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 #include <linux/module.h> 19 #include <linux/moduleloader.h> 20 #include <linux/elf.h> 21 #include <linux/vmalloc.h> 22 #include <linux/fs.h> 23 #include <linux/string.h> 24 #include <linux/kernel.h> 25 #include <linux/ftrace.h> 26 #include <linux/cache.h> 27 #include <linux/bug.h> 28 #include <linux/sort.h> 29 30 #include "setup.h" 31 32 #if 0 33 #define DEBUGP printk 34 #else 35 #define DEBUGP(fmt , ...) 36 #endif 37 38 /* Count how many different relocations (different symbol, different 39 addend) */ 40 static unsigned int count_relocs(const Elf32_Rela *rela, unsigned int num) 41 { 42 unsigned int i, r_info, r_addend, _count_relocs; 43 44 _count_relocs = 0; 45 r_info = 0; 46 r_addend = 0; 47 for (i = 0; i < num; i++) 48 /* Only count 24-bit relocs, others don't need stubs */ 49 if (ELF32_R_TYPE(rela[i].r_info) == R_PPC_REL24 && 50 (r_info != ELF32_R_SYM(rela[i].r_info) || 51 r_addend != rela[i].r_addend)) { 52 _count_relocs++; 53 r_info = ELF32_R_SYM(rela[i].r_info); 54 r_addend = rela[i].r_addend; 55 } 56 57 #ifdef CONFIG_DYNAMIC_FTRACE 58 _count_relocs++; /* add one for ftrace_caller */ 59 #endif 60 return _count_relocs; 61 } 62 63 static int relacmp(const void *_x, const void *_y) 64 { 65 const Elf32_Rela *x, *y; 66 67 y = (Elf32_Rela *)_x; 68 x = (Elf32_Rela *)_y; 69 70 /* Compare the entire r_info (as opposed to ELF32_R_SYM(r_info) only) to 71 * make the comparison cheaper/faster. It won't affect the sorting or 72 * the counting algorithms' performance 73 */ 74 if (x->r_info < y->r_info) 75 return -1; 76 else if (x->r_info > y->r_info) 77 return 1; 78 else if (x->r_addend < y->r_addend) 79 return -1; 80 else if (x->r_addend > y->r_addend) 81 return 1; 82 else 83 return 0; 84 } 85 86 static void relaswap(void *_x, void *_y, int size) 87 { 88 uint32_t *x, *y, tmp; 89 int i; 90 91 y = (uint32_t *)_x; 92 x = (uint32_t *)_y; 93 94 for (i = 0; i < sizeof(Elf32_Rela) / sizeof(uint32_t); i++) { 95 tmp = x[i]; 96 x[i] = y[i]; 97 y[i] = tmp; 98 } 99 } 100 101 /* Get the potential trampolines size required of the init and 102 non-init sections */ 103 static unsigned long get_plt_size(const Elf32_Ehdr *hdr, 104 const Elf32_Shdr *sechdrs, 105 const char *secstrings, 106 int is_init) 107 { 108 unsigned long ret = 0; 109 unsigned i; 110 111 /* Everything marked ALLOC (this includes the exported 112 symbols) */ 113 for (i = 1; i < hdr->e_shnum; i++) { 114 /* If it's called *.init*, and we're not init, we're 115 not interested */ 116 if ((strstr(secstrings + sechdrs[i].sh_name, ".init") != 0) 117 != is_init) 118 continue; 119 120 /* We don't want to look at debug sections. */ 121 if (strstr(secstrings + sechdrs[i].sh_name, ".debug") != 0) 122 continue; 123 124 if (sechdrs[i].sh_type == SHT_RELA) { 125 DEBUGP("Found relocations in section %u\n", i); 126 DEBUGP("Ptr: %p. Number: %u\n", 127 (void *)hdr + sechdrs[i].sh_offset, 128 sechdrs[i].sh_size / sizeof(Elf32_Rela)); 129 130 /* Sort the relocation information based on a symbol and 131 * addend key. This is a stable O(n*log n) complexity 132 * alogrithm but it will reduce the complexity of 133 * count_relocs() to linear complexity O(n) 134 */ 135 sort((void *)hdr + sechdrs[i].sh_offset, 136 sechdrs[i].sh_size / sizeof(Elf32_Rela), 137 sizeof(Elf32_Rela), relacmp, relaswap); 138 139 ret += count_relocs((void *)hdr 140 + sechdrs[i].sh_offset, 141 sechdrs[i].sh_size 142 / sizeof(Elf32_Rela)) 143 * sizeof(struct ppc_plt_entry); 144 } 145 } 146 147 return ret; 148 } 149 150 int module_frob_arch_sections(Elf32_Ehdr *hdr, 151 Elf32_Shdr *sechdrs, 152 char *secstrings, 153 struct module *me) 154 { 155 unsigned int i; 156 157 /* Find .plt and .init.plt sections */ 158 for (i = 0; i < hdr->e_shnum; i++) { 159 if (strcmp(secstrings + sechdrs[i].sh_name, ".init.plt") == 0) 160 me->arch.init_plt_section = i; 161 else if (strcmp(secstrings + sechdrs[i].sh_name, ".plt") == 0) 162 me->arch.core_plt_section = i; 163 } 164 if (!me->arch.core_plt_section || !me->arch.init_plt_section) { 165 printk("Module doesn't contain .plt or .init.plt sections.