boot-architecture

boot-architecture@lists.linaro.org

1 participants
688 discussions

by Loïc Minier

Hey (followup to today's call0 This is an attempt to write down an use case which expresses the concept of "modules" that the boot architecture would cover. I don't really like the name modules, if you have better names please propose! So here's the writeup; this is completely fictional, and is just meant to illustrate modules. Here are the steps that could be taken to load a plain linux kernel: a) your SoC starts up in a SoC-specific way b) the boot architecture mandates how vmlinuz is loaded and started c) control is passed to linux d) profit!1! in a very dumbed down version of our boot architecture, we could say for b): a file named "bootme" is loaded from the first FAT partition of the SD card; its type is detected and if it's a linux kernel, it's started with a device tree blob provided by the firmware to the kernel Good: * easy to install or update a kernel by replacing the vmlinuz file Bad: * miss way to pass kernel cmdline * miss way to pass (optional) initrd * miss way to load/replace the DT all of the above bad points could be alleviated by pushing this data in the vmlinuz file, but it's not as practical as the modern linux systems we know. Another approach would be to put U-Boot or Barebox in the "bootme" file, but then U-Boot or Barebox would have to decide how to load the kernel and implement drivers for the SD card and this wouldn't be a SoC-agnostic boot image anymore. So the only possible approach I see in this case is to put a general purpose ARM bootloader in the "bootme" file which will talk to firmware to load additional files from the SD card (thanks to non-resident support from the firmware); this would then go away once linux runs. Now to "modules": instead of defining b) as just loading a single "bootme" file, we'd define a config file which lists what to load (e.g. something like grub.cfg/menu.lst) so that we could pass combinations such as: - vmlinuz + initrd + DT - vmlinuz + DT - Xen + DT + the OS modules it should load (linux and initrd) it would also allow setting things like kernel cmdline or other OS specific things. Maybe I misunderstood Grant's idea, but it felt like he was mandating a single payload from being loaded and just deferring to that payload. I feel that if we go that route, we've specified too little to be able to construct useful images and have deffered to an implementation specific architecture (even if it could support multiple SoCs). So my conclusion is that we should specify: * either a single payload to start which would be something like a generic ARM bootloader talking to the firmware to load the other bits (e.g. via UEFI), but then also how it loads the next things * or a config file which points at "modules" (by lack of a better name) to load; these will get loaded by SoC specific code (likely an UEFI implementation) the main difference is whether we specify how a generic ARM bootloader is loaded and then defer to it to decide how to load the OS, or whether we specify OS-ish bits to load, and leave the loading to the implementation. Does that make any sense? Cheers, -- Loïc Minier

15 years, 1 month

Re: Linux Boot Architecture coordination meeting

by Grant Likely

On Thu, Jun 23, 2011 at 5:25 AM, Olivier Martin <olivier.martin(a)arm.com> wrote: > Thanks Nicolas for the link. You right the zImage has a signature. I read > again the code I wrote and it is the signature for the non compressed image > I have not found. > My function was able to detect uImage and zImage but I had to assume if it > is not one of these formats the image was a non-compressed image. Which it > is ok as far as we have got only 3 formats, but that could cause trouble for > any additional formats that would have some requirements from the boot > loader. > > > FYI, our UEFI implementation already supports ATAG (and partially DT). We > can pass a DT to the kernel but we have not implemented yet the update of > the tree in the firmware; for example to pass new arguments to the kernel. > Again same argument as the binary format, if in the future a new format > incompatible with the DT format is introduced to answer some limitations of > the Flat Device Tree at this time; should the ARM boot 'standardization' be > rewriting again and break the legacy mechanism ? > > > I had a look again to this page: > https://wiki.linaro.org/OfficeofCTO/BootArchitecture > It seems the current concern is more about the firmware itself than the > interface between the OS loader and the kernel. I guess this Blue Print has > been created to solve the issues of the boot fragmentation in the ARM world. > I suppose the idea is to introduce some requirements for booting ARM > platforms. > But should we only limit our view to the requirements of booting Linux 3.0 > (zImage? and Device Tree). Could we also think about defining some > 'standards' in the interface between the OS Loader and the Linux kernel to > leave some flexibility for any future technology that involves the boot > firmware to initialize the platform for the Linux kernel. I think in general, yes we should constrain our view to 3.0+. That doesn't preclude firmware from supporting what it already supports. Indeed it would be crazy to ask firmware projects to remove things that it currently supports. Rather, I think that the process of creating a standard implementable by any firmware should be /focused/ on new kernels since we cannot change the stuff that is already deployed anyway. > As I suggested in my first email, defining a signature (binary format:zImage > + machine type:DT) could be a way to define our current requirements and > leave some place for any future requirements I've added signature/CRC/identification as a topic to the boot architecture page. g.

