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