/* Kernel module help for Meta. 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. */ #include <linux/moduleloader.h> #include <linux/elf.h> #include <linux/vmalloc.h> #include <linux/fs.h> #include <linux/string.h> #include <linux/kernel.h> #include <linux/sort.h> #include <asm/unaligned.h> /* 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 relbranch relocs, others don't need stubs */ if (ELF32_R_TYPE(rela[i].r_info) == R_METAG_RELBRANCH && (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; } 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") != NULL) != is_init) continue; /* We don't want to look at debug sections. */ if (strstr(secstrings + sechdrs[i].sh_name, ".debug") != NULL) 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 metag_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.core_plt_section].sh_type = SHT_NOBITS; sechdrs[me->arch.init_plt_section].sh_size = get_plt_size(hdr, sechdrs, secstrings, 1); sechdrs[me->arch.init_plt_section].sh_type = SHT_NOBITS; 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, Elf32_Shdr *sechdrs, struct module *mod) { struct metag_plt_entry *entry; /* Instructions used to do the indirect jump. */ uint32_t tramp[2]; /* We have to trash a register, so we assume that any control transfer more than 21-bits away must be a function call (so we can use a call-clobbered register). */ /* MOVT D0Re0,#HI(v) */ tramp[0] = 0x02000005 | (((val & 0xffff0000) >> 16) << 3); /* JUMP D0Re0,#LO(v) */ tramp[1] = 0xac000001 | ((val & 0x0000ffff) << 3); /* Init, or core PLT? */ if (location >= mod->module_core && location < mod->module_core + mod->core_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->tramp[0]) if (entry->tramp[0] == tramp[0] && entry->tramp[1] == tramp[1]) return (uint32_t)entry; else entry++; entry->tramp[0] = tramp[0]; entry->tramp[1] = tramp[1]; return (uint32_t)entry; } int apply_relocate_add(Elf32_Shdr *sechdrs, const char *strtab, unsigned int symindex, unsigned int relsec, struct module *me) { unsigned int i; Elf32_Rela *rel = (void *)sechdrs[relsec].sh_addr; Elf32_Sym *sym; Elf32_Addr relocation; uint32_t *location; int32_t value; pr_debug("Applying relocate section %u to %u\n", relsec, sechdrs[relsec].sh_info); for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) { /* This is where to make the change */ location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr + rel[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(rel[i].r_info); relocation = sym->st_value + rel[i].r_addend; switch (ELF32_R_TYPE(rel[i].r_info)) { case R_METAG_NONE: break; case R_METAG_HIADDR16: relocation >>= 16; case R_METAG_LOADDR16: *location = (*location & 0xfff80007) | ((relocation & 0xffff) << 3); break; case R_METAG_ADDR32: /* * Packed data structures may cause a misaligned * R_METAG_ADDR32 to be emitted. */ put_unaligned(relocation, location); break; case R_METAG_GETSETOFF: *location += ((relocation & 0xfff) << 7); break; case R_METAG_RELBRANCH: if (*location & (0x7ffff << 5)) { pr_err("bad relbranch relocation\n"); break; } /* This jump is too big for the offset slot. Build * a PLT to jump through to get to where we want to go. * NB: 21bit check - not scaled to 19bit yet */ if (((int32_t)(relocation - (uint32_t)location) > 0xfffff) || ((int32_t)(relocation - (uint32_t)location) < -0xfffff)) { relocation = do_plt_call(location, relocation, sechdrs, me); } value = relocation - (uint32_t)location; /* branch instruction aligned */ value /= 4; if ((value > 0x7ffff) || (value < -0x7ffff)) { /* * this should have been caught by the code * above! */ pr_err("overflow of relbranch reloc\n"); } *location = (*location & (~(0x7ffff << 5))) | ((value & 0x7ffff) << 5); break; default: pr_err("module %s: Unknown relocation: %u\n", me->name, ELF32_R_TYPE(rel[i].r_info)); return -ENOEXEC; } } return 0; }