Re: [tip: x86/urgent] x86/cpu: Clean up SRSO return thunk mess

[Nathan Chancellor]

On Wed, Aug 16, 2023 at 07:55:16AM -0000, tip-bot2 for Peter Zijlstra wrote:
> The following commit has been merged into the x86/urgent branch of tip:
> 
> Commit-ID:     9010e01a8efffa0d14972b79fbe87bd329d79bfd
> Gitweb:        https://git.kernel.org/tip/9010e01a8efffa0d14972b79fbe87bd329d79bfd
> Author:        Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> AuthorDate:    Mon, 14 Aug 2023 13:44:31 +02:00
> Committer:     Borislav Petkov (AMD) <bp@xxxxxxxxx>
> CommitterDate: Wed, 16 Aug 2023 09:39:16 +02:00
> 
> x86/cpu: Clean up SRSO return thunk mess

<snip>

> diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S
> index a478eb5..fb81895 100644
> --- a/arch/x86/lib/retpoline.S
> +++ b/arch/x86/lib/retpoline.S
> @@ -151,22 +151,27 @@ SYM_CODE_END(__x86_indirect_jump_thunk_array)
>  	.section .text..__x86.rethunk_untrain
>  
>  SYM_START(srso_untrain_ret_alias, SYM_L_GLOBAL, SYM_A_NONE)
> +	UNWIND_HINT_FUNC
>  	ANNOTATE_NOENDBR
>  	ASM_NOP2
>  	lfence
> -	jmp __x86_return_thunk
> +	jmp srso_alias_return_thunk
>  SYM_FUNC_END(srso_untrain_ret_alias)
>  __EXPORT_THUNK(srso_untrain_ret_alias)
>  
>  	.section .text..__x86.rethunk_safe
> +#else
> +/* dummy definition for alternatives */
> +SYM_START(srso_untrain_ret_alias, SYM_L_GLOBAL, SYM_A_NONE)
> +	ANNOTATE_UNRET_SAFE
> +	ret
> +	int3
> +SYM_FUNC_END(srso_alias_untrain_ret)

Just a heads up, this series will have a small bisectability issue
because of this hunk, it needs

diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S
index fb818957955b..7df8582fb64e 100644
--- a/arch/x86/lib/retpoline.S
+++ b/arch/x86/lib/retpoline.S
@@ -166,7 +166,7 @@ SYM_START(srso_untrain_ret_alias, SYM_L_GLOBAL, SYM_A_NONE)
 	ANNOTATE_UNRET_SAFE
 	ret
 	int3
-SYM_FUNC_END(srso_alias_untrain_ret)
+SYM_FUNC_END(srso_untrain_ret_alias)
 #endif
 
 SYM_START(srso_safe_ret_alias, SYM_L_GLOBAL, SYM_A_NONE)

but it obviously gets fixed by commit a3fd3ac0a605 ("x86/cpu: Rename
srso_(.*)_alias to srso_alias_\1") so it is probably fine. I only
noticed it because I cherry-picked the first five changes to my patched
-next tree.

Cheers,
Nathan