Loading arch/arm/include/asm/module.h +2 −4 Original line number Diff line number Diff line Loading @@ -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 }; Loading arch/arm/kernel/module-plts.c +144 −99 Original line number Diff line number Diff line Loading @@ -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> Loading @@ -30,101 +31,142 @@ struct plt_entries { u32 lit[PLT_ENT_COUNT]; }; static bool in_init(const struct module *mod, u32 addr) { return addr - (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, *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; 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++; } /* Look for an existing entry pointing to 'val' */ for (c = *count; plt < plt_end; c -= PLT_ENT_COUNT, plt++) { int i; mod->arch.plt_count++; BUG_ON(mod->arch.plt_count * PLT_ENT_SIZE > mod->arch.plt->sh_size); if (!c) { if (!idx) /* 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; else plt->lit[idx] = val; return (u32)&plt->ldr[idx]; } if (plt->lit[i] == val) return (u32)&plt->ldr[i]; #define cmp_3way(a,b) ((a) < (b) ? -1 : (a) > (b)) static int cmp_rel(const void *a, const void *b) { const Elf32_Rel *x = a, *y = b; int 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; for (i = 0; i < num; i++) { if (rel[i].r_info != rel[num].r_info) continue; const Elf32_Rel *prev; /* * 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. * Entries are sorted by type and symbol index. That means that, * if a duplicate entry exists, it must be in the preceding * slot. */ loc1 = (u32 *)(base + rel[i].r_offset); loc2 = (u32 *)(base + rel[num].r_offset); if (((*loc1 ^ *loc2) & mask) == 0) return 1; } return 0; if (!num) return false; 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; } Loading @@ -132,52 +174,55 @@ static unsigned int count_plts(Elf32_Addr base, const Elf32_Rel *rel, int num) 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, 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.core_plt_count = 0; mod->arch.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); pr_debug("%s: plt=%x\n", __func__, mod->arch.plt->sh_size); return 0; } arch/arm/kernel/module.lds +1 −2 Original line number Diff line number Diff line SECTIONS { .core.plt : { BYTE(0) } .init.plt : { BYTE(0) } .plt : { BYTE(0) } } Loading
arch/arm/include/asm/module.h +2 −4 Original line number Diff line number Diff line Loading @@ -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 }; Loading
arch/arm/kernel/module-plts.c +144 −99 Original line number Diff line number Diff line Loading @@ -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> Loading @@ -30,101 +31,142 @@ struct plt_entries { u32 lit[PLT_ENT_COUNT]; }; static bool in_init(const struct module *mod, u32 addr) { return addr - (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, *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; 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++; } /* Look for an existing entry pointing to 'val' */ for (c = *count; plt < plt_end; c -= PLT_ENT_COUNT, plt++) { int i; mod->arch.plt_count++; BUG_ON(mod->arch.plt_count * PLT_ENT_SIZE > mod->arch.plt->sh_size); if (!c) { if (!idx) /* 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; else plt->lit[idx] = val; return (u32)&plt->ldr[idx]; } if (plt->lit[i] == val) return (u32)&plt->ldr[i]; #define cmp_3way(a,b) ((a) < (b) ? -1 : (a) > (b)) static int cmp_rel(const void *a, const void *b) { const Elf32_Rel *x = a, *y = b; int 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; for (i = 0; i < num; i++) { if (rel[i].r_info != rel[num].r_info) continue; const Elf32_Rel *prev; /* * 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. * Entries are sorted by type and symbol index. That means that, * if a duplicate entry exists, it must be in the preceding * slot. */ loc1 = (u32 *)(base + rel[i].r_offset); loc2 = (u32 *)(base + rel[num].r_offset); if (((*loc1 ^ *loc2) & mask) == 0) return 1; } return 0; if (!num) return false; 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; } Loading @@ -132,52 +174,55 @@ static unsigned int count_plts(Elf32_Addr base, const Elf32_Rel *rel, int num) 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, 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.core_plt_count = 0; mod->arch.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); pr_debug("%s: plt=%x\n", __func__, mod->arch.plt->sh_size); return 0; }
arch/arm/kernel/module.lds +1 −2 Original line number Diff line number Diff line SECTIONS { .core.plt : { BYTE(0) } .init.plt : { BYTE(0) } .plt : { BYTE(0) } }
