commit e1f2641b5926d20f63d36f0de45206be774da8da
author Luiz Capitulino <lcapitulino@redhat.com> Mon Mar 25 13:52:26 2013 -0400
committer Luiz Capitulino <lcapitulino@redhat.com> Fri Apr 05 08:42:29 2013 -0400
tree a8d77c01cc146a6627c4ca50e2c44d7f6e93da45
parent 54d49ac99227aff646ac940abfab3417f5cb1693

Monitor: Make output buffer dynamic

Commit f628926bb423fa8a7e0b114511400ea9df38b76a changed monitor_flush()
to retry on qemu_chr_fe_write() errors. However, the Monitor's output
buffer can keep growing while the retry is not issued and this can
cause the buffer to overflow.

To reproduce this issue, just start qemu and type on the Monitor:

(qemu) ?

This will cause an assertion to trig.

To fix this problem this commit makes the Monitor buffer dynamic,
which means that it can grow as much as needed.

Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>

monitor.c

diff --git a/monitor.c b/monitor.c
index 4ec1db9..8712c53 100644
--- a/monitor.c
+++ b/monitor.c
@@ -188,8 +188,7 @@
     int reset_seen;
     int flags;
     int suspend_cnt;
-    uint8_t outbuf[1024];
-    int outbuf_index;
+    QString *outbuf;
     ReadLineState *rs;
     MonitorControl *mc;
     CPUArchState *mon_cpu;
@@ -271,45 +270,52 @@
 void monitor_flush(Monitor *mon)
 {
     int rc;
+    size_t len;
+    const char *buf;
 
-    if (mon && mon->outbuf_index != 0 && !mon->mux_out) {
-        rc = qemu_chr_fe_write(mon->chr, mon->outbuf, mon->outbuf_index);
-        if (rc == mon->outbuf_index) {
+    buf = qstring_get_str(mon->outbuf);
+    len = qstring_get_length(mon->outbuf);
+
+    if (mon && len && !mon->mux_out) {
+        rc = qemu_chr_fe_write(mon->chr, (const uint8_t *) buf, len);
+        if (rc == len) {
             /* all flushed */
-            mon->outbuf_index = 0;
+            QDECREF(mon->outbuf);
+            mon->outbuf = qstring_new();
             return;
         }
         if (rc > 0) {
             /* partinal write */
-            memmove(mon->outbuf, mon->outbuf + rc, mon->outbuf_index - rc);
-            mon->outbuf_index -= rc;
+            QString *tmp = qstring_from_str(buf + rc);
+            QDECREF(mon->outbuf);
+            mon->outbuf = tmp;
         }
         qemu_chr_fe_add_watch(mon->chr, G_IO_OUT, monitor_unblocked, mon);
     }
 }
 
-/* flush at every end of line or if the buffer is full */
+/* flush at every end of line */
 static void monitor_puts(Monitor *mon, const char *str)
 {
     char c;
 
     for(;;) {
-        assert(mon->outbuf_index < sizeof(mon->outbuf) - 1);
         c = *str++;
         if (c == '\0')
             break;
-        if (c == '\n')
-            mon->outbuf[mon->outbuf_index++] = '\r';
-        mon->outbuf[mon->outbuf_index++] = c;
-        if (mon->outbuf_index >= (sizeof(mon->outbuf) - 1)
-            || c == '\n')
+        if (c == '\n') {
+            qstring_append_chr(mon->outbuf, '\r');
+        }
+        qstring_append_chr(mon->outbuf, c);
+        if (c == '\n') {
             monitor_flush(mon);
+        }
     }
 }
 
 void monitor_vprintf(Monitor *mon, const char *fmt, va_list ap)
 {
-    char buf[4096];
+    char *buf;
 
     if (!mon)
         return;
@@ -318,8 +324,9 @@
         return;
     }
 
-    vsnprintf(buf, sizeof(buf), fmt, ap);
+    buf = g_strdup_vprintf(fmt, ap);
     monitor_puts(mon, buf);
+    g_free(buf);
 }
 
 void monitor_printf(Monitor *mon, const char *fmt, ...)
@@ -671,6 +678,8 @@
     CharDriverState mchar;
 
     memset(&hmp, 0, sizeof(hmp));
+    hmp.outbuf = qstring_new();
+
     qemu_chr_init_mem(&mchar);
     hmp.chr = &mchar;
 
@@ -699,6 +708,7 @@
     }
 
 out:
+    QDECREF(hmp.outbuf);
     qemu_chr_close_mem(hmp.chr);
     return output;
 }
@@ -4749,6 +4759,7 @@
     }
 
     mon = g_malloc0(sizeof(*mon));
+    mon->outbuf = qstring_new();
 
     mon->chr = chr;
     mon->flags = flags;