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
  30 #include "setup.h"
  31
  32 #if 0
  33 #define DEBUGP printk
  34 #else
  35 #define DEBUGP(fmt , ...)
  36 #endif
  37
  38 /* Count how many different relocations (different symbol, different
  39    addend) */
  40 static unsigned int count_relocs(const Elf32_Rela *rela, unsigned int num)
  41 {
  42         unsigned int i, r_info, r_addend, _count_relocs;
  43
  44         _count_relocs = 0;
  45         r_info = 0;
  46         r_addend = 0;
  47         for (i = 0; i < num; i++)
  48                 /* Only count 24-bit relocs, others don't need stubs */
  49                 if (ELF32_R_TYPE(rela[i].r_info) == R_PPC_REL24 &&
  50                     (r_info != ELF32_R_SYM(rela[i].r_info) ||
  51                      r_addend != rela[i].r_addend)) {
  52                         _count_relocs++;
  53                         r_info = ELF32_R_SYM(rela[i].r_info);
  54                         r_addend = rela[i].r_addend;
  55                 }
  56
  57 #ifdef CONFIG_DYNAMIC_FTRACE
  58         _count_relocs++;        /* add one for ftrace_caller */
  59 #endif
  60         return _count_relocs;
  61 }
  62
  63 static int relacmp(const void *_x, const void *_y)
  64 {
  65         const Elf32_Rela *x, *y;
  66
  67         y = (Elf32_Rela *)_x;
  68         x = (Elf32_Rela *)_y;
  69
  70         /* Compare the entire r_info (as opposed to ELF32_R_SYM(r_info) only) to
  71          * make the comparison cheaper/faster. It won't affect the sorting or
  72          * the counting algorithms' performance
  73          */
  74         if (x->r_info < y->r_info)
  75                 return -1;
  76         else if (x->r_info > y->r_info)
  77                 return 1;
  78         else if (x->r_addend < y->r_addend)
  79                 return -1;
  80         else if (x->r_addend > y->r_addend)
  81                 return 1;
  82         else
  83                 return 0;
  84 }
  85
  86 static void relaswap(void *_x, void *_y, int size)
  87 {
  88         uint32_t *x, *y, tmp;
  89         int i;
  90
  91         y = (uint32_t *)_x;
  92         x = (uint32_t *)_y;
  93
  94         for (i = 0; i < sizeof(Elf32_Rela) / sizeof(uint32_t); i++) {
  95                 tmp = x[i];
  96                 x[i] = y[i];
  97                 y[i] = tmp;
  98         }
  99 }
 100
 101 /* Get the potential trampolines size required of the init and
 102    non-init sections */
 103 static unsigned long get_plt_size(const Elf32_Ehdr *hdr,
 104                                   const Elf32_Shdr *sechdrs,
 105                                   const char *secstrings,
 106                                   int is_init)
 107 {
 108         unsigned long ret = 0;
 109         unsigned i;
 110
 111         /* Everything marked ALLOC (this includes the exported
 112            symbols) */
 113         for (i = 1; i < hdr->e_shnum; i++) {
 114                 /* If it's called *.init*, and we're not init, we're
 115                    not interested */
 116                 if ((strstr(secstrings + sechdrs[i].sh_name, ".init") != 0)
 117                     != is_init)
 118                         continue;
 119
 120                 /* We don't want to look at debug sections. */
 121                 if (strstr(secstrings + sechdrs[i].sh_name, ".debug") != 0)
 122                         continue;
 123
 124                 if (sechdrs[i].sh_type == SHT_RELA) {
 125                         DEBUGP("Found relocations in section %u\n", i);
 126                         DEBUGP("Ptr: %p.  Number: %u\n",
 127                                (void *)hdr + sechdrs[i].sh_offset,
 128                                sechdrs[i].sh_size / sizeof(Elf32_Rela));
 129
 130                         /* Sort the relocation information based on a symbol and
 131                          * addend key. This is a stable O(n*log n) complexity
 132                          * alogrithm but it will reduce the complexity of
 133                          * count_relocs() to linear complexity O(n)
 134                          */
