From: piliu <piliu@redhat.com>
To: "HAGIO KAZUHITO(萩尾 一仁)" <k-hagio-ab@nec.com>,
"kexec@lists.infradead.org" <kexec@lists.infradead.org>
Subject: Re: makedumpfile: a feature question about filtering
Date: Tue, 15 Sep 2020 10:30:37 +0800 [thread overview]
Message-ID: <80e79f89-4d9d-b4de-5d90-4a9d4d242e70@redhat.com> (raw)
In-Reply-To: <OSBPR01MB1991A2DAB9596B60910C9CE6DD230@OSBPR01MB1991.jpnprd01.prod.outlook.com>
On 09/14/2020 05:15 PM, HAGIO KAZUHITO(萩尾 一仁) wrote:
> -----Original Message-----
>> On 09/14/2020 04:15 PM, HAGIO KAZUHITO(萩尾 一仁) wrote:
>>> -----Original Message-----
>>>> On 09/11/2020 04:53 PM, HAGIO KAZUHITO(萩尾 一仁) wrote:
>>>>> Hi Pingfan,
>>>>>
>>>>> -----Original Message-----
>>>>>> Hello,
>>>>>>
>>>>>> There is an appeal which only wants to save some user page including env
>>>>>> and args pages, and discards the other user space pages.
>>>>>
>>>>> I understand that it's helpful to get them even with -d 31 for crash's
>>>>> "ps -a" option..
>>>>>
>>>>>>
>>>>>> To achieve this feature, mm_struct's members "arg_start, arg_end,
>>>>>> env_start, env_end;" should be accessed. So we need to export mm_struct
>>>>>> and init_mm through vmcore.
>>>>>
>>>>> How many offsets/sizes will be required to walk all tasks?
>>>> At present, I think only the info "arg_start, arg_end, env_start,
>>>> env_end" in mm_struct are required.
>>>
>>> ah what I wanted to ask mainly was the number of the offsets/sizes used to
>>> walk through all (user) tasks in a system, because makedumpfile cannot get
>>> to a task's arg_start only with OFFSET(mm_struct.arg_start). Is it easy
>>> enough to do it only with several vmcoreinfo entries?
>> Yes, it is. Iterating over tasks requires to expose
>> OFFSET(mm_struct.mmlist, and &init_mm. Then for each mm_struct, we need
>> an access to "arg_start, arg_end, env_start,env_end"
>
> Hmm, but a Fedora 32 machine has an empty init_mm.mmlist.
> (because of no used swap?)
Aha, sorry that I made a mistake and mmlist is not used to organize all
the mm any more.
In order to access all mm_strcut in the system, init_task.tasks
linked-list should be exposed, and for each task we can access its
mm_struct by OFFSET(task_struct.mm), then OFFSET(mm_struct.arg_start).
>
> crash> p init_mm.mmlist
> $1 = {
> next = 0xffffffff826ee200 <init_mm+160>,
> prev = 0xffffffff826ee200 <init_mm+160>
> }
> crash> swap
> SWAP_INFO_STRUCT TYPE SIZE USED PCT PRI FILENAME
> ffff8badb5385a00 PARTITION 4153340k 0k 0% -2 /dev/dm-1
>
> I might be still missing something.
You are right. And could you foresee any problem with my new try?
Thanks,
Pingfan
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next prev parent reply other threads:[~2020-09-15 2:30 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-08 1:38 makedumpfile: a feature question about filtering piliu
2020-09-11 8:53 ` HAGIO KAZUHITO(萩尾 一仁)
2020-09-14 4:55 ` piliu
2020-09-14 8:15 ` HAGIO KAZUHITO(萩尾 一仁)
2020-09-14 8:30 ` piliu
2020-09-14 9:15 ` HAGIO KAZUHITO(萩尾 一仁)
2020-09-15 2:30 ` piliu [this message]
2020-09-16 8:40 ` HAGIO KAZUHITO(萩尾 一仁)
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