Syslinux - Mar 2018 - garbage on serial console after pxelinux.0 is loaded

We have some x86_64 systems that have DisplayPort and USB ports for a monitor
& keyboard and when I use these to PXE boot, everything works fine. 
However, these systems will eventually become headless and in the production
process access to the console will be via serial port.  Using the serial port
mostly works in that once we get to the PXE boot: prompt we can type in the name
of the desired stanza from default and the kernel and initramfs specified will
be loaded & executed.  But when the system initially reaches that boot:
prompt, something starts spitting small strings of garbage, say 20-40
characters, in random places on the screen, about once per second or every other
second.  The strings contain bits of text that were previously displayed, e.g.,
I can make out part of Peter Anvin's name sometimes in the garbage,
suggesting it has something to do with the screen refresh.  Entering the name of
the desired stanza works at this point, although it looks like what is being
typed is getting messed up (even if that is just an illusion).  But the
production folks won't put up with this, and they shouldn't have to, so
I have to fix it.

I don't think it's a baud rate mismatch between the terminal software
(minicom) and the system board because all the text about choosing network boot,
broadcasting for a DHCP server, etc. looks just fine (and we see the same
behavior using putty on Windows for the terminal program).  The problem
doesn't appear until the pxelinux.0 module is loaded.  I vaguely recall
seeing a similar problem with pxelinux five or six years ago, but I could be
imagining that.  Any ideas as to what is going on?

BTW, has syslinux gotten so stable that the latest release is really from Oct.
2014?  That's amazing!

Peter

A little more info:
I was mistaken in saying that the garbage on the screen doesn't interfere
with typed commands/stanzas; it does.  If I can type the name of a stanza and
hit enter quickly enough before the garbage is spat to the screen, it seems to
start loading a kernel, but then it aborts.

And the garbage appears to be varying quantities of '[0n', as in
sometimes there will be one instance of that in the string spit out, and
sometimes there will be a dozen, or any quantity in between.  Sometimes it's
all just blank spaces; and sometimes, as mentioned, there are fragments of text
that was previously displayed.

Any ideas as to what [0n is?  Some sort of screen formatting?

Peter

-----Original Message-----
From: Syslinux [mailto:syslinux-bounces at zytor.com] On Behalf Of Scheie, Peter
M via Syslinux
Sent: Monday, March 05, 2018 11:57 AM
To: syslinux at zytor.com
Subject: [syslinux] garbage on serial console after pxelinux.0 is loaded

We have some x86_64 systems that have DisplayPort and USB ports for a monitor
& keyboard and when I use these to PXE boot, everything works fine. 
However, these systems will eventually become headless and in the production
process access to the console will be via serial port.  Using the serial port
mostly works in that once we get to the PXE boot: prompt we can type in the name
of the desired stanza from default and the kernel and initramfs specified will
be loaded & executed.  But when the system initially reaches that boot:
prompt, something starts spitting small strings of garbage, say 20-40
characters, in random places on the screen, about once per second or every other
second.  The strings contain bits of text that were previously displayed, e.g.,
I can make out part of Peter Anvin's name sometimes in the garbage,
suggesting it has something to do with the screen refresh.  Entering the name of
the desired stanza works at this point, although it looks like what is bein!
 g typed is getting messed up (even if that is just an illusion).  But the
production folks won't put up with this, and they shouldn't have to, so
I have to fix it.

I don't think it's a baud rate mismatch between the terminal software
(minicom) and the system board because all the text about choosing network boot,
broadcasting for a DHCP server, etc. looks just fine (and we see the same
behavior using putty on Windows for the terminal program).  The problem
doesn't appear until the pxelinux.0 module is loaded.  I vaguely recall
seeing a similar problem with pxelinux five or six years ago, but I could be
imagining that.  Any ideas as to what is going on?

BTW, has syslinux gotten so stable that the latest release is really from Oct.
2014?  That's amazing!

