linux-kernel - [PATCH 1/2] [stable-4.9] x86: fix build without CONFIG_X86_VSYSCALL

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Date:   Thu, 15 Feb 2018 16:16:56 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     stable@...r.kernel.org
Cc:     x86@...nel.org, Dave Hansen <dave.hansen@...ux.intel.com>,
        Ben Hutchings <ben.hutchings@...ethink.co.uk>,
        Arnd Bergmann <arnd@...db.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Borislav Petkov <bp@...e.de>, Hugh Dickins <hughd@...gle.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH 1/2] [stable-4.9] x86: fix build without CONFIG_X86_VSYSCALL_EMULATION

I ran into a 4.9 build regression in randconfig testing, starting with the
KAISER patches:

arch/x86/mm/kaiser.c: In function 'kaiser_init':
arch/x86/mm/kaiser.c:347:8: error: 'vsyscall_pgprot' undeclared (first use in this function); did you mean 'massage_pgprot'?

This is easy enough to fix, we just need to make the declaration visible
outside of the #ifdef. This works because the code using it is optimized
away when vsyscall_enabled() returns false at compile time.

Fixes: 9a0be5afbfbb ("vsyscall: Fix permissions for emulate mode with KAISER/PTI")
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 arch/x86/include/asm/vsyscall.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/vsyscall.h b/arch/x86/include/asm/vsyscall.h
index 9ee85066f407..c98c21b7f4cd 100644
--- a/arch/x86/include/asm/vsyscall.h
+++ b/arch/x86/include/asm/vsyscall.h
@@ -13,7 +13,6 @@ extern void map_vsyscall(void);
  */
 extern bool emulate_vsyscall(struct pt_regs *regs, unsigned long address);
 extern bool vsyscall_enabled(void);
-extern unsigned long vsyscall_pgprot;
 #else
 static inline void map_vsyscall(void) {}
 static inline bool emulate_vsyscall(struct pt_regs *regs, unsigned long address)
@@ -23,4 +22,6 @@ static inline bool emulate_vsyscall(struct pt_regs *regs, unsigned long address)
 static inline bool vsyscall_enabled(void) { return false; }
 #endif
 
+extern unsigned long vsyscall_pgprot;
+
 #endif /* _ASM_X86_VSYSCALL_H */
-- 
2.9.0