\n"); 166 return -ENOEXEC; 167 } 168 169 /* Override their sizes */ 170 sechdrs[me->arch.core_plt_section].sh_size 171 = get_plt_size(hdr, sechdrs, secstrings, 0); 172 sechdrs[me->arch.init_plt_section].sh_size 173 = get_plt_size(hdr, sechdrs, secstrings, 1); 174 return 0; 175 } 176 177 static inline int entry_matches(struct ppc_plt_entry *entry, Elf32_Addr val) 178 { 179 if (entry->jump[0] == 0x3d600000 + ((val + 0x8000) >> 16) 180 && entry->jump[1] == 0x396b0000 + (val & 0xffff)) 181 return 1; 182 return 0; 183 } 184 185 /* Set up a trampoline in the PLT to bounce us to the distant function */ 186 static uint32_t do_plt_call(void *location, 187 Elf32_Addr val, 188 Elf32_Shdr *sechdrs, 189 struct module *mod) 190 { 191 struct ppc_plt_entry *entry; 192 193 DEBUGP("Doing plt for call to 0x%x at 0x%x\n", val, (unsigned int)location); 194 /* Init, or core PLT? */ 195 if (location >= mod->module_core 196 && location < mod->module_core + mod->core_size) 197 entry = (void *)sechdrs[mod->arch.core_plt_section].sh_addr; 198 else 199 entry = (void *)sechdrs[mod->arch.init_plt_section].sh_addr; 200 201 /* Find this entry, or if that fails, the next avail. entry */ 202 while (entry->jump[0]) { 203 if (entry_matches(entry, val)) return (uint32_t)entry; 204 entry++; 205 } 206 207 /* Stolen from Paul Mackerras as well... */ 208 entry->jump[0] = 0x3d600000+((val+0x8000)>>16); /* lis r11,sym@ha */ 209 entry->jump[1] = 0x396b0000 + (val&0xffff); /* addi r11,r11,sym@l*/ 210 entry->jump[2] = 0x7d6903a6; /* mtctr r11 */ 211 entry->jump[3] = 0x4e800420; /* bctr */ 212 213 DEBUGP("Initialized plt for 0x%x at %p\n", val, entry); 214 return (uint32_t)entry; 215 } 216 217 int apply_relocate_add(Elf32_Shdr *sechdrs, 218 const char *strtab, 219 unsigned int symindex, 220 unsigned int relsec, 221 struct module *module) 222 { 223 unsigned int i; 224 Elf32_Rela *rela = (void *)sechdrs[relsec].sh_addr; 225 Elf32_Sym *sym; 226 uint32_t *location; 227 uint32_t value; 228 229 DEBUGP("Applying ADD relocate section %u to %u\n", relsec, 230 sechdrs[relsec].sh_info); 231 for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rela); i++) { 232 /* This is where to make the change */ 233 location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr 234 + rela[i].r_offset; 235 /* This is the symbol it is referring to. Note that all 236 undefined symbols have been resolved. */ 237 sym = (Elf32_Sym *)sechdrs[symindex].sh_addr 238 + ELF32_R_SYM(rela[i].r_info); 239 /* `Everything is relative'. */ 240 value = sym->st_value + rela[i].r_addend; 241 242 switch (ELF32_R_TYPE(rela[i].r_info)) { 243 case R_PPC_ADDR32: 244 /* Simply set it */ 245 *(uint32_t *)location = value; 246 break; 247 248 case R_PPC_ADDR16_LO: 249 /* Low half of the symbol */ 250 *(uint16_t *)location = value; 251 break; 252 253 case R_PPC_ADDR16_HI: 254 /* Higher half of the symbol */ 255 *(uint16_t *)location = (value >> 16); 256 break; 257 258 case R_PPC_ADDR16_HA: 259 /* Sign-adjusted lower 16 bits: PPC ELF ABI says: 260 (((x >> 16) + ((x & 0x8000) ? 1 : 0))) & 0xFFFF. 261 This is the same, only sane. 262 */ 263 *(uint16_t *)location = (value + 0x8000) >> 16; 264 break; 265 266 case R_PPC_REL24: 267 if ((int)(value - (uint32_t)location) < -0x02000000 268 || (int)(value - (uint32_t)location) >= 0x02000000) 269 value = do_plt_call(location, value, 270 sechdrs, module); 271 272 /* Only replace bits 2 through 26 */ 273 DEBUGP("REL24 value = %08X. location = %08X\n", 274 value, (uint32_t)location); 275 DEBUGP("Location before: %08X.\n", 276 *(uint32_t *)location); 277 *(uint32_t *)location 278 = (*(uint32_t *)location & ~0x03fffffc) 279 | ((value - (uint32_t)location) 280 & 0x03fffffc); 281 DEBUGP("Location after: %08X.\n", 282 *(uint32_t *)location); 283 DEBUGP("ie. jump to %08X+%08X = %08X\n", 284 *(uint32_t *)location & 0x03fffffc, 285 (uint32_t)location, 286 (*(uint32_t *)location & 0x03fffffc) 287 + (uint32_t)location); 288 break; 289 290 case R_PPC_REL32: 291 /* 32-bit relative jump. */ 292 *(uint32_t *)location = value - (uint32_t)location; 293 break; 294 295 default: 296 printk("%s: unknown ADD relocation: %u\n", 297 module->name, 298 ELF32_R_TYPE(rela[i].r_info)); 299 return -ENOEXEC; 300 } 301 } 302 #ifdef CONFIG_DYNAMIC_FTRACE 303 module->arch.tramp = 304 do_plt_call(module->module_core, 305 (unsigned long)ftrace_caller, 306 sechdrs, module); 307 #endif 308 return 0; 309 } 310