Re: [systemd-devel] systemd-coredump, coredump is truncated to exactly 2GiB

2016-07-25 Thread Lennart Poettering 
On Sat, 23.07.16 17:41, Zbigniew Jędrzejewski-Szmek (zbys...@in.waw.pl) wrote:

> Sounds like a bug in the logic. 2GiB is the default value for ProcessSizeMax=
> and ExternalSizeMax=. coredump.conf(5) implies coredumps larger than that
> will not be stored. I don't think it's useful to have truncated coredumps,
> so I think we should:

Truncated coredumps (and coredumps lacking some memory regions) are
actually not as problematic and useless as they may sound, as gdb is
pretty good as making use of what is there, and just letting invidual
operations fail where the relevant memory is missing in the
dump. Truncated coredumps is after all the traditional effect of
RLIMIT_CORE...

Lennart

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Re: [systemd-devel] systemd-coredump, coredump is truncated to exactly 2GiB

2016-07-24 Thread Zbigniew Jędrzejewski-Szmek 
On Sat, Jul 23, 2016 at 02:10:51PM -0600, Chris Murphy wrote:
> On Sat, Jul 23, 2016 at 11:41 AM, Zbigniew Jędrzejewski-Szmek
>  wrote:
> > On Fri, Jul 22, 2016 at 07:40:25PM -0600, Chris Murphy wrote:
> >> qemu-system-x86 core dumped on me for some reason, and I see it in the 
> >> journal:
> >>
> >> Jul 22 13:24:30 f24m systemd-coredump[3914]: Process 3829
> >> (qemu-system-x86) of user 107 dumped core.
> >>
> >> OK no problem.
> >>
> >> [chris@f24m ~]$ sudo coredumpctl gdb 3829
> >> [...snip...]
> >> BFD: Warning: /var/tmp/coredump-DtRBEA is truncated: expected core
> >> file size >= 4115308544, found: 2147483648.
> >>
> >> OK let's extract the coredump to its own file:
> >>
> >> # sudo coredumpctl -o qemu-system-x86.coredump dump 
> >> /usr/bin/qemu-system-x86_64
> >> # ls -l
> >> -rw-r--r--. 1 chris chris 2147483648 Jul 22 14:08 qemu-system-x86.coredump
> >>
> >> Huh, 2147483648 is 0x8000 or exactly 2GiB. Suspicious? Is there a
> >> misconfiguration of some kind causing this truncation? Or?
> >>
> >> This is Fedora 24, systemd-229-8.fc24.x86_64
> >
> > Sounds like a bug in the logic. 2GiB is the default value for 
> > ProcessSizeMax=
> > and ExternalSizeMax=. coredump.conf(5) implies coredumps larger than that
> > will not be stored. I don't think it's useful to have truncated coredumps,
> > so I think we should:
> > 1. make sure that coredumps which exceed the allowed size not saved
> > 2. consider increasing the maximum coredump size. 2GiB feels a bit low
> >in this day and age.
> 
> What's the significance of the path in the gdb complaint...
> 
> BFD: Warning: /var/tmp/coredump-S2qIGu is truncated: expected core
> file size >= 4115308544, found: 2147483648.
> 
> ...compared to the path coredumpctl info reports?
> 
>   Coredump:
> /var/lib/systemd/coredump/core.qemu-system-x86.107.b91161300395440f96b49cd0b879488d.3829.1469215461.lz4
> 
> Does 'coredumpctl gdb' grab the compressed coredump and decompresses
> it into /var/tmp and then hands it off to gdb? I just want to make
> sure there's no other source for truncation.

Yes, coredumps are stored with lz4 compression. GDB (and also other
tools) needs it uncompressed.

Zbyszek
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Re: [systemd-devel] systemd-coredump, coredump is truncated to exactly 2GiB

