x86/bugs: Fix the SRSO mitigation on Zen3/4

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The original version of the mitigation would patch in the calls to the
untraining routines directly.  That is, the alternative() in UNTRAIN_RET
will patch in the CALL to srso_alias_untrain_ret() directly.

However, even if commit e7c25c441e ("x86/cpu: Cleanup the untrain
mess") meant well in trying to clean up the situation, due to micro-
architectural reasons, the untraining routine srso_alias_untrain_ret()
must be the target of a CALL instruction and not of a JMP instruction as
it is done now.

Reshuffle the alternative macros to accomplish that.

Fixes: e7c25c441e ("x86/cpu: Cleanup the untrain mess")
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

...

This commit is contained in:

Borislav Petkov (AMD) 2024-03-28 13:59:05 +01:00 • committed by Linus Torvalds

parent 091619baac

commit 4535e1a417

3 changed files with 23 additions and 10 deletions

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1

arch/x86/include/asm/asm-prototypes.h

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21

arch/x86/include/asm/nospec-branch.h

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11

arch/x86/lib/retpoline.S

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