1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* Kernel module help for PPC. 3 Copyright (C) 2001 Rusty Russell. 4 5 */ 6 7 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 8 9 #include <linux/module.h> 10 #include <linux/moduleloader.h> 11 #include <linux/elf.h> 12 #include <linux/vmalloc.h> 13 #include <linux/fs.h> 14 #include <linux/string.h> 15 #include <linux/kernel.h> 16 #include <linux/ftrace.h> 17 #include <linux/cache.h> 18 #include <linux/bug.h> 19 #include <linux/sort.h> 20 #include <asm/setup.h> 21 22 /* Count how many different relocations (different symbol, different 23 addend) */ 24 static unsigned int count_relocs(const Elf32_Rela *rela, unsigned int num) 25 { 26 unsigned int i, r_info, r_addend, _count_relocs; 27 28 _count_relocs = 0; 29 r_info = 0; 30 r_addend = 0; 31 for (i = 0; i < num; i++) 32 /* Only count 24-bit relocs, others don't need stubs */ 33 if (ELF32_R_TYPE(rela[i].r_info) == R_PPC_REL24 && 34 (r_info != ELF32_R_SYM(rela[i].r_info) || 35 r_addend != rela[i].r_addend)) { 36 _count_relocs++; 37 r_info = ELF32_R_SYM(rela[i].r_info); 38 r_addend = rela[i].r_addend; 39 } 40 41 #ifdef CONFIG_DYNAMIC_FTRACE 42 _count_relocs++; /* add one for ftrace_caller */ 43 #endif 44 return _count_relocs; 45 } 46 47 static int relacmp(const void *_x, const void *_y) 48 { 49 const Elf32_Rela *x, *y; 50 51 y = (Elf32_Rela *)_x; 52 x = (Elf32_Rela *)_y; 53 54 /* Compare the entire r_info (as opposed to ELF32_R_SYM(r_info) only) to 55 * make the comparison cheaper/faster. It won't affect the sorting or 56 * the counting algorithms' performance 57 */ 58 if (x->r_info < y->r_info) 59 return -1; 60 else if (x->r_info > y->r_info) 61 return 1; 62 else if (x->r_addend < y->r_addend) 63 return -1; 64 else if (x->r_addend > y->r_addend) 65 return 1; 66 else 67 return 0; 68 } 69 70 static void relaswap(void *_x, void *_y, int size) 71 { 72 uint32_t *x, *y, tmp; 73 int i; 74 75 y = (uint32_t *)_x; 76 x = (uint32_t *)_y; 77 78 for (i = 0; i < sizeof(Elf32_Rela) / sizeof(uint32_t); i++) { 79 tmp = x[i]; 80 x[i] = y[i]; 81 y[i] = tmp; 82 } 83 } 84 85 /* Get the potential trampolines size required of the init and 86 non-init sections */ 87 static unsigned long get_plt_size(const Elf32_Ehdr *hdr, 88 const Elf32_Shdr *sechdrs, 89 const char *secstrings, 90 int is_init) 91 { 92 unsigned long ret = 0; 93 unsigned i; 94 95 /* Everything marked ALLOC (this includes the exported 96 symbols) */ 97 for (i = 1; i < hdr->e_shnum; i++) { 98 /* If it's called *.init*, and we're not init, we're 99 not interested */ 100 if ((strstr(secstrings + sechdrs[i].sh_name, ".init") != NULL) 101 != is_init) 102 continue; 103 104 /* We don't want to look at debug sections. */ 105 if (strstr(secstrings + sechdrs[i].sh_name, ".debug")) 106 continue; 107 108 if (sechdrs[i].sh_type == SHT_RELA) { 109 pr_debug("Found relocations in section %u\n", i); 110 pr_debug("Ptr: %p. Number: %u\n", 111 (void *)hdr + sechdrs[i].sh_offset, 112 sechdrs[i].sh_size / sizeof(Elf32_Rela)); 113 114 /* Sort the relocation information based on a symbol and 115 * addend key. This is a stable O(n*log n) complexity 116 * alogrithm but it will reduce the complexity of 117 * count_relocs() to linear complexity O(n) 118 */ 119 sort((void *)hdr + sechdrs[i].sh_offset, 120 sechdrs[i].sh_size / sizeof(Elf32_Rela), 121 sizeof(Elf32_Rela), relacmp, relaswap); 122 123 ret += count_relocs((void *)hdr 124 + sechdrs[i].sh_offset, 125 sechdrs[i].sh_size 126 / sizeof(Elf32_Rela)) 127 * sizeof(struct ppc_plt_entry); 128 } 129 } 130 131 return ret; 132 } 133 134 int module_frob_arch_sections(Elf32_Ehdr *hdr, 135 Elf32_Shdr *sechdrs, 136 char *secstrings, 137 struct module *me) 138 { 139 unsigned int i; 140 141 /* Find .plt and .init.plt sections */ 142 for (i = 0; i < hdr->e_shnum; i++) { 143 if (strcmp(secstrings + sechdrs[i].sh_name, ".init.plt") == 0) 144 me->arch.init_plt_section = i; 145 else if (strcmp(secstrings + sechdrs[i].sh_name, ".plt") == 0) 146 me->arch.core_plt_section = i; 147 } 148 if (!me->arch.core_plt_section || !me->arch.init_plt_section) { 149 pr_err("Module doesn't contain .plt or .init.plt sections.