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| author | Josh Poimboeuf <jpoimboe@kernel.org> | 2023-09-04 22:04:54 -0700 |
|---|---|---|
| committer | Borislav Petkov (AMD) <bp@alien8.de> | 2023-09-22 18:52:39 +0200 |
| commit | 4ba89dd6ddeca2a733bdaed7c9a5cbe4e19d9124 (patch) | |
| tree | eaf1884b908beb6032fc97e35e925c969e5c73a5 | |
| parent | ce9ecca0238b140b88f43859b211c9fdfd8e5b70 (diff) | |
| download | lwn-4ba89dd6ddeca2a733bdaed7c9a5cbe4e19d9124.tar.gz lwn-4ba89dd6ddeca2a733bdaed7c9a5cbe4e19d9124.zip | |
x86/alternatives: Remove faulty optimization
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.1693889988.git.jpoimboe@kernel.org
| -rw-r--r-- | arch/x86/kernel/alternative.c | 8 |
1 files changed, 0 insertions, 8 deletions
diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c index a5ead6a6d233..c850f5a9b1bb 100644 --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -720,14 +720,6 @@ 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; |