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->module_core + me->core_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 } 283