Syslinux - Aug 2013 - [PATCH 1/1] core: Check if ldlinux.sys exceeds the limit at its building time.

Calc the size of ldlinux.sys from ldlinux.bin, and check if it exceeds the
limit.
ldlinux.sys must fit between the bootsector and two copies of ADV whose size may
vary.
Thus, the size of ldlinux.sys (limit) can be at most: 65536 - 2 * ADV_SIZE -
512.

Certain file systems (such as BTRFS and UFS2) will rely on ldlinux.sys being
installed on the 0-64k range,
thus it can't exceed the limit, otherwise the superblock would be corrupted.

Signed-off-by: Raphael S.Carvalho <raphael.scarv at gmail.com>
---
 core/Makefile         |    1 +
 core/ldlinux_limit.pl |   39 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 40 insertions(+), 0 deletions(-)
 create mode 100755 core/ldlinux_limit.pl

diff --git a/core/Makefile b/core/Makefile
index f795a5c..e0daafc 100644
--- a/core/Makefile
+++ b/core/Makefile
@@ -220,6 +220,7 @@ ldlinux.bss: ldlinux.bin
 	dd if=$< of=$@ bs=512 count=1
 
 ldlinux.sys: ldlinux.bin
+	$(PERL) $(SRC)/ldlinux_limit.pl $< \
 	dd if=$< of=$@ bs=512 skip=2
 
 codepage.cp: $(OBJ)/../codepage/$(CODEPAGE).cp
diff --git a/core/ldlinux_limit.pl b/core/ldlinux_limit.pl
new file mode 100755
index 0000000..923d516
--- /dev/null
+++ b/core/ldlinux_limit.pl
@@ -0,0 +1,39 @@
+#!/usr/bin/perl
+## -----------------------------------------------------------------------
+##
+##   Copyright 2013 Raphael S. Carvalho <raphael.scarv at gmail.com>
+##
+##   This program is free software; you can redistribute it and/or modify
+##   it under the terms of the GNU General Public License as published by
+##   the Free Software Foundation, Inc., 53 Temple Place Ste 330,
+##   Boston MA 02111-1307, USA; either version 2 of the License, or
+##   (at your option) any later version; incorporated herein by reference.
+##
+## -----------------------------------------------------------------------
+
+## ldlinux_limit.pl: Calc the size of ldlinux.sys and check if it exceeds the
limit.
+## ldlinux.sys must fit between the bootsector and two copies of ADV whose size
may vary.
+##
+## Certain file systems will simply install ldlinux.sys as an ordinary file,
but UFS2 and
+## BTRFS for example, rely on ldlinux.sys being installed on the 0-64k range.
+##
+## 0-64k range:
+## [0](bootsector)[512](ldlinux.sys)[65536 - 2 * ADV_SIZE](2 copies of
ADV)[65536]
+
+use File::stat;
+
+($ldlinux_bin) = @ARGV;
+$adv_size = 512;
+$limit = 65536 - 2 * $adv_size - 512;
+$pad = 512;
+
+$ldlinux_size = stat($ldlinux_bin)->size - 1024;
+$align = $ldlinux_size % $pad;
+$ldlinux_size += $pad - $align;
+
+if ($ldlinux_size > $limit) {
+	print STDERR "$0: ldlinux.sys ($ldlinux_size) larger than limit
($limit).\n";
+	exit 1;
+}
+
+exit 0;
-- 
1.7.2.5

Peter, does this look OK to you?

Raphael, I can't work out why ADV_SIZE is a constant in this file?

