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author | Russell King <rmk+kernel@armlinux.org.uk> | 2016-10-06 08:57:07 +0100 |
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committer | Russell King <rmk+kernel@armlinux.org.uk> | 2016-10-06 08:57:07 +0100 |
commit | 81a63001862f92d47c8c40a7fad870d5fbd8680b (patch) | |
tree | 21e45333a5501bec2ebc2ce46bb8847de5621814 /arch/arm | |
parent | 301a36fa700f9add6e14f5a95c7573e01578343a (diff) | |
parent | 32b63776931acc7dbaaf336a99dd7306a815a254 (diff) | |
download | linux-81a63001862f92d47c8c40a7fad870d5fbd8680b.tar.bz2 |
Merge branch 'devel-stable' into for-linus
Diffstat (limited to 'arch/arm')
-rw-r--r-- | arch/arm/include/asm/module.h | 6 | ||||
-rw-r--r-- | arch/arm/kernel/module-plts.c | 243 | ||||
-rw-r--r-- | arch/arm/kernel/module.lds | 3 |
3 files changed, 147 insertions, 105 deletions
diff --git a/arch/arm/include/asm/module.h b/arch/arm/include/asm/module.h index e358b7966c06..464748b9fd7d 100644 --- a/arch/arm/include/asm/module.h +++ b/arch/arm/include/asm/module.h @@ -23,10 +23,8 @@ struct mod_arch_specific { struct unwind_table *unwind[ARM_SEC_MAX]; #endif #ifdef CONFIG_ARM_MODULE_PLTS - struct elf32_shdr *core_plt; - struct elf32_shdr *init_plt; - int core_plt_count; - int init_plt_count; + struct elf32_shdr *plt; + int plt_count; #endif }; diff --git a/arch/arm/kernel/module-plts.c b/arch/arm/kernel/module-plts.c index 0c7efc3446c0..3a5cba90c971 100644 --- a/arch/arm/kernel/module-plts.c +++ b/arch/arm/kernel/module-plts.c @@ -9,6 +9,7 @@ #include <linux/elf.h> #include <linux/kernel.h> #include <linux/module.h> +#include <linux/sort.h> #include <asm/cache.h> #include <asm/opcodes.h> @@ -30,154 +31,198 @@ struct plt_entries { u32 lit[PLT_ENT_COUNT]; }; -static bool in_init(const struct module *mod, u32 addr) +u32 get_module_plt(struct module *mod, unsigned long loc, Elf32_Addr val) { - return addr - (u32)mod->init_layout.base < mod->init_layout.size; + struct plt_entries *plt = (struct plt_entries *)mod->arch.plt->sh_addr; + int idx = 0; + + /* + * Look for an existing entry pointing to 'val'. Given that the + * 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 (plt->lit[idx] == val) + return (u32)&plt->ldr[idx]; + + idx = (idx + 1) % PLT_ENT_COUNT; + if (!idx) + plt++; + } + + mod->arch.plt_count++; + BUG_ON(mod->arch.plt_count * PLT_ENT_SIZE > mod->arch.plt->sh_size); + + if (!idx) + /* Populate a new set of entries */ + *plt = (struct plt_entries){ + { [0 ... PLT_ENT_COUNT - 1] = PLT_ENT_LDR, }, + { val, } + }; + else + plt->lit[idx] = val; + + return (u32)&plt->ldr[idx]; } -u32 get_module_plt(struct module *mod, unsigned long loc, Elf32_Addr val) +#define cmp_3way(a,b) ((a) < (b) ? -1 : (a) > (b)) + +static int cmp_rel(const void *a, const void *b) { - struct plt_entries *plt, *plt_end; - int c, *count; - - if (in_init(mod, loc)) { - plt = (void *)mod->arch.init_plt->sh_addr; - plt_end = (void *)plt + mod->arch.init_plt->sh_size; - count = &mod->arch.init_plt_count; - } else { - plt = (void *)mod->arch.core_plt->sh_addr; - plt_end = (void *)plt + mod->arch.core_plt->sh_size; - count = &mod->arch.core_plt_count; - } + const Elf32_Rel *x = a, *y = b; + int i; - /* Look for an existing entry pointing to 'val' */ - for (c = *count; plt < plt_end; c -= PLT_ENT_COUNT, plt++) { - int i; - - if (!c) { - /* Populate a new set of entries */ - *plt = (struct plt_entries){ - { [0 ... PLT_ENT_COUNT - 1] = PLT_ENT_LDR, }, - { val, } - }; - ++*count; - return (u32)plt->ldr; - } - for (i = 0; i < PLT_ENT_COUNT; i++) { - if (!plt->lit[i]) { - plt->lit[i] = val; - ++*count; - } - if (plt->lit[i] == val) - return (u32)&plt->ldr[i]; - } + /* sort by type and symbol index */ + i = cmp_3way(ELF32_R_TYPE(x->r_info), ELF32_R_TYPE(y->r_info)); + if (i == 0) + i = cmp_3way(ELF32_R_SYM(x->r_info), ELF32_R_SYM(y->r_info)); + return i; +} + +static bool is_zero_addend_relocation(Elf32_Addr base, const Elf32_Rel *rel) +{ + u32 *tval = (u32 *)(base + rel->r_offset); + + /* + * Do a bitwise compare on the raw addend rather than fully decoding + * the offset and doing an arithmetic comparison. + * Note that a zero-addend jump/call relocation is encoded taking the + * PC bias into account, i.e., -8 for ARM and -4 for Thumb2. + */ + switch (ELF32_R_TYPE(rel->r_info)) { + u16 upper, lower; + + case R_ARM_THM_CALL: + case R_ARM_THM_JUMP24: + upper = __mem_to_opcode_thumb16(((u16 *)tval)[0]); + lower = __mem_to_opcode_thumb16(((u16 *)tval)[1]); + + return (upper & 0x7ff) == 0x7ff && (lower & 0x2fff) == 0x2ffe; + + case R_ARM_CALL: + case R_ARM_PC24: + case R_ARM_JUMP24: + return (__mem_to_opcode_arm(*tval) & 0xffffff) == 