].sh_name, ".init") != 0)
  91                     != is_init)
  92                         continue;
  93
  94                 /* We don't want to look at debug sections. */
  95                 if (strstr(secstrings + sechdrs[i].sh_name, ".debug") != 0)
  96                         continue;
  97
  98                 if (sechdrs[i].sh_type == SHT_RELA) {
  99                         DEBUGP("Found relocations in section %u\n", i);
 100                         DEBUGP("Ptr: %p.  Number: %u\n",
 101                                (void *)hdr + sechdrs[i].sh_offset,
 102                                sechdrs[i].sh_size / sizeof(Elf32_Rela));
 103                         ret += count_relocs((void *)hdr
 104                                              + sechdrs[i].sh_offset,
 105                                              sechdrs[i].sh_size
 106                                              / sizeof(Elf32_Rela))
 107                                 * sizeof(struct ppc_plt_entry);
 108                 }
 109         }
 110
 111         return ret;
 112 }
 113
 114 int module_frob_arch_sections(Elf32_Ehdr *hdr,
 115                               Elf32_Shdr *sechdrs,
 116                               char *secstrings,
 117                               struct module *me)
 118 {
 119         unsigned int i;
 120
 121         /* Find .plt and .init.plt sections */
 122         for (i = 0; i < hdr->e_shnum; i++) {
 123                 if (strcmp(secstrings + sechdrs[i].sh_name, ".init.plt") == 0)
 124                         me->arch.init_plt_section = i;
 125                 else if (strcmp(secstrings + sechdrs[i].sh_name, ".plt") == 0)
 126                         me->arch.core_plt_section = i;
 127         }
 128         if (!me->arch.core_plt_section || !me->arch.init_plt_section) {
 129                 printk("Module doesn't contain .plt or .init.plt sections.\n");
 130                 return -ENOEXEC;
 131         }
 132
 133         /* Override their sizes */
 134         sechdrs[me->arch.core_plt_section].sh_size
 135                 = get_plt_size(hdr, sechdrs, secstrings, 0);
 136         sechdrs[me->arch.init_plt_section].sh_size
 137                 = get_plt_size(hdr, sechdrs, secstrings, 1);
 138         return 0;
 139 }
 140
 141 int apply_relocate(Elf32_Shdr *sechdrs,
 142                    const char *strtab,
 143                    unsigned int symindex,
 144                    unsigned int relsec,
 145                    struct module *module)
 146 {
 147         printk(KERN_ERR "%s: Non-ADD RELOCATION unsupported\n",
 148                module->name);
 149         return -ENOEXEC;
 150 }
 151
 152 static inline int entry_matches(struct ppc_plt_entry *entry, Elf32_Addr val)
 153 {
 154         if (entry->jump[0] == 0x3d600000 + ((val + 0x8000) >> 16)
 155             && entry->jump[1] == 0x396b0000 + (val & 0xffff))
 156                 return 1;
 157         return 0;
 158 }
 159
 160 /* Set up a trampoline in the PLT to bounce us to the distant function */
 161 static uint32_t do_plt_call(void *location,
 162                             Elf32_Addr val,
 163                             Elf32_Shdr *sechdrs,
 164                             struct module *mod)
 165 {
 166         struct ppc_plt_entry *entry;
 167
 168         DEBUGP("Doing plt for call to 0x%x at 0x%x\n", val, (unsigned int)location);
 169         /* Init, or core PLT? */
 170         if (location >= mod->module_core
 171             && location < mod->module_core + mod->core_size)
 172                 entry = (void *)sechdrs[mod->arch.core_plt_section].sh_addr;
 173         else
 174                 entry = (void *)sechdrs[mod->arch.init_plt_section].sh_addr;
 175
 176         /* Find this entry, or if that fails, the next avail. entry */
 177         while (entry->jump[0]) {
 178                 if (entry_matches(entry, val)) return (uint32_t)entry;
 179                 entry++;
 180         }
 181
 182         /* Stolen from Paul Mackerras as well... */
 183         entry->jump[0] = 0x3d600000+((val+0x8000)>>16); /* lis r11,sym@ha */
 184         entry->jump[1] = 0x396b0000 + (val&0xffff);     /* addi r11,r11,sym@l*/
 185         entry->jump[2] = 0x7d6903a6;                    /* mtctr r11 */
 186         entry->jump[3] = 0x4e800420;                    /* bctr */
 187
 188         DEBUGP("Initialized plt for 0x%x at %p\n", val, entry);
 189         return (uint32_t)entry;
 190 }
 191
 192 int apply_relocate_add(Elf32_Shdr *sechdrs,
 193                        const char *strtab,
 194                        unsigned int symindex,
 195                        unsigned int relsec,
 196                        struct module *module)
 197 {
 198         unsigned int i;
 199         Elf32_Rela *rela = (void *)sechdrs[relsec].sh_addr;
 200         Elf32_Sym *sym;
 201         uint32_t *location;
 202         uint32_t value;
 203
 204         DEBUGP("Applying ADD relocate section %u to %u\n", relsec,
 205                sechdrs[relsec].sh_info);
 206         for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rela); i++) {
 207                 /* This is where to make the change */
 208                 location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
 209                         + rela[i].r_offset;
 210                 /* This is the symbol it is referring to.  Note that all
 211                    undefined symbols have been resolved.  */
 212                 sym = (Elf32_Sym *)sechdrs[symindex].sh_addr
 213                         + ELF32_R_SYM(rela[i].r_info);
 214                 /* `Everything is relative'. */
 215                 value = sym->st_value + rela[i].r_addend;
 216
 217                 switch (ELF32_R_TYPE(rela[i].r_info)) {
 218                 case R_PPC_ADDR32:
 219                         /* Simply set it */
 220                         *(uint32_t *)location = value;
 221                         break;
 222
 223                 case R_PPC_ADDR16_LO:
 224                         /* Low half of the symbol */
 225                         *(uint16_t *)location = value;
 226                         break;
 227
 228                 case R_PPC_ADDR16_HA:
 229                         /* Sign-adjusted lower 16 bits: PPC ELF ABI says:
 230                            (((x >> 16) + ((x & 0x8000) ? 1 : 0))) & 0xFFFF.
