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 /* Get the potential trampolines size required of the init and 71 non-init sections */ 72 static unsigned long get_plt_size(const Elf32_Ehdr *hdr, 73 const Elf32_Shdr *sechdrs, 74 const char *secstrings, 75 int is_init) 76 { 77 unsigned long ret = 0; 78 unsigned i; 79 80 /* Everything marked ALLOC (this includes the exported 81 symbols) */ 82 for (i = 1; i < hdr->e_shnum; i++) { 83 /* If it's called *.init*, and we're not init, we're 84 not interested */ 85 if ((strstr(secstrings + sechdrs[i].sh_name, ".init") != NULL) 86 != is_init) 87 continue; 88 89 /* We don't want to look at debug sections. */ 90 if (strstr(secstrings + sechdrs[i].sh_name, ".debug")) 91 continue; 92 93 if (sechdrs[i].sh_type == SHT_RELA) { 94 pr_debug("Found relocations in section %u\n", i); 95 pr_debug("Ptr: %p. Number: %u\n", 96 (void *)hdr + sechdrs[i].sh_offset, 97 sechdrs[i].sh_size / sizeof(Elf32_Rela)); 98 99 /* Sort the relocation information based on a symbol and 100 * addend key. This is a stable O(n*log n) complexity 101 * alogrithm but it will reduce the complexity of 102 * count_relocs() to linear complexity O(n) 103 */ 104 sort((void *)hdr + sechdrs[i].sh_offset, 105 sechdrs[i].sh_size / sizeof(Elf32_Rela), 106 sizeof(Elf32_Rela), relacmp, NULL); 107 108 ret += count_relocs((void *)hdr 109 + sechdrs[i].sh_offset, 110 sechdrs[i].sh_size 111 / sizeof(Elf32_Rela)) 112 * sizeof(struct ppc_plt_entry); 113 } 114 } 115 116 return ret; 117 } 118 119 int module_frob_arch_sections(Elf32_Ehdr *hdr, 120 Elf32_Shdr *sechdrs, 121 char *secstrings, 122 struct module *me) 123 { 124 unsigned int i; 125 126 /* Find .plt and .init.plt sections */ 127 for (i = 0; i < hdr->e_shnum; i++) { 128 if (strcmp(secstrings + sechdrs[i].sh_name, ".init.plt") == 0) 129 me->arch.init_plt_section = i; 130 else if (strcmp(secstrings + sechdrs[i].sh_name, ".plt") == 0) 131 me->arch.core_plt_section = i; 132 } 133 if (!me->arch.core_plt_section || !me->arch.init_plt_section) { 134 pr_err("Module doesn't contain .plt or .init.plt sections.\n"); 135 return -ENOEXEC; 136 } 137 138 /* Override their sizes */ 139 sechdrs[me->arch.core_plt_section].sh_size 140 = get_plt_size(hdr, sechdrs, secstrings, 0); 141 sechdrs[me->arch.init_plt_section].sh_size 142 = get_plt_size(hdr, sechdrs, secstrings, 1); 143 return 0; 144 } 145 146 static inline int entry_matches(struct ppc_plt_entry *entry, Elf32_Addr val) 147 { 148 if (entry->jump[0] != PPC_RAW_LIS(_R12, PPC_HA(val))) 149 return 0; 150 if (entry->jump[1] != PPC_RAW_ADDI(_R12, _R12, PPC_LO(val))) 151 return 0; 152 return 1; 153 } 154 155 /* Set up a trampoline in the PLT to bounce us to the distant function */ 156 static uint32_t do_plt_call(void *location, 157 Elf32_Addr val, 158 const Elf32_Shdr *sechdrs, 159 struct module *mod) 160 { 161 struct ppc_plt_entry *entry; 162 163 pr_debug("Doing plt for call to 0x%x at 0x%x\n", val, (unsigned int)location); 164 /* Init, or core PLT? */ 165 if (location >= mod->core_layout.base 166 && location < mod->core_layout.base + mod->core_layout.size) 167 entry = (void *)sechdrs[mod->arch.core_plt_section].sh_addr; 168 else 169 entry = (void *)sechdrs[mod->arch.init_plt_section].sh_addr; 170 171 /* Find this entry, or if that fails, the next avail. entry */ 172 while (entry->jump[0]) { 173 if (entry_matches(entry, val)) return (uint32_t)entry; 174 entry++; 175 } 176 177 entry->jump[0] = PPC_RAW_LIS(_R12, PPC_HA(val)); 178 entry->jump[1] = PPC_RAW_ADDI(_R12, _R12, PPC_LO(val)); 179 entry->jump[2] = PPC_RAW_MTCTR(_R12); 180 entry->jump[3] = PPC_RAW_BCTR(); 181 182 pr_debug("Initialized plt for 0x%x at %p\n", val, entry); 183 return (uint32_t)entry; 184 } 185 186 int apply_relocate_add(Elf32_Shdr *sechdrs, 187 const char *strtab, 