arch/alpha/kernel/module.c

   1 /*  Kernel module help for Alpha.
   2     Copyright (C) 2002 Richard Henderson.
   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/moduleloader.h>
  19 #include <linux/elf.h>
  20 #include <linux/vmalloc.h>
  21 #include <linux/fs.h>
  22 #include <linux/string.h>
  23 #include <linux/kernel.h>
  24 #include <linux/slab.h>
  25
  26 #if 0
  27 #define DEBUGP printk
  28 #else
  29 #define DEBUGP(fmt...)
  30 #endif
  31
  32 /* Allocate the GOT at the end of the core sections.  */
  33
  34 struct got_entry {
  35         struct got_entry *next;
  36         Elf64_Sxword r_addend;
  37         int got_offset;
  38 };
  39
  40 static inline void
  41 process_reloc_for_got(Elf64_Rela *rela,
  42                       struct got_entry *chains, Elf64_Xword *poffset)
  43 {
  44         unsigned long r_sym = ELF64_R_SYM (rela->r_info);
  45         unsigned long r_type = ELF64_R_TYPE (rela->r_info);
  46         Elf64_Sxword r_addend = rela->r_addend;
  47         struct got_entry *g;
  48
  49         if (r_type != R_ALPHA_LITERAL)
  50                 return;
  51
  52         for (g = chains + r_sym; g ; g = g->next)
  53                 if (g->r_addend == r_addend) {
  54                         if (g->got_offset == 0) {
  55                                 g->got_offset = *poffset;
  56                                 *poffset += 8;
  57                         }
  58                         goto found_entry;
  59                 }
  60
  61         g = kmalloc (sizeof (*g), GFP_KERNEL);
  62         g->next = chains[r_sym].next;
  63         g->r_addend = r_addend;
  64         g->got_offset = *poffset;
  65         *poffset += 8;
  66         chains[r_sym].next = g;
  67
  68  found_entry:
  69         /* Trick: most of the ELF64_R_TYPE field is unused.  There are
  70            42 valid relocation types, and a 32-bit field.  Co-opt the
  71            bits above 256 to store the got offset for this reloc.  */
  72         rela->r_info |= g->got_offset << 8;
  73 }
  74
  75 int
  76 module_frob_arch_sections(Elf64_Ehdr *hdr, Elf64_Shdr *sechdrs,
  77                           char *secstrings, struct module *me)
  78 {
  79         struct got_entry *chains;
  80         Elf64_Rela *rela;
  81         Elf64_Shdr *esechdrs, *symtab, *s, *got;
  82         unsigned long nsyms, nrela, i;
  83
  84         esechdrs = sechdrs + hdr->e_shnum;
  85         symtab = got = NULL;
  86
  87         /* Find out how large the symbol table is.  Allocate one got_entry
  88            head per symbol.  Normally this will be enough, but not always.
  89            We'll chain different offsets for the symbol down each head.  */
  90         for (s = sechdrs; s < esechdrs; ++s)
  91                 if (s->sh_type == SHT_SYMTAB)
  92                         symtab = s;
  93                 else if (!strcmp(".got", secstrings + s->sh_name)) {
  94                         got = s;
  95                         me->arch.gotsecindex = s - sechdrs;
  96                 }
  97
  98         if (!symtab) {
  99                 printk(KERN_ERR "module %s: no symbol table\n", me->name);
 100                 return -ENOEXEC;
 101         }
 102         if (!got) {
 103                 printk(KERN_ERR "module %s: no got section\n", me->name);
 104                 return -ENOEXEC;
 105         }
 106
 107         nsyms = symtab->sh_size / sizeof(Elf64_Sym);
 108         chains = kcalloc(nsyms, sizeof(struct got_entry), GFP_KERNEL);
 109         if (!chains) {
 110                 printk(KERN_ERR
 111                        "module %s: no memory for symbol chain buffer\n",
 112                        me->name);
 113                 return -ENOMEM;
 114         }
 115
 116         got->sh_size = 0;
 117         got->sh_addralign = 8;
 118         got->sh_type = SHT_NOBITS;
 119
 120         /* Examine all LITERAL relocations to find out what GOT entries
 121            are required.  This sizes the GOT section as well.  */
 122         for (s = sechdrs; s < esechdrs; ++s)
 123                 if (s->sh_type == SHT_RELA) {
 124                         nrela = s->sh_size / sizeof(Elf64_Rela);
 125                         rela = (void *)hdr + s->sh_offset;
 126                         for (i = 0; i < nrela; ++i)
 127                                 process_reloc_for_got(rela+i, chains,
 128                                                       &got->sh_size);
 129                 }
 130
 131         /* Free the memory we allocated.  */
 132         for (i = 0; i < nsyms; ++i) {
 133                 struct got_entry *g, *n;
 134                 for (g = chains[i].next; g ; g = n) {
 135                         n = g->next;
 136                         kfree(g);
 137                 }
 138         }
 139         kfree(chains);
 140
 141         return 0;
 142 }
 143
 144 int
 145 apply_relocate_add(Elf64_Shdr *sechdrs, const char *strtab,
 146                    unsigned int symindex, unsigned int relsec,
 147                    struct module *me)
 148 {
 149         Elf64_Rela *rela = (void *)sechdrs[relsec].sh_addr;
 150         unsigned long i, n = sechdrs[relsec].sh_size / sizeof(*rela);
 151         Elf64_Sym *symtab, *sym;
 152         void *base, *location;
 153         unsigned long got, gp;
 154
 155         DEBUGP("Applying relocate section %u to %u\n", relsec,
 156                sechdrs[relsec].sh_info);
 157
 158         base = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr;
 159         symtab = (Elf64_Sym *)sechdrs[symindex].sh_addr;
 160
 161         /* The small sections were sorted to the end of the segment.