Peter
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On 03/05/18 12:17, Scheie, Peter M via Syslinux wrote:
> A little more info:
> I was mistaken in saying that the garbage on the screen doesn't
interfere with typed commands/stanzas; it does.  If I can type the name of a
stanza and hit enter quickly enough before the garbage is spat to the screen, it
seems to start loading a kernel, but then it aborts.
> 
> And the garbage appears to be varying quantities of '[0n', as in
sometimes there will be one instance of that in the string spit out, and
sometimes there will be a dozen, or any quantity in between.  Sometimes it's
all just blank spaces; and sometimes, as mentioned, there are fragments of text
that was previously displayed.
> 
> Any ideas as to what [0n is?  Some sort of screen formatting?
> 
Yes, that's an attribute code <ESC>[0m.  Most likely you have BIOS
serial redirection *and* Syslinux serial port enabled at the same time.

	-hpa

-----Original Message-----
From: hpa at zytor.com [mailto:hpa at zytor.com] 
Sent: Wednesday, April 04, 2018 4:26 PM
To: Scheie, Peter M
Subject: RE: [syslinux] garbage on serial console after pxelinux.0 is loaded

On April 4, 2018 2:08:12 PM PDT, "Scheie, Peter M" <Petre.Scheie at
gd-ms.com> wrote:
>-----Original Message-----
>From: Syslinux [mailto:syslinux-bounces at zytor.com] On Behalf Of H.
>Peter Anvin via Syslinux
>Sent: Wednesday, April 04, 2018 1:54 PM
>To: syslinux at zytor.com
>Subject: Re: [syslinux] garbage on serial console after pxelinux.0 is 
>loaded
>
>On 03/05/18 12:17, Scheie, Peter M via Syslinux wrote:
>> A little more info:
>> I was mistaken in saying that the garbage on the screen doesn't
>interfere with typed commands/stanzas; it does.  If I can type the name 
>of a stanza and hit enter quickly enough before the garbage is spat to 
>the screen, it seems to start loading a kernel, but then it aborts.
>> 
>> And the garbage appears to be varying quantities of '[0n', as
in
>sometimes there will be one instance of that in the string spit out, 
>and sometimes there will be a dozen, or any quantity in between.
>Sometimes it's all just blank spaces; and sometimes, as mentioned, 
>there are fragments of text that was previously displayed.
>> 
>> Any ideas as to what [0n is?  Some sort of screen formatting?
>> 
>
>Yes, that's an attribute code <ESC>[0m.  Most likely you have BIOS
>serial redirection *and* Syslinux serial port enabled at the same time.
>
>	-hpa
>
>_______________________________________________
>Syslinux mailing list
>Submissions to Syslinux at zytor.com
>Unsubscribe or set options at:
>http://www.zytor.com/mailman/listinfo/syslinux
>
>Ah, yes, of course.  Disabling it in the 'default' menu file fixed
the
>issue.  Well, sort of.  The real problem is we have a few different 
>hardware platforms.  Some have a built-in DisplayPort, which we don't 
>use, while others do not.  The SERIAL setting in 'default' is for
those
>systems that don't have a DP.  Those systems with DP default to having 
>their console redirected to COM1 (ttyS0) which is what we connect to.
>But as you pointed out, having the serial port setting in both places 
>causes problems.
>
>If we take the SERIAL setting out, those machines w/o DP appear to load
>pxelinux.0 but don't display anything.  However, they still respond to 
>keyboard input, as we have stanzas in 'default' that use
pxechain.com
>to redirect them to other PXE servers.  That suggests that we could 
>have a stanza in 'default' that simply redirects to the same PXE
server
>but to a different menu file, e.g., default.serial.  Is that possible?
>
>Peter
Yes, that works. 
--

I setup a stanza that points to a submenu, i.e., a menu from a separate file,
thusly:

LABEL m
MENU LABEL DisplayPort
KERNEL vesamenu.c32
APPEND dpmenu.cfg

So, when this stanza is selected, is vesamenu.c32 reloaded with new menu
arguments?  dpmenu.cfg is just a copy of 'default' but without the
SERIAL settings.  But when I bootup one of the machines that has DP and try to
choose 'm', I get a "Initial menu has no LABEL entries" error.
The first line in 'default' is

DEFAULT vesamenu.c32

so that's also the first line in dpmenu.cfg; is that a problem?  Is it
necessary, since the 'm' stanza called vesamenu.c32 with dpmenu.cfg as
an APPEND?

