File 0085-dump-simplify-write_start_flat_head.patch of Package qemu.313

From 8e8178214a0973705d8d97f8959a4e2b6288b862 Mon Sep 17 00:00:00 2001
From: Laszlo Ersek <lersek@redhat.com>
Date: Tue, 20 May 2014 13:39:42 +0200
Subject: [PATCH] dump: simplify write_start_flat_header()

Currently, the function
- defines and populates an auto variable of type MakedumpfileHeader
- allocates and zeroes a buffer of size MAX_SIZE_MDF_HEADER (4096)
- copies the former into the latter (covering an initial portion of the
  latter)

Fill in the MakedumpfileHeader structure in its final place (the alignment
is OK because the structure lives at the address returned by g_malloc0()).

Approximately-suggested-by: Luiz Capitulino <lcapitulino@redhat.com>
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
---
 dump.c | 20 +++++++++-----------
 1 file changed, 9 insertions(+), 11 deletions(-)

diff --git a/dump.c b/dump.c
index ac4505e..6dec8d2 100644
--- a/dump.c
+++ b/dump.c
@@ -711,27 +711,25 @@ static int create_vmcore(DumpState *s)
 
 static int write_start_flat_header(int fd)
 {
-    uint8_t *buf;
-    MakedumpfileHeader mh;
+    MakedumpfileHeader *mh;
     int ret = 0;
 
-    memset(&mh, 0, sizeof(mh));
-    memcpy(mh.signature, MAKEDUMPFILE_SIGNATURE,
-           MIN(sizeof mh.signature, sizeof MAKEDUMPFILE_SIGNATURE));
+    QEMU_BUILD_BUG_ON(sizeof *mh > MAX_SIZE_MDF_HEADER);
+    mh = g_malloc0(MAX_SIZE_MDF_HEADER);
 
-    mh.type = cpu_to_be64(TYPE_FLAT_HEADER);
-    mh.version = cpu_to_be64(VERSION_FLAT_HEADER);
+    memcpy(mh->signature, MAKEDUMPFILE_SIGNATURE,
+           MIN(sizeof mh->signature, sizeof MAKEDUMPFILE_SIGNATURE));
 
-    buf = g_malloc0(MAX_SIZE_MDF_HEADER);
-    memcpy(buf, &mh, sizeof(mh));
+    mh->type = cpu_to_be64(TYPE_FLAT_HEADER);
+    mh->version = cpu_to_be64(VERSION_FLAT_HEADER);
 
     size_t written_size;
-    written_size = qemu_write_full(fd, buf, MAX_SIZE_MDF_HEADER);
+    written_size = qemu_write_full(fd, mh, MAX_SIZE_MDF_HEADER);
     if (written_size != MAX_SIZE_MDF_HEADER) {
         ret = -1;
     }
 
-    g_free(buf);
+    g_free(mh);
     return ret;
 }