x86/asm/entry/64: Fix MSR_IA32_SYSENTER_CS MSR value

From: Borislav Petkov <[email protected]>

Commit

d56fe4bf5f3c ("x86/asm/entry/64: Always set up SYSENTER MSRs")

missed to add "ULL" to the 0 and wrmsrl_safe() complains:

arch/x86/kernel/cpu/common.c: In function ‘syscall_init’:
arch/x86/kernel/cpu/common.c:1226:2: warning: right shift count >= width of type

    wrmsrl_safe(MSR_IA32_SYSENTER_CS, 0);

Fix it.

Signed-off-by Borislav Petkov <[email protected]>

Cc Denys Vlasenko <[email protected]>

Cc Andy Lutomirski <[email protected]>

Cc Alexei Starovoitov <[email protected]>

Cc Frederic Weisbecker <[email protected]>

Cc H. Peter Anvin <[email protected]>

Cc Kees Cook <[email protected]>

Cc Linus Torvalds <[email protected]>

Cc Oleg Nesterov <[email protected]>

Cc Steven Rostedt <[email protected]>

Cc Will Drewry <[email protected]>

Cc Ingo Molnar <[email protected]>

---
 arch/x86/kernel/cpu/common.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

arch/x86/kernel/cpu/common.c +0 -0

index bb6633a87a19..2c249b57e4b5 100644

Quoted 35 lines · Borislav Petkov

From: Borislav Petkov <[email protected]>

Commit

d56fe4bf5f3c ("x86/asm/entry/64: Always set up SYSENTER MSRs")

missed to add "ULL" to the 0 and wrmsrl_safe() complains:

arch/x86/kernel/cpu/common.c: In function ‘syscall_init’:
arch/x86/kernel/cpu/common.c:1226:2: warning: right shift count >= width of type

    wrmsrl_safe(MSR_IA32_SYSENTER_CS, 0);

Fix it.

Signed-off-by Borislav Petkov <[email protected]>

Cc Denys Vlasenko <[email protected]>

Cc Andy Lutomirski <[email protected]>

Cc Alexei Starovoitov <[email protected]>

Cc Frederic Weisbecker <[email protected]>

Cc H. Peter Anvin <[email protected]>

Cc Kees Cook <[email protected]>

Cc Linus Torvalds <[email protected]>

Cc Oleg Nesterov <[email protected]>

Cc Steven Rostedt <[email protected]>

Cc Will Drewry <[email protected]>

Cc Ingo Molnar <[email protected]>

---
 arch/x86/kernel/cpu/common.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

arch/x86/kernel/cpu/common.c +0 -0

index bb6633a87a19..2c249b57e4b5 100644

arch/x86/kernel/cpu/common.c void syscall_init(void) · line 1226

Quoted 5 lines

arch/x86/kernel/cpu/common.c +1 -1

@@ -1223,7 +1223,7 @@ 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, 0);
+	wrmsrl_safe(MSR_IA32_SYSENTER_CS, 0ULL);

Btw, we probably should define an invalid segment

#define GDT_ENTRY_INVALID_SEGMENT 0ULL

and use that value instead of the naked 0.

Why? Segment selectors aren't "long long", they are in fact "short" (16-bit ints).

The "ULL" is used here in wrmsrl not because it's a segment, but because wrmsrl expects a u64 parameter.

We can probably add a cast in its definition...

Let me do a patch.