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 19 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 20 21 #include <linux/module.h> 22 #include <linux/moduleloader.h> 23 #include <linux/elf.h> 24 #include <linux/vmalloc.h> 25 #include <linux/fs.h> 26 #include <linux/string.h> 27 #include <linux/kernel.h> 28 #include <linux/ftrace.h> 29 #include <linux/cache.h> 30 #include <linux/bug.h> 31 #include <linux/sort.h> 32 #include <asm/setup.h> 33 34 /* Count how many different relocations (different symbol, different 35 addend) */ 36 static unsigned int count_relocs(const Elf32_Rela *rela, unsigned int num) 37 { 38 unsigned int i, r_info, r_addend, _count_relocs; 39 40 _count_relocs = 0; 41 r_info = 0; 42 r_addend = 0; 43 for (i = 0; i < num; i++) 44 /* Only count 24-bit relocs, others don't need stubs */ 45 if (ELF32_R_TYPE(rela[i].r_info) == R_PPC_REL24 && 46 (r_info != ELF32_R_SYM(rela[i].r_info) || 47 r_addend != rela[i].r_addend)) { 48 _count_relocs++; 49 r_info = ELF32_R_SYM(rela[i].r_info); 50 r_addend = rela[i].r_addend; 51 } 52 53 #ifdef CONFIG_DYNAMIC_FTRACE 54 _count_relocs++; /* add one for ftrace_caller */ 55 #endif 56 return _count_relocs; 57 } 58 59 static int relacmp(const void *_x, const void *_y) 60 { 61 const Elf32_Rela *x, *y; 62 63 y = (Elf32_Rela *)_x; 64 x = (Elf32_Rela *)_y; 65 66 /* Compare the entire r_info (as opposed to ELF32_R_SYM(r_info) only) to 67 * make the comparison cheaper/faster. It won't affect the sorting or 68 * the counting algorithms' performance 69 */ 70 if (x->r_info < y->r_info) 71 return -1; 72 else if (x->r_info > y->r_info) 73 return 1; 74 else if (x->r_addend < y->r_addend) 75 return -1; 76 else if (x->r_addend > y->r_addend) 77 return 1; 78 else 79 return 0; 80 } 81 82 static void relaswap(void *_x, void *_y, int size) 83 { 84 uint32_t *x, *y, tmp; 85 int i; 86 87 y = (uint32_t *)_x; 88 x = (uint32_t *)_y; 89 90 for (i = 0; i < sizeof(Elf32_Rela) / sizeof(uint32_t); i++) { 91 tmp = x[i]; 92 x[i] = y[i]; 93 y[i] = tmp; 94 } 95 } 96 97 /* Get the potential trampolines size required of the init and 98 non-init sections */ 99 static unsigned long get_plt_size(const Elf32_Ehdr *hdr, 100 const Elf32_Shdr *sechdrs, 101 const char *secstrings, 102 int is_init) 103 { 104 unsigned long ret = 0; 105 unsigned i; 106 107 /* Everything marked ALLOC (this includes the exported 108 symbols) */ 109 for (i = 1; i < hdr->e_shnum; i++) { 110 /* If it's called *.init*, and we're not init, we're 111 not interested */ 112 if ((strstr(secstrings + sechdrs[i].sh_name, ".init") != NULL) 113 != is_init) 114 continue; 115 116 /* We don't want to look at debug sections. */ 117 if (strstr(secstrings + sechdrs[i].sh_name, ".debug")) 118 continue; 119 120 if (sechdrs[i].sh_type == SHT_RELA) { 121 pr_debug("Found relocations in section %u\n", i); 122 pr_debug("Ptr: %p. Number: %u\n", 123 (void *)hdr + sechdrs[i].sh_offset, 124 sechdrs[i].sh_size / sizeof(Elf32_Rela)); 125 126 /* Sort the relocation information based on a symbol and 127 * addend key. This is a stable O(n*log n) complexity 128 * alogrithm but it will reduce the complexity of 129 * count_relocs() to linear complexity O(n) 130 */ 131 sort((void *)hdr + sechdrs[i].sh_offset, 132 sechdrs[i].sh_size / sizeof(Elf32_Rela), 133 sizeof(Elf32_Rela), relacmp, relaswap); 134 135 ret += count_relocs((void *)hdr 136 + sechdrs[i].sh_offset, 137 sechdrs[i].sh_size 138 / sizeof(Elf32_Rela)) 139 * sizeof(struct ppc_plt_entry); 140 } 141 } 142 143 return ret; 144 } 145 146 int module_frob_arch_sections(Elf32_Ehdr *hdr, 147 Elf32_Shdr *sechdrs, 148 char *secstrings, 149 struct module *me) 150 { 151 unsigned int i; 152 153 /* Find .plt and .init.plt sections */ 154 for (i = 0; i < hdr->e_shnum; i++) { 155 if (strcmp(secstrings + sechdrs[i].sh_name, ".init.plt") == 0) 156 me->arch.init_plt_section = i; 157 else if (strcmp(secstrings + sechdrs[i].sh_name, ".plt") == 0) 158 me->arch.core_plt_section = i; 159 } 160 if (!me->arch.core_plt_section || !me->arch.init_plt_section) { 161 pr_err("Module doesn't contain .plt or .init.plt sections.