[PATCH v7 26/26] selftests/x86: Add tests for instruction str and sldt

[Ricardo Neri]

The instructions str and sldt are not recognized when running on virtual-
8086 mode and generate an invalid operand exception. These two
instructions are protected by the Intel User-Mode Instruction Prevention
(UMIP) security feature. In protected mode, if UMIP is enabled, these
instructions generate a general protection fault if called from CPL > 0.
Linux traps the general protection fault and emulate the results with
dummy values.

These tests are added to verify that the emulation code does not emulate
these two instructions but issue the expected invalid operand exception.

Tests fallback to exit with int3 in case emulation does happen.

Cc: Andy Lutomirski <luto at kernel.org>
Cc: Andrew Morton <akpm at linux-foundation.org>
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>
Signed-off-by: Ricardo Neri <ricardo.neri-calderon at linux.intel.com>
---
 tools/testing/selftests/x86/entry_from_vm86.c | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/x86/entry_from_vm86.c b/tools/testing/selftests/x86/entry_from_vm86.c
index 130e8ad..b7a0c90 100644
--- a/tools/testing/selftests/x86/entry_from_vm86.c
+++ b/tools/testing/selftests/x86/entry_from_vm86.c
@@ -111,6 +111,11 @@ asm (
 	"smsw %ax\n\t"
 	"mov %ax, (2080)\n\t"
 	"int3\n\t"
+	"vmcode_umip_str:\n\t"
+	"str %eax\n\t"
+	"vmcode_umip_sldt:\n\t"
+	"sldt %eax\n\t"
+	"int3\n\t"
 	".size vmcode, . - vmcode\n\t"
 	"end_vmcode:\n\t"
 	".code32\n\t"
@@ -119,7 +124,8 @@ asm (
 
 extern unsigned char vmcode[], end_vmcode[];
 extern unsigned char vmcode_bound[], vmcode_sysenter[], vmcode_syscall[],
-	vmcode_sti[], vmcode_int3[], vmcode_int80[], vmcode_umip[];
+	vmcode_sti[], vmcode_int3[], vmcode_int80[], vmcode_umip[],
+	vmcode_umip_str[], vmcode_umip_sldt[];
 
 /* Returns false if the test was skipped. */
 static bool do_test(struct vm86plus_struct *v86, unsigned long eip,
@@ -226,6 +232,16 @@ void do_umip_tests(struct vm86plus_struct *vm86, unsigned char *test_mem)
 		printf("[FAIL]\tAll the results of SIDT should be the same.\n");
 	else
 		printf("[PASS]\tAll the results from SIDT are identical.\n");
+
+	sethandler(SIGILL, sighandler, 0);
+	do_test(vm86, vmcode_umip_str - vmcode, VM86_SIGNAL, 0,
+		"STR instruction");
+	clearhandler(SIGILL);
+
+	sethandler(SIGILL, sighandler, 0);
+	do_test(vm86, vmcode_umip_sldt - vmcode, VM86_SIGNAL, 0,
+		"SLDT instruction");
+	clearhandler(SIGILL);
 }
 
 int main(void)
-- 
2.9.3