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Subject[PATCH 2/3] selftests/x86/entry_from_vm86: Add test cases for POPF
Date
POPF is currently broken -- add tests to catch the error.  This
results in:

[RUN] POPF with VIP set and IF clear from vm86 mode
[INFO] Exited vm86 mode due to STI
[FAIL] Incorrect return reason (started at eip = 0xd, ended at eip = 0xf)

because POPF currently fails to check IF before reporting a pending
interrupt.

This patch also makes the FAIL message a bit more informative.

Cc: stable@vger.kernel.org
Reported-by: Bart Oldeman <bartoldeman@gmail.com>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
tools/testing/selftests/x86/entry_from_vm86.c | 30 ++++++++++++++++++++++++---
1 file changed, 27 insertions(+), 3 deletions(-)

diff --git a/tools/testing/selftests/x86/entry_from_vm86.c b/tools/testing/selftests/x86/entry_from_vm86.c
index 6e85f0d0498d..ade443a88421 100644
--- a/tools/testing/selftests/x86/entry_from_vm86.c
+++ b/tools/testing/selftests/x86/entry_from_vm86.c
@@ -95,6 +95,10 @@ asm (
"int3\n\t"
"vmcode_int80:\n\t"
"int $0x80\n\t"
+ "vmcode_popf_hlt:\n\t"
+ "push %ax\n\t"
+ "popf\n\t"
+ "hlt\n\t"
"vmcode_umip:\n\t"
/* addressing via displacements */
"smsw (2052)\n\t"
@@ -124,8 +128,8 @@ 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_umip_str[], vmcode_umip_sldt[];
+ vmcode_sti[], vmcode_int3[], vmcode_int80[], vmcode_popf_hlt[],
+ 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,
@@ -175,7 +179,7 @@ static bool do_test(struct vm86plus_struct *v86, unsigned long eip,
(VM86_TYPE(ret) == rettype && VM86_ARG(ret) == retarg)) {
printf("[OK]\tReturned correctly\n");
} else {
- printf("[FAIL]\tIncorrect return reason\n");
+ printf("[FAIL]\tIncorrect return reason (started at eip = 0x%lx, ended at eip = 0x%lx)\n", eip, v86->regs.eip);
nerrs++;
}

@@ -264,6 +268,9 @@ int main(void)
v86.regs.ds = load_addr / 16;
v86.regs.es = load_addr / 16;

+ /* Use the end of the page as our stack. */
+ v86.regs.esp = 4096;
+
assert((v86.regs.cs & 3) == 0); /* Looks like RPL = 0 */

/* #BR -- should deliver SIG??? */
@@ -295,6 +302,23 @@ int main(void)
v86.regs.eflags &= ~X86_EFLAGS_IF;
do_test(&v86, vmcode_sti - vmcode, VM86_STI, 0, "STI with VIP set");

+ /* POPF with VIP set but IF clear: should not trap */
+ v86.regs.eflags = X86_EFLAGS_VIP;
+ v86.regs.eax = 0;
+ do_test(&v86, vmcode_popf_hlt - vmcode, VM86_UNKNOWN, 0, "POPF with VIP set and IF clear");
+
+ /* POPF with VIP set and IF set: should trap */
+ v86.regs.eflags = X86_EFLAGS_VIP;
+ v86.regs.eax = X86_EFLAGS_IF;
+ do_test(&v86, vmcode_popf_hlt - vmcode, VM86_STI, 0, "POPF with VIP and IF set");
+
+ /* POPF with VIP clear and IF set: should not trap */
+ v86.regs.eflags = 0;
+ v86.regs.eax = X86_EFLAGS_IF;
+ do_test(&v86, vmcode_popf_hlt - vmcode, VM86_UNKNOWN, 0, "POPF with VIP clear and IF set");
+
+ v86.regs.eflags = 0;
+
/* INT3 -- should cause #BP */
do_test(&v86, vmcode_int3 - vmcode, VM86_TRAP, 3, "INT3");

--
2.14.3
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