 135                         sort((void *)hdr + sechdrs[i].sh_offset,
 136                              sechdrs[i].sh_size / sizeof(Elf32_Rela),
 137                              sizeof(Elf32_Rela), relacmp, relaswap);
 138
 139                         ret += count_relocs((void *)hdr
 140                                              + sechdrs[i].sh_offset,
 141                                              sechdrs[i].sh_size
 142                                              / sizeof(Elf32_Rela))
 143                                 * sizeof(struct ppc_plt_entry);
 144                 }
 145         }
 146
 147         return ret;
 148 }
 149
 150 int module_frob_arch_sections(Elf32_Ehdr *hdr,
 151                               Elf32_Shdr *sechdrs,
 152                               char *secstrings,
 153                               struct module *me)
 154 {
 155         unsigned int i;
 156
 157         /* Find .plt and .init.plt sections */
 158         for (i = 0; i < hdr->e_shnum; i++) {
 159                 if (strcmp(secstrings + sechdrs[i].sh_name, ".init.plt") == 0)
 160                         me->arch.init_plt_section = i;
 161                 else if (strcmp(secstrings + sechdrs[i].sh_name, ".plt") == 0)
 162                         me->arch.core_plt_section = i;
 163         }
 164         if (!me->arch.core_plt_section || !me->arch.init_plt_section) {
 165                 printk("Module doesn't contain .plt or .init.plt sections.\n");
 166                 return -ENOEXEC;
 167         }
 168
 169         /* Override their sizes */
 170         sechdrs[me->arch.core_plt_section].sh_size
 171                 = get_plt_size(hdr, sechdrs, secstrings, 0);
 172         sechdrs[me->arch.init_plt_section].sh_size
 173                 = get_plt_size(hdr, sechdrs, secstrings, 1);
 174         return 0;
 175 }
 176
 177 static inline int entry_matches(struct ppc_plt_entry *entry, Elf32_Addr val)
 178 {
 179         if (entry->jump[0] == 0x3d600000 + ((val + 0x8000) >> 16)
 180             && entry->jump[1] == 0x396b0000 + (val & 0xffff))
 181                 return 1;
 182         return 0;
 183 }
 184
 185 /* Set up a trampoline in the PLT to bounce us to the distant function */
 186 static uint32_t do_plt_call(void *location,
 187                             Elf32_Addr val,
 188                             Elf32_Shdr *sechdrs,
 189                             struct module *mod)
 190 {
 191         struct ppc_plt_entry *entry;
 192
 193         DEBUGP("Doing plt for call to 0x%x at 0x%x\n", val, (unsigned int)location);
 194         /* Init, or core PLT? */
 195         if (location >= mod->module_core
 196             && location < mod->module_core + mod->core_size)
 197                 entry = (void *)sechdrs[mod->arch.core_plt_section].sh_addr;
 198         else
 199                 entry = (void *)sechdrs[mod->arch.init_plt_section].sh_addr;
 200
 201         /* Find this entry, or if that fails, the next avail. entry */
 202         while (entry->jump[0]) {
 203                 if (entry_matches(entry, val)) return (uint32_t)entry;
 204                 entry++;
 205         }
 206
 207         /* Stolen from Paul Mackerras as well... */
 208         entry->jump[0] = 0x3d600000+((val+0x8000)>>16); /* lis r11,sym@ha */
 209         entry->jump[1] = 0x396b0000 + (val&0xffff);     /* addi r11,r11,sym@l*/
 210         entry->jump[2] = 0x7d6903a6;                    /* mtctr r11 */
 211         entry->jump[3] = 0x4e800420;                    /* bctr */
 212
 213         DEBUGP("Initialized plt for 0x%x at %p\n", val, entry);
 214         return (uint32_t)entry;
 215 }
 216
 217 int apply_relocate_add(Elf32_Shdr *sechdrs,
 218                        const char *strtab,
 219                        unsigned int symindex,
 220                        unsigned int relsec,
 221                        struct module *module)
 222 {
 223         unsigned int i;
 224         Elf32_Rela *rela = (void *)sechdrs[relsec].sh_addr;
 225         Elf32_Sym *sym;
 226         uint32_t *location;
 227         uint32_t value;
 228
