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authorPeter Zijlstra <peterz@infradead.org>2021-10-26 14:01:42 +0200
committerPeter Zijlstra <peterz@infradead.org>2021-10-28 23:25:27 +0200
commit7508500900814d14e2e085cdc4e28142721abbdf (patch)
tree4776ae7d32fa640324f929a0bb23bfd56a86e1bc /arch/um
parent1a6f74429c42a3854980359a758e222005712aee (diff)
downloadlinux-7508500900814d14e2e085cdc4e28142721abbdf.tar.bz2
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/um')
-rw-r--r--arch/um/kernel/um_arch.c4
1 files changed, 4 insertions, 0 deletions
diff --git a/arch/um/kernel/um_arch.c b/arch/um/kernel/um_arch.c
index a149a5e9a16a..54447690de11 100644
--- a/arch/um/kernel/um_arch.c
+++ b/arch/um/kernel/um_arch.c
@@ -421,6 +421,10 @@ void __init check_bugs(void)
os_check_bugs();
}
+void apply_retpolines(s32 *start, s32 *end)
+{
+}
+
void apply_alternatives(struct alt_instr *start, struct alt_instr *end)
{
}