From 9151dde40356880bb445f719f5ebbb1319054d5f Mon Sep 17 00:00:00 2001 From: Huacai Chen Date: Sat, 10 Dec 2022 22:40:15 +0800 Subject: [PATCH] LoongArch: module: Use got/plt section indices for relocations Instead of saving a pointer to the .got, .plt and .plt_idx sections to apply {got,plt}-based relocations, save and use their section indices instead. The mod->arch.{core,init}.{got,plt} pointers were problematic for live- patch because they pointed within temporary section headers (provided by the module loader via info->sechdrs) that would be freed after module load. Since livepatch modules may need to apply relocations post-module- load (for example, to patch a module that is loaded later), using section indices to offset into the section headers (instead of accessing them through a saved pointer) allows livepatch modules on LoongArch to pass in their own copy of the section headers to apply_relocate_add() to apply delayed relocations. The method used is same as commit c8ebf64eab743 ("arm64/module: use plt section indices for relocations"). Signed-off-by: Hongchen Zhang Signed-off-by: Huacai Chen --- arch/loongarch/include/asm/module.h | 22 ++++++++------ arch/loongarch/kernel/module-sections.c | 54 ++++++++++++++++++--------------- arch/loongarch/kernel/module.c | 39 ++++++++++++++++-------- 3 files changed, 68 insertions(+), 47 deletions(-) diff --git a/arch/loongarch/include/asm/module.h b/arch/loongarch/include/asm/module.h index b29b19a..60dc62a 100644 --- a/arch/loongarch/include/asm/module.h +++ b/arch/loongarch/include/asm/module.h @@ -11,7 +11,7 @@ #define RELA_STACK_DEPTH 16 struct mod_section { - Elf_Shdr *shdr; + int shndx; int num_entries; int max_entries; }; @@ -37,8 +37,8 @@ struct plt_idx_entry { Elf_Addr symbol_addr; }; -Elf_Addr module_emit_got_entry(struct module *mod, Elf_Addr val); -Elf_Addr module_emit_plt_entry(struct module *mod, Elf_Addr val); +Elf_Addr module_emit_got_entry(struct module *mod, Elf_Shdr *sechdrs, Elf_Addr val); +Elf_Addr module_emit_plt_entry(struct module *mod, Elf_Shdr *sechdrs, Elf_Addr val); static inline struct got_entry emit_got_entry(Elf_Addr val) { @@ -62,10 +62,10 @@ static inline struct plt_idx_entry emit_plt_idx_entry(unsigned long val) return (struct plt_idx_entry) { val }; } -static inline int get_plt_idx(unsigned long val, const struct mod_section *sec) +static inline int get_plt_idx(unsigned long val, Elf_Shdr *sechdrs, const struct mod_section *sec) { int i; - struct plt_idx_entry *plt_idx = (struct plt_idx_entry *)sec->shdr->sh_addr; + struct plt_idx_entry *plt_idx = (struct plt_idx_entry *)sechdrs[sec->shndx].sh_addr; for (i = 0; i < sec->num_entries; i++) { if (plt_idx[i].symbol_addr == val) @@ -76,11 +76,12 @@ static inline int get_plt_idx(unsigned long val, const struct mod_section *sec) } static inline struct plt_entry *get_plt_entry(unsigned long val, - const struct mod_section *sec_plt, - const struct mod_section *sec_plt_idx) + Elf_Shdr *sechdrs, + const struct mod_section *sec_plt, + const struct mod_section *sec_plt_idx) { - int plt_idx = get_plt_idx(val, sec_plt_idx); - struct plt_entry *plt = (struct plt_entry *)sec_plt->shdr->sh_addr; + int plt_idx = get_plt_idx(val, sechdrs, sec_plt_idx); + struct plt_entry *plt = (struct plt_entry *)sechdrs[sec_plt->shndx].sh_addr; if (plt_idx < 0) return NULL; @@ -89,10 +90,11 @@ static inline struct plt_entry *get_plt_entry(unsigned long val, } static inline struct got_entry *get_got_entry(Elf_Addr val, + Elf_Shdr *sechdrs, const struct mod_section *sec) { - struct got_entry *got = (struct got_entry *)sec->shdr->sh_addr; int i; + struct got_entry *got = (struct got_entry *)sechdrs[sec->shndx].sh_addr; for (i = 0; i < sec->num_entries; i++) if (got[i].symbol_addr == val) diff --git a/arch/loongarch/kernel/module-sections.c b/arch/loongarch/kernel/module-sections.c index d296a70..13d9a42 100644 --- a/arch/loongarch/kernel/module-sections.c +++ b/arch/loongarch/kernel/module-sections.c @@ -7,17 +7,17 @@ #include #include -Elf_Addr module_emit_got_entry(struct module *mod, Elf_Addr val) +Elf_Addr module_emit_got_entry(struct module *mod, Elf_Shdr *sechdrs, Elf_Addr val) { struct mod_section *got_sec = &mod->arch.got; int i = got_sec->num_entries; - struct got_entry *got = get_got_entry(val, got_sec); + struct got_entry *got = get_got_entry(val, sechdrs, got_sec); if (got) return (Elf_Addr)got; /* There is no GOT entry for val yet, create a new one. */ - got = (struct got_entry *)got_sec->shdr->sh_addr; + got = (struct got_entry *)sechdrs[got_sec->shndx].sh_addr; got[i] = emit_got_entry(val); got_sec->num_entries++; @@ -33,12 +33,12 @@ Elf_Addr module_emit_got_entry(struct module *mod, Elf_Addr val) return (Elf_Addr)&got[i]; } -Elf_Addr module_emit_plt_entry(struct module *mod, Elf_Addr val) +Elf_Addr module_emit_plt_entry(struct module *mod, Elf_Shdr *sechdrs, Elf_Addr val) { int nr; struct mod_section *plt_sec = &mod->arch.plt; struct mod_section *plt_idx_sec = &mod->arch.plt_idx; - struct plt_entry *plt = get_plt_entry(val, plt_sec, plt_idx_sec); + struct plt_entry *plt = get_plt_entry(val, sechdrs, plt_sec, plt_idx_sec); struct plt_idx_entry *plt_idx; if (plt) @@ -47,9 +47,9 @@ Elf_Addr module_emit_plt_entry(struct module *mod, Elf_Addr val) nr = plt_sec->num_entries; /* There is no duplicate entry, create a new one */ - plt = (struct plt_entry *)plt_sec->shdr->sh_addr; + plt = (struct plt_entry *)sechdrs[plt_sec->shndx].sh_addr; plt[nr] = emit_plt_entry(val); - plt_idx = (struct plt_idx_entry *)plt_idx_sec->shdr->sh_addr; + plt_idx = (struct plt_idx_entry *)sechdrs[plt_idx_sec->shndx].sh_addr; plt_idx[nr] = emit_plt_idx_entry(val); plt_sec->num_entries++; @@ -103,28 +103,29 @@ int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs, char *secstrings, struct module *mod) { unsigned int i, num_plts = 0, num_gots = 0; + Elf_Shdr *got_sec, *plt_sec, *plt_idx_sec; /* * Find the empty .plt sections. */ for (i = 0; i < ehdr->e_shnum; i++) { if (!strcmp(secstrings + sechdrs[i].sh_name, ".got")) - mod->arch.got.shdr = sechdrs + i; + mod->arch.got.shndx = i; else if (!strcmp(secstrings + sechdrs[i].sh_name, ".plt")) - mod->arch.plt.shdr = sechdrs + i; + mod->arch.plt.shndx = i; else if (!strcmp(secstrings + sechdrs[i].sh_name, ".plt.idx")) - mod->arch.plt_idx.shdr = sechdrs + i; + mod->arch.plt_idx.shndx = i; } - if (!mod->arch.got.shdr) { + if (!mod->arch.got.shndx) { pr_err("%s: module GOT section(s) missing\n", mod->name); return -ENOEXEC; } - if (!mod->arch.plt.shdr) { + if (!mod->arch.plt.shndx) { pr_err("%s: module PLT section(s) missing\n", mod->name); return -ENOEXEC; } - if (!mod->arch.plt_idx.shdr) { + if (!mod->arch.plt_idx.shndx) { pr_err("%s: module PLT.IDX section(s) missing\n", mod->name); return -ENOEXEC; } @@ -145,24 +146,27 @@ int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs, count_max_entries(relas, num_rela, &num_plts, &num_gots); } - mod->arch.got.shdr->sh_type = SHT_NOBITS; - mod->arch.got.shdr->sh_flags = SHF_ALLOC; - mod->arch.got.shdr->sh_addralign = L1_CACHE_BYTES; - mod->arch.got.shdr->sh_size = (num_gots + 1) * sizeof(struct got_entry); + got_sec = sechdrs + mod->arch.got.shndx; + got_sec->sh_type = SHT_NOBITS; + got_sec->sh_flags = SHF_ALLOC; + got_sec->sh_addralign = L1_CACHE_BYTES; + got_sec->sh_size = (num_gots + 1) * sizeof(struct got_entry); mod->arch.got.num_entries = 0; mod->arch.got.max_entries = num_gots; - mod->arch.plt.shdr->sh_type = SHT_NOBITS; - mod->arch.plt.shdr->sh_flags = SHF_EXECINSTR | SHF_ALLOC; - mod->arch.plt.shdr->sh_addralign = L1_CACHE_BYTES; - mod->arch.plt.shdr->sh_size = (num_plts + 1) * sizeof(struct plt_entry); + plt_sec = sechdrs + mod->arch.plt.shndx; + plt_sec->sh_type = SHT_NOBITS; + plt_sec->sh_flags = SHF_EXECINSTR | SHF_ALLOC; + plt_sec->sh_addralign = L1_CACHE_BYTES; + plt_sec->sh_size = (num_plts + 1) * sizeof(struct plt_entry); mod->arch.plt.num_entries = 0; mod->arch.plt.max_entries = num_plts; - mod->arch.plt_idx.shdr->sh_type = SHT_NOBITS; - mod->arch.plt_idx.shdr->sh_flags = SHF_ALLOC; - mod->arch.plt_idx.shdr->sh_addralign = L1_CACHE_BYTES; - mod->arch.plt_idx.shdr->sh_size = (num_plts + 1) * sizeof(struct plt_idx_entry); + plt_idx_sec = sechdrs + mod->arch.plt_idx.shndx; + plt_idx_sec->sh_type = SHT_NOBITS; + plt_idx_sec->sh_flags = SHF_ALLOC; + plt_idx_sec->sh_addralign = L1_CACHE_BYTES; + plt_idx_sec->sh_size = (num_plts + 1) * sizeof(struct plt_idx_entry); mod->arch.plt_idx.num_entries = 0; mod->arch.plt_idx.max_entries = num_plts; diff --git a/arch/loongarch/kernel/module.c b/arch/loongarch/kernel/module.c index 825fcf7..899dc67 100644 --- a/arch/loongarch/kernel/module.c +++ b/arch/loongarch/kernel/module.c @@ -99,16 +99,17 @@ static int apply_r_larch_sop_push_dup(struct module *mod, u32 *location, Elf_Add return 0; } -static int apply_r_larch_sop_push_plt_pcrel(struct module *mod, u32 *location, Elf_Addr v, +static int apply_r_larch_sop_push_plt_pcrel(struct module *mod, + Elf_Shdr *sechdrs, u32 *location, Elf_Addr v, s64 *rela_stack, size_t *rela_stack_top, unsigned int type) { ptrdiff_t offset = (void *)v - (void *)location; if (offset >= SZ_128M) - v = module_emit_plt_entry(mod, v); + v = module_emit_plt_entry(mod, sechdrs, v); if (offset < -SZ_128M) - v = module_emit_plt_entry(mod, v); + v = module_emit_plt_entry(mod, sechdrs, v); return apply_r_larch_sop_push_pcrel(mod, location, v, rela_stack, rela_stack_top, type); } @@ -272,17 +273,18 @@ static int apply_r_larch_add_sub(struct module *mod, u32 *location, Elf_Addr v, } } -static int apply_r_larch_b26(struct module *mod, u32 *location, Elf_Addr v, +static int apply_r_larch_b26(struct module *mod, + Elf_Shdr *sechdrs, u32 *location, Elf_Addr v, s64 *rela_stack, size_t *rela_stack_top, unsigned int type) { ptrdiff_t offset = (void *)v - (void *)location; union loongarch_instruction *insn = (union loongarch_instruction *)location; if (offset >= SZ_128M) - v = module_emit_plt_entry(mod, v); + v = module_emit_plt_entry(mod, sechdrs, v); if (offset < -SZ_128M) - v = module_emit_plt_entry(mod, v); + v = module_emit_plt_entry(mod, sechdrs, v); offset = (void *)v - (void *)location; @@ -339,10 +341,11 @@ static int apply_r_larch_pcala(struct module *mod, u32 *location, Elf_Addr v, return 0; } -static int apply_r_larch_got_pc(struct module *mod, u32 *location, Elf_Addr v, +static int apply_r_larch_got_pc(struct module *mod, + Elf_Shdr *sechdrs, u32 *location, Elf_Addr v, s64 *rela_stack, size_t *rela_stack_top, unsigned int type) { - Elf_Addr got = module_emit_got_entry(mod, v); + Elf_Addr got = module_emit_got_entry(mod, sechdrs, v); if (!got) return -EINVAL; @@ -387,13 +390,10 @@ static reloc_rela_handler reloc_rela_handlers[] = { [R_LARCH_SOP_PUSH_PCREL] = apply_r_larch_sop_push_pcrel, [R_LARCH_SOP_PUSH_ABSOLUTE] = apply_r_larch_sop_push_absolute, [R_LARCH_SOP_PUSH_DUP] = apply_r_larch_sop_push_dup, - [R_LARCH_SOP_PUSH_PLT_PCREL] = apply_r_larch_sop_push_plt_pcrel, [R_LARCH_SOP_SUB ... R_LARCH_SOP_IF_ELSE] = apply_r_larch_sop, [R_LARCH_SOP_POP_32_S_10_5 ... R_LARCH_SOP_POP_32_U] = apply_r_larch_sop_imm_field, [R_LARCH_ADD32 ... R_LARCH_SUB64] = apply_r_larch_add_sub, - [R_LARCH_B26] = apply_r_larch_b26, [R_LARCH_PCALA_HI20...R_LARCH_PCALA64_HI12] = apply_r_larch_pcala, - [R_LARCH_GOT_PC_HI20...R_LARCH_GOT_PC_LO12] = apply_r_larch_got_pc, }; int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab, @@ -444,7 +444,22 @@ int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab, sym->st_value, rel[i].r_addend, (u64)location); v = sym->st_value + rel[i].r_addend; - err = handler(mod, location, v, rela_stack, &rela_stack_top, type); + switch (type) { + case R_LARCH_B26: + err = apply_r_larch_b26(mod, sechdrs, location, + v, rela_stack, &rela_stack_top, type); + break; + case R_LARCH_GOT_PC_HI20...R_LARCH_GOT_PC_LO12: + err = apply_r_larch_got_pc(mod, sechdrs, location, + v, rela_stack, &rela_stack_top, type); + break; + case R_LARCH_SOP_PUSH_PLT_PCREL: + err = apply_r_larch_sop_push_plt_pcrel(mod, sechdrs, location, + v, rela_stack, &rela_stack_top, type); + break; + default: + err = handler(mod, location, v, rela_stack, &rela_stack_top, type); + } if (err) return err; } -- 2.7.4