On Sat, 31 Aug, at 05:01:20PM, Raphael S.Carvalho wrote:
> Calc the size of ldlinux.sys from ldlinux.bin, and check if it exceeds the
limit.
> ldlinux.sys must fit between the bootsector and two copies of ADV whose
size may vary.
> Thus, the size of ldlinux.sys (limit) can be at most: 65536 - 2 * ADV_SIZE
- 512.
> 
> Certain file systems (such as BTRFS and UFS2) will rely on ldlinux.sys
being installed on the 0-64k range,
> thus it can't exceed the limit, otherwise the superblock would be
corrupted.
> 
> Signed-off-by: Raphael S.Carvalho <raphael.scarv at gmail.com>
> ---
>  core/Makefile         |    1 +
>  core/ldlinux_limit.pl |   39 +++++++++++++++++++++++++++++++++++++++
>  2 files changed, 40 insertions(+), 0 deletions(-)
>  create mode 100755 core/ldlinux_limit.pl
> 
> diff --git a/core/Makefile b/core/Makefile
> index f795a5c..e0daafc 100644
> --- a/core/Makefile
> +++ b/core/Makefile
> @@ -220,6 +220,7 @@ ldlinux.bss: ldlinux.bin
>  	dd if=$< of=$@ bs=512 count=1
>  
>  ldlinux.sys: ldlinux.bin
> +	$(PERL) $(SRC)/ldlinux_limit.pl $< \
>  	dd if=$< of=$@ bs=512 skip=2
>  
>  codepage.cp: $(OBJ)/../codepage/$(CODEPAGE).cp
> diff --git a/core/ldlinux_limit.pl b/core/ldlinux_limit.pl
> new file mode 100755
> index 0000000..923d516
> --- /dev/null
> +++ b/core/ldlinux_limit.pl
> @@ -0,0 +1,39 @@
> +#!/usr/bin/perl
> +## -----------------------------------------------------------------------
> +##
> +##   Copyright 2013 Raphael S. Carvalho <raphael.scarv at gmail.com>
> +##
> +##   This program is free software; you can redistribute it and/or modify
> +##   it under the terms of the GNU General Public License as published by
> +##   the Free Software Foundation, Inc., 53 Temple Place Ste 330,
> +##   Boston MA 02111-1307, USA; either version 2 of the License, or
> +##   (at your option) any later version; incorporated herein by reference.
> +##
> +## -----------------------------------------------------------------------
> +
> +## ldlinux_limit.pl: Calc the size of ldlinux.sys and check if it exceeds
the limit.
> +## ldlinux.sys must fit between the bootsector and two copies of ADV whose
size may vary.
> +##
> +## Certain file systems will simply install ldlinux.sys as an ordinary
file, but UFS2 and
> +## BTRFS for example, rely on ldlinux.sys being installed on the 0-64k
range.
> +##
> +## 0-64k range:
> +## [0](bootsector)[512](ldlinux.sys)[65536 - 2 * ADV_SIZE](2 copies of
ADV)[65536]
> +
> +use File::stat;
> +
> +($ldlinux_bin) = @ARGV;
> +$adv_size = 512;
> +$limit = 65536 - 2 * $adv_size - 512;
> +$pad = 512;
> +
> +$ldlinux_size = stat($ldlinux_bin)->size - 1024;
> +$align = $ldlinux_size % $pad;
> +$ldlinux_size += $pad - $align;
> +
> +if ($ldlinux_size > $limit) {
> +	print STDERR "$0: ldlinux.sys ($ldlinux_size) larger than limit
($limit).\n";
> +	exit 1;
> +}
> +
> +exit 0;
> -- 
> 1.7.2.5
> 
-- 
Matt Fleming, Intel Open Source Technology Center

On Mon, Sep 16, 2013 at 11:08 AM, Matt Fleming <matt at console-pimps.org>
wrote:
> Peter, does this look OK to you?
>
> Raphael, I can't work out why ADV_SIZE is a constant in this file?
Matt, ADV_SIZE is currently a constant value, but it may change in the future.
So it would need some care.

Regards,
Raphael S. Carvalho

While going throug old posts found:

