selftests/x86: Add tests for User-Mode Instruction Prevention

selftests/x86: Add tests for User-Mode Instruction Prevention

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 fault is issued if UMIP is enabled. When
such a fault happens, the kernel traps it and emulates the results of
these instructions with dummy values. 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 INT3.

The instructions protected by UMIP are executed in representative use
cases:

 a) displacement-only memory addressing
 b) register-indirect memory addressing
 c) results stored directly in operands

Unfortunately, it is not possible to check the results against a set of
expected values because no emulation will occur in systems that do not
have the UMIP feature. Instead, results are printed for verification. A
simple verification is done to ensure that results of all tests are
identical.

Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Borislav Petkov <bp@suse.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Chen Yucong <slaoub@gmail.com>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Huang Rui <ray.huang@amd.com>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi V. Shankar <ravi.v.shankar@intel.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: ricardo.neri@intel.com
Link: http://lkml.kernel.org/r/1509935277-22138-12-git-send-email-ricardo.neri-calderon@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>