makedumpfile: a feature question about filtering

[HAGIO KAZUHITO(萩尾 一仁)]

-----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?

Thanks,
Kazu

> > If kernel maintainers accept it, I will not oppose that feature..
> OK, I will start with kernel side as the first step.
> >
> > (or it would be simpler to mark the pages something special when allocating,
> > but I don't feel like it's easy to change kernel to do so.)
> Yes, I agree. From kernel side, the page is a normal user space page,
> there should not be exception.
> 
> Thanks,
> Pingfan