x86/alternative: Optimize returns patching

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Instead of decoding each instruction in the return sites range only to
realize that that return site is a jump to the default return thunk
which is needed - X86_FEATURE_RETHUNK is enabled - lift that check
before the loop and get rid of that loop overhead.

Add comments about what gets patched, while at it.

Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20230512120952.7924-1-bp@alien8.de

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Borislav Petkov (AMD) 2023-05-12 14:05:11 +02:00

parent b6c881b248

commit d2408e043e

1 changed files with 10 additions and 3 deletions

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arch/x86/kernel/alternative.c

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