linux-kernel - [PATCH 2/2] x86: make __ibp

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Date:   Mon,  5 Feb 2018 16:12:53 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Andi Kleen <ak@...ux.intel.com>
Cc:     nico@...aro.org, linux-kernel@...r.kernel.org,
        Arnd Bergmann <arnd@...db.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        David Woodhouse <dwmw@...zon.co.uk>,
        Borislav Petkov <bp@...e.de>
Subject: [PATCH 2/2] x86: make __ibp_barrier visible

LTO linking was broken by the addition of __ibp_barrier, which only
has relocations from assembler code, and not from C, so the linker
decides to drop it:

./ccfzUJ1l.ltrans0.ltrans.o:(.altinstr_replacement+0x42): undefined reference to `__ibp_barrier'

Fixes: 64e16720ea08 ("x86/speculation: Simplify indirect_branch_prediction_barrier()")
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 arch/x86/kernel/cpu/bugs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 71949bf2de5a..c3f5fe1c6e83 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -338,7 +338,7 @@ ssize_t cpu_show_spectre_v2(struct device *dev,
 }
 #endif
 
-void __ibp_barrier(void)
+void __visible __ibp_barrier(void)
 {
 	__wrmsr(MSR_IA32_PRED_CMD, PRED_CMD_IBPB, 0);
 }
-- 
2.9.0