[PATCH 2/2] tests/tcg/s390x: Test DR overflow (INT64_MIN / -1)

[Ilya Leoshkevich <iii@linux.ibm.com>]

Check that DR with a non-representable quotient raises SIGFPE rather than
crashing the emulator.

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
---
 tests/tcg/s390x/div.c | 37 +++++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)

diff --git a/tests/tcg/s390x/div.c b/tests/tcg/s390x/div.c
index 6ad9900e082..124c9ecc339 100644
--- a/tests/tcg/s390x/div.c
+++ b/tests/tcg/s390x/div.c
@@ -1,6 +1,15 @@
 #include <assert.h>
+#include <signal.h>
 #include <stdint.h>
 
+/* Set asynchronously by the signal handler. */
+static volatile int signum;
+
+static void signal_handler(int n)
+{
+    signum = n;
+}
+
 static void test_dr(void)
 {
     register int32_t r0 asm("r0") = -1;
@@ -65,11 +74,39 @@ static void test_dlgr(void)
     assert(r == 1);
 }
 
+/*
+ * The most negative dividend divided by -1 yields a quotient that does not
+ * fit into 32 bits, so DR must raise a fixed-point-divide exception.
+ */
+static void test_dr_overflow(void)
+{
+    struct sigaction act = { .sa_handler = signal_handler };
+    register int32_t r0 asm("r0");
+    register int32_t r1 asm("r1");
+    int32_t b = -1;
+    int err;
+
+    err = sigaction(SIGFPE, &act, NULL);
+    assert(err == 0);
+    signum = -1;
+
+    r0 = 0x80000000;
+    r1 = 0;
+    asm volatile("dr %[r0],%[b]"
+                 : [r0] "+r" (r0), [r1] "+r" (r1)
+                 : [b] "r" (b)
+                 : "cc");
+    assert(signum == SIGFPE);
+
+    signal(SIGFPE, SIG_DFL);
+}
+
 int main(void)
 {
     test_dr();
     test_dlr();
     test_dsgr();
     test_dlgr();
+    test_dr_overflow();
     return 0;
 }
-- 
2.55.0