tests/tcg: Add the PROT_NONE gdbstub test

Make sure that qemu gdbstub, like gdbserver, allows reading from and
writing to PROT_NONE pages.

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Message-Id: <20240129093410.3151-4-iii@linux.ibm.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

1 files changed, 40 insertions, 0 deletions

diff --git a/tests/tcg/multiarch/prot-none.c b/tests/tcg/multiarch/prot-none.c
new file mode 100644
index 0000000000..dc56aadb3c
--- /dev/null
+++ b/tests/tcg/multiarch/prot-none.c
@@ -0,0 +1,40 @@
+/*
+ * Test that GDB can access PROT_NONE pages.
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+#include <assert.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/mman.h>
+#include <unistd.h>
+
+void break_here(void *q)
+{
+}
+
+int main(void)
+{
+    long pagesize = sysconf(_SC_PAGESIZE);
+    void *p, *q;
+    int err;
+
+    p = mmap(NULL, pagesize * 2, PROT_READ | PROT_WRITE,
+             MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+    assert(p != MAP_FAILED);
+    q = p + pagesize - 1;
+    strcpy(q, "42");
+
+    err = mprotect(p, pagesize * 2, PROT_NONE);
+    assert(err == 0);
+
+    break_here(q);
+
+    err = mprotect(p, pagesize * 2, PROT_READ);
+    assert(err == 0);
+    if (getenv("PROT_NONE_PY")) {
+        assert(strcmp(q, "24") == 0);
+    }
+
+    return EXIT_SUCCESS;
+}