diff options
| author | Peter Zijlstra <peterz@infradead.org> | 2021-10-26 14:01:42 +0200 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2021-10-28 23:25:27 +0200 |
| commit | 7508500900814d14e2e085cdc4e28142721abbdf (patch) | |
| tree | 4776ae7d32fa640324f929a0bb23bfd56a86e1bc /arch/x86/kernel/module.c | |
| parent | 1a6f74429c42a3854980359a758e222005712aee (diff) | |
x86/alternative: Implement .retpoline_sites support
Rewrite retpoline thunk call sites to be indirect calls for
spectre_v2=off. This ensures spectre_v2=off is as near to a
RETPOLINE=n build as possible.
This is the replacement for objtool writing alternative entries to
ensure the same and achieves feature-parity with the previous
approach.
One noteworthy feature is that it relies on the thunks to be in
machine order to compute the register index.
Specifically, this does not yet address the Jcc __x86_indirect_thunk_*
calls generated by clang, a future patch will add this.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Borislav Petkov <bp@suse.de>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Tested-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/r/20211026120310.232495794@infradead.org
Diffstat (limited to 'arch/x86/kernel/module.c')
| -rw-r--r-- | arch/x86/kernel/module.c | 9 |
1 files changed, 8 insertions, 1 deletions
diff --git a/arch/x86/kernel/module.c b/arch/x86/kernel/module.c index 5e9a34b5bd74..169fb6f4cd2e 100644 --- a/arch/x86/kernel/module.c +++ b/arch/x86/kernel/module.c @@ -251,7 +251,8 @@ int module_finalize(const Elf_Ehdr *hdr, struct module *me) { const Elf_Shdr *s, *text = NULL, *alt = NULL, *locks = NULL, - *para = NULL, *orc = NULL, *orc_ip = NULL; + *para = NULL, *orc = NULL, *orc_ip = NULL, + *retpolines = NULL; char *secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset; for (s = sechdrs; s < sechdrs + hdr->e_shnum; s++) { @@ -267,8 +268,14 @@ int module_finalize(const Elf_Ehdr *hdr, orc = s; if (!strcmp(".orc_unwind_ip", secstrings + s->sh_name)) orc_ip = s; + if (!strcmp(".retpoline_sites", secstrings + s->sh_name)) + retpolines = s; } + if (retpolines) { + void *rseg = (void *)retpolines->sh_addr; + apply_retpolines(rseg, rseg + retpolines->sh_size); + } if (alt) { /* patch .altinstructions */ void *aseg = (void *)alt->sh_addr; |