Hi Bhupesh, On 04/03/18 at 07:28pm, Bhupesh Sharma wrote: > Hi James, > > Sorry for the delay, I had a long weekend last week. > > On Tue, Mar 27, 2018 at 7:01 PM, James Morse <james.morse@xxxxxxx> wrote: > > Hi Akashi, Bhupesh, > > > > On 27/03/18 10:04, AKASHI Takahiro wrote: > >> On Mon, Mar 26, 2018 at 02:29:31PM +0530, Bhupesh Sharma wrote: > >>> On Tue, Mar 20, 2018 at 12:36 AM, Bhupesh Sharma <bhsharma@xxxxxxxxxx> wrote: > >>>> On Mon, Mar 19, 2018 at 8:15 PM, AKASHI Takahiro > >>>> <takahiro.akashi@xxxxxxxxxx> wrote: > >>>>> On Mon, Mar 19, 2018 at 04:05:38PM +0530, Bhupesh Sharma wrote: > >>>>>> At several occasions it would be useful to dump the fdt > >>>>>> blob being passed to the second (kexec/kdump) kernel > >>>>>> when '-d' flag is specified while invoking kexec/kdump. > >>>>> > >>>>> Why not just save binary data to a file and interpret it > >>>>> with dtc command? > > > > I'd prefer this too. It would also let us debug any issue where kexec-tools > > produces an invalid DTB. It also lets us test booting the kernel from firmware > > with that DTB. > > I captured the use case where it is not possible to do so. I have seen > primary kernel crash before we can get to the command prompt to save > the dtb blob. Since the arm64 crashkernel still seems to have issues > itself while booting on acpi enabled machines (see > <https://www.spinics.net/lists/arm-kernel/msg616632.html>), so we are > trying to debug a problem which has two undefined variables :) > > >>>> Well, there are a couple of reasons for that which can be understood > >>>> from a system which is in a production environment (for e.g. I have > >>>> worked on one arm64 system in the past which used a yocto based > >>>> distribution in which kexec -p was launched with a -d option as a part > >>>> of initial ramfs scriptware): > > > > and panics before you get an interactive prompt or persistent storage? I think > > this would be a pretty niche use-case. You could always base64-dump the dtb to > > stdout from your script. > > That is pretty basic case on several new arm64 development boards > (e.g. qualcomm, huawei etc) where we are debugging issues in primary > kernel boot (and we are not even able to reach the command prompt). > > If the crashkernel crashes even before the primary kernel does because > of the issues in the way DTB is passed to the crashkernel (which can > include wrong DTB fields), we better have mechanisms to track the same > rather than adding debug prints to the kernels. In this case, since userspace always need to run 'kexec -l', there should be chance to save dtb and dump them in scripts if needed. If this is doable in scripts I also tend not to add the code in kexec-tools. [snip] Thanks Dave _______________________________________________ kexec mailing list kexec@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/kexec
