From: Josh Poimboeuf jpoimboe@kernel.org
commit 4ba89dd6ddeca2a733bdaed7c9a5cbe4e19d9124 upstream.
The following commit
095b8303f383 ("x86/alternative: Make custom return thunk unconditional")
made '__x86_return_thunk' a placeholder value. All code setting X86_FEATURE_RETHUNK also changes the value of 'x86_return_thunk'. So the optimization at the beginning of apply_returns() is dead code.
Also, before the above-mentioned commit, the optimization actually had a bug It bypassed __static_call_fixup(), causing some raw returns to remain unpatched in static call trampolines. Thus the 'Fixes' tag.
Fixes: d2408e043e72 ("x86/alternative: Optimize returns patching") Signed-off-by: Josh Poimboeuf jpoimboe@kernel.org Signed-off-by: Ingo Molnar mingo@kernel.org Signed-off-by: Borislav Petkov (AMD) bp@alien8.de Acked-by: Borislav Petkov (AMD) bp@alien8.de Link: https://lore.kernel.org/r/16d19d2249d4485d8380fb215ffaae81e6b8119e.169388998... Signed-off-by: Pawan Gupta pawan.kumar.gupta@linux.intel.com --- arch/x86/kernel/alternative.c | 8 -------- 1 file changed, 8 deletions(-)
diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c index 9de566a77a8e..3102e7cf6a48 100644 --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -793,14 +793,6 @@ void __init_or_module noinline apply_returns(s32 *start, s32 *end) { s32 *s;
- /* - * Do not patch out the default return thunks if those needed are the - * ones generated by the compiler. - */ - if (cpu_feature_enabled(X86_FEATURE_RETHUNK) && - (x86_return_thunk == __x86_return_thunk)) - return; - for (s = start; s < end; s++) { void *dest = NULL, *addr = (void *)s + *s; struct insn insn;