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) */ 25static 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 45static 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 68static 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 */ 85static 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 132int 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 */ 162static 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 198int 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} 285