arch/metag/kernel/module.c

   1 /*  Kernel module help for Meta.
   2
   3     This program is free software; you can redistribute it and/or modify
   4     it under the terms of the GNU General Public License as published by
   5     the Free Software Foundation; either version 2 of the License, or
   6     (at your option) any later version.
   7
   8     This program is distributed in the hope that it will be useful,
   9     but WITHOUT ANY WARRANTY; without even the implied warranty of
  10     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11     GNU General Public License for more details.
  12 */
  13 #include <linux/moduleloader.h>
  14 #include <linux/elf.h>
  15 #include <linux/vmalloc.h>
  16 #include <linux/fs.h>
  17 #include <linux/string.h>
  18 #include <linux/kernel.h>
  19 #include <linux/sort.h>
  20
  21 #include <asm/unaligned.h>
  22
  23 /* Count how many different relocations (different symbol, different
  24    addend) */
  25 static unsigned int count_relocs(const Elf32_Rela *rela, unsigned int num)
  26 {
  27         unsigned int i, r_info, r_addend, _count_relocs;
  28
  29         _count_relocs = 0;
  30         r_info = 0;
  31         r_addend = 0;
  32         for (i = 0; i < num; i++)
  33                 /* Only count relbranch relocs, others don't need stubs */
  34                 if (ELF32_R_TYPE(rela[i].r_info) == R_METAG_RELBRANCH &&
  35                     (r_info != ELF32_R_SYM(rela[i].r_info) ||
  36                      r_addend != rela[i].r_addend)) {
  37                         _count_relocs++;
  38                         r_info = ELF32_R_SYM(rela[i].r_info);
  39                         r_addend = rela[i].r_addend;
  40                 }
  41
  42         return _count_relocs;
  43 }
  44
  45 static int relacmp(const void *_x, const void *_y)
  46 {
  47         const Elf32_Rela *x, *y;
  48
  49         y = (Elf32_Rela *)_x;
  50         x = (Elf32_Rela *)_y;
  51
  52         /* Compare the entire r_info (as opposed to ELF32_R_SYM(r_info) only) to
  53          * make the comparison cheaper/faster. It won't affect the sorting or
  54          * the counting algorithms' performance
  55          */
  56         if (x->r_info < y->r_info)
  57                 return -1;
  58         else if (x->r_info > y->r_info)
  59                 return 1;
  60         else if (x->r_addend < y->r_addend)
  61                 return -1;
  62         else if (x->r_addend > y->r_addend)
  63                 return 1;
  64         else
  65                 return 0;
  66 }
  67
  68 static void relaswap(void *_x, void *_y, int size)
  69 {
  70         uint32_t *x, *y, tmp;
  71         int i;
  72
  73         y = (uint32_t *)_x;
  74         x = (uint32_t *)_y;
  75
  76         for (i = 0; i < sizeof(Elf32_Rela) / sizeof(uint32_t); i++) {
  77                 tmp = x[i];
  78                 x[i] = y[i];
  79                 y[i] = tmp;
  80         }
  81 }
  82
  83 /* Get the potential trampolines size required of the init and
  84    non-init sections */
  85 static unsigned long get_plt_size(const Elf32_Ehdr *hdr,
  86                                   const Elf32_Shdr *sechdrs,
  87                                   const char *secstrings,
  88                                   int is_init)
  89 {
  90         unsigned long ret = 0;
  91         unsigned i;
  92
  93         /* Everything marked ALLOC (this includes the exported
  94            symbols) */
  95         for (i = 1; i < hdr->e_shnum; i++) {
  96                 /* If it's called *.init*, and we're not init, we're
  97                    not interested */
  98                 if ((strstr(secstrings + sechdrs[i].sh_name, ".init") != NULL)
  99                     != is_init)
 100                         continue;
 101
 102                 /* We don't want to look at debug sections. */
 103                 if (strstr(secstrings + sechdrs[i].sh_name, ".debug") != NULL)
 104                         continue;
 105
 106                 if (sechdrs[i].sh_type == SHT_RELA) {
 107                         pr_debug("Found relocations in section %u\n", i);
 108                         pr_debug("Ptr: %p.  Number: %u\n",
 109                                  (void *)hdr + sechdrs[i].sh_offset,
 110                                  sechdrs[i].sh_size / sizeof(Elf32_Rela));
 111
 112                         /* Sort the relocation information based on a symbol and
 113                          * addend key. This is a stable O(n*log n) complexity
 114                          * alogrithm but it will reduce the complexity of
 115                          * count_relocs() to linear complexity O(n)
 116                          */
 117                         sort((void *)hdr + sechdrs[i].sh_offset,
 118                              sechdrs[i].sh_size / sizeof(Elf32_Rela),
 119                              sizeof(Elf32_Rela), relacmp, relaswap);
 120
 121                         ret += count_relocs((void *)hdr
 122                                              + sechdrs[i].sh_offset,
 123                                              sechdrs[i].sh_size
 124                                              / sizeof(Elf32_Rela))
 125                                 * sizeof(struct metag_plt_entry);
 126                 }
 127         }
 128
 129         return ret;
 130 }
 131
 132 int module_frob_arch_sections(Elf32_Ehdr *hdr,
 133                               Elf32_Shdr *sechdrs,
 134                               char *secstrings,
 135                               struct module *me)
 136 {
 137         unsigned int i;
 138
 139         /* Find .plt and .init.plt sections */
 140         for (i = 0; i < hdr->e_shnum; i++) {
 141                 if (strcmp(secstrings + sechdrs[i].sh_name, ".init.plt") == 0)
 142                         me->arch.init_plt_section = i;
 143                 else if (strcmp(secstrings + sechdrs[i].sh_name, ".plt") == 0)
 144                         me->arch.core_plt_section = i;
 145         }
 146         if (!me->arch.core_plt_section || !me->arch.init_plt_section) {
 147                 pr_err("Module doesn't contain .plt or .init.plt sections.\n");
 148                 return -ENOEXEC;
 149         }