Petre

On Thu, Apr 5, 2018 at 10:20 AM, Scheie, Peter M via Syslinux
<syslinux at zytor.com> wrote:
>
>
> -----Original Message-----
> From: hpa at zytor.com [mailto:hpa at zytor.com]
> Sent: Wednesday, April 04, 2018 4:26 PM
> To: Scheie, Peter M
> Subject: RE: [syslinux] garbage on serial console after pxelinux.0 is
loaded
>
> On April 4, 2018 2:08:12 PM PDT, "Scheie, Peter M"
<Petre.Scheie at gd-ms.com> wrote:
>>-----Original Message-----
>>From: Syslinux [mailto:syslinux-bounces at zytor.com] On Behalf Of H.
>>Peter Anvin via Syslinux
>>Sent: Wednesday, April 04, 2018 1:54 PM
>>To: syslinux at zytor.com
>>Subject: Re: [syslinux] garbage on serial console after pxelinux.0 is
>>loaded
>>
>>On 03/05/18 12:17, Scheie, Peter M via Syslinux wrote:
>>> A little more info:
>>> I was mistaken in saying that the garbage on the screen doesn't
>>interfere with typed commands/stanzas; it does.  If I can type the name
>>of a stanza and hit enter quickly enough before the garbage is spat to
>>the screen, it seems to start loading a kernel, but then it aborts.
>>>
>>> And the garbage appears to be varying quantities of '[0n',
as in
>>sometimes there will be one instance of that in the string spit out,
>>and sometimes there will be a dozen, or any quantity in between.
>>Sometimes it's all just blank spaces; and sometimes, as mentioned,
>>there are fragments of text that was previously displayed.
>>>
>>> Any ideas as to what [0n is?  Some sort of screen formatting?
>>>
>>
>>Yes, that's an attribute code <ESC>[0m.  Most likely you have
BIOS
>>serial redirection *and* Syslinux serial port enabled at the same time.
>>
>>       -hpa
>>
>>_______________________________________________
>>Syslinux mailing list
>>Submissions to Syslinux at zytor.com
>>Unsubscribe or set options at:
>>http://www.zytor.com/mailman/listinfo/syslinux
>>
>>Ah, yes, of course.  Disabling it in the 'default' menu file
fixed the
>>issue.  Well, sort of.  The real problem is we have a few different
>>hardware platforms.  Some have a built-in DisplayPort, which we
don't
>>use, while others do not.  The SERIAL setting in 'default' is
for those
>>systems that don't have a DP.  Those systems with DP default to
having
>>their console redirected to COM1 (ttyS0) which is what we connect to.
>>But as you pointed out, having the serial port setting in both places
>>causes problems.
>>
>>If we take the SERIAL setting out, those machines w/o DP appear to load
>>pxelinux.0 but don't display anything.  However, they still respond
to
>>keyboard input, as we have stanzas in 'default' that use
pxechain.com
>>to redirect them to other PXE servers.  That suggests that we could
>>have a stanza in 'default' that simply redirects to the same PXE
server
>>but to a different menu file, e.g., default.serial.  Is that possible?
>>
>>Peter
>
> Yes, that works.
> --
>
> I setup a stanza that points to a submenu, i.e., a menu from a separate
file, thusly:
>
> LABEL m
> MENU LABEL DisplayPort
> KERNEL vesamenu.c32
> APPEND dpmenu.cfg
>
> So, when this stanza is selected, is vesamenu.c32 reloaded with new menu
arguments?  dpmenu.cfg is just a copy of 'default' but without the
SERIAL settings.  But when I bootup one of the machines that has DP and try to
choose 'm', I get a "Initial menu has no LABEL entries" error.
The first line in 'default' is
>
> DEFAULT vesamenu.c32
>
> so that's also the first line in dpmenu.cfg; is that a problem?  Is it
necessary, since the 'm' stanza called vesamenu.c32 with dpmenu.cfg as
an APPEND?
>
> Petre
1) If present, always put the SERIAL directive on the first line to
ensure early processing.

2) DEFAULT should point to a LABEL to prevent some of the other warnings.

3) UI should be used to call vesamenu.c32/menu.c32 instead of DEFAULT.

4) What does dpmenu.cfg look like?  It sounds like there's other
errors.  Perhaps Mac line-end instead of Unix?  Looking back at
Syslinux-2.00's syslinux.doc (text), it would seem any version with
pxechain.com should be fine with Unix and DOS line ends.

-- 
-Gene