\n"); 162 return -ENOEXEC; 163 } 164 165 /* Override their sizes */ 166 sechdrs[me->arch.core_plt_section].sh_size 167 = get_plt_size(hdr, sechdrs, secstrings, 0); 168 sechdrs[me->arch.init_plt_section].sh_size 169 = get_plt_size(hdr, sechdrs, secstrings, 1); 170 return 0; 171 } 172 173 static inline int entry_matches(struct ppc_plt_entry *entry, Elf32_Addr val) 174 { 175 if (entry->jump[0] == 0x3d800000 + ((val + 0x8000) >> 16) 176 && entry->jump[1] == 0x398c0000 + (val & 0xffff)) 177 return 1; 178 return 0; 179 } 180 181 /* Set up a trampoline in the PLT to bounce us to the distant function */ 182 static uint32_t do_plt_call(void *location, 183 Elf32_Addr val, 184 const Elf32_Shdr *sechdrs, 185 struct module *mod) 186 { 187 struct ppc_plt_entry *entry; 188 189 pr_debug("Doing plt for call to 0x%x at 0x%x\n", val, (unsigned int)location); 190 /* Init, or core PLT? */ 191 if (location >= mod->core_layout.base 192 && location < mod->core_layout.base + mod->core_layout.size) 193 entry = (void *)sechdrs[mod->arch.core_plt_section].sh_addr; 194 else 195 entry = (void *)sechdrs[mod->arch.init_plt_section].sh_addr; 196 197 /* Find this entry, or if that fails, the next avail. entry */ 198 while (entry->jump[0]) { 199 if (entry_matches(entry, val)) return (uint32_t)entry; 200 entry++; 201 } 202 203 entry->jump[0] = 0x3d800000+((val+0x8000)>>16); /* lis r12,sym@ha */ 204 entry->jump[1] = 0x398c0000 + (val&0xffff); /* addi r12,r12,sym@l*/ 205 entry->jump[2] = 0x7d8903a6; /* mtctr r12 */ 206 entry->jump[3] = 0x4e800420; /* bctr */ 207 208 pr_debug("Initialized plt for 0x%x at %p\n", val, entry); 209 return (uint32_t)entry; 210 } 211 212 int apply_relocate_add(Elf32_Shdr *sechdrs, 213 const char *strtab, 214 unsigned int symindex, 215 unsigned int relsec, 216 struct module *module) 217 { 218 unsigned int i; 219 Elf32_Rela *rela = (void *)sechdrs[relsec].sh_addr; 220 Elf32_Sym *sym; 221 uint32_t *location; 222 uint32_t value; 223 224 pr_debug("Applying ADD relocate section %u to %u\n", relsec, 225 sechdrs[relsec].sh_info); 226 for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rela); i++) { 227 /* This is where to make the change */ 228 location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr 229 + rela[i].r_offset; 230 /* This is the symbol it is referring to. Note that all 231 undefined symbols have been resolved. */ 232 sym = (Elf32_Sym *)sechdrs[symindex].sh_addr 233 + ELF32_R_SYM(rela[i].r_info); 234 /* `Everything is relative'. */ 235 value = sym->st_value + rela[i].r_addend; 236 237 switch (ELF32_R_TYPE(rela[i].r_info)) { 238 case R_PPC_ADDR32: 239 /* Simply set it */ 240 *(uint32_t *)location = value; 241 break; 242 243 case R_PPC_ADDR16_LO: 244 /* Low half of the symbol */ 245 *(uint16_t *)location = value; 246 break; 247 248 case R_PPC_ADDR16_HI: 249 /* Higher half of the symbol */ 250 *(uint16_t *)location = (value >> 16); 251 break; 252 253 case R_PPC_ADDR16_HA: 254 /* Sign-adjusted lower 16 bits: PPC ELF ABI says: 255 (((x >> 16) + ((x & 0x8000) ? 1 : 0))) & 0xFFFF. 256 This is the same, only sane. 257 */ 258 *(uint16_t *)location = (value + 0x8000) >> 16; 259 break; 260 261 case R_PPC_REL24: 262 if ((int)(value - (uint32_t)location) < -0x02000000 263 || (int)(value - (uint32_t)location) >= 0x02000000) 264 value = do_plt_call(location, value, 265 sechdrs, module); 266 267 /* Only replace bits 2 through 26 */ 268 pr_debug("REL24 value = %08X. location = %08X\n", 269 value, (uint32_t)location); 270 pr_debug("Location before: %08X.\n", 271 *(uint32_t *)location); 272 *(uint32_t *)location 273 = (*(uint32_t *)location & ~0x03fffffc) 274 | ((value - (uint32_t)location) 275 & 0x03fffffc); 276 pr_debug("Location after: %08X.\n", 277 *(uint32_t *)location); 278 pr_debug("ie. jump to %08X+%08X = %08X\n", 279 *(uint32_t *)location & 0x03fffffc, 280 (uint32_t)location, 281 (*(uint32_t *)location & 0x03fffffc) 282 + (uint32_t)location); 283 break; 284 285 case R_PPC_REL32: 286 /* 32-bit relative jump. */ 287 *(uint32_t *)location = value - (uint32_t)location; 288 break; 289 290 default: 291 pr_err("%s: unknown ADD relocation: %u\n", 292 module->name, 293 ELF32_R_TYPE(rela[i].r_info)); 294 return -ENOEXEC; 295 } 296 } 297 298 return 0; 299 } 300 301 #ifdef CONFIG_DYNAMIC_FTRACE 302 int module_finalize_ftrace(struct module *module, const Elf_Shdr *sechdrs) 303 { 304 module->arch.tramp = do_plt_call(module->core_layout.base, 305 (unsigned long)ftrace_caller, 306 sechdrs, module); 307 if (!module->arch.tramp) 308 return -ENOENT; 309 310 return 0; 311 } 312 #endif 313