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Bug#977562: systemd: Incorrect order of agetty arguments in serial-getty@ttyS0.service definition file

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  Bug#977562: systemd: Incorrect order of agetty arguments in serial-getty@ttyS0.service definition file Michael Biebl <biebl@debian.org> - 2021-01-14 15:10 +0100
    Bug#977562: systemd: Incorrect order of agetty arguments in serial-getty@ttyS0.service definition file Marcin Krol <mrkafk@gmail.com> - 2021-01-14 17:30 +0100
      Bug#977562: systemd: Incorrect order of agetty arguments in serial-getty@ttyS0.service definition file Michael Biebl <biebl@debian.org> - 2021-01-14 17:40 +0100
        Bug#977562: systemd: Incorrect order of agetty arguments in serial-getty@ttyS0.service definition file Karel Zak <kzak@redhat.com> - 2021-01-18 11:30 +0100
      Bug#977562: systemd: Incorrect order of agetty arguments in serial-getty@ttyS0.service definition file Andreas Henriksson <andreas@fatal.se> - 2021-01-14 18:00 +0100

#1042472 — Bug#977562: systemd: Incorrect order of agetty arguments in serial-getty@ttyS0.service definition file

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Am 19.12.20 um 16:47 schrieb Andreas Henriksson:
> Control: tags -1 + moreinfo
> 
> On Wed, Dec 16, 2020 at 11:39:06PM +0100, Michael Biebl wrote:
>> Am 16.12.20 um 20:49 schrieb MK:
>>> Package: systemd
>>> Version: 241-7~deb10u5
>>> Severity: normal
> [...]
>>> Incorrect order of arguments to agetty in the serial-getty@ttyS0.service
>>> unit file.
>>>
>>> It is:
>>>
>>> ExecStart=/sbin/agetty --autologin root -8 --keep-baud 115200,38400,9600 ttyS0 xterm-256color
>>>
>>>
>>> While it should be like:
>>>
>>> ExecStart=/sbin/agetty --autologin root -8 --keep-baud ttyS0 115200 xterm-256color
> [...]
>> According to the examples in man agetty, both should work.
>>
>> Andreas, can you comment here?
>> If what MK is saying, should the "EXAMPLE" section in man agetty be updated?
>>
> 
> I don't really have much prior knowledge about *getty, but in my past
> experience with other util-linux tools it is often the case that
> (likely for historical reasons/compatibility) the arguments that
> doesn't come in a dash-form is attempted to be accepted in either
> order based on guessing which one was specified. In my past experience
> something that was guessable in the past might in later years become
> sometimes impossible to correctly guess right, so sticking with
> what synopsis describes is usually the safest as far as I'm concerned.
> 
> In the agetty case, the guessing is done here:
> https://sources.debian.org/src/util-linux/2.36.1-2/term-utils/agetty.c/#L897
> 
> is_speed basically checks if the current argument only consists of
> either 0-9 or ','.
> 
> It is not obvious to me how it could go wrong in the example originally
> described in this bug report.
> 
> Please also note that for example sysvinit's inittab also uses getty
> with arguments in both orders.
> 
> Simply it should work either way.
> 
> Please also note that the argument order is not the only thing changed.
> It was also changed from specifying 3 speeds to only 1.
> 
> Maybe the real issue here is that line speed detection isn't working?
> I'd appreciate if the bug reporter could dive a bit deeper into the
> problem.


@MK any further feedback? Otherwise I would close this bug report.

Regards,
Michael

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#1042497

Well, I hoped that you'd simply change that order in the service file 
(I'm new to this, do you expect me to produce patch or something like 
that?). Otherwise serial comm doesn't work, at least for me.




