Hi Vicenç, Sorry I was on holidays and came back to office just yesterday. On Sat, Oct 27, 2018 at 3:56 PM Vicente Bergas <vicencb@xxxxxxxxx> wrote: > > On Sat, Oct 27, 2018 at 12:55 AM Bhupesh Sharma <bhsharma@xxxxxxxxxx> wrote: > > > > Hi Vicenç, > > > > On Fri, Oct 26, 2018 at 6:42 PM Vicente Bergas <vicencb@xxxxxxxxx> wrote: > > > > > > Hello, > > > when executing > > > kexec -d --dtb dtb_without_chosen_node.dtb --append 'cmdline' --load Image > > > it reports > > > dtb_set_property: fdt_add_subnode failed: <valid offset/length> > > > kexec: Set device tree bootargs failed. > > > > > > It has been tested on the arm64 architecture with version v2.0.17 and > > > v2.0.18-rc1 > > > > Can you share some details on the underlying platform and kernel > > version you are using? Again, would request you to share the above details, which would help me answer your queries in a better way. > > Looking at the logs, I am assuming you are running 'kexec' on a arm64 > > platform (as it depends on creating a dtb to be passed to the 2nd > > kernel). > > > > My general advice is to avoid the --dtb option as it is known to cause > > issues with kexec in the past (see [0] for details) > > Ideally, if you don't use the --dtb option, then kexec will read the existing > > kernel's dtb from /proc/device-tree, and that device tree will include > > all the changes that the boot loader has done, including adding details > > of the available memory in the system. > > > > [0]. https://www.spinics.net/lists/arm-kernel/msg618236.html > > > > Hope this helps. > > > > Regards, > > Bhupesh > > Hi Bhupesh, thanks for answering and yes, this helps! > > As you say, when not using the --dtb option it works fine. But this > way is not applicable in my use case. > > I am trying to use Linux as a bootloader. This bootloader will reside > in a difficult-to-write memory (SPI-NOR Flash) and, because of that, > will rarely be updated. > Over time, new kernel versions will provide updated DTB files, so, > the DT from both kernels will diverge over time. > This is the reason to use the --dtb option. > > Thanks for the information you provided, now I see a bug and also a > missing feature. > > > Focusing on the bug, I have traced it down to here: > https://git.kernel.org/pub/scm/utils/kernel/kexec/kexec-tools.git/tree/kexec/dt-ops.c#n87 > the result is tested for non-zero as error condition, but, as seen here > https://git.kernel.org/pub/scm/utils/kernel/kexec/kexec-tools.git/tree/kexec/libfdt/fdt_rw.c#n345 > it looks like positive values are not errors. Hmmm.. looking hard at it, I am not sure if its indeed a bug, but more on the same below ... > Now, focusing on the missing feature. > kexec-tools already has the (buggy) ability to add the "/chosen/bootargs" node. > I assume that it also adds or updates the "/chosen/linux,initrd-start" > and "/chosen/linux,initrd-end" nodes because it has the --initrd option. > Again, I assume it also adds/updates all "/memreserve" nodes with > the location where the DTB and initrd reside in memory. > So, just adding the "/memory" node will make it feature complete. > This node can be populated with data provided from the command line as > parameters or with data extracted from /proc/device-tree. > > Adding "/ethernetX/local-mac-address" would be a bonus. ... Not really, as again this is very board specific. For e.g. I can have a 'usb' (or even multiple Ethernet cards on the board) as the transport media, which means that the 'kexec-tools' must be able to handle all of those via the --dtb option and prepare the dtb to be sent to the 2nd kernel accordingly. I hope you understand my point here that we have a minimalistic implementation intentionally as catering to all dtb nodes in kexec-tools is probably equivalent to adding functionality similar to how a bootloader (like u-boot) allows dtb properties to be changed. And even if we add some basic skeleton for the same, we cannot be sure that it will be suitable for all arm64 hardware available. > As a side node, can I suggest updating libfdt with latest upstream? > from: > https://git.kernel.org/pub/scm/utils/kernel/kexec/kexec-tools.git/tree/kexec/libfdt > to: > https://git.kernel.org/pub/scm/utils/dtc/dtc.git/tree/libfdt This is a good suggestion. I have this already on my to-do queue. I will find some time to complete it over the weekend and share a patch on the same probably by next week. Thanks, Bhupesh _______________________________________________ kexec mailing list kexec@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/kexec
