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 #include <linux/sort.h>
  28
  29 #include "setup.h"
  30
  31 #if 0
  32 #define DEBUGP printk
  33 #else
  34 #define DEBUGP(fmt , ...)
  35 #endif
  36
  37 /* Count how many different relocations (different symbol, different
  38    addend) */
  39 static unsigned int count_relocs(const Elf32_Rela *rela, unsigned int num)
  40 {
  41         unsigned int i, r_info, r_addend, _count_relocs;
  42
  43         _count_relocs = 0;
  44         r_info = 0;
  45         r_addend = 0;
  46         for (i = 0; i < num; i++)
  47                 /* Only count 24-bit relocs, others don't need stubs */
  48                 if (ELF32_R_TYPE(rela[i].r_info) == R_PPC_REL24 &&
  49                     (r_info != ELF32_R_SYM(rela[i].r_info) ||
  50                      r_addend != rela[i].r_addend)) {
  51                         _count_relocs++;
  52                         r_info = ELF32_R_SYM(rela[i].r_info);
  53                         r_addend = rela[i].r_addend;
  54                 }
  55
  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") != 0)
 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") != 0)
 118                         continue;
 119
 120                 if (sechdrs[i].sh_type == SHT_RELA) {
 121                         DEBUGP("Found relocations in section %u\n", i);
 122                         DEBUGP("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                 printk("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 int apply_relocate(Elf32_Shdr *sechdrs,
 174                    const char *strtab,
 175                    unsigned int symindex,
 176                    unsigned int relsec,
 177                    struct module *module)
 178 {
 179         printk(KERN_ERR "%s: Non-ADD RELOCATION unsupported\n",
 180                module->name);
 181         return -ENOEXEC;
 182 }
 183
 184 static inline int entry_matches(struct ppc_plt_entry *entry, Elf32_Addr val)
 185 {
 186         if (entry->jump[0] == 0x3d600000 + ((val + 0x8000) >> 16)
 187             && entry->jump[1] == 0x396b0000 + (val & 0xffff))
 188                 return 1;
 189         return 0;
 190 }
 191
 192 /* Set up a trampoline in the PLT to bounce us to the distant function */
 193 static uint32_t do_plt_call(void *location,
 194                             Elf32_Addr val,
 195                             Elf32_Shdr *sechdrs,
 196                             struct module *mod)
 197 {
 198         struct ppc_plt_entry *entry;
 199
 200         DEBUGP("Doing plt for call to 0x%x at 0x%x\n", val, (unsigned int)location);
 201         /* Init, or core PLT? */
 202         if (location >= mod->module_core
 203             && location < mod->module_core + mod->core_size)
 204                 entry = (void *)sechdrs[mod->arch.core_plt_section].sh_addr;
 205         else
 206                 entry = (void *)sechdrs[mod->arch.init_plt_section].sh_addr;
 207
 208         /* Find this entry, or if that fails, the next avail. entry */
 209         while (entry->jump[0]) {
 210                 if (entry_matches(entry, val)) return (uint32_t)entry;
 211                 entry++;
 212         }
 213
 214         /* Stolen from Paul Mackerras as well... */
 215         entry->jump[0] = 0x3d600000+((val+0x8000)>>16); /* lis r11,sym@ha */
 216         entry->jump[1] = 0x396b0000 + (val&0xffff);     /* addi r11,r11,sym@l*/
 217         entry->jump[2] = 0x7d6903a6;                    /* mtctr r11 */
 218         entry->jump[3] = 0x4e800420;                    /* bctr */
 219
 220         DEBUGP("Initialized plt for 0x%x at %p\n", val, entry);
 221         return (uint32_t)entry;
 222 }
 223
 224 int apply_relocate_add(Elf32_Shdr *sechdrs,
 225                        const char *strtab,
 226                        unsigned int symindex,
 227                        unsigned int relsec,
 228                        struct module *module)
 229 {
 230         unsigned int i;
 231         Elf32_Rela *rela = (void *)sechdrs[relsec].sh_addr;
 232         Elf32_Sym *sym;
 233         uint32_t *location;
 234         uint32_t value;
 235
 236         DEBUGP("Applying ADD relocate section %u to %u\n", relsec,
 237                sechdrs[relsec].sh_info);
 238         for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rela); i++) {
 239                 /* This is where to make the change */
 240                 location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
 241                         + rela[i].r_offset;
 242                 /* This is the symbol it is referring to.  Note that all
 243                    undefined symbols have been resolved.  */
 244                 sym = (Elf32_Sym *)sechdrs[symindex].sh_addr
 245                         + ELF32_R_SYM(rela[i].r_info);
 246                 /* `Everything is relative'. */
 247                 value = sym->st_value + rela[i].r_addend;
 248
 249                 switch (ELF32_R_TYPE(rela[i].r_info)) {
 250                 case R_PPC_ADDR32:
 251                         /* Simply set it */
 252                         *(uint32_t *)location = value;
 253                         break;
 254
 255                 case R_PPC_ADDR16_LO:
 256                         /* Low half of the symbol */
 257                         *(uint16_t *)location = value;
 258                         break;
 259
 260                 case R_PPC_ADDR16_HI:
 261                         /* Higher half of the symbol */
 262                         *(uint16_t *)location = (value >> 16);
 263                         break;
 264
 265                 case R_PPC_ADDR16_HA:
 266                         /* Sign-adjusted lower 16 bits: PPC ELF ABI says:
 267                            (((x >> 16) + ((x & 0x8000) ? 1 : 0))) & 0xFFFF.
 268                            This is the same, only sane.
 269                          */
 270                         *(uint16_t *)location = (value + 0x8000) >> 16;
 271                         break;
 272
 273                 case R_PPC_REL24:
 274                         if ((int)(value - (uint32_t)location) < -0x02000000
 275                             || (int)(value - (uint32_t)location) >= 0x02000000)
 276                                 value = do_plt_call(location, value,
 277                                                     sechdrs, module);
 278
 279                         /* Only replace bits 2 through 26 */
 280                         DEBUGP("REL24 value = %08X. location = %08X\n",
 281                                value, (uint32_t)location);
 282                         DEBUGP("Location before: %08X.\n",
 283                                *(uint32_t *)location);
 284                         *(uint32_t *)location
 285                                 = (*(uint32_t *)location & ~0x03fffffc)
 286                                 | ((value - (uint32_t)location)
 287                                    & 0x03fffffc);
 288                         DEBUGP("Location after: %08X.\n",
 289                                *(uint32_t *)location);
 290                         DEBUGP("ie. jump to %08X+%08X = %08X\n",
 291                                *(uint32_t *)location & 0x03fffffc,
 292                                (uint32_t)location,
 293                                (*(uint32_t *)location & 0x03fffffc)
 294                                + (uint32_t)location);
 295                         break;
 296
 297                 case R_PPC_REL32:
 298                         /* 32-bit relative jump. */
 299                         *(uint32_t *)location = value - (uint32_t)location;
 300                         break;
 301
 302                 default:
 303                         printk("%s: unknown ADD relocation: %u\n",
 304                                module->name,
 305                                ELF32_R_TYPE(rela[i].r_info));
 306                         return -ENOEXEC;
 307                 }
 308         }
 309         return 0;
 310 }