On 1/14/21 3:06 PM, Michael Biebl wrote:
> Am 19.12.20 um 16:47 schrieb Andreas Henriksson:
>> Control: tags -1 + moreinfo
>>
>> On Wed, Dec 16, 2020 at 11:39:06PM +0100, Michael Biebl wrote:
>>> Am 16.12.20 um 20:49 schrieb MK:
>>>> Package: systemd
>>>> Version: 241-7~deb10u5
>>>> Severity: normal
>> [...]
>>>> Incorrect order of arguments to agetty in the 
>>>> serial-getty@ttyS0.service
>>>> unit file.
>>>>
>>>> It is:
>>>>
>>>> ExecStart=/sbin/agetty --autologin root -8 --keep-baud 
>>>> 115200,38400,9600 ttyS0 xterm-256color
>>>>
>>>>
>>>> While it should be like:
>>>>
>>>> ExecStart=/sbin/agetty --autologin root -8 --keep-baud ttyS0 115200 
>>>> xterm-256color
>> [...]
>>> According to the examples in man agetty, both should work.
>>>
>>> Andreas, can you comment here?
>>> If what MK is saying, should the "EXAMPLE" section in man agetty be 
>>> updated?
>>>
>>
>> I don't really have much prior knowledge about *getty, but in my past
>> experience with other util-linux tools it is often the case that
>> (likely for historical reasons/compatibility) the arguments that
>> doesn't come in a dash-form is attempted to be accepted in either
>> order based on guessing which one was specified. In my past experience
>> something that was guessable in the past might in later years become
>> sometimes impossible to correctly guess right, so sticking with
>> what synopsis describes is usually the safest as far as I'm concerned.
>>
>> In the agetty case, the guessing is done here:
>> https://sources.debian.org/src/util-linux/2.36.1-2/term-utils/agetty.c/#L897 
>>
>>
>> is_speed basically checks if the current argument only consists of
>> either 0-9 or ','.
>>
>> It is not obvious to me how it could go wrong in the example originally
>> described in this bug report.
>>
>> Please also note that for example sysvinit's inittab also uses getty
>> with arguments in both orders.
>>
>> Simply it should work either way.
>>
>> Please also note that the argument order is not the only thing changed.
>> It was also changed from specifying 3 speeds to only 1.
>>
>> Maybe the real issue here is that line speed detection isn't working?
>> I'd appreciate if the bug reporter could dive a bit deeper into the
>> problem.
> 
> 
> @MK any further feedback? Otherwise I would close this bug report.
> 
> Regards,
> Michael
> 
> 

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#1042499

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Karel,

sorry for poking you directly: Could you weigh in here?

Regards,
Michael

Am 14.01.21 um 17:21 schrieb Marcin Krol:
> 
> Well, I hoped that you'd simply change that order in the service file 
> (I'm new to this, do you expect me to produce patch or something like 
> that?). Otherwise serial comm doesn't work, at least for me.
> 
> 
> 
> 
> On 1/14/21 3:06 PM, Michael Biebl wrote:
>> Am 19.12.20 um 16:47 schrieb Andreas Henriksson:
>>> Control: tags -1 + moreinfo
>>>
>>> On Wed, Dec 16, 2020 at 11:39:06PM +0100, Michael Biebl wrote:
>>>> Am 16.12.20 um 20:49 schrieb MK:
>>>>> Package: systemd
>>>>> Version: 241-7~deb10u5
>>>>> Severity: normal
>>> [...]
>>>>> Incorrect order of arguments to agetty in the 
>>>>> serial-getty@ttyS0.service
>>>>> unit file.
>>>>>
>>>>> It is:
>>>>>
>>>>> ExecStart=/sbin/agetty --autologin root -8 --keep-baud 
>>>>> 115200,38400,9600 ttyS0 xterm-256color
>>>>>
>>>>>
>>>>> While it should be like:
>>>>>
>>>>> ExecStart=/sbin/agetty --autologin root -8 --keep-baud ttyS0 115200 
>>>>> xterm-256color
>>> [...]
>>>> According to the examples in man agetty, both should work.
>>>>
>>>> Andreas, can you comment here?
>>>> If what MK is saying, should the "EXAMPLE" section in man agetty be 
>>>> updated?
>>>>
>>>
>>> I don't really have much prior knowledge about *getty, but in my past
>>> experience with other util-linux tools it is often the case that
>>> (likely for historical reasons/compatibility) the arguments that
>>> doesn't come in a dash-form is attempted to be accepted in either
>>> order based on guessing which one was specified. In my past experience
>>> something that was guessable in the past might in later years become
>>> sometimes impossible to correctly guess right, so sticking with
>>> what synopsis describes is usually the safest as far as I'm concerned.
>>>
>>> In the agetty case, the guessing is done here:
>>> https://sources.debian.org/src/util-linux/2.36.1-2/term-utils/agetty.c/#L897 
>>>
>>>
>>> is_speed basically checks if the current argument only consists of
>>> either 0-9 or ','.
>>>
>>> It is not obvious to me how it could go wrong in the example originally
>>> described in this bug report.
>>>
>>> Please also note that for example sysvinit's inittab also uses getty
>>> with arguments in both orders.
>>>
>>> Simply it should work either way.
>>>
>>> Please also note that the argument order is not the only thing changed.
>>> It was also changed from specifying 3 speeds to only 1.
>>>
>>> Maybe the real issue here is that line speed detection isn't working?
>>> I'd appreciate if the bug reporter could dive a bit deeper into the
>>> problem.
>>
>>
>> @MK any further feedback? Otherwise I would close this bug report.
>>
>> Regards,
>> Michael
>>
>>

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#1043087

On Thu, Jan 14, 2021 at 05:26:40PM +0100, Michael Biebl wrote:
> Karel,
> 
> sorry for poking you directly: Could you weigh in here?

agetty accepts both:

        agetty --help

        Usage:
         agetty [options] <line> [<baud_rate>,...] [<termtype>]
         agetty [options] <baud_rate>,... <line> [<termtype>]

and code differentiates between these variants by digits, if the string
contains only "0123456789," than it <baud_rate>.

