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#define DEBUGP(fmt , ...) 33 34/* Count how many different relocations (different symbol, different 35 addend) */ 36static 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 59static 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 82static 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 */ 99static 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") != 0) 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") != 0) 118 continue; 119 120 if (sechdrs[i].sh_type == SHT_RELA) { 121 DEBUGP("Found relocations in section %u\n", i); 122 DEBUGP("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 146int 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 printk("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 173int apply_relocate(Elf32_Shdr *sechdrs, 174 const char *strtab, 175 unsigned int symindex, 176 unsigned int relsec, 177 struct module *module) 178{ 179 printk(KERN_ERR "%s: Non-ADD RELOCATION unsupported\n", 180 module->name); 181 return -ENOEXEC; 182} 183 184static inline int entry_matches(struct ppc_plt_entry *entry, Elf32_Addr val) 185{ 186 if (entry->jump[0] == 0x3d600000 + ((val + 0x8000) >> 16) 187 && entry->jump[1] == 0x396b0000 + (val & 0xffff)) 188 return 1; 189 return 0; 190} 191 192/* Set up a trampoline in the PLT to bounce us to the distant function */ 193static uint32_t do_plt_call(void *location, 194 Elf32_Addr val, 195 Elf32_Shdr *sechdrs, 196 struct module *mod) 197{ 198 struct ppc_plt_entry *entry; 199 200 DEBUGP("Doing plt for call to 0x%x at 0x%x\n", val, (unsigned int)location); 201 /* Init, or core PLT? */ 202 if (location >= mod->module_core 203 && location < mod->module_core + mod->core_size) 204 entry = (void *)sechdrs[mod->arch.core_plt_section].sh_addr; 205 else 206 entry = (void *)sechdrs[mod->arch.init_plt_section].sh_addr; 207 208 /* Find this entry, or if that fails, the next avail. entry */ 209 while (entry->jump[0]) { 210 if (entry_matches(entry, val)) return (uint32_t)entry; 211 entry++; 212 } 213 214 /* Stolen from Paul Mackerras as well... */ 215 entry->jump[0] = 0x3d600000+((val+0x8000)>>16); /* lis r11,sym@ha */ 216 entry->jump[1] = 0x396b0000 + (val&0xffff); /* addi r11,r11,sym@l*/ 217 entry->jump[2] = 0x7d6903a6; /* mtctr r11 */ 218 entry->jump[3] = 0x4e800420; /* bctr */ 219 220 DEBUGP("Initialized plt for 0x%x at %p\n", val, entry); 221 return (uint32_t)entry; 222} 223 224int apply_relocate_add(Elf32_Shdr *sechdrs, 225 const char *strtab, 226 unsigned int symindex, 227 unsigned int relsec, 228 struct module *module) 229{ 230 unsigned int i; 231 Elf32_Rela *rela = (void *)sechdrs[relsec].sh_addr; 232 Elf32_Sym *sym; 233 uint32_t *location; 234 uint32_t value; 235 236 DEBUGP("Applying ADD relocate section %u to %u\n", relsec, 237 sechdrs[relsec].sh_info); 238 for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rela); i++) { 239 /* This is where to make the change */ 240 location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr 241 + rela[i].r_offset; 242 /* This is the symbol it is referring to. Note that all 243 undefined symbols have been resolved. */ 244 sym = (Elf32_Sym *)sechdrs[symindex].sh_addr 245 + ELF32_R_SYM(rela[i].r_info); 246 /* `Everything is relative'. */ 247 value = sym->st_value + rela[i].r_addend; 248 249 switch (ELF32_R_TYPE(rela[i].r_info)) { 250 case R_PPC_ADDR32: 251 /* Simply set it */ 252 *(uint32_t *)location = value; 253 break; 254 255 case R_PPC_ADDR16_LO: 256 /* Low half of the symbol */ 257 *(uint16_t *)location = value; 258 break; 259 260 case R_PPC_ADDR16_HI: 261 /* Higher half of the symbol */ 262 *(uint16_t *)location = (value >> 16); 263 break; 264 265 case R_PPC_ADDR16_HA: 266 /* Sign-adjusted lower 16 bits: PPC ELF ABI says: 267 (((x >> 16) + ((x & 0x8000) ? 1 : 0))) & 0xFFFF. 268 This is the same, only sane. 269 */ 270 *(uint16_t *)location = (value + 0x8000) >> 16; 271 break; 272 273 case R_PPC_REL24: 274 if ((int)(value - (uint32_t)location) < -0x02000000 275 || (int)(value - (uint32_t)location) >= 0x02000000) 276 value = do_plt_call(location, value, 277 sechdrs, module); 278 279 /* Only replace bits 2 through 26 */ 280 DEBUGP("REL24 value = %08X. location = %08X\n", 281 value, (uint32_t)location); 282 DEBUGP("Location before: %08X.\n", 283 *(uint32_t *)location); 284 *(uint32_t *)location 285 = (*(uint32_t *)location & ~0x03fffffc) 286 | ((value - (uint32_t)location) 287 & 0x03fffffc); 288 DEBUGP("Location after: %08X.\n", 289 *(uint32_t *)location); 290 DEBUGP("ie. jump to %08X+%08X = %08X\n", 291 *(uint32_t *)location & 0x03fffffc, 292 (uint32_t)location, 293 (*(uint32_t *)location & 0x03fffffc) 294 + (uint32_t)location); 295 break; 296 297 case R_PPC_REL32: 298 /* 32-bit relative jump. */ 299 *(uint32_t *)location = value - (uint32_t)location; 300 break; 301 302 default: 303 printk("%s: unknown ADD relocation: %u\n", 304 module->name, 305 ELF32_R_TYPE(rela[i].r_info)); 306 return -ENOEXEC; 307 } 308 } 309#ifdef CONFIG_DYNAMIC_FTRACE 310 module->arch.tramp = 311 do_plt_call(module->module_core, 312 (unsigned long)ftrace_caller, 313 sechdrs, module); 314#endif 315 return 0; 316} 317