[Qemu-devel] [PATCH v4 19/21] tests/tcg/arm: account for pauth randomness

[Alex Bennée]

Pointer authentication isn't guaranteed to always detect a clash
between different keys. Take this into account in the test by running
several times and checking the percentage hit rate of the test.

Cc: Richard Henderson <address@hidden>
Signed-off-by: Alex Bennée <address@hidden>
---
 tests/tcg/aarch64/pauth-1.c | 26 ++++++++++++++++++++------
 1 file changed, 20 insertions(+), 6 deletions(-)

diff --git a/tests/tcg/aarch64/pauth-1.c b/tests/tcg/aarch64/pauth-1.c
index ae6dc05c2b..a3c1443cd0 100644
--- a/tests/tcg/aarch64/pauth-1.c
+++ b/tests/tcg/aarch64/pauth-1.c
@@ -1,5 +1,6 @@
 #include <assert.h>
 #include <sys/prctl.h>
+#include <stdio.h>
 
 asm(".arch armv8.4-a");
 
@@ -8,16 +9,29 @@ asm(".arch armv8.4-a");
 #define PR_PAC_APDAKEY     (1 << 2)
 #endif
 
+#define TESTS 1000
+
 int main()
 {
-    int x;
+    int x, i, count = 0;
     void *p0 = &x, *p1, *p2;
+    float perc;
+
+    for (i = 0; i < TESTS; i++) {
+        asm volatile("pacdza %0" : "=r"(p1) : "0"(p0));
+        prctl(PR_PAC_RESET_KEYS, PR_PAC_APDAKEY, 0, 0, 0);
+        asm volatile("pacdza %0" : "=r"(p2) : "0"(p0));
 
-    asm volatile("pacdza %0" : "=r"(p1) : "0"(p0));
-    prctl(PR_PAC_RESET_KEYS, PR_PAC_APDAKEY, 0, 0, 0);
-    asm volatile("pacdza %0" : "=r"(p2) : "0"(p0));
+        if (p1 != p0) {
+            count++;
+        }
+        if (p1 != p2) {
+            count++;
+        }
+    }
 
-    assert(p1 != p0);
-    assert(p1 != p2);
+    perc = (float) count / (float) (TESTS * 2);
+    printf("Ptr Check: %0.2f%%", perc * 100.0);
+    assert(perc > 0.95);
     return 0;
 }
-- 
2.20.1