Op 2013-08-31 om 17:01 schreef Raphael S.Carvalho:
> Calc the size of ldlinux.sys from ldlinux.bin, and check if it exceeds the
limit.
> ldlinux.sys must fit between the bootsector and two copies of ADV whose
size may vary.
> Thus, the size of ldlinux.sys (limit) can be at most: 65536 - 2 * ADV_SIZE
- 512.
> 
> Certain file systems (such as BTRFS and UFS2) will rely on ldlinux.sys
being installed on the 0-64k range,
> thus it can't exceed the limit, otherwise the superblock would be
corrupted.
> 
> Signed-off-by: Raphael S.Carvalho <raphael.scarv at gmail.com>
> ---
>  core/Makefile         |    1 +
>  core/ldlinux_limit.pl |   39 +++++++++++++++++++++++++++++++++++++++
>  2 files changed, 40 insertions(+), 0 deletions(-)
>  create mode 100755 core/ldlinux_limit.pl
> 
> diff --git a/core/Makefile b/core/Makefile
> index f795a5c..e0daafc 100644
> --- a/core/Makefile
> +++ b/core/Makefile
> @@ -220,6 +220,7 @@ ldlinux.bss: ldlinux.bin
>  	dd if=$< of=$@ bs=512 count=1
>  
>  ldlinux.sys: ldlinux.bin
> +	$(PERL) $(SRC)/ldlinux_limit.pl $< \
>  	dd if=$< of=$@ bs=512 skip=2
>  
>  codepage.cp: $(OBJ)/../codepage/$(CODEPAGE).cp
> diff --git a/core/ldlinux_limit.pl b/core/ldlinux_limit.pl
> new file mode 100755
> index 0000000..923d516
> --- /dev/null
> +++ b/core/ldlinux_limit.pl
> @@ -0,0 +1,39 @@
> +#!/usr/bin/perl
> +## -----------------------------------------------------------------------
> +##
> +##   Copyright 2013 Raphael S. Carvalho <raphael.scarv at gmail.com>
> +##
> +##   This program is free software; you can redistribute it and/or modify
> +##   it under the terms of the GNU General Public License as published by
> +##   the Free Software Foundation, Inc., 53 Temple Place Ste 330,
> +##   Boston MA 02111-1307, USA; either version 2 of the License, or
> +##   (at your option) any later version; incorporated herein by reference.
> +##
> +## -----------------------------------------------------------------------
> +
> +## ldlinux_limit.pl: Calc the size of ldlinux.sys and check if it exceeds
the limit.
> +## ldlinux.sys must fit between the bootsector and two copies of ADV whose
size may vary.
> +##
> +## Certain file systems will simply install ldlinux.sys as an ordinary
file, but UFS2 and
> +## BTRFS for example, rely on ldlinux.sys being installed on the 0-64k
range.
> +##
> +## 0-64k range:
> +## [0](bootsector)[512](ldlinux.sys)[65536 - 2 * ADV_SIZE](2 copies of
ADV)[65536]
> +
> +use File::stat;
> +
> +($ldlinux_bin) = @ARGV;
> +$adv_size = 512;
> +$limit = 65536 - 2 * $adv_size - 512;
> +$pad = 512;
> +
> +$ldlinux_size = stat($ldlinux_bin)->size - 1024;
> +$align = $ldlinux_size % $pad;
> +$ldlinux_size += $pad - $align;
> +
> +if ($ldlinux_size > $limit) {
> +	print STDERR "$0: ldlinux.sys ($ldlinux_size) larger than limit
($limit).\n";
> +	exit 1;
> +}
> +
> +exit 0;
> -- 
> 1.7.2.5
> 
Among the follow-up messsages was

| op 2013-09-16 om 17:23 schreef Matt Fleming:
| > On Mon, 16 Sep, at 09:49:01AM, H. Peter Anvin wrote:
| > > We probably will need to increase out to 4K because of newer drives.
| >
| > Raphael, is there any way we could extract the ADV_SIZE value from
| > libinstaller/setadv.h and pass it to ldlinux_limit.pl? That would allow
| > things to keep working in future when we do upgrade to 4K.
| >


IMNSHO is including core/ldlinux_limit.pl better
than waiting for a better core/ldlinux_limit.pl



Groeten
Geert Stappers
-- 
Leven en laten leven

On May 25, 2014 3:39 AM, "Geert Stappers" <stappers at
stappers.nl> wrote:
>
>
> While going throug old posts found:
>
> Op 2013-08-31 om 17:01 schreef Raphael S.Carvalho:
> > Calc the size of ldlinux.sys from ldlinux.bin, and check if it exceeds
the limit.
> > ldlinux.sys must fit between the bootsector and two copies of ADV
whose
size may vary.
> > Thus, the size of ldlinux.sys (limit) can be at most: 65536 - 2 *
ADV_SIZE - 512.
> >
> > Certain file systems (such as BTRFS and UFS2) will rely on ldlinux.sys
being installed on the 0-64k range,
> > thus it can't exceed the limit, otherwise the superblock would be
corrupted.

Raphael/Paulo: does UFS2 have a hard 64kiB limit?  I know it's not
installed to the first sector where the first superblock is located.
> IMNSHO is including core/ldlinux_limit.pl better
> than waiting for a better core/ldlinux_limit.pl
This should be rendered obsolete and unnecessary with the recent patch for
ldlinux.sys on btrfs (but might be relevant for UFS2).

--Gene