/* Kernel module help for PPC. Copyright (C) 2001 Rusty Russell. This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt #include #include #include #include #include #include #include #include #include #include #include #include /* Count how many different relocations (different symbol, different addend) */ static unsigned int count_relocs(const Elf32_Rela *rela, unsigned int num) { unsigned int i, r_info, r_addend, _count_relocs; _count_relocs = 0; r_info = 0; r_addend = 0; for (i = 0; i < num; i++) /* Only count 24-bit relocs, others don't need stubs */ if (ELF32_R_TYPE(rela[i].r_info) == R_PPC_REL24 && (r_info != ELF32_R_SYM(rela[i].r_info) || r_addend != rela[i].r_addend)) { _count_relocs++; r_info = ELF32_R_SYM(rela[i].r_info); r_addend = rela[i].r_addend; } #ifdef CONFIG_DYNAMIC_FTRACE _count_relocs++; /* add one for ftrace_caller */ #endif return _count_relocs; } static int relacmp(const void *_x, const void *_y) { const Elf32_Rela *x, *y; y = (Elf32_Rela *)_x; x = (Elf32_Rela *)_y; /* Compare the entire r_info (as opposed to ELF32_R_SYM(r_info) only) to * make the comparison cheaper/faster. It won't affect the sorting or * the counting algorithms' performance */ if (x->r_info < y->r_info) return -1; else if (x->r_info > y->r_info) return 1; else if (x->r_addend < y->r_addend) return -1; else if (x->r_addend > y->r_addend) return 1; else return 0; } static void relaswap(void *_x, void *_y, int size) { uint32_t *x, *y, tmp; int i; y = (uint32_t *)_x; x = (uint32_t *)_y; for (i = 0; i < sizeof(Elf32_Rela) / sizeof(uint32_t); i++) { tmp = x[i]; x[i] = y[i]; y[i] = tmp; } } /* Get the potential trampolines size required of the init and non-init sections */ static unsigned long get_plt_size(const Elf32_Ehdr *hdr, const Elf32_Shdr *sechdrs, const char *secstrings, int is_init) { unsigned long ret = 0; unsigned i; /* Everything marked ALLOC (this includes the exported symbols) */ for (i = 1; i < hdr->e_shnum; i++) { /* If it's called *.init*, and we're not init, we're not interested */ if ((strstr(secstrings + sechdrs[i].sh_name, ".init") != 0) != is_init) continue; /* We don't want to look at debug sections. */ if (strstr(secstrings + sechdrs[i].sh_name, ".debug") != 0) continue; if (sechdrs[i].sh_type == SHT_RELA) { pr_debug("Found relocations in section %u\n", i); pr_debug("Ptr: %p. Number: %u\n", (void *)hdr + sechdrs[i].sh_offset, sechdrs[i].sh_size / sizeof(Elf32_Rela)); /* Sort the relocation information based on a symbol and * addend key. This is a stable O(n*log n) complexity * alogrithm but it will reduce the complexity of * count_relocs() to linear complexity O(n) */ sort((void *)hdr + sechdrs[i].sh_offset, sechdrs[i].sh_size / sizeof(Elf32_Rela), sizeof(Elf32_Rela), relacmp, relaswap); ret += count_relocs((void *)hdr + sechdrs[i].sh_offset, sechdrs[i].sh_size / sizeof(Elf32_Rela)) * sizeof(struct ppc_plt_entry); } } return ret; } int module_frob_arch_sections(Elf32_Ehdr *hdr, Elf32_Shdr *sechdrs, char *secstrings, struct module *me) { unsigned int i; /* Find .plt and .init.plt sections */ for (i = 0; i < hdr->e_shnum; i++) { if (strcmp(secstrings + sechdrs[i].sh_name, ".init.plt") == 0) me->arch.init_plt_section = i; else if (strcmp(secstrings + sechdrs[i].sh_name, ".plt") == 0) me->arch.core_plt_section = i; } if (!me->arch.core_plt_section || !me->arch.init_plt_section) { pr_err("Module doesn't contain .plt or .init.plt sections.