In its current form, user_64bit_mode() can only be used when CONFIG_X86_64
is selected. This implies that code built with CONFIG_X86_64=n cannot use
it. If a piece of code needs to be built for both CONFIG_X86_64=y and
CONFIG_X86_64=n and wants to use this function, it needs to wrap it in
an #ifdef/#endif; potentially, in multiple places.

This can be easily avoided with a single #ifdef/#endif pair within
user_64bit_mode() itself.

Suggested-by: Borislav Petkov <b...@suse.de>
Cc: Dave Hansen <dave.han...@linux.intel.com>
Cc: Adam Buchbinder <adam.buchbin...@gmail.com>
Cc: Colin Ian King <colin.k...@canonical.com>
Cc: Lorenzo Stoakes <lstoa...@gmail.com>
Cc: Qiaowei Ren <qiaowei....@intel.com>
Cc: Arnaldo Carvalho de Melo <a...@redhat.com>
Cc: Masami Hiramatsu <mhira...@kernel.org>
Cc: Adrian Hunter <adrian.hun...@intel.com>
Cc: Kees Cook <keesc...@chromium.org>
Cc: Thomas Garnier <thgar...@google.com>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Borislav Petkov <b...@suse.de>
Cc: Dmitry Vyukov <dvyu...@google.com>
Cc: Ravi V. Shankar <ravi.v.shan...@intel.com>
Cc: x...@kernel.org
Signed-off-by: Ricardo Neri <ricardo.neri-calde...@linux.intel.com>
---
 arch/x86/include/asm/ptrace.h | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/ptrace.h b/arch/x86/include/asm/ptrace.h
index 2b5d686..ea78a84 100644
--- a/arch/x86/include/asm/ptrace.h
+++ b/arch/x86/include/asm/ptrace.h
@@ -115,9 +115,9 @@ static inline int v8086_mode(struct pt_regs *regs)
 #endif
 }
 
-#ifdef CONFIG_X86_64
 static inline bool user_64bit_mode(struct pt_regs *regs)
 {
+#ifdef CONFIG_X86_64
 #ifndef CONFIG_PARAVIRT
        /*
         * On non-paravirt systems, this is the only long mode CPL 3
@@ -128,8 +128,12 @@ static inline bool user_64bit_mode(struct pt_regs *regs)
        /* Headers are too twisted for this to go in paravirt.h. */
        return regs->cs == __USER_CS || regs->cs == pv_info.extra_user_64bit_cs;
 #endif
+#else /* !CONFIG_X86_64 */
+       return false;
+#endif
 }
 
+#ifdef CONFIG_X86_64
 #define current_user_stack_pointer()   current_pt_regs()->sp
 #define compat_user_stack_pointer()    current_pt_regs()->sp
 #endif
-- 
2.9.3

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