diff options
Diffstat (limited to 'arch/arm64')
-rw-r--r-- | arch/arm64/include/asm/module.h | 9 | ||||
-rw-r--r-- | arch/arm64/kernel/module-plts.c | 108 | ||||
-rw-r--r-- | arch/arm64/kernel/module.c | 2 | ||||
-rw-r--r-- | arch/arm64/kernel/module.lds | 1 |
4 files changed, 72 insertions, 48 deletions
diff --git a/arch/arm64/include/asm/module.h b/arch/arm64/include/asm/module.h index e12af67..d57693f 100644 --- a/arch/arm64/include/asm/module.h +++ b/arch/arm64/include/asm/module.h @@ -21,14 +21,19 @@ #define MODULE_ARCH_VERMAGIC "aarch64" #ifdef CONFIG_ARM64_MODULE_PLTS -struct mod_arch_specific { +struct mod_plt_sec { struct elf64_shdr *plt; int plt_num_entries; int plt_max_entries; }; + +struct mod_arch_specific { + struct mod_plt_sec core; + struct mod_plt_sec init; +}; #endif -u64 module_emit_plt_entry(struct module *mod, const Elf64_Rela *rela, +u64 module_emit_plt_entry(struct module *mod, void *loc, const Elf64_Rela *rela, Elf64_Sym *sym); #ifdef CONFIG_RANDOMIZE_BASE diff --git a/arch/arm64/kernel/module-plts.c b/arch/arm64/kernel/module-plts.c index 1ce90d8..d05dbe6 100644 --- a/arch/arm64/kernel/module-plts.c +++ b/arch/arm64/kernel/module-plts.c @@ -1,5 +1,5 @@ /* - * Copyright (C) 2014-2016 Linaro Ltd. <ard.biesheuvel@linaro.org> + * Copyright (C) 2014-2017 Linaro Ltd. <ard.biesheuvel@linaro.org> * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License version 2 as @@ -26,35 +26,21 @@ struct plt_entry { __le32 br; /* br x16 */ }; -u64 module_emit_plt_entry(struct module *mod, const Elf64_Rela *rela, +static bool in_init(const struct module *mod, void *loc) +{ + return (u64)loc - (u64)mod->init_layout.base < mod->init_layout.size; +} + +u64 module_emit_plt_entry(struct module *mod, void *loc, const Elf64_Rela *rela, Elf64_Sym *sym) { - struct plt_entry *plt = (struct plt_entry *)mod->arch.plt->sh_addr; - int i = mod->arch.plt_num_entries; + struct mod_plt_sec *pltsec = !in_init(mod, loc) ? &mod->arch.core : + &mod->arch.init; + struct plt_entry *plt = (struct plt_entry *)pltsec->plt->sh_addr; + int i = pltsec->plt_num_entries; u64 val = sym->st_value + rela->r_addend; /* - * We only emit PLT entries against undefined (SHN_UNDEF) symbols, - * which are listed in the ELF symtab section, but without a type - * or a size. - * So, similar to how the module loader uses the Elf64_Sym::st_value - * field to store the resolved addresses of undefined symbols, let's - * borrow the Elf64_Sym::st_size field (whose value is never used by - * the module loader, even for symbols that are defined) to record - * the address of a symbol's associated PLT entry as we emit it for a - * zero addend relocation (which is the only kind we have to deal with - * in practice). This allows us to find duplicates without having to - * go through the table every time. - */ - if (rela->r_addend == 0 && sym->st_size != 0) { - BUG_ON(sym->st_size < (u64)plt || sym->st_size >= (u64)&plt[i]); - return sym->st_size; - } - - mod->arch.plt_num_entries++; - BUG_ON(mod->arch.plt_num_entries > mod->arch.plt_max_entries); - - /* * MOVK/MOVN/MOVZ opcode: * +--------+------------+--------+-----------+-------------+---------+ * | sf[31] | opc[30:29] | 100101 | hw[22:21] | imm16[20:5] | Rd[4:0] | @@ -72,8 +58,19 @@ u64 module_emit_plt_entry(struct module *mod, const Elf64_Rela *rela, cpu_to_le32(0xd61f0200) }; - if (rela->r_addend == 0) - sym->st_size = (u64)&plt[i]; + /* + * Check if the entry we just created is a duplicate. Given that the + * relocations are sorted, this will be the last entry we allocated. + * (if one exists). + */ + if (i > 0 && + plt[i].mov0 == plt[i - 1].mov0 && + plt[i].mov1 == plt[i - 1].mov1 && + plt[i].mov2 == plt[i - 1].mov2) + return (u64)&plt[i - 1]; + + pltsec->plt_num_entries++; + BUG_ON(pltsec->plt_num_entries > pltsec->plt_max_entries); return (u64)&plt[i]; } @@ -104,7 +101,8 @@ static bool duplicate_rel(const Elf64_Rela *rela, int num) return num > 0 && cmp_rela(rela + num, rela + num - 1) == 0; } -static unsigned int count_plts(Elf64_Sym *syms, Elf64_Rela *rela, int num) +static unsigned int count_plts(Elf64_Sym *syms, Elf64_Rela *rela, int num, + Elf64_Word dstidx) { unsigned