15 years, 1 month

RE: Linux Boot Architecture coordination meeting

by Nicolas Pitre

On Tue, 21 Jun 2011, Olivier Martin wrote: > Thanks Grant for adding me to the list, > To introduce myself, I am part of the UEFI team at ARM Ltd. I am also the > maintainer of the ARM Packages in the Open Source implementation of UEFI > (http://www.tianocore.org/ ). > > Maybe an issue this "ARM Boot Architecture" topic should solve is the > interface between the boot loader and the Linux kernel binary. > > Recently, I was trying to extend our ARM UEFI boot loader to detect the type > of the Linux kernel binary: > - zImage, non-compressed Image, uImage format > - ATAG or FDT support > ... to start any kernel by passing the correct parameters and jump to the > right offset. > > Unfortunately, it was not as easy as it should be. In fact it does not look > to be possible right now. Defining a signature (eg: kernel binary format + > machine type) in the kernel binary would make the task easier. Some of the > formats have a signature (eg: u-boot) but not all the formats. The zImage format has a signature too. I documented it here a _long_ time ago: http://lists.arm.linux.org.uk/lurker/message/20020226.165754.4c7e6539.en.ht… Of course some things have changed since then. For a while now, the zImage is fully position independent. I can be loaded anywhere in memory and branched directly to it as it takes care of relocating itself when needed. Therefore the load address at offset 0x28 is now always zero, except when the zImage is linked to be executed directly from flash memory (but I doubt that case is relevant to UEFI). For that matter, the uImage format is broken. It insists on absolute addresses in its header. This is therefore not a good format if we want to support multiple SoCs with the same kernel binary, as some of them have their physical RAM at different addresses. You may want to support it if you want, but it is likely not to be suitable anymore in the future. Hence having the ability to boot a zImage directly is likely to be the most flexible option. > Actually, if we try to boot a Linux kernel with the wrong settings then the > kernel would crash or raise an error. And it is not be possible to recover > from this state without restarting the platform. What kind of parameters do you have in mind? > Making these information available to the boot loader (u-boot, uefi, etc) > would also make easier the migration from the legacy ATAG to the Flat Device > Tree (FDT) support. How would it make that transition easier? The link between those issues is not obvious to me. With regard to ATAGs, I don't think UEFI should bother with them. If we really want to move to device tree, and it seems we do, then ATAGs should be left behind. We do have a compatibility layer going into zImage to convert ATAGs into DT properties at run time to allow booting a DT kernel on legacy bootloaders. Adding ATAg support to UEFI might impair the move to DT in the kernel by making it a lower priority. Nicolas

