From 0be30e54e957587b6672dbe27056611786c86526 Mon Sep 17 00:00:00 2001
From: Roger Pau Monne <roger.pau@citrix.com>
Date: Fri, 26 Sep 2014 17:31:35 +0200
Subject: [PATCH] pygrub: fix read sizes on FreeBSD
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FreeBSD only allows reading multiples of sector size from raw disk devices
(character devices). This fix should only alter the behaviour of pygrub on
FreeBSD, the other supported OSes will continue using the same size.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Cc: Ian Jackson <ian.jackson@eu.citrix.com>
Cc: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Cc: Ian Campbell <ian.campbell@citrix.com>
Cc: Wei Liu <wei.liu2@citrix.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>
---
 tools/pygrub/src/pygrub | 17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/tools/pygrub/src/pygrub b/tools/pygrub/src/pygrub
index e73a17487f..1ae34a26a7 100644
--- a/tools/pygrub/src/pygrub
+++ b/tools/pygrub/src/pygrub
@@ -13,7 +13,7 @@
 # Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 #
 
-import os, sys, string, struct, tempfile, re, traceback
+import os, sys, string, struct, tempfile, re, traceback, stat
 import copy
 import logging
 import platform
@@ -29,6 +29,16 @@ import grub.ExtLinuxConf
 
 PYGRUB_VER = 0.6
 FS_READ_MAX = 1024 * 1024
+SECTOR_SIZE = 512
+
+def read_size_roundup(fd, size):
+    if platform.system() != 'FreeBSD':
+        return size
+    st = os.fstat(fd)
+    if (not stat.S_ISCHR(st.st_mode)):
+        return size
+    # Round up to sector size if it's a raw character device
+    return (((size)+((SECTOR_SIZE)-1))&(~((SECTOR_SIZE)-1)))
 
 def enable_cursor(ison):
     if ison:
@@ -45,7 +55,7 @@ DISK_TYPE_RAW, DISK_TYPE_HYBRIDISO, DISK_TYPE_DOS = range(3)
 def identify_disk_image(file):
     """Detect DOS partition table or HybridISO format."""
     fd = os.open(file, os.O_RDONLY)
-    buf = os.read(fd, 0x8006)
+    buf = os.read(fd, read_size_roundup(fd, 0x8006))
     os.close(fd)
 
     if len(buf) >= 512 and \
@@ -56,7 +66,6 @@ def identify_disk_image(file):
         return DISK_TYPE_DOS
     return DISK_TYPE_RAW
 
-SECTOR_SIZE=512
 DK_LABEL_LOC=1
 DKL_MAGIC=0xdabe
 V_ROOT=0x2
@@ -91,7 +100,7 @@ def get_fs_offset_gpt(file):
     i = partcount
     offsets = []
     while i>0:
-        buf = os.read(fd, partsize)
+        buf = os.read(fd, read_size_roundup(fd, partsize))
         offsets.append(struct.unpack("<Q", buf[32:40])[0] * SECTOR_SIZE)
         i -= 1
     os.close(fd)
-- 
2.30.2