tests/tcg/s390x: Test BRASL and BRCL with large negative offsets

Add a small test in order to prevent regressions.

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Message-Id: <20220314104232.675863-4-iii@linux.ibm.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>

tests/tcg/s390x/Makefile.target

@@ -15,6 +15,7 @@ TESTS+=mvc
 TESTS+=shift
 TESTS+=trap
 TESTS+=signals-s390x
+TESTS+=branch-relative-long
 
 ifneq ($(HAVE_GDB_BIN),)
 GDB_SCRIPT=$(SRC_PATH)/tests/guest-debug/run-test.py

tests/tcg/s390x/branch-relative-long.c

@@ -0,0 +1,68 @@
+#include <stddef.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/mman.h>
+
+#define DEFINE_ASM(_name, _code) \
+    extern const char _name[]; \
+    extern const char _name ## _end[]; \
+    asm("    .globl " #_name "\n" \
+        #_name ":\n" \
+        "    " _code "\n" \
+        "    .globl " #_name "_end\n" \
+        #_name "_end:\n");
+
+DEFINE_ASM(br_r14, "br %r14");
+DEFINE_ASM(brasl_r0, "brasl %r0,.-0x100000000");
+DEFINE_ASM(brcl_0xf, "brcl 0xf,.-0x100000000");
+
+struct test {
+    const char *code;
+    const char *code_end;
+};
+
+static const struct test tests[] = {
+    {
+        .code = brasl_r0,
+        .code_end = brasl_r0_end,
+    },
+    {
+        .code = brcl_0xf,
+        .code_end = brcl_0xf_end,
+    },
+};
+
+int main(void)
+{
+    unsigned char *buf;
+    size_t length = 0;
+    size_t i;
+
+    for (i = 0; i < sizeof(tests) / sizeof(tests[0]); i++) {
+        size_t test_length = 0x100000000 + (tests[i].code_end - tests[i].code);
+
+        if (test_length > length) {
+            length = test_length;
+        }
+    }
+
+    buf = mmap(NULL, length, PROT_READ | PROT_WRITE | PROT_EXEC,
+               MAP_PRIVATE | MAP_ANONYMOUS | MAP_NORESERVE, -1, 0);
+    if (buf == MAP_FAILED) {
+        perror("SKIP: mmap() failed");
+        return 0;
+    }
+
+    memcpy(buf, br_r14, br_r14_end - br_r14);
+    for (i = 0; i < sizeof(tests) / sizeof(tests[0]); i++) {
+        void (*code)(void) = (void *)(buf + 0x100000000);
+
+        memcpy(code, tests[i].code, tests[i].code_end - tests[i].code);
+        code();
+        memset(code, 0, tests[i].code_end - tests[i].code);
+    }
+
+    munmap(buf, length);
+
+    return 0;
+}