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

[Ricardo Neri]

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 <luto at kernel.org>
Cc: Andrew Morton <akpm at linux-foundation.org>
Cc: H. Peter Anvin <hpa at zytor.com>
Cc: Borislav Petkov <bp at suse.de>
Cc: Brian Gerst <brgerst at gmail.com>
Cc: Chen Yucong <slaoub at gmail.com>
Cc: Chris Metcalf <cmetcalf at mellanox.com>
Cc: Dave Hansen <dave.hansen at linux.intel.com>
Cc: Fenghua Yu <fenghua.yu at intel.com>
Cc: Huang Rui <ray.huang at amd.com>
Cc: Jiri Slaby <jslaby at suse.cz>
Cc: Jonathan Corbet <corbet at lwn.net>
Cc: Michael S. Tsirkin <mst at redhat.com>
Cc: Paul Gortmaker <paul.gortmaker at windriver.com>
Cc: Peter Zijlstra <peterz at infradead.org>
Cc: Ravi V. Shankar <ravi.v.shankar at intel.com>
Cc: Shuah Khan <shuah at kernel.org>
Cc: Vlastimil Babka <vbabka at suse.cz>
Cc: Tony Luck <tony.luck at intel.com>
Cc: Paolo Bonzini <pbonzini at redhat.com>
Cc: Liang Z. Li <liang.z.li at intel.com>
Cc: Alexandre Julliard <julliard at winehq.org>
Cc: Stas Sergeev <stsp at list.ru>
Cc: x86 at kernel.org
Cc: linux-msdos at vger.kernel.org
Signed-off-by: Ricardo Neri <ricardo.neri-calderon at linux.intel.com>
---
 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