[PATCH v11 8/9] selftests/x86: Update the negative vsyscall tests to expect a #GP

Sohil Mehta
2025-10-29T21:06:17Z

Some of the vsyscall selftests expect a #PF when vsyscalls are disabled.
However, with LASS enabled, an invalid access results in a SIGSEGV due
to a #GP instead of a #PF. One such negative test fails because it is
expecting X86_PF_INSTR to be set.

Update the failing test to expect either a #GP or a #PF. Also, update
the printed messages to show the trap number (denoting the type of
fault) instead of assuming a #PF.

Signed-off-by: Sohil Mehta <sohil.mehta@intel.com>
---
v11:
- New patch (Fixes a vsyscall selftest failure)
---
tools/testing/selftests/x86/test_vsyscall.c | 21 ++++++++++++---------
1 file changed, 12 insertions(+), 9 deletions(-)

diff --git a/tools/testing/selftests/x86/test_vsyscall.c b/tools/testing/selftests/x86/test_vsyscall.c
index 05e1e6774fba..918eaec8bfbe 100644
--- a/tools/testing/selftests/x86/test_vsyscall.c
+++ b/tools/testing/selftests/x86/test_vsyscall.c
@@ -308,12 +308,13 @@ static void test_getcpu(int cpu)
#ifdef __x86_64__

static jmp_buf jmpbuf;
-static volatile unsigned long segv_err;
+static volatile unsigned long segv_err, segv_trapno;

static void sigsegv(int sig, siginfo_t *info, void *ctx_void)
{
ucontext_t *ctx = (ucontext_t *)ctx_void;

+ segv_trapno = ctx->uc_mcontext.gregs[REG_TRAPNO];
segv_err = ctx->uc_mcontext.gregs[REG_ERR];
siglongjmp(jmpbuf, 1);
}
@@ -336,7 +337,8 @@ static void test_vsys_r(void)
else if (can_read)
ksft_test_result_pass("We have read access\n");
else
- ksft_test_result_pass("We do not have read access: #PF(0x%lx)\n", segv_err);
+ ksft_test_result_pass("We do not have read access (trap=%ld, error=0x%lx)\n",
+ segv_trapno, segv_err);
}

static void test_vsys_x(void)
@@ -347,7 +349,7 @@ static void test_vsys_x(void)
return;
}

- ksft_print_msg("Make sure that vsyscalls really page fault\n");
+ ksft_print_msg("Make sure that vsyscalls really cause a fault\n");

bool can_exec;
if (sigsetjmp(jmpbuf, 1) == 0) {
@@ -358,13 +360,14 @@ static void test_vsys_x(void)
}

if (can_exec)
- ksft_test_result_fail("Executing the vsyscall did not page fault\n");
- else if (segv_err & (1 << 4)) /* INSTR */
- ksft_test_result_pass("Executing the vsyscall page failed: #PF(0x%lx)\n",
- segv_err);
+ ksft_test_result_fail("Executing the vsyscall did not fault\n");
+ /* #GP or #PF (with X86_PF_INSTR) */
+ else if ((segv_trapno == 13) || ((segv_trapno == 14) && (segv_err & (1 << 4))))
+ ksft_test_result_pass("Executing the vsyscall page failed (trap=%ld, error=0x%lx)\n",
+ segv_trapno, segv_err);
else
- ksft_test_result_fail("Execution failed with the wrong error: #PF(0x%lx)\n",
- segv_err);
+ ksft_test_result_fail("Execution failed with the wrong error (trap=%ld, error=0x%lx)\n",
+ segv_trapno, segv_err);
}

/*
--
2.43.0