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From:   Ricardo Ribalda <ribalda@chromium.org>
Date:   Fri, 25 Nov 2022 08:31:06 +0100
Message-ID: <CANiDSCuy-uZ4r2x6xujiPGTowzN8JuOvTXh3r0Rc7J+YmpqZiw@mail.gmail.com>
Subject: Re: [PATCH] kexec: Enable runtime allocation of crash_image
To:     Baoquan He <bhe@redhat.com>
Cc:     Eric Biederman <ebiederm@xmission.com>,
        Philipp Rudo <prudo@redhat.com>,
        Sergey Senozhatsky <senozhatsky@chromium.org>,
        Ross Zwisler <zwisler@kernel.org>, kexec@lists.infradead.org,
        linux-kernel@vger.kernel.org
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Hi

On Fri, 25 Nov 2022 at 08:27, Baoquan He <bhe@redhat.com> wrote:
>
> On 11/25/22 at 06:52am, Ricardo Ribalda wrote:
> > Hi Baoquan
> >
> > Thanks for your review!
> >
> > On Fri, 25 Nov 2022 at 03:58, Baoquan He <bhe@redhat.com> wrote:
> > >
> > > On 11/24/22 at 11:23pm, Ricardo Ribalda wrote:
> > > > Usually crash_image is defined statically via the crashkernel parameter
> > > > or DT.
> > > >
> > > > But if the crash kernel is not used, or is smaller than then
> > > > area pre-allocated that memory is wasted.
> > > >
> > > > Also, if the crash kernel was not defined at bootime, there is no way to
> > > > use the crash kernel.
> > > >
> > > > Enable runtime allocation of the crash_image if the crash_image is not
> > > > defined statically. Following the same memory allocation/validation path
> > > > that for the reboot kexec kernel.
> > >
> > > We don't check if the crashkernel memory region is valid in kernel, but
> > > we do have done the check in kexec-tools utility. Since both kexec_load and
> > > kexec_file_load need go through path of kexec-tools loading, we haven't
> > > got problem with lack of the checking in kernel.
> >
> > Not sure if I follow you.
> >
> > We currently check if the crash kernel is in the right place at
> > sanity_check_segment_list()
> > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/kernel/kexec_core.c#n239
>
> And it's not checking if crashkernel memory is valid in
> sanity_check_segment_list(), right? It's checking if the segments
> are placed correctly.

If it is not valid, then this condition is not met.

/* Ensure we are within the crash kernel limits */
if ((mstart < phys_to_boot_phys(crashk_res.start)) ||
    (mend > phys_to_boot_phys(crashk_res.end)))
          return -EADDRNOTAVAIL;


>


-- 
Ricardo Ribalda