tests/tcg: target/s390x: Test MVC

Let's add a test that especially verifies that no data will be touched
in case we cross page boundaries and one page access triggers a fault.

Before the fault-safe handling fixes, the test failes with:
      TEST    mvc on s390x
    data modified during a fault
    make[2]: *** [../Makefile.target:116: run-mvc] Error 1

Acked-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: David Hildenbrand <david@redhat.com>

tests/tcg/s390x/Makefile.target

@@ -7,3 +7,4 @@ TESTS+=exrl-trt
 TESTS+=exrl-trtr
 TESTS+=pack
 TESTS+=mvo
+TESTS+=mvc

tests/tcg/s390x/mvc.c

@@ -0,0 +1,109 @@
+#include <stdint.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/mman.h>
+#include <signal.h>
+#include <setjmp.h>
+
+jmp_buf jmp_env;
+
+static void handle_sigsegv(int sig)
+{
+    siglongjmp(jmp_env, 1);
+}
+
+#define ALLOC_SIZE (2 * 4096)
+
+static inline void mvc_256(const char *dst, const char *src)
+{
+    asm volatile (
+        "    mvc 0(256,%[dst]),0(%[src])\n"
+        :
+        : [dst] "d" (dst),
+          [src] "d" (src)
+        : "memory");
+}
+
+int main(void)
+{
+    char *src, *dst;
+    int i;
+
+    /* register the SIGSEGV handler */
+    if (signal(SIGSEGV, handle_sigsegv) == SIG_ERR) {
+        fprintf(stderr, "SIGSEGV not registered\n");
+        return 1;
+    }
+
+    /* prepare the buffers - two consecutive pages */
+    src = valloc(ALLOC_SIZE);
+    dst = valloc(ALLOC_SIZE);
+    memset(src, 0xff, ALLOC_SIZE);
+    memset(dst, 0x0, ALLOC_SIZE);
+
+    /* protect the second pages */
+    if (mprotect(src + 4096, 4096, PROT_NONE) ||
+        mprotect(dst + 4096, 4096, PROT_NONE)) {
+        fprintf(stderr, "mprotect failed\n");
+        return 1;
+    }
+
+    /* fault on second destination page */
+    if (sigsetjmp(jmp_env, 1) == 0) {
+        mvc_256(dst + 4096 - 128, src);
+        fprintf(stderr, "fault not triggered\n");
+        return 1;
+    }
+
+    /* fault on second source page */
+    if (sigsetjmp(jmp_env, 1) == 0) {
+        mvc_256(dst, src + 4096 - 128);
+        fprintf(stderr, "fault not triggered\n");
+        return 1;
+    }
+
+    /* fault on second source and second destination page */
+    if (sigsetjmp(jmp_env, 1) == 0) {
+        mvc_256(dst + 4096 - 128, src + 4096 - 128);
+        fprintf(stderr, "fault not triggered\n");
+        return 1;
+    }
+
+    /* restore permissions */
+    if (mprotect(src + 4096, 4096, PROT_READ | PROT_WRITE) ||
+        mprotect(dst + 4096, 4096, PROT_READ | PROT_WRITE)) {
+        fprintf(stderr, "mprotect failed\n");
+        return 1;
+    }
+
+    /* no data must be touched during the faults */
+    for (i = 0; i < ALLOC_SIZE; i++) {
+        if (src[i] != 0xff || dst[i]) {
+            fprintf(stderr, "data modified during a fault\n");
+            return 1;
+        }
+    }
+
+    /* test if MVC works now correctly accross page boundaries */
+    mvc_256(dst + 4096 - 128, src + 4096 - 128);
+    for (i = 0; i < ALLOC_SIZE; i++) {
+        if (src[i] != 0xff) {
+            fprintf(stderr, "src modified\n");
+            return 1;
+        }
+        if (i < 4096 - 128 || i >= 4096 + 128) {
+            if (dst[i]) {
+                fprintf(stderr, "wrong dst modified\n");
+                return 1;
+            }
+        } else {
+            if (dst[i] != 0xff) {
+                fprintf(stderr, "wrong data moved\n");
+                return 1;
+            }
+        }
+    }
+
+    return 0;
+}