linux-kernel - [PATCH v2] x86/alternative: fix undefined reference to __ibt_endbr_seal[

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Message-ID: <20221011113803.956808-1-linmiaohe@huawei.com>
Date:   Tue, 11 Oct 2022 19:38:03 +0800
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     <tglx@...utronix.de>, <mingo@...hat.com>, <bp@...en8.de>,
        <dave.hansen@...ux.intel.com>
CC:     <hpa@...or.com>, <x86@...nel.org>, <linux-kernel@...r.kernel.org>,
        <linmiaohe@...wei.com>
Subject: [PATCH v2] x86/alternative: fix undefined reference to __ibt_endbr_seal[_end]

Due to the explicit 'noinline' GCC-7.3 is not able to optimize away the
argument setup of:

	apply_ibt_endbr(__ibt_endbr_seal, __ibt_enbr_seal_end);

even when X86_KERNEL_IBT=n and the function is an empty stub which leads
to link errors due to missing __ibt_endbr_seal* symbols like below:

ld: arch/x86/kernel/alternative.o: in function
`alternative_instructions':
alternative.c:(.init.text+0x15d): undefined reference to
`__ibt_endbr_seal_end'
ld: alternative.c:(.init.text+0x164): undefined reference to
`__ibt_endbr_seal'

Remove explicit 'noinline' to help gcc optimize them away.
[Thanks Peter Zijlstra for tweaking the commit log.]

Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
---
 arch/x86/kernel/alternative.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index 5cadcea035e0..beaf9fc44e2f 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -624,7 +624,7 @@ void __init_or_module noinline apply_ibt_endbr(s32 *start, s32 *end)
 
 #else
 
-void __init_or_module noinline apply_ibt_endbr(s32 *start, s32 *end) { }
+void __init_or_module apply_ibt_endbr(s32 *start, s32 *end) { }
 
 #endif /* CONFIG_X86_KERNEL_IBT */
 
-- 
2.23.0