188 unsigned int symindex, 189 unsigned int relsec, 190 struct module *module) 191 { 192 unsigned int i; 193 Elf32_Rela *rela = (void *)sechdrs[relsec].sh_addr; 194 Elf32_Sym *sym; 195 uint32_t *location; 196 uint32_t value; 197 198 pr_debug("Applying ADD relocate section %u to %u\n", relsec, 199 sechdrs[relsec].sh_info); 200 for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rela); i++) { 201 /* This is where to make the change */ 202 location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr 203 + rela[i].r_offset; 204 /* This is the symbol it is referring to. Note that all 205 undefined symbols have been resolved. */ 206 sym = (Elf32_Sym *)sechdrs[symindex].sh_addr 207 + ELF32_R_SYM(rela[i].r_info); 208 /* `Everything is relative'. */ 209 value = sym->st_value + rela[i].r_addend; 210 211 switch (ELF32_R_TYPE(rela[i].r_info)) { 212 case R_PPC_ADDR32: 213 /* Simply set it */ 214 *(uint32_t *)location = value; 215 break; 216 217 case R_PPC_ADDR16_LO: 218 /* Low half of the symbol */ 219 *(uint16_t *)location = value; 220 break; 221 222 case R_PPC_ADDR16_HI: 223 /* Higher half of the symbol */ 224 *(uint16_t *)location = (value >> 16); 225 break; 226 227 case R_PPC_ADDR16_HA: 228 /* Sign-adjusted lower 16 bits: PPC ELF ABI says: 229 (((x >> 16) + ((x & 0x8000) ? 1 : 0))) & 0xFFFF. 230 This is the same, only sane. 231 */ 232 *(uint16_t *)location = (value + 0x8000) >> 16; 233 break; 234 235 case R_PPC_REL24: 236 if ((int)(value - (uint32_t)location) < -0x02000000 237 || (int)(value - (uint32_t)location) >= 0x02000000) 238 value = do_plt_call(location, value, 239 sechdrs, module); 240 241 /* Only replace bits 2 through 26 */ 242 pr_debug("REL24 value = %08X. location = %08X\n", 243 value, (uint32_t)location); 244 pr_debug("Location before: %08X.\n", 245 *(uint32_t *)location); 246 *(uint32_t *)location 247 = (*(uint32_t *)location & ~0x03fffffc) 248 | ((value - (uint32_t)location) 249 & 0x03fffffc); 250 pr_debug("Location after: %08X.\n", 251 *(uint32_t *)location); 252 pr_debug("ie. jump to %08X+%08X = %08X\n", 253 *(uint32_t *)location & 0x03fffffc, 254 (uint32_t)location, 255 (*(uint32_t *)location & 0x03fffffc) 256 + (uint32_t)location); 257 break; 258 259 case R_PPC_REL32: 260 /* 32-bit relative jump. */ 261 *(uint32_t *)location = value - (uint32_t)location; 262 break; 263 264 default: 265 pr_err("%s: unknown ADD relocation: %u\n", 266 module->name, 267 ELF32_R_TYPE(rela[i].r_info)); 268 return -ENOEXEC; 269 } 270 } 271 272 return 0; 273 } 274 275 #ifdef CONFIG_DYNAMIC_FTRACE 276 int module_trampoline_target(struct module *mod, unsigned long addr, 277 unsigned long *target) 278 { 279 unsigned int jmp[4]; 280 281 /* Find where the trampoline jumps to */ 282 if (copy_from_kernel_nofault(jmp, (void *)addr, sizeof(jmp))) 283 return -EFAULT; 284 285 /* verify that this is what we expect it to be */ 286 if ((jmp[0] & 0xffff0000) != PPC_RAW_LIS(_R12, 0) || 287 (jmp[1] & 0xffff0000) != PPC_RAW_ADDI(_R12, _R12, 0) || 288 jmp[2] != PPC_RAW_MTCTR(_R12) || 289 jmp[3] != PPC_RAW_BCTR()) 290 return -EINVAL; 291 292 addr = (jmp[1] & 0xffff) | ((jmp[0] & 0xffff) << 16); 293 if (addr & 0x8000) 294 addr -= 0x10000; 295 296 *target = addr; 297 298 return 0; 299 } 300 301 int module_finalize_ftrace(struct module *module, const Elf_Shdr *sechdrs) 302 { 303 module->arch.tramp = do_plt_call(module->core_layout.base, 304 (unsigned long)ftrace_caller, 305 sechdrs, module); 306 if (!module->arch.tramp) 307 return -ENOENT; 308 309 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS 310 module->arch.tramp_regs = do_plt_call(module->core_layout.base, 311 (unsigned long)ftrace_regs_caller, 312 sechdrs, module); 313 if (!module->arch.tramp_regs) 314 return -ENOENT; 315 #endif 316 317 return 0; 318 } 319 #endif 320