tests/tcg/multiarch: Add sigbus.c

A mostly generic test for unaligned access raising SIGBUS.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

tests/tcg/multiarch/sigbus.c

@@ -0,0 +1,68 @@
+#define _GNU_SOURCE 1
+
+#include <assert.h>
+#include <stdlib.h>
+#include <signal.h>
+#include <endian.h>
+
+
+unsigned long long x = 0x8877665544332211ull;
+void * volatile p = (void *)&x + 1;
+
+void sigbus(int sig, siginfo_t *info, void *uc)
+{
+    assert(sig == SIGBUS);
+    assert(info->si_signo == SIGBUS);
+#ifdef BUS_ADRALN
+    assert(info->si_code == BUS_ADRALN);
+#endif
+    assert(info->si_addr == p);
+    exit(EXIT_SUCCESS);
+}
+
+int main()
+{
+    struct sigaction sa = {
+        .sa_sigaction = sigbus,
+        .sa_flags = SA_SIGINFO
+    };
+    int allow_fail = 0;
+    int tmp;
+
+    tmp = sigaction(SIGBUS, &sa, NULL);
+    assert(tmp == 0);
+
+    /*
+     * Select an operation that's likely to enforce alignment.
+     * On many guests that support unaligned accesses by default,
+     * this is often an atomic operation.
+     */
+#if defined(__aarch64__)
+    asm volatile("ldxr %w0,[%1]" : "=r"(tmp) : "r"(p) : "memory");
+#elif defined(__alpha__)
+    asm volatile("ldl_l %0,0(%1)" : "=r"(tmp) : "r"(p) : "memory");
+#elif defined(__arm__)
+    asm volatile("ldrex %0,[%1]" : "=r"(tmp) : "r"(p) : "memory");
+#elif defined(__powerpc__)
+    asm volatile("lwarx %0,0,%1" : "=r"(tmp) : "r"(p) : "memory");
+#elif defined(__riscv_atomic)
+    asm volatile("lr.w %0,(%1)" : "=r"(tmp) : "r"(p) : "memory");
+#else
+    /* No insn known to fault unaligned -- try for a straight load. */
+    allow_fail = 1;
+    tmp = *(volatile int *)p;
+#endif
+
+    assert(allow_fail);
+
+    /*
+     * We didn't see a signal.
+     * We might as well validate the unaligned load worked.
+     */
+    if (BYTE_ORDER == LITTLE_ENDIAN) {
+        assert(tmp == 0x55443322);
+    } else {
+        assert(tmp == 0x77665544);
+    }
+    return EXIT_SUCCESS;
+}