linux-kernel - Re: [RFC][PATCH] coredump: Document coredump code exclusively used by cell spufs

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Message-ID: <CAK8P3a0iMjZOHm3pAR+V3Ctdfd6Xa0WiWHcVP3nX7dEuFFXd1Q@mail.gmail.com>
Date:   Wed, 2 Dec 2020 16:58:33 +0100
From:   Arnd Bergmann <arnd@...nel.org>
To:     "Eric W. Biederman" <ebiederm@...ssion.com>
Cc:     Geoff Levand <geoff@...radead.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Oleg Nesterov <oleg@...hat.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Michael Ellerman <mpe@...erman.id.au>,
        Arnd Bergmann <arnd@...db.de>
Subject: Re: [RFC][PATCH] coredump: Document coredump code exclusively used by
 cell spufs

On Wed, Dec 2, 2020 at 4:20 PM Eric W. Biederman <ebiederm@...ssion.com> wrote:
>
> ebiederm@...ssion.com (Eric W. Biederman) writes:
>
> > Oleg Nesterov recently asked[1] why is there an unshare_files in
> > do_coredump.  After digging through all of the callers of lookup_fd it
> > turns out that it is
> > arch/powerpc/platforms/cell/spufs/coredump.c:coredump_next_context
> > that needs the unshare_files in do_coredump.
> >
> > Looking at the history[2] this code was also the only piece of coredump code
> > that required the unshare_files when the unshare_files was added.
> >
> > Looking at that code it turns out that cell is also the only
> > architecture that implements elf_coredump_extra_notes_size and
> > elf_coredump_extra_notes_write.
> >
> > I looked at the gdb repo[3] support for cell has been removed[4] in binutils
> > 2.34.  Geoff Levand reports he is still getting questions on how to
> > run modern kernels on the PS3, from people using 3rd party firmware so
> > this code is not dead.  According to Wikipedia the last PS3 shipped in
> > Japan sometime in 2017.  So it will probably be a little while before
> > everyone's hardware dies.
> >
> > Add some comments briefly documenting the coredump code that exists
> > only to support cell spufs to make it easier to understand the
> > coredump code.  Eventually the hardware will be dead, or their won't
> > be userspace tools, or the coredump code will be refactored and it
> > will be too difficult to update a dead architecture and these comments
> > make it easy to tell where to pull to remove cell spufs support.
> >
> > [1] https://lkml.kernel.org/r/20201123175052.GA20279@redhat.com
> > [2] 179e037fc137 ("do_coredump(): make sure that descriptor table isn't shared")
> > [3] git://sourceware.org/git/binutils-gdb.git
> > [4] abf516c6931a ("Remove Cell Broadband Engine debugging support").
> > Signed-off-by: Eric W. Biederman <ebiederm@...ssion.com>
> > ---
> >
> > Does this change look good to people?  I think it captures this state of
> > things and makes things clearer without breaking anything or removing
> > functionality for anyone.
>
> I haven't heard anything except a general ack to the concept of
> comments.  So I am applying this.
>

Sorry I missed it when you originally sent it. Looks good ot me,

Acked-by: Arnd Bergmann <arnd@...db.de>