 231                            This is the same, only sane.
 232                          */
 233                         *(uint16_t *)location = (value + 0x8000) >> 16;
 234                         break;
 235
 236                 case R_PPC_REL24:
 237                         if ((int)(value - (uint32_t)location) < -0x02000000
 238                             || (int)(value - (uint32_t)location) >= 0x02000000)
 239                                 value = do_plt_call(location, value,
 240                                                     sechdrs, module);
 241
 242                         /* Only replace bits 2 through 26 */
 243                         DEBUGP("REL24 value = %08X. location = %08X\n",
 244                                value, (uint32_t)location);
 245                         DEBUGP("Location before: %08X.\n",
 246                                *(uint32_t *)location);
 247                         *(uint32_t *)location
 248                                 = (*(uint32_t *)location & ~0x03fffffc)
 249                                 | ((value - (uint32_t)location)
 250                                    & 0x03fffffc);
 251                         DEBUGP("Location after: %08X.\n",
 252                                *(uint32_t *)location);
 253                         DEBUGP("ie. jump to %08X+%08X = %08X\n",
 254                                *(uint32_t *)location & 0x03fffffc,
 255                                (uint32_t)location,
 256                                (*(uint32_t *)location & 0x03fffffc)
 257                                + (uint32_t)location);
 258                         break;
 259
 260                 case R_PPC_REL32:
 261                         /* 32-bit relative jump. */
 262                         *(uint32_t *)location = value - (uint32_t)location;
 263                         break;
 264
 265                 default:
 266                         printk("%s: unknown ADD relocation: %u\n",
 267                                module->name,
 268                                ELF32_R_TYPE(rela[i].r_info));
 269                         return -ENOEXEC;
 270                 }
 271         }
 272         return 0;
 273 }
 274
 275 static const Elf_Shdr *find_section(const Elf_Ehdr *hdr,
 276                                     const Elf_Shdr *sechdrs,
 277                                     const char *name)
 278 {
 279         char *secstrings;
 280         unsigned int i;
 281
 282         secstrings = (char *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
 283         for (i = 1; i < hdr->e_shnum; i++)
 284                 if (strcmp(secstrings+sechdrs[i].sh_name, name) == 0)
 285                         return &sechdrs[i];
 286         return NULL;
 287 }
 288
 289 int module_finalize(const Elf_Ehdr *hdr,
 290                     const Elf_Shdr *sechdrs,
 291                     struct module *me)
 292 {
 293         const Elf_Shdr *sect;
 294         int err;
 295
 296         err = module_bug_finalize(hdr, sechdrs, me);
 297         if (err)                /* never true, currently */
 298                 return err;
 299
 300         /* Apply feature fixups */
 301         sect = find_section(hdr, sechdrs, "__ftr_fixup");
 302         if (sect != NULL)
 303                 do_feature_fixups(cur_cpu_spec->cpu_features,
 304                                   (void *)sect->sh_addr,
 305                                   (void *)sect->sh_addr + sect->sh_size);
 306
 307         return 0;
 308 }
 309
 310 void module_arch_cleanup(struct module *mod)
 311 {
 312         module_bug_cleanup(mod);
 313 }
 314
 315 struct bug_entry *module_find_bug(unsigned long bugaddr)
 316 {
 317         struct mod_arch_specific *mod;
 318         unsigned int i;
 319         struct bug_entry *bug;
 320
 321         list_for_each_entry(mod, &module_bug_list, bug_list) {
 322                 bug = mod->bug_table;
 323                 for (i = 0; i < mod->num_bugs; ++i, ++bug)
 324                         if (bugaddr == bug->bug_addr)
 325                                 return bug;
 326         }
 327         return NULL;
 328 }