\n"); 150 return -ENOEXEC; 151 } 152 153 /* Override their sizes */ 154 sechdrs[me->arch.core_plt_section].sh_size 155 = get_plt_size(hdr, sechdrs, secstrings, 0); 156 sechdrs[me->arch.init_plt_section].sh_size 157 = get_plt_size(hdr, sechdrs, secstrings, 1); 158 return 0; 159 } 160 161 static inline int entry_matches(struct ppc_plt_entry *entry, Elf32_Addr val) 162 { 163 if (entry->jump[0] != (PPC_INST_ADDIS | __PPC_RT(R12) | PPC_HA(val))) 164 return 0; 165 if (entry->jump[1] != (PPC_INST_ADDI | __PPC_RT(R12) | __PPC_RA(R12) | 166 PPC_LO(val))) 167 return 0; 168 return 1; 169 } 170 171 /* Set up a trampoline in the PLT to bounce us to the distant function */ 172 static uint32_t do_plt_call(void *location, 173 Elf32_Addr val, 174 const Elf32_Shdr *sechdrs, 175 struct module *mod) 176 { 177 struct ppc_plt_entry *entry; 178 179 pr_debug("Doing plt for call to 0x%x at 0x%x\n", val, (unsigned int)location); 180 /* Init, or core PLT? */ 181 if (location >= mod->core_layout.base 182 && location < mod->core_layout.base + mod->core_layout.size) 183 entry = (void *)sechdrs[mod->arch.core_plt_section].sh_addr; 184 else 185 entry = (void *)sechdrs[mod->arch.init_plt_section].sh_addr; 186 187 /* Find this entry, or if that fails, the next avail. entry */ 188 while (entry->jump[0]) { 189 if (entry_matches(entry, val)) return (uint32_t)entry; 190 entry++; 191 } 192 193 /* 194 * lis r12, sym@ha 195 * addi r12, r12, sym@l 196 * mtctr r12 197 * bctr 198 */ 199 entry->jump[0] = PPC_INST_ADDIS | __PPC_RT(R12) | PPC_HA(val); 200 entry->jump[1] = PPC_INST_ADDI | __PPC_RT(R12) | __PPC_RA(R12) | PPC_LO(val); 201 entry->jump[2] = PPC_INST_MTCTR | __PPC_RS(R12); 202 entry->jump[3] = PPC_INST_BCTR; 203 204 pr_debug("Initialized plt for 0x%x at %p\n", val, entry); 205 return (uint32_t)entry; 206 } 207 208 int apply_relocate_add(Elf32_Shdr *sechdrs, 209 const char *strtab, 210 unsigned int symindex, 211 unsigned int relsec, 212 struct module *module) 213 { 214 unsigned int i; 215 Elf32_Rela *rela = (void *)sechdrs[relsec].sh_addr; 216 Elf32_Sym *sym; 217 uint32_t *location; 218 uint32_t value; 219 220 pr_debug("Applying ADD relocate section %u to %u\n", relsec, 221 sechdrs[relsec].sh_info); 222 for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rela); i++) { 223 /* This is where to make the change */ 224 location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr 225 + rela[i].r_offset; 226 /* This is the symbol it is referring to. Note that all 227 undefined symbols have been resolved. */ 228 sym = (Elf32_Sym *)sechdrs[symindex].sh_addr 229 + ELF32_R_SYM(rela[i].r_info); 230 /* `Everything is relative'. */ 231 value = sym->st_value + rela[i].r_addend; 232 233 switch (ELF32_R_TYPE(rela[i].r_info)) { 234 case R_PPC_ADDR32: 235 /* Simply set it */ 236 *(uint32_t *)location = value; 237 break; 238 239 case R_PPC_ADDR16_LO: 240 /* Low half of the symbol */ 241 *(uint16_t *)location = value; 242 break; 243 244 case R_PPC_ADDR16_HI: 245 /* Higher half of the symbol */ 246 *(uint16_t *)location = (value >> 16); 247 break; 248 249 case R_PPC_ADDR16_HA: 250 /* Sign-adjusted lower 16 bits: PPC ELF ABI says: 251 (((x >> 16) + ((x & 0x8000) ? 1 : 0))) & 0xFFFF. 252 This is the same, only sane. 253 */ 254 *(uint16_t *)location = (value + 0x8000) >> 16; 255 break; 256 257 case R_PPC_REL24: 258 if ((int)(value - (uint32_t)location) < -0x02000000 259 || (int)(value - (uint32_t)location) >= 0x02000000) 260 value = do_plt_call(location, value, 261 sechdrs, module); 262 263 /* Only replace bits 2 through 26 */ 264 pr_debug("REL24 value = %08X. location = %08X\n", 265 value, (uint32_t)location); 266 pr_debug("Location before: %08X.\n", 267 *(uint32_t *)location); 268 *(uint32_t *)location 269 = (*(uint32_t *)location & ~0x03fffffc) 270 | ((value - (uint32_t)location) 271 & 0x03fffffc); 272 pr_debug("Location after: %08X.\n", 273 *(uint32_t *)location); 274 pr_debug("ie. jump to %08X+%08X = %08X\n", 275 *(uint32_t *)location & 0x03fffffc, 276 (uint32_t)location, 277 (*(uint32_t *)location & 0x03fffffc) 278 + (uint32_t)location); 279 break; 280 281 case R_PPC_REL32: 282 /* 32-bit relative jump. */ 283 *(uint32_t *)location = value - (uint32_t)location; 284 break; 285 286 default: 287 pr_err("%s: unknown ADD relocation: %u\n", 288 module->name, 289 ELF32_R_TYPE(rela[i].r_info)); 290 return -ENOEXEC; 291 } 292 } 293 294 return 0; 295 } 296 297 #ifdef CONFIG_DYNAMIC_FTRACE 298 int module_finalize_ftrace(struct module *module, const Elf_Shdr *sechdrs) 299 { 300 module->arch.tramp = do_plt_call(module->core_layout.base, 301 (unsigned long)ftrace_caller, 302 sechdrs, module); 303 if (!module->arch.tramp) 304 return -ENOENT; 305 306 return 0; 307 } 308 #endif 309