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/ftrace.h>
  26 #include <linux/cache.h>
  27 #include <linux/bug.h>
  28 #include <linux/sort.h>
  29 #include <asm/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 #ifdef CONFIG_DYNAMIC_FTRACE
  57         _count_relocs++;        /* add one for ftrace_caller */
  58 #endif
  59         return _count_relocs;
  60 }
  61
  62 static int relacmp(const void *_x, const void *_y)
  63 {
  64         const Elf32_Rela *x, *y;
  65
  66         y = (Elf32_Rela *)_x;
  67         x = (Elf32_Rela *)_y;
  68
  69         /* Compare the entire r_info (as opposed to ELF32_R_SYM(r_info) only) to
  70          * make the comparison cheaper/faster. It won't affect the sorting or
  71          * the counting algorithms' performance
  72          */
  73         if (x->r_info < y->r_info)
  74                 return -1;
  75         else if (x->r_info > y->r_info)
  76                 return 1;
  77         else if (x->r_addend < y->r_addend)
  78                 return -1;
  79         else if (x->r_addend > y->r_addend)
  80                 return 1;
  81         else
  82                 return 0;
  83 }
  84
  85 static void relaswap(void *_x, void *_y, int size)
  86 {
  87         uint32_t *x, *y, tmp;
  88         int i;
  89
  90         y = (uint32_t *)_x;
  91         x = (uint32_t *)_y;
  92
  93         for (i = 0; i < sizeof(Elf32_Rela) / sizeof(uint32_t); i++) {
  94                 tmp = x[i];
  95                 x[i] = y[i];
  96                 y[i] = tmp;
  97         }
  98 }
  99
 100 /* Get the potential trampolines size required of the init and
 101    non-init sections */
 102 static unsigned long get_plt_size(const Elf32_Ehdr *hdr,
 103                                   const Elf32_Shdr *sechdrs,
 104                                   const char *secstrings,
 105                                   int is_init)
 106 {
 107         unsigned long ret = 0;
 108         unsigned i;
 109
 110         /* Everything marked ALLOC (this includes the exported
 111            symbols) */
 112         for (i = 1; i < hdr->e_shnum; i++) {
 113                 /* If it's called *.init*, and we're not init, we're
 114                    not interested */
 115                 if ((strstr(secstrings + sechdrs[i].sh_name, ".init") != 0)
 116                     != is_init)
 117                         continue;
 118
 119                 /* We don't want to look at debug sections. */
 120                 if (strstr(secstrings + sechdrs[i].sh_name, ".debug") != 0)
 121                         continue;
 122
 123                 if (sechdrs[i].sh_type == SHT_RELA) {
 124                         DEBUGP("Found relocations in section %u\n", i);
 125                         DEBUGP("Ptr: %p.  Number: %u\n",
 126                                (void *)hdr + sechdrs[i].sh_offset,
 127                                sechdrs[i].sh_size / sizeof(Elf32_Rela));
 128
 129                         /* Sort the relocation information based on a symbol and
 130                          * addend key. This is a stable O(n*log n) complexity
 131                          * alogrithm but it will reduce the complexity of
 132                          * count_relocs() to linear complexity O(n)
 133                          */
 134                         sort((void *)hdr + sechdrs[i].sh_offset,
 135                              sechdrs[i].sh_size / sizeof(Elf32_Rela),
 136                              sizeof(Elf32_Rela), relacmp, relaswap);
 137
 138                         ret += count_relocs((void *)hdr
 139                                              + sechdrs[i].sh_offset,
 140                                              sechdrs[i].sh_size
 141                                              / sizeof(Elf32_Rela))
 142                                 * sizeof(struct ppc_plt_entry);
 143                 }
 144         }
 145
 146         return ret;
 147 }
 148
 149 int module_frob_arch_sections(Elf32_Ehdr *hdr,
 150                               Elf32_Shdr *sechdrs,
 151                               char *secstrings,
 152                               struct module *me)
 153 {
 154         unsigned int i;
 155
 156         /* Find .plt and .init.plt sections */
 157         for (i = 0; i < hdr->e_shnum; i++) {
 158                 if (strcmp(secstrings + sechdrs[i].sh_name, ".init.plt") == 0)
 159                         me->arch.init_plt_section = i;
 160                 else if (strcmp(secstrings + sechdrs[i].sh_name, ".plt") == 0)
 161                         me->arch.core_plt_section = i;
 162         }
 163         if (!me->arch.core_plt_section || !me->arch.init_plt_section) {
 164                 printk("Module doesn't contain .plt or .init.plt sections.\n");
 165                 return -ENOEXEC;
 166         }
 167
 168         /* Override their sizes */
 169         sechdrs[me->arch.core_plt_section].sh_size
 170                 = get_plt_size(hdr, sechdrs, secstrings, 0);
 171         sechdrs[me->arch.init_plt_section].sh_size
 172                 = get_plt_size(hdr, sechdrs, secstrings, 1);
 173         return 0;
 174 }
 175
 176 static inline int entry_matches(struct ppc_plt_entry *entry, Elf32_Addr val)
 177 {
 178         if (entry->jump[0] == 0x3d800000 + ((val + 0x8000) >> 16)
 179             && entry->jump[1] == 0x398c0000 + (val & 0xffff))
 180                 return 1;
 181         return 0;
 182 }
 183
 184 /* Set up a trampoline in the PLT to bounce us to the distant function */
 185 static uint32_t do_plt_call(void *location,
 186                             Elf32_Addr val,
 187                             Elf32_Shdr *sechdrs,
 188                             struct module *mod)
