| Message ID | 20181105175722.removbbpilqxu7tr@redbean (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | arm64/module: use plt section indices for relocations | expand |
On 5 November 2018 at 18:57, Jessica Yu <jeyu@kernel.org> wrote: > Instead of saving a pointer to the .plt and .init.plt sections to apply > plt-based relocations, save and use their section indices instead. > > The mod->arch.{core,init}.plt pointers were problematic for livepatch > 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 arm64 to pass in > their own copy of the section headers to apply_relocate_add() to apply > delayed relocations. > > Signed-off-by: Jessica Yu <jeyu@kernel.org> > --- > > Note: Addressed Will's comment about the pltsec -> plt_info rename and > removed that change to reduce unnecessary code churn. That is the only > change from the first version. I didn't include the Ack's for this reason > so let me know if this version is OK as well. > > arch/arm64/include/asm/module.h | 8 +++++--- > arch/arm64/kernel/module-plts.c | 36 ++++++++++++++++++++---------------- > arch/arm64/kernel/module.c | 9 +++++---- > 3 files changed, 30 insertions(+), 23 deletions(-) > > diff --git a/arch/arm64/include/asm/module.h > b/arch/arm64/include/asm/module.h > index 97d0ef12e2ff..f81c1847312d 100644 > --- a/arch/arm64/include/asm/module.h > +++ b/arch/arm64/include/asm/module.h > @@ -22,7 +22,7 @@ > > #ifdef CONFIG_ARM64_MODULE_PLTS > struct mod_plt_sec { > - struct elf64_shdr *plt; > + int plt_shndx; > int plt_num_entries; > int plt_max_entries; > }; > @@ -36,10 +36,12 @@ struct mod_arch_specific { > }; > #endif > > -u64 module_emit_plt_entry(struct module *mod, void *loc, const Elf64_Rela > *rela, > +u64 module_emit_plt_entry(struct module *mod, Elf64_Shdr *sechdrs, > + void *loc, const Elf64_Rela *rela, > Elf64_Sym *sym); > > -u64 module_emit_veneer_for_adrp(struct module *mod, void *loc, u64 val); > +u64 module_emit_veneer_for_adrp(struct module *mod, Elf64_Shdr *sechdrs, > + void *loc, u64 val); > > #ifdef CONFIG_RANDOMIZE_BASE > extern u64 module_alloc_base; > diff --git a/arch/arm64/kernel/module-plts.c > b/arch/arm64/kernel/module-plts.c > index f0690c2ca3e0..c04b0d6abde0 100644 > --- a/arch/arm64/kernel/module-plts.c > +++ b/arch/arm64/kernel/module-plts.c > @@ -16,12 +16,13 @@ static bool in_init(const struct module *mod, void *loc) > return (u64)loc - (u64)mod->init_layout.base < > mod->init_layout.size; > } > > -u64 module_emit_plt_entry(struct module *mod, void *loc, const Elf64_Rela > *rela, > +u64 module_emit_plt_entry(struct module *mod, Elf64_Shdr *sechdrs, > + void *loc, const Elf64_Rela *rela, > Elf64_Sym *sym) > { > struct mod_plt_sec *pltsec = !in_init(mod, loc) ? &mod->arch.core : > &mod->arch.init; > - struct plt_entry *plt = (struct plt_entry *)pltsec->plt->sh_addr; > + struct plt_entry *plt = (struct plt_entry *)(sechdrs + > pltsec->plt_shndx)->sh_addr; What's wrong with (struct plt_entry *)sechdrs[pltsec->plt_shndx].sh_addr ? > int i = pltsec->plt_num_entries; > u64 val = sym->st_value + rela->r_addend; > > @@ -43,11 +44,12 @@ u64 module_emit_plt_entry(struct module *mod, void *loc, > const Elf64_Rela *rela, > } > > #ifdef CONFIG_ARM64_ERRATUM_843419 > -u64 module_emit_veneer_for_adrp(struct module *mod, void *loc, u64 val) > +u64 module_emit_veneer_for_adrp(struct module *mod, Elf64_Shdr *sechdrs, > + void *loc, u64 val) > { > struct mod_plt_sec *pltsec = !in_init(mod, loc) ? &mod->arch.core : > &mod->arch.init; > - struct plt_entry *plt = (struct plt_entry *)pltsec->plt->sh_addr; > + struct plt_entry *plt = (struct plt_entry *)(sechdrs + > pltsec->plt_shndx)->sh_addr; > int i = pltsec->plt_num_entries++; > u32 mov0, mov1, mov2, br; > int rd; > @@ -202,7 +204,7 @@ int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr > *sechdrs, > unsigned long core_plts = 0; > unsigned long init_plts = 0; > Elf64_Sym *syms = NULL; > - Elf_Shdr *tramp = NULL; > + Elf_Shdr *pltsec, *tramp = NULL; > int i; > > /* > @@ -211,9 +213,9 @@ int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr > *sechdrs, > */ > for (i = 0; i < ehdr->e_shnum; i++) { > if (!strcmp(secstrings + sechdrs[i].sh_name, ".plt")) > - mod->arch.core.plt = sechdrs + i; > + mod->arch.core.plt_shndx = i; > else if (!strcmp(secstrings + sechdrs[i].sh_name, > ".init.plt")) > - mod->arch.init.plt = sechdrs + i; > + mod->arch.init.plt_shndx = i; > else if (IS_ENABLED(CONFIG_DYNAMIC_FTRACE) && > !strcmp(secstrings + sechdrs[i].sh_name, > ".text.ftrace_trampoline")) > @@ -222,7 +224,7 @@ int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr > *sechdrs, > syms = (Elf64_Sym *)sechdrs[i].sh_addr; > } > > - if (!mod->arch.core.plt || !mod->arch.init.plt) { > + if (!mod->arch.core.plt_shndx || !mod->arch.init.plt_shndx) { > pr_err("%s: module PLT section(s) missing\n", mod->name); > return -ENOEXEC; > } > @@ -254,17 +256,19 @@ int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr > *sechdrs, > sechdrs[i].sh_info, dstsec); > } > > - 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 = (core_plts + 1) * sizeof(struct > plt_entry); > + pltsec = sechdrs + mod->arch.core.plt_shndx; > + pltsec->sh_type = SHT_NOBITS; > + pltsec->sh_flags = SHF_EXECINSTR | SHF_ALLOC; > + pltsec->sh_addralign = L1_CACHE_BYTES; > + pltsec->sh_size = (core_plts + 1) * sizeof(struct plt_entry); > mod->arch.core.plt_num_entries = 0; > mod->arch.core.plt_max_entries = core_plts; > > - 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 = (init_plts + 1) * sizeof(struct > plt_entry); > + pltsec = sechdrs + mod->arch.init.plt_shndx; > + pltsec->sh_type = SHT_NOBITS; > + pltsec->sh_flags = SHF_EXECINSTR | SHF_ALLOC; > + pltsec->sh_addralign = L1_CACHE_BYTES; > + pltsec->sh_size = (init_plts + 1) * sizeof(struct plt_entry); > mod->arch.init.plt_num_entries = 0; > mod->arch.init.plt_max_entries = init_plts; > > diff --git a/arch/arm64/kernel/module.c b/arch/arm64/kernel/module.c > index f0f27aeefb73..c2abe59c6f8f 100644 > --- a/arch/arm64/kernel/module.c > +++ b/arch/arm64/kernel/module.c > @@ -198,7 +198,8 @@ static int reloc_insn_imm(enum aarch64_reloc_op op, > __le32 *place, u64 val, > return 0; > } > > -static int reloc_insn_adrp(struct module *mod, __le32 *place, u64 val) > +static int reloc_insn_adrp(struct module *mod, Elf64_Shdr *sechdrs, > + __le32 *place, u64 val) > { > u32 insn; > > @@ -215,7 +216,7 @@ static int reloc_insn_adrp(struct module *mod, __le32 > *place, u64 val) > insn &= ~BIT(31); > } else { > /* out of range for ADR -> emit a veneer */ > - val = module_emit_veneer_for_adrp(mod, place, val & ~0xfff); > + val = module_emit_veneer_for_adrp(mod, sechdrs, place, val & > ~0xfff); > if (!val) > return -ENOEXEC; > insn = aarch64_insn_gen_branch_imm((u64)place, val, > @@ -368,7 +369,7 @@ int apply_relocate_add(Elf64_Shdr *sechdrs, > case R_AARCH64_ADR_PREL_PG_HI21_NC: > overflow_check = false; > case R_AARCH64_ADR_PREL_PG_HI21: > - ovf = reloc_insn_adrp(me, loc, val); > + ovf = reloc_insn_adrp(me, sechdrs, loc, val); > if (ovf && ovf != -ERANGE) > return ovf; > break; > @@ -413,7 +414,7 @@ int apply_relocate_add(Elf64_Shdr *sechdrs, > > if (IS_ENABLED(CONFIG_ARM64_MODULE_PLTS) && > ovf == -ERANGE) { > - val = module_emit_plt_entry(me, loc, > &rel[i], sym); > + val = module_emit_plt_entry(me, sechdrs, > loc, &rel[i], sym); > if (!val) > return -ENOEXEC; > ovf = reloc_insn_imm(RELOC_OP_PREL, loc, > val, 2, > -- > 2.14.5 >
