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arm64/module: use plt section indices for relocations

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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.

Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Signed-off-by: Jessica Yu <jeyu@kernel.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
This commit is contained in:
Jessica Yu
2018-11-05 19:53:23 +01:00
committed by Will Deacon
parent c55191e96c
commit c8ebf64eab
3 changed files with 30 additions and 23 deletions
Download Patch File Download Diff File Expand all files Collapse all files

36
arch/arm64/kernel/module-plts.c
View File

@@ -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;