15 years, 1 month

Re: Linux Boot Architecture coordination meeting

by Jean-Christophe PLAGNIOL-VILLARD

On 18:01 Tue 21 Jun , Olivier Martin wrote: > Thanks Grant for adding me to the list, > To introduce myself, I am part of the UEFI team at ARM Ltd. I am also the > maintainer of the ARM Packages in the Open Source implementation of UEFI > (http://www.tianocore.org/ ). > > Maybe an issue this "ARM Boot Architecture" topic should solve is the > interface between the boot loader and the Linux kernel binary. > > Recently, I was trying to extend our ARM UEFI boot loader to detect the type > of the Linux kernel binary: > - zImage, non-compressed Image, uImage format > - ATAG or FDT support > ... to start any kernel by passing the correct parameters and jump to the > right offset. > > Unfortunately, it was not as easy as it should be. In fact it does not look > to be possible right now. Defining a signature (eg: kernel binary format + > machine type) in the kernel binary would make the task easier. Some of the > formats have a signature (eg: u-boot) but not all the formats. > > Actually, if we try to boot a Linux kernel with the wrong settings then the > kernel would crash or raise an error. And it is not be possible to recover > from this state without restarting the platform. > Making these information available to the boot loader (u-boot, uefi, etc) > would also make easier the migration from the legacy ATAG to the Flat Device > Tree (FDT) support. in Barebox we use the same as u-boot but we can boot a zImage directly > > > BTW, Thursday 15:00UTC is fine for me. 15:00UTC is a bit late for I as I live now in China Shanghai I'd prefer 14:00UTC as if the call take 2h it will be already midnight here Best Regards, J.

15 years, 1 month

Linux Boot Architecture coordination meeting

by Grant Likely

Hi all, Following up from the decisions made at UDS last month[1], we need to organize a boot architecture coordination meeting. Currently the proposal is to hold a meeting either as part of the Linaro platform sprint[2] in the week on August 1-5, 2011, or in the weekend between the platform sprint and the ARM Partners Meeting the week after. Personally, my preference is to schedule a full day meeting on Friday, Aug 5 as part of the platform sprint, but I'd like to get some feedback before settling on that date. [1] https://blueprints.launchpad.net/linaro/+spec/linaro-kernel-o-bootarchitect… [2] https://wiki.linaro.org/Events/2011-08-LDS Right now I'm in the process of organizing the information and topics which were discussed during UDS and get them out onto the Linaro wiki. Expect to see some early draft documents showing up late this week or early next week. After that, I'm going to be soliciting feedback and help to make them reflect the priorities and requirements that Linux vendors, users and developers have for the boot architecture. By the time the Linaro platform sprint rolls around, we should have a solid set of documents covering both requirements and a draft boot architecture. At the boot architecture meeting, my goal is to first come to agreement on the general approach and draft design, second to make decisions about how the boot architecture fits in with existing technologies like Fastboot, UEFI and U-Boot, and third to kick off work on implementation and detailed design. In order to be successful, we need to make sure the appropriate people are involved. I've started by sending this email to the people who I know are interested in the topic, but I know I've missed folks. I'm also going to cc: the boot-architecture(a)lists.linaro.org[3] for any boot architecture traffic. Please let me know if there is anybody else that I should be inviting. In addition to the meeting in August, I'm considering a regular boot architecture conference call as part of the document drafting process, so I'd like to put together a list of critical stakeholders by the end of next week. [3] http://lists.linaro.org/mailman/listinfo/boot-architecture -- Grant Likely, B.Sc., P.Eng. Secret Lab Technologies Ltd.

15 years, 1 month

Re: Linux Boot Architecture coordination meeting

by Grant Likely

On Mon, Jun 13, 2011 at 7:56 AM, Steve McIntyre <steve.mcintyre(a)linaro.org> wrote: > On Mon, Jun 13, 2011 at 07:51:05AM -0600, Grant Likely wrote: >>Hi everyone, >> >>Note: I'm sending this directly to everyone on my 'interested >>individuals' list, but future traffic will only get sent to the >>boot-architecture(a)lists.linaro.org mailing list. If you're not >>already, and would like to stay in the loop, please subscribe to the >>list. >> >>Given the feedback I've received so far, I'm going to tentatively >>schedule the meeting for Friday, July 5, at the end of the Linaro > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^August, surely? Gah! yes. Friday, August 5th. Thanks for catching that. g.