diff --git a/arch/arm64/include/asm/module.h b/arch/arm64/include/asm/module.h index 97d0ef12e2ff..f81c1847312d 100644 --- a/arch/arm64/include/asm/module.h +++ b/arch/arm64/include/asm/module.h @@ -22,7 +22,7 @@ #ifdef CONFIG_ARM64_MODULE_PLTS struct mod_plt_sec { - struct elf64_shdr *plt; + int plt_shndx; int plt_num_entries; int plt_max_entries; }; @@ -36,10 +36,12 @@ struct mod_arch_specific { }; #endif -u64 module_emit_plt_entry(struct module *mod, void *loc, const Elf64_Rela *rela, +u64 module_emit_plt_entry(struct module *mod, Elf64_Shdr *sechdrs, + void *loc, const Elf64_Rela *rela, Elf64_Sym *sym); -u64 module_emit_veneer_for_adrp(struct module *mod, void *loc, u64 val); +u64 module_emit_veneer_for_adrp(struct module *mod, Elf64_Shdr *sechdrs, + void *loc, u64 val); #ifdef CONFIG_RANDOMIZE_BASE extern u64 module_alloc_base; diff --git a/arch/arm64/kernel/module-plts.c b/arch/arm64/kernel/module-plts.c index f0690c2ca3e0..c04b0d6abde0 100644 --- a/arch/arm64/kernel/module-plts.c +++ b/arch/arm64/kernel/module-plts.c @@ -16,12 +16,13 @@ static bool in_init(const struct module *mod, void *loc) return (u64)loc - (u64)mod->init_layout.base < mod->init_layout.size; } -u64 module_emit_plt_entry(struct module *mod, void *loc, const Elf64_Rela *rela, +u64 module_emit_plt_entry(struct module *mod, Elf64_Shdr *sechdrs, + void *loc, const Elf64_Rela *rela, Elf64_Sym *sym) { struct mod_plt_sec *pltsec = !in_init(mod, loc) ? &mod->arch.core : &mod->arch.init; - struct plt_entry *plt = (struct plt_entry *)pltsec->plt->sh_addr; + struct plt_entry *plt = (struct plt_entry *)(sechdrs + pltsec->plt_shndx)->sh_addr; int i = pltsec->plt_num_entries; u64 val = sym->st_value + rela->r_addend; @@ -43,11 +44,12 @@ u64 module_emit_plt_entry(struct module *mod, void *loc, const Elf64_Rela *rela, } #ifdef CONFIG_ARM64_ERRATUM_843419 -u64 module_emit_veneer_for_adrp(struct module *mod, void *loc, u64 val) +u64 module_emit_veneer_for_adrp(struct module *mod, Elf64_Shdr *sechdrs, + void *loc, u64 val) { struct mod_plt_sec *pltsec = !in_init(mod, loc) ? &mod->arch.core : &mod->arch.init; - struct plt_entry *plt = (struct plt_entry *)pltsec->plt->sh_addr; + struct plt_entry *plt = (struct plt_entry *)(sechdrs + pltsec->plt_shndx)->sh_addr; int i = pltsec->plt_num_entries++; u32 mov0, mov1, mov2, br; int rd; @@ -202,7 +204,7 @@ int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs, unsigned long core_plts = 0; unsigned long init_plts = 0; Elf64_Sym *syms = NULL; - Elf_Shdr *tramp = NULL; + Elf_Shdr *pltsec, *tramp = NULL; int i; /* @@ -211,9 +213,9 @@ int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs, */ for (i = 0; i < ehdr->e_shnum; i++) { if (!strcmp(secstrings + sechdrs[i].sh_name, ".plt")) - mod->arch.core.plt = sechdrs + i; + mod->arch.core.plt_shndx = i; else if (!strcmp(secstrings + sechdrs[i].sh_name, ".init.plt")) - mod->arch.init.plt = sechdrs + i; + mod->arch.init.plt_shndx = i; else if (IS_ENABLED(CONFIG_DYNAMIC_FTRACE) && !strcmp(secstrings + sechdrs[i].sh_name, ".text.ftrace_trampoline")) @@ -222,7 +224,7 @@ int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs, syms = (Elf64_Sym *)sechdrs[i].sh_addr; } - if (!mod->arch.core.plt || !mod->arch.init.plt) { + if (!mod->arch.core.plt_shndx || !mod->arch.init.plt_shndx) { pr_err("%s: module PLT section(s) missing\n", mod->name); return -ENOEXEC; } @@ -254,17 +256,19 @@ int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs, sechdrs[i].sh_info, dstsec); } - 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 = (core_plts + 1) * sizeof(struct plt_entry); + pltsec = sechdrs + mod->arch.core.plt_shndx; + pltsec->sh_type = SHT_NOBITS; + pltsec->sh_flags = SHF_EXECINSTR | SHF_ALLOC; + pltsec->sh_addralign = L1_CACHE_BYTES; + pltsec->sh_size = (core_plts + 1) * sizeof(struct plt_entry); mod->arch.core.plt_num_entries = 0; mod->arch.core.plt_max_entries = core_plts; - 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 = (init_plts + 1) * sizeof(struct plt_entry); + pltsec = sechdrs + mod->arch.init.plt_shndx; + pltsec->sh_type = SHT_NOBITS; + pltsec->sh_flags = SHF_EXECINSTR | SHF_ALLOC; + pltsec->sh_addralign = L1_CACHE_BYTES; + pltsec->sh_size = (init_plts + 1) * sizeof(struct plt_entry); mod->arch.init.plt_num_entries = 0; mod->arch.init.plt_max_entries = init_plts; diff --git a/arch/arm64/kernel/module.c b/arch/arm64/kernel/module.c index f0f27aeefb73..c2abe59c6f8f 100644 --- a/arch/arm64/kernel/module.c +++ b/arch/arm64/kernel/module.c @@ -198,7 +198,8 @@ static int reloc_insn_imm(enum aarch64_reloc_op op, __le32 *place, u64 val, return 0; } -static int reloc_insn_adrp(struct module *mod, __le32 *place, u64 val) +static int reloc_insn_adrp(struct module *mod, Elf64_Shdr *sechdrs, + __le32 *place, u64 val) { u32 insn; @@ -215,7 +216,7 @@ static int reloc_insn_adrp(struct module *mod, __le32 *place, u64 val) insn &= ~BIT(31); } else { /* out of range for ADR -> emit a veneer */ - val = module_emit_veneer_for_adrp(mod, place, val & ~0xfff); + val = module_emit_veneer_for_adrp(mod, sechdrs, place, val & ~0xfff); if (!val) return -ENOEXEC; insn = aarch64_insn_gen_branch_imm((u64)place, val, @@ -368,7 +369,7 @@ int apply_relocate_add(Elf64_Shdr *sechdrs, case R_AARCH64_ADR_PREL_PG_HI21_NC: overflow_check = false; case R_AARCH64_ADR_PREL_PG_HI21: - ovf = reloc_insn_adrp(me, loc, val); + ovf = reloc_insn_adrp(me, sechdrs, loc, val); if (ovf && ovf != -ERANGE) return ovf; break; @@ -413,7 +414,7 @@ int apply_relocate_add(Elf64_Shdr *sechdrs, if (IS_ENABLED(CONFIG_ARM64_MODULE_PLTS) && ovf == -ERANGE) { - val = module_emit_plt_entry(me, loc, &rel[i], sym); + val = module_emit_plt_entry(me, sechdrs, loc, &rel[i], sym); if (!val) return -ENOEXEC; ovf = reloc_insn_imm(RELOC_OP_PREL, loc, val, 2,
Instead of saving a pointer to the .plt and .init.plt sections to apply plt-based relocations, save and use their section indices instead. The mod->arch.{core,init}.plt pointers were problematic for livepatch 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 arm64 to pass in their own copy of the section headers to apply_relocate_add() to apply delayed relocations. Signed-off-by: Jessica Yu <jeyu@kernel.org> --- Note: Addressed Will's comment about the pltsec -> plt_info rename and removed that change to reduce unnecessary code churn. That is the only change from the first version. I didn't include the Ack's for this reason so let me know if this version is OK as well. arch/arm64/include/asm/module.h | 8 +++++--- arch/arm64/kernel/module-plts.c | 36 ++++++++++++++++++++---------------- arch/arm64/kernel/module.c | 9 +++++---- 3 files changed, 30 insertions(+), 23 deletions(-)