> > On 1/14/21 3:06 PM, Michael Biebl wrote:
> > > Am 19.12.20 um 16:47 schrieb Andreas Henriksson:
> > > > Control: tags -1 + moreinfo
> > > > 
> > > > On Wed, Dec 16, 2020 at 11:39:06PM +0100, Michael Biebl wrote:
> > > > > Am 16.12.20 um 20:49 schrieb MK:
> > > > > > Package: systemd
> > > > > > Version: 241-7~deb10u5
> > > > > > Severity: normal
> > > > [...]
> > > > > > Incorrect order of arguments to agetty in the
> > > > > > serial-getty@ttyS0.service
> > > > > > unit file.
> > > > > > 
> > > > > > It is:
> > > > > > 
> > > > > > ExecStart=/sbin/agetty --autologin root -8 --keep-baud
> > > > > > 115200,38400,9600 ttyS0 xterm-256color
> > > > > > 
> > > > > > 
> > > > > > While it should be like:
> > > > > > 
> > > > > > ExecStart=/sbin/agetty --autologin root -8 --keep-baud
> > > > > > ttyS0 115200 xterm-256color
> > > > [...]
> > > > > According to the examples in man agetty, both should work.
> > > > > 
> > > > > Andreas, can you comment here?
> > > > > If what MK is saying, should the "EXAMPLE" section in man
> > > > > agetty be updated?

I think the man page is correct.

> > > > I don't really have much prior knowledge about *getty, but in my past
> > > > experience with other util-linux tools it is often the case that
> > > > (likely for historical reasons/compatibility) the arguments that
> > > > doesn't come in a dash-form is attempted to be accepted in either
> > > > order based on guessing which one was specified. In my past experience
> > > > something that was guessable in the past might in later years become
> > > > sometimes impossible to correctly guess right, so sticking with
> > > > what synopsis describes is usually the safest as far as I'm concerned.
> > > > 
> > > > In the agetty case, the guessing is done here:
> > > > https://sources.debian.org/src/util-linux/2.36.1-2/term-utils/agetty.c/#L897
> > > > 
> > > > 
> > > > is_speed basically checks if the current argument only consists of
> > > > either 0-9 or ','.

Yes

> > > > It is not obvious to me how it could go wrong in the example originally
> > > > described in this bug report.
> > > > 
> > > > Please also note that for example sysvinit's inittab also uses getty
> > > > with arguments in both orders.
> > > > 
> > > > Simply it should work either way.
> > > > 
> > > > Please also note that the argument order is not the only thing changed.
> > > > It was also changed from specifying 3 speeds to only 1.
> > > > 
> > > > Maybe the real issue here is that line speed detection isn't working?
> > > > I'd appreciate if the bug reporter could dive a bit deeper into the
> > > > problem.

Yes.

 Karel



-- 
 Karel Zak  <kzak@redhat.com>
 http://karelzak.blogspot.com

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#1042501

Hello Marcin Krol,

On Thu, Jan 14, 2021 at 05:21:17PM +0100, Marcin Krol wrote:
> 
> Well, I hoped that you'd simply change that order in the service file (I'm
> new to this, do you expect me to produce patch or something like that?).
> Otherwise serial comm doesn't work, at least for me.

As I tried to explain in my previous mail, I'm claiming that:

a/ it's impossible the ordering fixed your problem

   (I actually hacked up agetty to print out the structure the
   command-line parsing is stored into and verified that the structure
   ends up exactly the same no matter which order you give the arguments
   in. Before doing that I also checked the code and could not see any
   reason why the argument ordering detection code would not work.)

b/ You changed (atleast) 2 things, not only the order.

   (For example, in your example with order reversed you also dropped
   all alternative speed settings and just gave a single speed setting
   instead of a list.)

Given this there's no evidence that implementing your suggested change
will fix anything. Please provide more input. Try to change one thing
at a time in your testing to isolate which change actually fixes your
problem.

Regards,
Andreas Henriksson

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