[v2 6/7] x86/traps: Fixup general protection faults caused by UMIP

If the User-Mode Instruction Prevention CPU feature is available and
enabled, a general protection fault will be issued if the instructions
sgdt, sldt, sidt, str or smsw are executed from user-mode context
(CPL > 0). If the fault was caused by any of the instructions protected
by UMIP, fixup_umip_exceptino will emulate dummy results for these
instructions.

Cc: Andy Lutomirski <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Brian Gerst <[email protected]>
Cc: Chen Yucong <[email protected]>
Cc: Chris Metcalf <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Fenghua Yu <[email protected]>
Cc: Huang Rui <[email protected]>
Cc: Jiri Slaby <[email protected]>
Cc: Jonathan Corbet <[email protected]>
Cc: Michael S. Tsirkin <[email protected]>
Cc: Paul Gortmaker <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Ravi V. Shankar <[email protected]>
Cc: Shuah Khan <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: Tony Luck <[email protected]>
Cc: Paolo Bonzini <[email protected]>
Cc: Liang Z. Li <[email protected]>
Cc: Alexandre Julliard <[email protected]>
Cc: Stas Sergeev <[email protected]>
Cc: [email protected]
Cc: [email protected]
Signed-off-by: Ricardo Neri <[email protected]>
---
 arch/x86/kernel/traps.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index bf0c6d0..5044fb3 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -64,6 +64,7 @@
 #include <asm/trace/mpx.h>
 #include <asm/mpx.h>
 #include <asm/vm86.h>
+#include <asm/umip.h>
 
 #ifdef CONFIG_X86_64
 #include <asm/x86_init.h>
@@ -491,6 +492,9 @@ do_general_protection(struct pt_regs *regs, long error_code)
 	RCU_LOCKDEP_WARN(!rcu_is_watching(), "entry code didn't wake RCU");
 	cond_local_irq_enable(regs);
 
+	if (user_mode(regs) && !fixup_umip_exception(regs))
+		return;
+
 	if (v8086_mode(regs)) {
 		local_irq_enable();
 		handle_vm86_fault((struct kernel_vm86_regs *) regs, error_code);
-- 
2.9.3