new file mode 100644
@@ -0,0 +1,82 @@
+/*
+ * Test modifying code using the MVC instruction.
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#include <minilib.h>
+
+#define PAGE_SIZE 4096
+#define BR_14_SIZE 2
+#define RWX_OFFSET 2
+
+static unsigned char rw[PAGE_SIZE + BR_14_SIZE];
+static unsigned char rwx[RWX_OFFSET + sizeof(rw)]
+ __attribute__((aligned(PAGE_SIZE)));
+
+typedef unsigned long (*function_t)(unsigned long);
+
+static int emit_function(unsigned char *p, int n)
+{
+ int i = 0, val = 0;
+
+ while (i < n - 2) {
+ /* aghi %r2,1 */
+ p[i++] = 0xa7;
+ p[i++] = 0x2b;
+ p[i++] = 0x00;
+ p[i++] = 0x01;
+ val++;
+ }
+
+ /* br %r14 */
+ p[i++] = 0x07;
+ p[i++] = 0xfe;
+
+ return val;
+}
+
+static void memcpy_mvc(void *dest, void *src, unsigned long n)
+{
+ while (n >= 256) {
+ asm("mvc 0(256,%[dest]),0(%[src])"
+ :
+ : [dest] "a" (dest)
+ , [src] "a" (src)
+ : "memory");
+ dest += 256;
+ src += 256;
+ n -= 256;
+ }
+ asm("exrl %[n],0f\n"
+ "j 1f\n"
+ "0: mvc 0(1,%[dest]),0(%[src])\n"
+ "1:"
+ :
+ : [dest] "a" (dest)
+ , [src] "a" (src)
+ , [n] "a" (n)
+ : "memory");
+}
+
+int main(void)
+{
+ int expected, size;
+
+ /* Create a TB. */
+ size = sizeof(rwx) - RWX_OFFSET - 4;
+ expected = emit_function(rwx + RWX_OFFSET, size);
+ if (((function_t)(rwx + RWX_OFFSET))(0) != expected) {
+ return 1;
+ }
+
+ /* Overwrite the TB. */
+ size += 4;
+ expected = emit_function(rw, size);
+ memcpy_mvc(rwx + RWX_OFFSET, rw, size);
+ if (((function_t)(rwx + RWX_OFFSET))(0) != expected) {
+ return 2;
+ }
+
+ return 0;
+}
@@ -42,6 +42,7 @@ $(ASM_TESTS): LDFLAGS += -Wl,-T$(LINK_SCRIPT) -Wl,--build-id=none
$(ASM_TESTS): $(LINK_SCRIPT)
TESTS += $(ASM_TESTS)
+MULTIARCH_TESTS += mvc-smc
S390X_MULTIARCH_RUNTIME_OBJS = head64.o console.o $(MINILIB_OBJS)
$(MULTIARCH_TESTS): $(S390X_MULTIARCH_RUNTIME_OBJS)
$(MULTIARCH_TESTS): LDFLAGS += $(S390X_MULTIARCH_RUNTIME_OBJS)