libqtest: handle zero length memwrite/memread

Some recently added tests pass a zero length to qtest_memwrite().
Unfortunately, the qtest protocol doesn't implement an on-the-wire
syntax for zero-length writes and the current code happily sends
garbage to QEMU. This causes intermittent failures.

It isn't worth the pain to enhance the protocol, so this patch
simply fixes the issue by "just return, doing nothing". The same
fix is applied to qtest_memread() since the issue also exists in
the QEMU part of the "memread" command.

Suggested-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>
Message-id: 148412457273.22750.983275587432075569.stgit@bahia
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

diff --git a/qtest.c b/qtest.c
index 46b99aed5291c827bde5ea3857d7d3cfb7cd55e4..bd9d4178129be85b02d0824273de2032ad6e6c9c 100644 (file)
--- a/qtest.c
+++ b/qtest.c
@@ -430,6 +430,8 @@ static void qtest_process_command(CharBackend *chr, gchar **words)
         g_assert(words[1] && words[2]);
         g_assert(qemu_strtoull(words[1], NULL, 0, &addr) == 0);
         g_assert(qemu_strtoull(words[2], NULL, 0, &len) == 0);
+        /* We'd send garbage to libqtest if len is 0 */
+        g_assert(len);
 
         data = g_malloc(len);
         cpu_physical_memory_read(addr, data, len);

diff --git a/tests/libqtest.c b/tests/libqtest.c
index 6f6975248fae1e33e1076f93933a12e8766e2dc2..d8fba6647a1777f8d037c80a92dc9d7269aa281c 100644 (file)
--- a/tests/libqtest.c
+++ b/tests/libqtest.c
@@ -768,6 +768,10 @@ void qtest_memread(QTestState *s, uint64_t addr, void *data, size_t size)
     gchar **args;
     size_t i;
 
+    if (!size) {
+        return;
+    }
+
     qtest_sendf(s, "read 0x%" PRIx64 " 0x%zx\n", addr, size);
     args = qtest_rsp(s, 2);
 
@@ -858,7 +862,13 @@ void qtest_memwrite(QTestState *s, uint64_t addr, const void *data, size_t size)
 {
     const uint8_t *ptr = data;
     size_t i;
-    char *enc = g_malloc(2 * size + 1);
+    char *enc;
+
+    if (!size) {
+        return;
+    }
+
+    enc = g_malloc(2 * size + 1);
 
     for (i = 0; i < size; i++) {
         sprintf(&enc[i * 2], "%02x", ptr[i]);