15 years, 2 months

Barebox

by Jean-Christophe PLAGNIOL-VILLARD

Hi all, I've like to open the discussion about barebox What is Barebox? Barebox is a fork of U-Boot which was named before the elce 2009 U-Boot-V2 with the target to have a modern internal Implememtation derived from the Linux kernel and user friendly interface The current design of barebox is very near from the kernel as example on AT91 I've update the current API to be as near as possible as the one in the kernel so it's now really easy to port a new board and on contrary of U-Boot we can have the multy instance of the drivers. I'm start to push the SH with the same idea As example have the prompt on all uart at the same time or be able to use them independently. We also support FastBoot, Framebuffer, USB ohci & Ehci, network, nor, nandflash, dfu, usb ethernet (very usefull for soc without net device), Menu Framework, etc... inprogress mmc, spi flash DFU for Device Firmware Upgrade is very use full to update device from usb device from a PC so you will have an generic updater from the bootloader The Menu Framework will help you to create friendly interface to manage the booloader via key specially on device without keyboard as cellphone, STB etc... We have also a true shell support with scripting so it's very easy to create complex command via sheel script and also complex boot sequence We have modules support as the kernel which allow to load code based on the need and speed up the boot but also allow to update the bootloader functionnality in the feature etc... Best Regards, J.

15 years, 11 months

Re: ARM Boot Architecture working group idea

by Grant Likely

Follow up to the initial poll for interest on an ARM Boot Architecture working group (You can read the initial posting below for those people I've just added to the to: list). Linaro has graciously offered to host a mailing list and provide a conference bridge for meetings. You can subscribe to the mailing list here: http://lists.linaro.org/mailman/listinfo/boot-architecture I'm ready to kick off the first phase of the working group, which is to start collecting requirements and to define the boot use-cases that the working group will focus on solving (for example, one use-case is supporting a generic ARM distro on netbooks and tablets). There is a start to capturing requirements on the wiki page[1] and some discussion on the associated talk page[2]. [1] http://devicetree.org/Boot_Architecture [2] http://devicetree.org/Talk:Boot_Architecture I propose having a kick-off conference call in about 2 weeks (week of September 13th). Goal of the first call will be settle on a first-draft for the requirements, and to figure out if there are additional people or companies that we should be soliciting feedback from. Then we can begin drafting the interface and recommended practices document. If you're interested in being in on the call, let me know and I'll send you an invite and if you've got a preference on a day of the week. Regardless of the day, It will probably have to be at about 9:00MDT/16:00GMT to handle everyone's timezones. Cheers, g. ---------- Forwarded message ---------- From: Grant Likely <grant.likely(a)secretlab.ca> Date: Wed, Jul 21, 2010 at 1:31 PM Subject: ARM Boot Architecture working group idea Following up on a discussion from UDS-M in Brussels this year, the idea was raised to put together a working group to define a recommended firmware architecture for ARM systems. The goal being to have something usable by both the hardware and operating system vendors (notably Android and Linaro) to reduce the cost associated with board ports, and to have a common method for operating system installation across a wide range of devices. The goal of this working group would be to produce a specification including the following 3 things: 1) A set of requirements that meets the needs of hardware vendors, operating systems vendors, and software engineers 2) A recommended architecture for boot firmware. 3) A reference design implementing the first two items in a form usable by hardware vendors. I'm in the early planning stages now, and I'm looking for volunteers and interested parties to join the working group. To get things rolling, I've set up a wiki page[1] with a very early draft of requirements which captures some of the issues brought up at UDS-M. [1] http://devicetree.org/Boot_Architecture I've not yet set up any kind of charter or procedures for the working group. Nor have I done an exhaustive search for people who should be involved, so if there is anybody you can think of who I should contact, then please let me know. If you (or your company) is interested and would like to be involved, then please let me know. Once we've got a few people to kick things off, I'll set up a mailing list, try to pull together something about how this working group will be organized, and probably make an lwn or linux-embedded announcement. Cheers, g. -- Grant Likely, B.Sc., P.Eng. Secret Lab Technologies Ltd. -- Grant Likely, B.Sc., P.Eng. Secret Lab Technologies Ltd.

15 years, 11 months

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boot-architecture