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 <[email protected]> Cc: Andrew Morton <[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]> Signed-off-by: Ricardo Neri <[email protected]> --- 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
