diff --git a/arch/arm/include/asm/module.h b/arch/arm/include/asm/module.h index 464748b9fd7d..ed2319663a1e 100644 --- a/arch/arm/include/asm/module.h +++ b/arch/arm/include/asm/module.h @@ -18,13 +18,18 @@ enum { }; #endif +struct mod_plt_sec { + struct elf32_shdr *plt; + int plt_count; +}; + struct mod_arch_specific { #ifdef CONFIG_ARM_UNWIND struct unwind_table *unwind[ARM_SEC_MAX]; #endif #ifdef CONFIG_ARM_MODULE_PLTS - struct elf32_shdr *plt; - int plt_count; + struct mod_plt_sec core; + struct mod_plt_sec init; #endif }; diff --git a/arch/arm/kernel/module-plts.c b/arch/arm/kernel/module-plts.c index 3a5cba90c971..3d0c2e4dda1d 100644 --- a/arch/arm/kernel/module-plts.c +++ b/arch/arm/kernel/module-plts.c @@ -1,5 +1,5 @@ /* - * Copyright (C) 2014 Linaro Ltd. + * Copyright (C) 2014-2017 Linaro Ltd. * * 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 @@ -31,9 +31,17 @@ struct plt_entries { u32 lit[PLT_ENT_COUNT]; }; +static bool in_init(const struct module *mod, unsigned long loc) +{ + return loc - (u32)mod->init_layout.base < mod->init_layout.size; +} + u32 get_module_plt(struct module *mod, unsigned long loc, Elf32_Addr val) { - struct plt_entries *plt = (struct plt_entries *)mod->arch.plt->sh_addr; + struct mod_plt_sec *pltsec = !in_init(mod, loc) ? &mod->arch.core : + &mod->arch.init; + + struct plt_entries *plt = (struct plt_entries *)pltsec->plt->sh_addr; int idx = 0; /* @@ -41,9 +49,9 @@ u32 get_module_plt(struct module *mod, unsigned long loc, Elf32_Addr val) * relocations are sorted, this will be the last entry we allocated. * (if one exists). */ - if (mod->arch.plt_count > 0) { - plt += (mod->arch.plt_count - 1) / PLT_ENT_COUNT; - idx = (mod->arch.plt_count - 1) % PLT_ENT_COUNT; + if (pltsec->plt_count > 0) { + plt += (pltsec->plt_count - 1) / PLT_ENT_COUNT; + idx = (pltsec->plt_count - 1) % PLT_ENT_COUNT; if (plt->lit[idx] == val) return (u32)&plt->ldr[idx]; @@ -53,8 +61,8 @@ u32 get_module_plt(struct module *mod, unsigned long loc, Elf32_Addr val) plt++; } - mod->arch.plt_count++; - BUG_ON(mod->arch.plt_count * PLT_ENT_SIZE > mod->arch.plt->sh_size); + pltsec->plt_count++; + BUG_ON(pltsec->plt_count * PLT_ENT_SIZE > pltsec->plt->sh_size); if (!idx) /* Populate a new set of entries */ @@ -129,7 +137,7 @@ static bool duplicate_rel(Elf32_Addr base, const Elf32_Rel *rel, int num) /* Count how many PLT entries we may need */ static unsigned int count_plts(const Elf32_Sym *syms, Elf32_Addr base, - const Elf32_Rel *rel, int num) + const Elf32_Rel *rel, int num, Elf32_Word dstidx) { unsigned int ret = 0; const Elf32_Sym *s; @@ -144,13 +152,17 @@ static unsigned int count_plts(const Elf32_Sym *syms, Elf32_Addr base, case R_ARM_THM_JUMP24: /* * 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 range - * 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 + ELF32_R_SYM(rel[i].r_info); - if (s->st_shndx != SHN_UNDEF) + if (s->st_shndx == dstidx) break; /* @@ -161,7 +173,12 @@ static unsigned int count_plts(const Elf32_Sym *syms, Elf32_Addr base, * So we need to support them, but there is no need to * take them into consideration when trying to optimize * this code. So let's only check for duplicates when - * the addend is zero. + * the addend is zero. (Note that calls into the core + * module via init PLT entries could involve section + * relative symbol references with non-zero addends, for + * which we may end up emitting duplicates, but the init + * PLT is released along with the rest of the .init + * region as soon as module loading completes.) */ if (!is_zero_addend_relocation(base, rel + i) || !duplicate_rel(base, rel, i)) @@ -174,7 +191,8 @@ static unsigned int count_plts(const Elf32_Sym *syms, Elf32_Addr base, int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs, char *secstrings, struct module *mod) { - unsigned long plts = 0; + unsigned long core_plts = 0; + unsigned long init_plts = 0; Elf32_Shdr *s, *sechdrs_end = sechdrs + ehdr->e_shnum; Elf32_Sym *syms = NULL; @@ -184,13 +202,15 @@ int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs, */ for (s = sechdrs; s < sechdrs_end; ++s) { if (strcmp(".plt", secstrings + s->sh_name) == 0) - mod->arch.plt = s; + mod->arch.core.plt = s; + else if (strcmp(".init.plt", secstrings + s->sh_name) == 0) + mod->arch.init.plt = s; else if (s->sh_type == SHT_SYMTAB) syms = (Elf32_Sym *)s->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) { @@ -213,16 +233,29 @@ int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs, /* sort by type and symbol index */ sort(rels, numrels, sizeof(Elf32_Rel), cmp_rel, NULL); - plts += count_plts(syms, dstsec->sh_addr, rels, numrels); + if (strncmp(secstrings + dstsec->sh_name, ".init", 5) != 0) + core_plts += count_plts(syms, dstsec->sh_addr, rels, + numrels, s->sh_info); + else + init_plts += count_plts(syms, dstsec->sh_addr, rels, + numrels, s->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 = round_up(plts * PLT_ENT_SIZE, - sizeof(struct plt_entries)); - mod->arch.plt_count = 0; + 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 = round_up(core_plts * PLT_ENT_SIZE, + sizeof(struct plt_entries)); + mod->arch.core.plt_count = 0; - pr_debug("%s: plt=%x\n", __func__, mod->arch.plt->sh_size); + 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 = round_up(init_plts * PLT_ENT_SIZE, + sizeof(struct plt_entries)); + mod->arch.init.plt_count = 0; + + pr_debug("%s: plt=%x, init.plt=%x\n", __func__, + mod->arch.core.plt->sh_size, mod->arch.init.plt->sh_size); return 0; } diff --git a/arch/arm/kernel/module.lds b/arch/arm/kernel/module.lds index 05881e2b414c..eacb5c67f61e 100644 --- a/arch/arm/kernel/module.lds +++ b/arch/arm/kernel/module.lds @@ -1,3 +1,4 @@ SECTIONS { .plt : { BYTE(0) } + .init.plt : { BYTE(0) } }