int ret = 0; Elf64_Sym *s; @@ -116,13 +114,17 @@ static unsigned int count_plts(Elf64_Sym *syms, Elf64_Rela *rela, int num) case R_AARCH64_CALL26: /* * We only have to consider branch targets that resolve - * to undefined symbols. This is not simply a heuristic, - * it is a fundamental limitation, since the PLT itself - * is part of the module, and needs to be within 128 MB - * as well, so modules can never grow beyond that limit. + * to symbols that are defined in a different section. + * This is not simply a heuristic, it is a fundamental + * limitation, since there is no guaranteed way to emit + * PLT entries sufficiently close to the branch if the + * section size exceeds the range of a branch + * instruction. So ignore relocations against defined + * symbols if they live in the same section as the + * relocation target. */ s = syms + ELF64_R_SYM(rela[i].r_info); - if (s->st_shndx != SHN_UNDEF) + if (s->st_shndx == dstidx) break; /* @@ -149,7 +151,8 @@ static unsigned int count_plts(Elf64_Sym *syms, Elf64_Rela *rela, int num) int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs, char *secstrings, struct module *mod) { - unsigned long plt_max_entries = 0; + unsigned long core_plts = 0; + unsigned long init_plts = 0; Elf64_Sym *syms = NULL; int i; @@ -158,14 +161,16 @@ int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs, * entries. Record the symtab address as well. */ for (i = 0; i < ehdr->e_shnum; i++) { - if (strcmp(".plt", secstrings + sechdrs[i].sh_name) == 0) - mod->arch.plt = sechdrs + i; + if (!strcmp(secstrings + sechdrs[i].sh_name, ".plt")) + mod->arch.core.plt = sechdrs + i; + else if (!strcmp(secstrings + sechdrs[i].sh_name, ".init.plt")) + mod->arch.init.plt = sechdrs + i; else if (sechdrs[i].sh_type == SHT_SYMTAB) syms = (Elf64_Sym *)sechdrs[i].sh_addr; } - if (!mod->arch.plt) { - pr_err("%s: module PLT section missing\n", mod->name); + if (!mod->arch.core.plt || !mod->arch.init.plt) { + pr_err("%s: module PLT section(s) missing\n", mod->name); return -ENOEXEC; } if (!syms) { @@ -188,14 +193,27 @@ int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs, /* sort by type, symbol index and addend */ sort(rels, numrels, sizeof(Elf64_Rela), cmp_rela, NULL); - plt_max_entries += count_plts(syms, rels, numrels); + if (strncmp(secstrings + dstsec->sh_name, ".init", 5) != 0) + core_plts += count_plts(syms, rels, numrels, + sechdrs[i].sh_info); + else + init_plts += count_plts(syms, rels, numrels, + sechdrs[i].sh_info); } - mod->arch.plt->sh_type = SHT_NOBITS; - mod->arch.plt->sh_flags = SHF_EXECINSTR | SHF_ALLOC; - mod->arch.plt->sh_addralign = L1_CACHE_BYTES; - mod->arch.plt->sh_size = plt_max_entries * sizeof(struct plt_entry); - mod->arch.plt_num_entries = 0; - mod->arch.plt_max_entries = plt_max_entries; + mod->arch.core.plt->sh_type = SHT_NOBITS; + mod->arch.core.plt->sh_flags = SHF_EXECINSTR | SHF_ALLOC; + mod->arch.core.plt->sh_addralign = L1_CACHE_BYTES; + mod->arch.core.plt->sh_size = (core_plts + 1) * sizeof(struct plt_entry); + mod->arch.core.plt_num_entries = 0; + mod->arch.core.plt_max_entries = core_plts; + + mod->arch.init.plt->sh_type = SHT_NOBITS; + mod->arch.init.plt->sh_flags = SHF_EXECINSTR | SHF_ALLOC; + mod->arch.init.plt->sh_addralign = L1_CACHE_BYTES; + mod->arch.init.plt->sh_size = (init_plts + 1) * sizeof(struct plt_entry); + mod->arch.init.plt_num_entries = 0; + mod->arch.init.plt_max_entries = init_plts; + return 0; } diff --git a/arch/arm64/kernel/module.c b/arch/arm64/kernel/module.c index 7f31698..c9a2ab4 100644 --- a/arch/arm64/kernel/module.c +++ b/arch/arm64/kernel/module.c @@ -380,7 +380,7 @@ int apply_relocate_add(Elf64_Shdr *sechdrs, if (IS_ENABLED(CONFIG_ARM64_MODULE_PLTS) && ovf == -ERANGE) { - val = module_emit_plt_entry(me, &rel[i], sym); + val = module_emit_plt_entry(me, loc, &rel[i], sym); ovf = reloc_insn_imm(RELOC_OP_PREL, loc, val, 2, 26, AARCH64_INSN_IMM_26); } diff --git a/arch/arm64/kernel/module.lds b/arch/arm64/kernel/module.lds index 8949f6c..f7c9781 100644 --- a/arch/arm64/kernel/module.lds +++ b/arch/arm64/kernel/module.lds @@ -1,3 +1,4 @@ SECTIONS { .plt (NOLOAD) : { BYTE(0) } + .init.plt (NOLOAD) : { BYTE(0) } } |