Certain user space programs that run on virtual-8086 mode may utilize
instructions protected by the User-Mode Instruction Prevention (UMIP)
security feature present in new Intel processors: SGDT, SIDT and SMSW. In
such a case, a general protection exception is issued if UMIP is enabled.
For the aforementioned reason, UMIP can be optionally disabled for virtual-
8086 tasks with the umip=novm86 kernel parameter. The purpose of this new
test is to verify whether the impacted instructions can be executed without
causing such #GP. If no #GP exceptions occur, we expect to exit virtual-
8086 mode from INT 0x80; provided umip=novm86 was used in the kernel
parameter.
Cc: Andy Lutomirski <l...@kernel.org>
Cc: Andrew Morton <a...@linux-foundation.org>
Cc: Borislav Petkov <b...@suse.de>
Cc: Brian Gerst <brge...@gmail.com>
Cc: Chen Yucong <sla...@gmail.com>
Cc: Chris Metcalf <cmetc...@mellanox.com>
Cc: Dave Hansen <dave.han...@linux.intel.com>
Cc: Fenghua Yu <fenghua...@intel.com>
Cc: Huang Rui <ray.hu...@amd.com>
Cc: Jiri Slaby <jsl...@suse.cz>
Cc: Jonathan Corbet <cor...@lwn.net>
Cc: Michael S. Tsirkin <m...@redhat.com>
Cc: Paul Gortmaker <paul.gortma...@windriver.com>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Ravi V. Shankar <ravi.v.shan...@intel.com>
Cc: Shuah Khan <sh...@kernel.org>
Cc: Vlastimil Babka <vba...@suse.cz>
Signed-off-by: Ricardo Neri <ricardo.neri-calde...@linux.intel.com>
---
tools/testing/selftests/x86/entry_from_vm86.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/tools/testing/selftests/x86/entry_from_vm86.c
b/tools/testing/selftests/x86/entry_from_vm86.c
index d075ea0..6efa6eb 100644
--- a/tools/testing/selftests/x86/entry_from_vm86.c
+++ b/tools/testing/selftests/x86/entry_from_vm86.c
@@ -95,6 +95,11 @@ asm (
"int3\n\t"
"vmcode_int80:\n\t"
"int $0x80\n\t"
+ "umip:\n\t"
+ "sgdt (2052)\n\t"
+ "sidt (2052)\n\t"
+ "smsw (2052)\n\t"
+ "int $0x80\n\t"
".size vmcode, . - vmcode\n\t"
"end_vmcode:\n\t"
".code32\n\t"
@@ -103,7 +108,7 @@ asm (
extern unsigned char vmcode[], end_vmcode[];
extern unsigned char vmcode_bound[], vmcode_sysenter[], vmcode_syscall[],
- vmcode_sti[], vmcode_int3[], vmcode_int80[];
+ vmcode_sti[], vmcode_int3[], vmcode_int80[], umip[];
/* Returns false if the test was skipped. */
static bool do_test(struct vm86plus_struct *v86, unsigned long eip,
@@ -218,6 +223,9 @@ int main(void)
v86.regs.eax = (unsigned int)-1;
do_test(&v86, vmcode_int80 - vmcode, VM86_INTx, 0x80, "int80");
+ /* UMIP -- should exit with INTx 0x80 unless UMIP was not disabled */
+ do_test(&v86, umip - vmcode, VM86_INTx, 0x80, "UMIP tests");
+
/* Execute a null pointer */
v86.regs.cs = 0;
v86.regs.ss = 0;
--
2.7.4
--
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