tests/tcg/s390x: Test precise self-modifying code handling

Add small softmmu and user tests to prevent regressions.

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Message-Id: <20230807114921.438881-2-iii@linux.ibm.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>

1 files changed, 39 insertions, 0 deletions

diff --git a/tests/tcg/s390x/precise-smc-user.c b/tests/tcg/s390x/precise-smc-user.c
new file mode 100644
index 0000000000..33a5270865
--- /dev/null
+++ b/tests/tcg/s390x/precise-smc-user.c
@@ -0,0 +1,39 @@
+/*
+ * Test s390x-linux-user precise self-modifying code handling.
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+#include <assert.h>
+#include <sys/mman.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+extern __uint128_t __attribute__((__aligned__(1))) smc;
+extern __uint128_t __attribute__((__aligned__(1))) patch;
+
+int main(void)
+{
+    char *aligned_smc = (char *)((uintptr_t)&smc & ~0xFFFULL);
+    char *smc_end = (char *)&smc + sizeof(smc);
+    uint64_t value = 21;
+    int err;
+
+    err = mprotect(aligned_smc, smc_end - aligned_smc,
+                   PROT_READ | PROT_WRITE | PROT_EXEC);
+    assert(err == 0);
+
+    asm("jg 0f\n"                           /* start a new TB */
+        "patch: .byte 0,0,0,0,0,0\n"        /* replaces padding */
+        ".byte 0,0,0,0,0,0\n"               /* replaces vstl */
+        "agr %[value],%[value]\n"           /* replaces sgr */
+        "smc: .org . + 6\n"                 /* pad patched code to 16 bytes */
+        "0: vstl %[patch],%[idx],%[smc]\n"  /* start writing before TB */
+        "sgr %[value],%[value]"             /* this becomes `agr %r0,%r0` */
+        : [smc] "=R" (smc)
+        , [value] "+r" (value)
+        : [patch] "v" (patch)
+        , [idx] "r" (sizeof(patch) - 1)
+        : "cc");
+
+    return value == 42 ? EXIT_SUCCESS : EXIT_FAILURE;
+}