 189 {
 190         struct ppc_plt_entry *entry;
 191
 192         DEBUGP("Doing plt for call to 0x%x at 0x%x\n", val, (unsigned int)location);
 193         /* Init, or core PLT? */
 194         if (location >= mod->module_core
 195             && location < mod->module_core + mod->core_size)
 196                 entry = (void *)sechdrs[mod->arch.core_plt_section].sh_addr;
 197         else
 198                 entry = (void *)sechdrs[mod->arch.init_plt_section].sh_addr;
 199
 200         /* Find this entry, or if that fails, the next avail. entry */
 201         while (entry->jump[0]) {
 202                 if (entry_matches(entry, val)) return (uint32_t)entry;
 203                 entry++;
 204         }
 205
 206         entry->jump[0] = 0x3d800000+((val+0x8000)>>16); /* lis r12,sym@ha */
 207         entry->jump[1] = 0x398c0000 + (val&0xffff);     /* addi r12,r12,sym@l*/
 208         entry->jump[2] = 0x7d8903a6;                    /* mtctr r12 */
 209         entry->jump[3] = 0x4e800420;                    /* bctr */
 210
 211         DEBUGP("Initialized plt for 0x%x at %p\n", val, entry);
 212         return (uint32_t)entry;
 213 }
 214
 215 int apply_relocate_add(Elf32_Shdr *sechdrs,
 216                        const char *strtab,
 217                        unsigned int symindex,
 218                        unsigned int relsec,
 219                        struct module *module)
 220 {
 221         unsigned int i;
 222         Elf32_Rela *rela = (void *)sechdrs[relsec].sh_addr;
 223         Elf32_Sym *sym;
 224         uint32_t *location;
 225         uint32_t value;
 226
 227         DEBUGP("Applying ADD relocate section %u to %u\n", relsec,
 228                sechdrs[relsec].sh_info);
 229         for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rela); i++) {
 230                 /* This is where to make the change */
 231                 location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
 232                         + rela[i].r_offset;
 233                 /* This is the symbol it is referring to.  Note that all
 234                    undefined symbols have been resolved.  */
 235                 sym = (Elf32_Sym *)sechdrs[symindex].sh_addr
 236                         + ELF32_R_SYM(rela[i].r_info);
 237                 /* `Everything is relative'. */
 238                 value = sym->st_value + rela[i].r_addend;
 239
 240                 switch (ELF32_R_TYPE(rela[i].r_info)) {
 241                 case R_PPC_ADDR32:
 242                         /* Simply set it */
 243                         *(uint32_t *)location = value;
 244                         break;
 245
 246                 case R_PPC_ADDR16_LO:
 247                         /* Low half of the symbol */
 248                         *(uint16_t *)location = value;
 249                         break;
 250
 251                 case R_PPC_ADDR16_HI:
 252                         /* Higher half of the symbol */
 253                         *(uint16_t *)location = (value >> 16);
 254                         break;
 255
 256                 case R_PPC_ADDR16_HA:
 257                         /* Sign-adjusted lower 16 bits: PPC ELF ABI says:
 258                            (((x >> 16) + ((x & 0x8000) ? 1 : 0))) & 0xFFFF.
 259                            This is the same, only sane.
 260                          */
 261                         *(uint16_t *)location = (value + 0x8000) >> 16;
 262                         break;
 263
 264                 case R_PPC_REL24:
 265                         if ((int)(value - (uint32_t)location) < -0x02000000
 266                             || (int)(value - (uint32_t)location) >= 0x02000000)
 267                                 value = do_plt_call(location, value,
 268                                                     sechdrs, module);
 269
 270                         /* Only replace bits 2 through 26 */
 271                         DEBUGP("REL24 value = %08X. location = %08X\n",
 272                                value, (uint32_t)location);
 273                         DEBUGP("Location before: %08X.\n",
 274                                *(uint32_t *)location);
 275                         *(uint32_t *)location
 276                                 = (*(uint32_t *)location & ~0x03fffffc)
 277                                 | ((value - (uint32_t)location)
 278                                    & 0x03fffffc);
 279                         DEBUGP("Location after: %08X.\n",
 280                                *(uint32_t *)location);
 281                         DEBUGP("ie. jump to %08X+%08X = %08X\n",
 282                                *(uint32_t *)location & 0x03fffffc,
 283                                (uint32_t)location,
 284                                (*(uint32_t *)location & 0x03fffffc)
 285                                + (uint32_t)location);
 286                         break;
 287
 288                 case R_PPC_REL32:
 289                         /* 32-bit relative jump. */
 290                         *(uint32_t *)location = value - (uint32_t)location;
 291                         break;
 292
 293                 default:
 294                         printk("%s: unknown ADD relocation: %u\n",
 295                                module->name,
 296                                ELF32_R_TYPE(rela[i].r_info));
 297                         return -ENOEXEC;
 298                 }
 299         }
 300 #ifdef CONFIG_DYNAMIC_FTRACE
 301         module->arch.tramp =
 302                 do_plt_call(module->module_core,
 303                             (unsigned long)ftrace_caller,
 304                             sechdrs, module);
 305 #endif
 306         return 0;
 307 }