0xfffffe; } BUG(); } -static int duplicate_rel(Elf32_Addr base, const Elf32_Rel *rel, int num, - u32 mask) +static bool duplicate_rel(Elf32_Addr base, const Elf32_Rel *rel, int num) { - u32 *loc1, *loc2; - int i; + const Elf32_Rel *prev; - for (i = 0; i < num; i++) { - if (rel[i].r_info != rel[num].r_info) - continue; + /* + * Entries are sorted by type and symbol index. That means that, + * if a duplicate entry exists, it must be in the preceding + * slot. + */ + if (!num) + return false; - /* - * Identical relocation types against identical symbols can - * still result in different PLT entries if the addend in the - * place is different. So resolve the target of the relocation - * to compare the values. - */ - loc1 = (u32 *)(base + rel[i].r_offset); - loc2 = (u32 *)(base + rel[num].r_offset); - if (((*loc1 ^ *loc2) & mask) == 0) - return 1; - } - return 0; + prev = rel + num - 1; + return cmp_rel(rel + num, prev) == 0 && + is_zero_addend_relocation(base, prev); } /* Count how many PLT entries we may need */ -static unsigned int count_plts(Elf32_Addr base, const Elf32_Rel *rel, int num) +static unsigned int count_plts(const Elf32_Sym *syms, Elf32_Addr base, + const Elf32_Rel *rel, int num) { unsigned int ret = 0; + const Elf32_Sym *s; int i; - /* - * Sure, this is order(n^2), but it's usually short, and not - * time critical - */ - for (i = 0; i < num; i++) + for (i = 0; i < num; i++) { switch (ELF32_R_TYPE(rel[i].r_info)) { case R_ARM_CALL: case R_ARM_PC24: case R_ARM_JUMP24: - if (!duplicate_rel(base, rel, i, - __opcode_to_mem_arm(0x00ffffff))) - ret++; - break; -#ifdef CONFIG_THUMB2_KERNEL case R_ARM_THM_CALL: case R_ARM_THM_JUMP24: - if (!duplicate_rel(base, rel, i, - __opcode_to_mem_thumb32(0x07ff2fff))) + /* + * 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. + */ + s = syms + ELF32_R_SYM(rel[i].r_info); + if (s->st_shndx != SHN_UNDEF) + break; + + /* + * Jump relocations with non-zero addends against + * undefined symbols are supported by the ELF spec, but + * do not occur in practice (e.g., 'jump n bytes past + * the entry point of undefined function symbol f'). + * 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. + */ + if (!is_zero_addend_relocation(base, rel + i) || + !duplicate_rel(base, rel, i)) ret++; -#endif } + } return ret; } int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs, char *secstrings, struct module *mod) { - unsigned long core_plts = 0, init_plts = 0; + unsigned long plts = 0; Elf32_Shdr *s, *sechdrs_end = sechdrs + ehdr->e_shnum; + Elf32_Sym *syms = NULL; /* * To store the PLTs, we expand the .text section for core module code - * and the .init.text section for initialization code. + * and for initialization code. */ - for (s = sechdrs; s < sechdrs_end; ++s) - if (strcmp(".core.plt", secstrings + s->sh_name) == 0) - mod->arch.core_plt = s; - else if (strcmp(".init.plt", secstrings + s->sh_name) == 0) - mod->arch.init_plt = s; - - if (!mod->arch.core_plt || !mod->arch.init_plt) { - pr_err("%s: sections missing\n", mod->name); + for (s = sechdrs; s < sechdrs_end; ++s) { + if (strcmp(".plt", secstrings + s->sh_name) == 0) + mod->arch.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); + return -ENOEXEC; + } + if (!syms) { + pr_err("%s: module symtab section missing\n", mod->name); return -ENOEXEC; } for (s = sechdrs + 1; s < sechdrs_end; ++s) { - const Elf32_Rel *rels = (void *)ehdr + s->sh_offset; + Elf32_Rel *rels = (void *)ehdr + s->sh_offset; int numrels = s->sh_size / sizeof(Elf32_Rel); Elf32_Shdr *dstsec = sechdrs + s->sh_info; if (s->sh_type != SHT_REL) continue; - if (strstr(secstrings + s->sh_name, ".init")) - init_plts += count_plts(dstsec->sh_addr, rels, numrels); - else - core_plts += count_plts(dstsec->sh_addr, rels, numrels); + /* ignore relocations that operate on non-exec sections */ + if (!(dstsec->sh_flags & SHF_EXECINSTR)) + continue; + + /* sort by type and symbol index */ + sort(rels, numrels, sizeof(Elf32_Rel), cmp_rel, NULL); + + plts += count_plts(syms, dstsec->sh_addr, rels, numrels); } - 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; - - 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: core.plt=%x, init.plt=%x\n", __func__, - mod->arch.core_plt->sh_size, mod->arch.init_plt->sh_size); + 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; + + pr_debug("%s: plt=%x\n", __func__, mod->arch.plt->sh_size); return 0; } diff --git a/arch/arm/kernel/module.lds b/arch/arm/kernel/module.lds index 3682fa107918..05881e2b414c 100644 --- a/arch/arm/kernel/module.lds +++ b/arch/arm/kernel/module.lds @@ -1,4 +1,3 @@ SECTIONS { - .core.plt : { BYTE(0) } - .init.plt : { BYTE(0) } + .plt : { BYTE(0) } } |