Re: [PATCH v3 01/21] vmcore: reference e_phoff member explicitly to get position of program header table

Vivek Goyal
2013-03-21T14:12:17Z

On Thu, Mar 21, 2013 at 11:50:41AM +0900, HATAYAMA Daisuke wrote:
> From: "Eric W. Biederman" <ebiederm@xmission.com>
> Subject: Re: [PATCH v3 01/21] vmcore: reference e_phoff member explicitly to get position of program header table
> Date: Tue, 19 Mar 2013 14:44:16 -0700
>
> > HATAYAMA Daisuke <d.hatayama@jp.fujitsu.com> writes:
> >
> >> Currently, the code assumes that position of program header table is
> >> next to ELF header. But future change can break the assumption on
> >> kexec-tools and the 1st kernel. To avoid worst case, reference e_phoff
> >> member explicitly to get position of program header table in
> >> file-offset.
> >
> > In principle this looks good. However when I read this it looks like
> > you are going a little too far.
> >
> > You are changing not only the reading of the supplied headers, but
> > you are changing the generation of the new new headers that describe
> > the data provided by /proc/vmcore.
> >
> > I get lost in following this after you mangle merge_note_headers.
> >
> > In principle removing silly assumptions seems reasonable, but I think
> > it is completely orthogonal to the task of maping vmcore mmapable.
> >
> > I think it is fine to claim that the assumptions made here in vmcore are
> > part of the kexec on panic ABI at this point, which would generally make
> > this change unnecessary.
>
> This was suggested by Vivek. He prefers generic one.
>
> Vivek, do you agree to this? Or is it better to re-post this and other
> clean-up patches as another one separately to this patch set?

Given the fact that current code has been working, I am fine to just
re-post and take care of mmap() related issues. And we can take care
of cleaning up of some assumptions about PT_NOTE headers later. Trying
to club large cleanup with mmap() patches is making it hard to review.

Thanks
Vivek