[tip:x86/asm] x86/asm/entry/64: Use a define for an invalid segment selector

[tip-bot for Borislav Petkov]

Commit-ID:  6b51311c976593fb7311322b1647a912cd456ec4
Gitweb:     http://git.kernel.org/tip/6b51311c976593fb7311322b1647a912cd456ec4
Author:     Borislav Petkov <bp@xxxxxxxxx>
AuthorDate: Fri, 3 Apr 2015 14:25:28 +0200
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Fri, 3 Apr 2015 15:29:13 +0200

x86/asm/entry/64: Use a define for an invalid segment selector

... instead of a naked number, for better readability.

Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Cc: Alexei Starovoitov <ast@xxxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Cc: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Will Drewry <wad@xxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/1428054130-25847-1-git-send-email-bp@xxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 arch/x86/include/asm/segment.h | 2 ++
 arch/x86/kernel/cpu/common.c   | 2 +-
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/segment.h b/arch/x86/include/asm/segment.h
index d394899..5a9856e 100644
--- a/arch/x86/include/asm/segment.h
+++ b/arch/x86/include/asm/segment.h
@@ -39,6 +39,8 @@
 /* ... GDT has it cleared */
 #define SEGMENT_GDT		0x0
 
+#define GDT_ENTRY_INVALID_SEG	0
+
 #ifdef CONFIG_X86_32
 /*
  * The layout of the per-CPU GDT under Linux:
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index d56d307..3f70538 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1184,7 +1184,7 @@ void syscall_init(void)
 	wrmsrl_safe(MSR_IA32_SYSENTER_EIP, (u64)ia32_sysenter_target);
 #else
 	wrmsrl(MSR_CSTAR, ignore_sysret);
-	wrmsrl_safe(MSR_IA32_SYSENTER_CS, 0ULL);
+	wrmsrl_safe(MSR_IA32_SYSENTER_CS, (u64)GDT_ENTRY_INVALID_SEG);
 	wrmsrl_safe(MSR_IA32_SYSENTER_ESP, 0ULL);
 	wrmsrl_safe(MSR_IA32_SYSENTER_EIP, 0ULL);
 #endif
--
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