[tip: x86/bugs] x86/srso: Improve i-cache locality for alias mitigation

From: tip-bot2 for Josh Poimboeuf
Date: Tue Sep 19 2023 - 05:54:06 EST


The following commit has been merged into the x86/bugs branch of tip:

Commit-ID: da3bd8872ee00f23b58c7f62dfd403dcc83e074b
Gitweb: https://git.kernel.org/tip/da3bd8872ee00f23b58c7f62dfd403dcc83e074b
Author: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
AuthorDate: Mon, 04 Sep 2023 22:04:55 -07:00
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitterDate: Tue, 19 Sep 2023 11:42:47 +02:00

x86/srso: Improve i-cache locality for alias mitigation

Move srso_alias_return_thunk() to the same section as
srso_alias_safe_ret() so they can share a cache line.

Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Acked-by: Borislav Petkov (AMD) <bp@xxxxxxxxx>
Link: https://lore.kernel.org/r/eadaf5530b46a7ae8b936522da45ae555d2b3393.1693889988.git.jpoimboe@xxxxxxxxxx
---
arch/x86/lib/retpoline.S | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S
index cd86aeb..9ab634f 100644
--- a/arch/x86/lib/retpoline.S
+++ b/arch/x86/lib/retpoline.S
@@ -177,15 +177,14 @@ SYM_START(srso_alias_safe_ret, SYM_L_GLOBAL, SYM_A_NONE)
int3
SYM_FUNC_END(srso_alias_safe_ret)

- .section .text..__x86.return_thunk
-
-SYM_CODE_START(srso_alias_return_thunk)
+SYM_CODE_START_NOALIGN(srso_alias_return_thunk)
UNWIND_HINT_FUNC
ANNOTATE_NOENDBR
call srso_alias_safe_ret
ud2
SYM_CODE_END(srso_alias_return_thunk)

+ .section .text..__x86.return_thunk
/*
* Some generic notes on the untraining sequences:
*