[PATCH v7 01/26] ptrace, x86: Make user_64bit_mode() available to 32-bit builds

[Ricardo Neri]

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 
Cc: Dave Hansen 
Cc: Adam Buchbinder 
Cc: Colin Ian King 
Cc: Lorenzo Stoakes 
Cc: Qiaowei Ren 
Cc: Arnaldo Carvalho de Melo 
Cc: Masami Hiramatsu 
Cc: Adrian Hunter 
Cc: Kees Cook 
Cc: Thomas Garnier 
Cc: Peter Zijlstra 
Cc: Borislav Petkov 
Cc: Dmitry Vyukov 
Cc: Ravi V. Shankar 
Cc: [e-mail]
Signed-off-by: Ricardo Neri 
---
 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