From b170e55f6dff27d44e32667af0f79a4c2704711b Mon Sep 17 00:00:00 2001
From: Laszlo Ersek <lersek@redhat.com>
Date: Fri, 7 Nov 2014 17:18:08 +0100
Subject: [PATCH 21/41] dump: simplify write_start_flat_header()

Message-id: <1415380693-16593-22-git-send-email-lersek@redhat.com>
Patchwork-id: 62207
O-Subject: [RHEL-7.1 qemu-kvm PATCH 21/26] dump: simplify write_start_flat_header()
Bugzilla: 1157798
RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
RH-Acked-by: Luiz Capitulino <lcapitulino@redhat.com>
RH-Acked-by: dgibson <dgibson@redhat.com>

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>
(cherry picked from commit 92ba1401e0f81ea170803045c1ae366bf5d9d87e)
Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
 dump.c | 20 +++++++++-----------
 1 file changed, 9 insertions(+), 11 deletions(-)

diff --git a/dump.c b/dump.c
index 533b914..ee28777 100644
--- a/dump.c
+++ b/dump.c
@@ -717,27 +717,25 @@ 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;
 }
 
-- 
1.8.3.1