[syslinux] syslinux (pxelinux.0) debug prints

[Gene Cumm]

On Thu, Jun 5, 2014 at 8:50 AM, Wissam Shoukair <wissams at mellanox.com> wrote:
> Hi Gene,
>
> More information about this…
>
> I have found in the syslinux git that this commit id is the last good
> commit:
>
> commit 41c29c26d70fde563d7c255872bbadad87a39dfa (tag:
> refs/tags/syslinux-5.02-pre3)
> Author: Matt Fleming <matt.fleming at intel.com>
> Date:   Fri Feb 22 15:13:38 2013 +0000
>
>     com32: Add com32_cmdline() which returns argv[1..argc-1]
>
>     cmd.c32 needs an equivalent of __com32.cs_cmdline now that the COMBOOT
>     code is dead. Introducing com32_cmdline(), which returns a string
>     consisting of module arguments from argv[1] to argv[argc-1], separated
>     by spaces.
>
>
>     Reported-by: Gene Cumm <gene.cumm at gmail.com>
>     Signed-off-by: Matt Fleming matt.fleming at intel.com
>
>
> This is the commit which the problem started to happen:
>
> commit 76da2ae050d72a31fd47c2fb53f7081781de62ff
>
> Merge: 41c29c2 7931230
> Author: Matt Fleming <matt.fleming at intel.com>
> Date:   Mon Feb 25 15:25:16 2013 +0000
>
>     Merge branch 'lwip' into elflink
>
>     Welcome to Syslinux 5.10.

So your observed issue is present post-lwIP merge.  Are you using
pxelinux.0 or lpxelinux.0 (the distinction is crucial)?

On Sun, Jun 8, 2014 at 9:12 AM, Wissam Shoukair <wissams at mellanox.com> wrote:
> Hi Gene,
>
> First of I want to thank you for replying…

> Regarding the dprintf(), how I can use it? I need to print strings before
> ldlinux.c32 is loaded. (do I need to compile the pxelinux.0 with specific
> flag?)

Depends, read further.

> For example If I want to print something in gpxe_init() which is at the
> start of the pxelinux.0 execution, how I can do that?

Can you use a serial port?  If you can't, this would mean you need to
avoid printf()/dprintf() for your debugging and you're looking at a
far simpler function, writestr() or attempting to restructure what's
in pxelinux.0 (a task that's likely non-trivial).

I'll try to test current head iPXE ISO with 6.03-pre12 tonight.

-- 
-Gene

A: Because it messes up the order in which people normally read text,
especially the archives of mailing lists.
Q: Why is Top-posting such a bad thing?

"No one ever says, 'I can't read that ASCII(plain text) e-mail you sent me.'"


> From: Gene Cumm [mailto:gene.cumm at gmail.com]
> Sent: יום ה 29 מאי 2014 13:28
> To: Wissam Shoukair; For discussion of Syslinux and tftp-hpa
> Subject: Re: syslinux (pxelinux.0) debug prints
>
>
>
> On May 29, 2014 5:25 AM, "Wissam Shoukair" <wissams at mellanox.com> wrote:
>>
>> Hi Gene,
>>
>> I was wondering how I can set the “printf” output to be visible on the
>> screen? (I’m using syslinux-6.03-pre02)
>
> printf () or dprintf ()? You need to watch what functions are available at
> the time you want to print.  For example, printf isn't available until
> ldlinux.c32 is loaded.
>
> Why not 6.03-pre12?
>
> --Gene