 150
 151         /* Override their sizes */
 152         sechdrs[me->arch.core_plt_section].sh_size
 153                 = get_plt_size(hdr, sechdrs, secstrings, 0);
 154         sechdrs[me->arch.core_plt_section].sh_type = SHT_NOBITS;
 155         sechdrs[me->arch.init_plt_section].sh_size
 156                 = get_plt_size(hdr, sechdrs, secstrings, 1);
 157         sechdrs[me->arch.init_plt_section].sh_type = SHT_NOBITS;
 158         return 0;
 159 }
 160
 161 /* Set up a trampoline in the PLT to bounce us to the distant function */
 162 static uint32_t do_plt_call(void *location, Elf32_Addr val,
 163                             Elf32_Shdr *sechdrs, struct module *mod)
 164 {
 165         struct metag_plt_entry *entry;
 166         /* Instructions used to do the indirect jump.  */
 167         uint32_t tramp[2];
 168
 169         /* We have to trash a register, so we assume that any control
 170            transfer more than 21-bits away must be a function call
 171            (so we can use a call-clobbered register).  */
 172
 173         /* MOVT D0Re0,#HI(v) */
 174         tramp[0] = 0x02000005 | (((val & 0xffff0000) >> 16) << 3);
 175         /* JUMP D0Re0,#LO(v) */
 176         tramp[1] = 0xac000001 | ((val & 0x0000ffff) << 3);
 177
 178         /* Init, or core PLT? */
 179         if (location >= mod->module_core
 180             && location < mod->module_core + mod->core_size)
 181                 entry = (void *)sechdrs[mod->arch.core_plt_section].sh_addr;
 182         else
 183                 entry = (void *)sechdrs[mod->arch.init_plt_section].sh_addr;
 184
 185         /* Find this entry, or if that fails, the next avail. entry */
 186         while (entry->tramp[0])
 187                 if (entry->tramp[0] == tramp[0] && entry->tramp[1] == tramp[1])
 188                         return (uint32_t)entry;
 189                 else
 190                         entry++;
 191
 192         entry->tramp[0] = tramp[0];
 193         entry->tramp[1] = tramp[1];
 194
 195         return (uint32_t)entry;
 196 }
 197
 198 int apply_relocate_add(Elf32_Shdr *sechdrs,
 199                    const char *strtab,
 200                    unsigned int symindex,
 201                    unsigned int relsec,
 202                    struct module *me)
 203 {
 204         unsigned int i;
 205         Elf32_Rela *rel = (void *)sechdrs[relsec].sh_addr;
 206         Elf32_Sym *sym;
 207         Elf32_Addr relocation;
 208         uint32_t *location;
 209         int32_t value;
 210
 211         pr_debug("Applying relocate section %u to %u\n", relsec,
 212                  sechdrs[relsec].sh_info);
 213         for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) {
 214                 /* This is where to make the change */
 215                 location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
 216                         + rel[i].r_offset;
 217                 /* This is the symbol it is referring to.  Note that all
 218                    undefined symbols have been resolved.  */
 219                 sym = (Elf32_Sym *)sechdrs[symindex].sh_addr
 220                         + ELF32_R_SYM(rel[i].r_info);
 221                 relocation = sym->st_value + rel[i].r_addend;
 222
 223                 switch (ELF32_R_TYPE(rel[i].r_info)) {
 224                 case R_METAG_NONE:
 225                         break;
 226                 case R_METAG_HIADDR16:
 227                         relocation >>= 16;
 228                 case R_METAG_LOADDR16:
 229                         *location = (*location & 0xfff80007) |
 230                                 ((relocation & 0xffff) << 3);
 231                         break;
 232                 case R_METAG_ADDR32:
 233                         /*
 234                          * Packed data structures may cause a misaligned
 235                          * R_METAG_ADDR32 to be emitted.
 236                          */
 237                         put_unaligned(relocation, location);
 238                         break;
 239                 case R_METAG_GETSETOFF:
 240                         *location += ((relocation & 0xfff) << 7);
 241                         break;
 242                 case R_METAG_RELBRANCH:
 243                         if (*location & (0x7ffff << 5)) {
 244                                 pr_err("bad relbranch relocation\n");
 245                                 break;
 246                         }
 247
 248                         /* This jump is too big for the offset slot. Build
 249                          * a PLT to jump through to get to where we want to go.
 250                          * NB: 21bit check - not scaled to 19bit yet
 251                          */
 252                         if (((int32_t)(relocation -
 253                                        (uint32_t)location) > 0xfffff) ||
 254                             ((int32_t)(relocation -
 255                                        (uint32_t)location) < -0xfffff)) {
 256                                 relocation = do_plt_call(location, relocation,
 257                                                          sechdrs, me);
 258                         }
 259
 260                         value = relocation - (uint32_t)location;
 261
 262                         /* branch instruction aligned */
 263                         value /= 4;
 264
 265                         if ((value > 0x7ffff) || (value < -0x7ffff)) {
 266                                 /*
 267                                  * this should have been caught by the code
 268                                  * above!
 269                                  */
 270                                 pr_err("overflow of relbranch reloc\n");
 271                         }
 272
 273                         *location = (*location & (~(0x7ffff << 5))) |
 274                                 ((value & 0x7ffff) << 5);
 275                         break;
 276
 277                 default:
 278                         pr_err("module %s: Unknown relocation: %u\n",
 279                                me->name, ELF32_R_TYPE(rel[i].r_info));
 280                         return -ENOEXEC;
 281                 }
 282         }
 283         return 0;
 284 }