checksumiso: pad isolinux.bin to a sector boundary

Always pad isolinux.bin to a full CD-ROM sector boundary.  This avoids
a lot of potential special cases.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>

1 files changed, 18 insertions, 3 deletions

diff --git a/core/checksumiso.pl b/core/checksumiso.pl
index b5527428..9b8c3ee5 100755
--- a/core/checksumiso.pl
+++ b/core/checksumiso.pl
@@ -9,11 +9,25 @@ use integer;
 
 ($file) = @ARGV;
 
-open(FILE, '+<', $file) or die "$0: Cannot open $file: $!\n";
+open(FILE, '+<', $file) or die "$0: cannot open $file: $!\n";
 binmode FILE;
 
+@fstat = stat(FILE) or die "$0: stat $file: $!\n";
+if (!$fstat[7]) {
+    die "$0: $file: cannot query length\n";
+}
+
+# Pad file to a multiple of 2048 bytes
+$frac = $fstat[7] % 2048;
+if ($frac) {
+    seek(FILE,$fstat[7],0)
+	or die "$0: $file: cannot seek to end\n";
+    print FILE "\0" x (2048-$frac);
+}
+
+# Checksum the file post header
 if ( !seek(FILE,64,0) ) {
-    die "$0: Cannot seek past header\n";
+    die "$0: $file: cannot seek past header\n";
 }
 
 $csum  = 0;
@@ -25,8 +39,9 @@ while ( ($n = read(FILE, $dw, 4)) > 0 ) {
     $bytes += $n;
 }
 
+# Update header
 if ( !seek(FILE,16,0) ) {
-    die "$0: Cannot seek to header\n";
+    die "$0: $file: cannot seek to header\n";
 }
 
 print FILE pack("VV", $bytes, $csum);