2016-07-23 Thread Chris Murphy 
On Sat, Jul 23, 2016 at 11:41 AM, Zbigniew Jędrzejewski-Szmek
 wrote:
> On Fri, Jul 22, 2016 at 07:40:25PM -0600, Chris Murphy wrote:
>> qemu-system-x86 core dumped on me for some reason, and I see it in the 
>> journal:
>>
>> Jul 22 13:24:30 f24m systemd-coredump[3914]: Process 3829
>> (qemu-system-x86) of user 107 dumped core.
>>
>> OK no problem.
>>
>> [chris@f24m ~]$ sudo coredumpctl gdb 3829
>> [...snip...]
>> BFD: Warning: /var/tmp/coredump-DtRBEA is truncated: expected core
>> file size >= 4115308544, found: 2147483648.
>>
>> OK let's extract the coredump to its own file:
>>
>> # sudo coredumpctl -o qemu-system-x86.coredump dump 
>> /usr/bin/qemu-system-x86_64
>> # ls -l
>> -rw-r--r--. 1 chris chris 2147483648 Jul 22 14:08 qemu-system-x86.coredump
>>
>> Huh, 2147483648 is 0x8000 or exactly 2GiB. Suspicious? Is there a
>> misconfiguration of some kind causing this truncation? Or?
>>
>> This is Fedora 24, systemd-229-8.fc24.x86_64
>
> Sounds like a bug in the logic. 2GiB is the default value for ProcessSizeMax=
> and ExternalSizeMax=. coredump.conf(5) implies coredumps larger than that
> will not be stored. I don't think it's useful to have truncated coredumps,
> so I think we should:
> 1. make sure that coredumps which exceed the allowed size not saved
> 2. consider increasing the maximum coredump size. 2GiB feels a bit low
>in this day and age.

What's the significance of the path in the gdb complaint...

BFD: Warning: /var/tmp/coredump-S2qIGu is truncated: expected core
file size >= 4115308544, found: 2147483648.

...compared to the path coredumpctl info reports?

  Coredump:
/var/lib/systemd/coredump/core.qemu-system-x86.107.b91161300395440f96b49cd0b879488d.3829.1469215461.lz4

Does 'coredumpctl gdb' grab the compressed coredump and decompresses
it into /var/tmp and then hands it off to gdb? I just want to make
sure there's no other source for truncation.

I'll file a bug.


-- 
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Re: [systemd-devel] systemd-coredump, coredump is truncated to exactly 2GiB

2016-07-23 Thread Chris Murphy 
https://bugzilla.redhat.com/show_bug.cgi?id=1359410
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Re: [systemd-devel] systemd-coredump, coredump is truncated to exactly 2GiB

2016-07-23 Thread Zbigniew Jędrzejewski-Szmek 
On Fri, Jul 22, 2016 at 07:40:25PM -0600, Chris Murphy wrote:
> qemu-system-x86 core dumped on me for some reason, and I see it in the 
> journal:
> 
> Jul 22 13:24:30 f24m systemd-coredump[3914]: Process 3829
> (qemu-system-x86) of user 107 dumped core.
> 
> OK no problem.
> 
> [chris@f24m ~]$ sudo coredumpctl gdb 3829
> [...snip...]
> BFD: Warning: /var/tmp/coredump-DtRBEA is truncated: expected core
> file size >= 4115308544, found: 2147483648.
> 
> OK let's extract the coredump to its own file:
> 
> # sudo coredumpctl -o qemu-system-x86.coredump dump 
> /usr/bin/qemu-system-x86_64
> # ls -l
> -rw-r--r--. 1 chris chris 2147483648 Jul 22 14:08 qemu-system-x86.coredump
> 
> Huh, 2147483648 is 0x8000 or exactly 2GiB. Suspicious? Is there a
> misconfiguration of some kind causing this truncation? Or?
> 
> This is Fedora 24, systemd-229-8.fc24.x86_64

Sounds like a bug in the logic. 2GiB is the default value for ProcessSizeMax=
and ExternalSizeMax=. coredump.conf(5) implies coredumps larger than that
will not be stored. I don't think it's useful to have truncated coredumps,
so I think we should:
1. make sure that coredumps which exceed the allowed size not saved
2. consider increasing the maximum coredump size. 2GiB feels a bit low
   in this day and age.

Zbyszek
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[systemd-devel] systemd-coredump, coredump is truncated to exactly 2GiB

2016-07-22 Thread Chris Murphy 
qemu-system-x86 core dumped on me for some reason, and I see it in the journal:

Jul 22 13:24:30 f24m systemd-coredump[3914]: Process 3829
(qemu-system-x86) of user 107 dumped core.

OK no problem.

[chris@f24m ~]$ sudo coredumpctl gdb 3829
[...snip...]
BFD: Warning: /var/tmp/coredump-DtRBEA is truncated: expected core
file size >= 4115308544, found: 2147483648.

OK let's extract the coredump to its own file:

# sudo coredumpctl -o qemu-system-x86.coredump dump /usr/bin/qemu-system-x86_64
# ls -l
-rw-r--r--. 1 chris chris 2147483648 Jul 22 14:08 qemu-system-x86.coredump

Huh, 2147483648 is 0x8000 or exactly 2GiB. Suspicious? Is there a
misconfiguration of some kind causing this truncation? Or?

This is Fedora 24, systemd-229-8.fc24.x86_64


-- 
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