diff options
| -rw-r--r-- | arch/arm/kernel/module-plts.c | 49 |
1 files changed, 37 insertions, 12 deletions
diff --git a/arch/arm/kernel/module-plts.c b/arch/arm/kernel/module-plts.c index 6832d1d6444e..6f93a905eeee 100644 --- a/arch/arm/kernel/module-plts.c +++ b/arch/arm/kernel/module-plts.c @@ -88,32 +88,45 @@ static int duplicate_rel(Elf32_Addr base, const Elf32_Rel *rel, int num, } /* 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; + u32 mask; int i; + if (IS_ENABLED(CONFIG_THUMB2_KERNEL)) + mask = __opcode_to_mem_thumb32(0x07ff2fff); + else + mask = __opcode_to_mem_arm(0x00ffffff); + /* * 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; + + if (!duplicate_rel(base, rel, i, mask)) ret++; -#endif } + } return ret; } @@ -122,19 +135,27 @@ int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs, { 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 for initialization code. */ - for (s = sechdrs; s < sechdrs_end; ++s) + 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; @@ -144,7 +165,11 @@ int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs, if (s->sh_type != SHT_REL) continue; - plts += count_plts(dstsec->sh_addr, rels, numrels); + /* ignore relocations that operate on non-exec sections */ + if (!(dstsec->sh_flags & SHF_EXECINSTR)) + continue; + + plts += count_plts(syms, dstsec->sh_addr, rels, numrels); } mod->arch.plt->sh_type = SHT_NOBITS; |