 229         DEBUGP("Applying ADD relocate section %u to %u\n", relsec,
 230                sechdrs[relsec].sh_info);
 231         for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rela); i++) {
 232                 /* This is where to make the change */
 233                 location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
 234                         + rela[i].r_offset;
 235                 /* This is the symbol it is referring to.  Note that all
 236                    undefined symbols have been resolved.  */
 237                 sym = (Elf32_Sym *)sechdrs[symindex].sh_addr
 238                         + ELF32_R_SYM(rela[i].r_info);
 239                 /* `Everything is relative'. */
 240                 value = sym->st_value + rela[i].r_addend;
 241
 242                 switch (ELF32_R_TYPE(rela[i].r_info)) {
 243                 case R_PPC_ADDR32:
 244                         /* Simply set it */
 245                         *(uint32_t *)location = value;
 246                         break;
 247
 248                 case R_PPC_ADDR16_LO:
 249                         /* Low half of the symbol */
 250                         *(uint16_t *)location = value;
 251                         break;
 252
 253                 case R_PPC_ADDR16_HI:
 254                         /* Higher half of the symbol */
 255                         *(uint16_t *)location = (value >> 16);
 256                         break;
 257
 258                 case R_PPC_ADDR16_HA:
 259                         /* Sign-adjusted lower 16 bits: PPC ELF ABI says:
 260                            (((x >> 16) + ((x & 0x8000) ? 1 : 0))) & 0xFFFF.
 261                            This is the same, only sane.
 262                          */
 263                         *(uint16_t *)location = (value + 0x8000) >> 16;
 264                         break;
 265
 266                 case R_PPC_REL24:
 267                         if ((int)(value - (uint32_t)location) < -0x02000000
 268                             || (int)(value - (uint32_t)location) >= 0x02000000)
 269                                 value = do_plt_call(location, value,
 270                                                     sechdrs, module);
 271
 272                         /* Only replace bits 2 through 26 */
 273                         DEBUGP("REL24 value = %08X. location = %08X\n",
 274                                value, (uint32_t)location);
 275                         DEBUGP("Location before: %08X.\n",
 276                                *(uint32_t *)location);
 277                         *(uint32_t *)location
 278                                 = (*(uint32_t *)location & ~0x03fffffc)
 279                                 | ((value - (uint32_t)location)
 280                                    & 0x03fffffc);
 281                         DEBUGP("Location after: %08X.\n",
 282                                *(uint32_t *)location);
 283                         DEBUGP("ie. jump to %08X+%08X = %08X\n",
 284                                *(uint32_t *)location & 0x03fffffc,
 285                                (uint32_t)location,
 286                                (*(uint32_t *)location & 0x03fffffc)
 287                                + (uint32_t)location);
 288                         break;
 289
 290                 case R_PPC_REL32:
 291                         /* 32-bit relative jump. */
 292                         *(uint32_t *)location = value - (uint32_t)location;
 293                         break;
 294
 295                 default:
 296                         printk("%s: unknown ADD relocation: %u\n",
 297                                module->name,
 298                                ELF32_R_TYPE(rela[i].r_info));
 299                         return -ENOEXEC;
 300                 }
 301         }
 302 #ifdef CONFIG_DYNAMIC_FTRACE
 303         module->arch.tramp =
 304                 do_plt_call(module->module_core,
 305                             (unsigned long)ftrace_caller,
 306                             sechdrs, module);
 307 #endif
 308         return 0;
 309 }