\n"); return -ENOEXEC; } /* Override their sizes */ sechdrs[me->arch.core_plt_section].sh_size = get_plt_size(hdr, sechdrs, secstrings, 0); sechdrs[me->arch.init_plt_section].sh_size = get_plt_size(hdr, sechdrs, secstrings, 1); return 0; } static inline int entry_matches(struct ppc_plt_entry *entry, Elf32_Addr val) { if (entry->jump[0] == 0x3d800000 + ((val + 0x8000) >> 16) && entry->jump[1] == 0x398c0000 + (val & 0xffff)) return 1; return 0; } /* Set up a trampoline in the PLT to bounce us to the distant function */ static uint32_t do_plt_call(void *location, Elf32_Addr val, const Elf32_Shdr *sechdrs, struct module *mod) { struct ppc_plt_entry *entry; pr_debug("Doing plt for call to 0x%x at 0x%x\n", val, (unsigned int)location); /* Init, or core PLT? */ if (location >= mod->core_layout.base && location < mod->core_layout.base + mod->core_layout.size) entry = (void *)sechdrs[mod->arch.core_plt_section].sh_addr; else entry = (void *)sechdrs[mod->arch.init_plt_section].sh_addr; /* Find this entry, or if that fails, the next avail. entry */ while (entry->jump[0]) { if (entry_matches(entry, val)) return (uint32_t)entry; entry++; } entry->jump[0] = 0x3d800000+((val+0x8000)>>16); /* lis r12,sym@ha */ entry->jump[1] = 0x398c0000 + (val&0xffff); /* addi r12,r12,sym@l*/ entry->jump[2] = 0x7d8903a6; /* mtctr r12 */ entry->jump[3] = 0x4e800420; /* bctr */ pr_debug("Initialized plt for 0x%x at %p\n", val, entry); return (uint32_t)entry; } int apply_relocate_add(Elf32_Shdr *sechdrs, const char *strtab, unsigned int symindex, unsigned int relsec, struct module *module) { unsigned int i; Elf32_Rela *rela = (void *)sechdrs[relsec].sh_addr; Elf32_Sym *sym; uint32_t *location; uint32_t value; pr_debug("Applying ADD relocate section %u to %u\n", relsec, sechdrs[relsec].sh_info); for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rela); i++) { /* This is where to make the change */ location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr + rela[i].r_offset; /* This is the symbol it is referring to. Note that all undefined symbols have been resolved. */ sym = (Elf32_Sym *)sechdrs[symindex].sh_addr + ELF32_R_SYM(rela[i].r_info); /* `Everything is relative'. */ value = sym->st_value + rela[i].r_addend; switch (ELF32_R_TYPE(rela[i].r_info)) { case R_PPC_ADDR32: /* Simply set it */ *(uint32_t *)location = value; break; case R_PPC_ADDR16_LO: /* Low half of the symbol */ *(uint16_t *)location = value; break; case R_PPC_ADDR16_HI: /* Higher half of the symbol */ *(uint16_t *)location = (value >> 16); break; case R_PPC_ADDR16_HA: /* Sign-adjusted lower 16 bits: PPC ELF ABI says: (((x >> 16) + ((x & 0x8000) ? 1 : 0))) & 0xFFFF. This is the same, only sane. */ *(uint16_t *)location = (value + 0x8000) >> 16; break; case R_PPC_REL24: if ((int)(value - (uint32_t)location) < -0x02000000 || (int)(value - (uint32_t)location) >= 0x02000000) value = do_plt_call(location, value, sechdrs, module); /* Only replace bits 2 through 26 */ pr_debug("REL24 value = %08X. location = %08X\n", value, (uint32_t)location); pr_debug("Location before: %08X.\n", *(uint32_t *)location); *(uint32_t *)location = (*(uint32_t *)location & ~0x03fffffc) | ((value - (uint32_t)location) & 0x03fffffc); pr_debug("Location after: %08X.\n", *(uint32_t *)location); pr_debug("ie. jump to %08X+%08X = %08X\n", *(uint32_t *)location & 0x03fffffc, (uint32_t)location, (*(uint32_t *)location & 0x03fffffc) + (uint32_t)location); break; case R_PPC_REL32: /* 32-bit relative jump. */ *(uint32_t *)location = value - (uint32_t)location; break; default: pr_err("%s: unknown ADD relocation: %u\n", module->name, ELF32_R_TYPE(rela[i].r_info)); return -ENOEXEC; } } return 0; } #ifdef CONFIG_DYNAMIC_FTRACE int module_finalize_ftrace(struct module *module, const Elf_Shdr *sechdrs) { module->arch.tramp = do_plt_call(module->core_layout.base, (unsigned long)ftrace_caller, sechdrs, module); if (!module->arch.tramp) return -ENOENT; return 0; } #endif