From 9a48d604672220545d209e9996c2a1edbb5637f6 Mon Sep 17 00:00:00 2001 From: "Borislav Petkov (AMD)" Date: Fri, 12 May 2023 23:12:26 +0200 Subject: [PATCH] x86/retbleed: Fix return thunk alignment SYM_FUNC_START_LOCAL_NOALIGN() adds an endbr leading to this layout (leaving only the last 2 bytes of the address): 3bff : 3bff: f3 0f 1e fa endbr64 3c03: f6 test $0xcc,%bl 3c04 <__x86_return_thunk>: 3c04: c3 ret 3c05: cc int3 3c06: 0f ae e8 lfence However, "the RET at __x86_return_thunk must be on a 64 byte boundary, for alignment within the BTB." Use SYM_START instead. Signed-off-by: Borislav Petkov (AMD) Reviewed-by: Thomas Gleixner Cc: Signed-off-by: Linus Torvalds --- arch/x86/lib/retpoline.S | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S index 27ef53fab6bd..b3b1e376dce8 100644 --- a/arch/x86/lib/retpoline.S +++ b/arch/x86/lib/retpoline.S @@ -144,8 +144,8 @@ SYM_CODE_END(__x86_indirect_jump_thunk_array) */ .align 64 .skip 63, 0xcc -SYM_FUNC_START_NOALIGN(zen_untrain_ret); - +SYM_START(zen_untrain_ret, SYM_L_GLOBAL, SYM_A_NONE) + ANNOTATE_NOENDBR /* * As executed from zen_untrain_ret, this is: * -- 2.11.0