On 04/03/2015 01:20 PM, Borislav Petkov wrote: > On Fri, Apr 03, 2015 at 11:42:10AM +0200, Borislav Petkov wrote: >> 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(-) >> >> diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c >> index bb6633a87a19..2c249b57e4b5 100644 >> --- a/arch/x86/kernel/cpu/common.c >> +++ b/arch/x86/kernel/cpu/common.c >> @@ -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... -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