 162            The following should definitely cover them.  */
 163         gp = (u64)me->core_layout.base + me->core_layout.size - 0x8000;
 164         got = sechdrs[me->arch.gotsecindex].sh_addr;
 165
 166         for (i = 0; i < n; i++) {
 167                 unsigned long r_sym = ELF64_R_SYM (rela[i].r_info);
 168                 unsigned long r_type = ELF64_R_TYPE (rela[i].r_info);
 169                 unsigned long r_got_offset = r_type >> 8;
 170                 unsigned long value, hi, lo;
 171                 r_type &= 0xff;
 172
 173                 /* This is where to make the change.  */
 174                 location = base + rela[i].r_offset;
 175
 176                 /* This is the symbol it is referring to.  Note that all
 177                    unresolved symbols have been resolved.  */
 178                 sym = symtab + r_sym;
 179                 value = sym->st_value + rela[i].r_addend;
 180
 181                 switch (r_type) {
 182                 case R_ALPHA_NONE:
 183                         break;
 184                 case R_ALPHA_REFQUAD:
 185                         /* BUG() can produce misaligned relocations. */
 186                         ((u32 *)location)[0] = value;
 187                         ((u32 *)location)[1] = value >> 32;
 188                         break;
 189                 case R_ALPHA_GPREL32:
 190                         value -= gp;
 191                         if ((int)value != value)
 192                                 goto reloc_overflow;
 193                         *(u32 *)location = value;
 194                         break;
 195                 case R_ALPHA_LITERAL:
 196                         hi = got + r_got_offset;
 197                         lo = hi - gp;
 198                         if ((short)lo != lo)
 199                                 goto reloc_overflow;
 200                         *(u16 *)location = lo;
 201                         *(u64 *)hi = value;
 202                         break;
 203                 case R_ALPHA_LITUSE:
 204                         break;
 205                 case R_ALPHA_GPDISP:
 206                         value = gp - (u64)location;
 207                         lo = (short)value;
 208                         hi = (int)(value - lo);
 209                         if (hi + lo != value)
 210                                 goto reloc_overflow;
 211                         *(u16 *)location = hi >> 16;
 212                         *(u16 *)(location + rela[i].r_addend) = lo;
 213                         break;
 214                 case R_ALPHA_BRSGP:
 215                         /* BRSGP is only allowed to bind to local symbols.
 216                            If the section is undef, this means that the
 217                            value was resolved from somewhere else.  */
 218                         if (sym->st_shndx == SHN_UNDEF)
 219                                 goto reloc_overflow;
 220                         if ((sym->st_other & STO_ALPHA_STD_GPLOAD) ==
 221                             STO_ALPHA_STD_GPLOAD)
 222                                 /* Omit the prologue. */
 223                                 value += 8;
 224                         /* FALLTHRU */
 225                 case R_ALPHA_BRADDR:
 226                         value -= (u64)location + 4;
 227                         if (value & 3)
 228                                 goto reloc_overflow;
 229                         value = (long)value >> 2;
 230                         if (value + (1<<21) >= 1<<22)
 231                                 goto reloc_overflow;
 232                         value &= 0x1fffff;
 233                         value |= *(u32 *)location & ~0x1fffff;
 234                         *(u32 *)location = value;
 235                         break;
 236                 case R_ALPHA_HINT:
 237                         break;
 238                 case R_ALPHA_SREL32:
 239                         value -= (u64)location;
 240                         if ((int)value != value)
 241                                 goto reloc_overflow;
 242                         *(u32 *)location = value;
 243                         break;
 244                 case R_ALPHA_SREL64:
 245                         value -= (u64)location;
 246                         *(u64 *)location = value;
 247                         break;
 248                 case R_ALPHA_GPRELHIGH:
 249                         value = (long)(value - gp + 0x8000) >> 16;
 250                         if ((short) value != value)
 251                                 goto reloc_overflow;
 252                         *(u16 *)location = value;
 253                         break;
 254                 case R_ALPHA_GPRELLOW:
 255                         value -= gp;
 256                         *(u16 *)location = value;
 257                         break;
 258                 case R_ALPHA_GPREL16:
 259                         value -= gp;
 260                         if ((short) value != value)
 261                                 goto reloc_overflow;
 262                         *(u16 *)location = value;
 263                         break;
 264                 default:
 265                         printk(KERN_ERR "module %s: Unknown relocation: %lu\n",
 266                                me->name, r_type);
 267                         return -ENOEXEC;
 268                 reloc_overflow:
 269                         if (ELF64_ST_TYPE (sym->st_info) == STT_SECTION)
 270                           printk(KERN_ERR
 271                                  "module %s: Relocation (type %lu) overflow vs section %d\n",
 272                                  me->name, r_type, sym->st_shndx);
 273                         else
 274                           printk(KERN_ERR
 275                                  "module %s: Relocation (type %lu) overflow vs %s\n",
 276                                  me->name, r_type, strtab + sym->st_name);
 277                         return -ENOEXEC;
 278                 }
 279         }
 280
 281         return 0;
 282 }