[PATCH 21/29] tools/libxl: Allow adding larger amounts of prefixdata to datacopier

[Andrew Cooper <andrew.cooper3@citrix.com>]

From: Ross Lagerwall <ross.lagerwall@citrix.com>

Previously, adding more than 1000 bytes of data would cause a segfault.
Now, the maximum amount of data that can be added is limited by maxsz.

Signed-off-by: Ross Lagerwall <ross.lagerwall@citrix.com>
---
 tools/libxl/libxl_aoutils.c |   14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/tools/libxl/libxl_aoutils.c b/tools/libxl/libxl_aoutils.c
index 3e0c0ae..caba637 100644
--- a/tools/libxl/libxl_aoutils.c
+++ b/tools/libxl/libxl_aoutils.c
@@ -160,6 +160,8 @@ void libxl__datacopier_prefixdata(libxl__egc *egc, libxl__datacopier_state *dc,
 {
     EGC_GC;
     libxl__datacopier_buf *buf;
+    const uint8_t *ptr;
+
     /*
      * It is safe for this to be called immediately after _start, as
      * is documented in the public comment.  _start's caller must have
@@ -170,12 +172,14 @@ void libxl__datacopier_prefixdata(libxl__egc *egc, libxl__datacopier_state *dc,
 
     assert(len < dc->maxsz - dc->used);
 
-    buf = libxl__zalloc(NOGC, sizeof(*buf));
-    buf->used = len;
-    memcpy(buf->buf, data, len);
+    for (ptr = data; len; len -= buf->used, ptr += buf->used) {
+        buf = libxl__zalloc(NOGC, sizeof(*buf));
+        buf->used = len < sizeof(buf->buf) ? len : sizeof(buf->buf);
+        memcpy(buf->buf, ptr, buf->used);
 
-    dc->used += len;
-    LIBXL_TAILQ_INSERT_TAIL(&dc->bufs, buf, entry);
+        dc->used += buf->used;
+        LIBXL_TAILQ_INSERT_TAIL(&dc->bufs, buf, entry);
+    }
 }
 
 static int datacopier_pollhup_handled(libxl__egc *egc,
-- 
1.7.10.4