Hi François,
On Mon, 1 Nov 2021 at 02:53, François Ozog francois.ozog@linaro.org wrote:
Hi Simon,
this seems a great endeavor. I'd like to better understand the scope of it.
Is it to be used as part of what could become a U-Boot entry ABI scheme? By that I mean giving some fixed aspects to U-Boot entry while letting boards to have flexibility (say for instance that the first 5 architecture ABI parameter registers are reserved for U-Boot), and the Passage is about specifying either those reserved registers or one of them?
The goal is to provide a standard entry scheme for all firmware binaries. Whether it achieves that (or can with some mods) is up for discussion.
Re the registers, do you think we need 5?
Thinking entry ABI, here is what I observed on Arm:
Linux has two entry ABIs:
- plain: x0 = dtb; command line = dtb:/chosen/bootargs; initrd = dtb:/chosen/linux,initrd-*
- EFI: x0=handle, x1=systemtable, x30=return address; dtb = EFI_UUID config table; initrd = efi:<loadfile2(INITRD vendor media UUID); command line = efi: image_protocol::load_options
U-Boot (proper) has plenty of schemes:
- dtb is passed as either x0, x1, fixed memory area (Qemu which is bad in itself), or other registers
- additional information passing: board specific register scheme, SMC calls
- U-Boot for RPI boards implement a Linux shaped entry ABI to be launched by Videocore firmware
Based on all the above, I would tend to think that RPI scheme is a good idea but also shall not prevent additional schemes for the boards.
I was not actually considering Linux since I believe/assume its entry scheme is fixed and not up for discussion.
I also did not think about the EFI case. As I understand it we cannot touch it as it is used by UEFI today. Maybe it is even in the standard?
Really I am hoping we can start afresh...?
What about a U-Boot Arm entry ABI like:
- plain: x0=dtb, x1=<Passage defined>, x2-x5 = <reserved>, other registers are per platform, SMC calls allowed too
Hmm we don't actually need the dtb as it is available in the bloblist. But I added an offset to it as a convenience.
- EFI: x0=handle, x1=systemtable, x30=return address; (when U-Boot is launched as an EFI app) dtb = EFI_UUID config table, + Passage = Passage UUID config table
I don't understand the last line. Where is the passage info / bloblist? Do you mean it goes in the HOB list with a UUID? I suppose that is the most EFI-compatible way.
What do you think about the idea of using an offset into the bloblist for the dtb? Also, can we make the standard passage ABI a build-time option, so it is deterministic?
We could further leverage Passage to pass Operating Systems parameters that could be removed from device tree (migration of /chosen to Passage). Memory inventory would still be in DT but allocations for CMA or GPUs would be in Passage. This idea is to reach a point where device tree is a "pristine" hardware description.
I'm worried about this becoming a substitute for devicetree. Really my intent is to provide a way to pass simple info, whereas what you talk about there seems like something that should be DT, just that it might need suitable bindings.
As you know I have more expansive views about what should be in DT.
Cheers
PS: as Ilias mentions, this patch set contains bug fixes, non immediately related additional functions (DM stats). It would be great to carve those out to fast path them and keep this one with the very core of your idea.
The DM stats is used in 'passage: Report the devicetree source'. I know it is sideways but I think it is better to make the output line more useful than just reporting the devicetree source.
The first patch is indeed unrelated. I will pick it up so we can drop it for the next rev.
Regards, Simon
On Mon, 1 Nov 2021 at 02:17, Simon Glass sjg@chromium.org wrote:
This series adds a standard way of passing information between different firmware phases. This already exists in U-Boot at a very basic level, in the form of a bloblist containing an spl_handoff structure, but the intent here is to define something useful across projects.
The need for this is growing as firmware fragments into multiple binaries each with its own purpose. Without any run-time connection, we must rely on build-time settings which are brittle and painful to keep in sync.
This feature is named 'standard passage' since the name is more unique than many others that could be chosen, it is a passage in the sense that information is flowing from one place to another and it is standard, because that is what we want to create.
The implementation is simply a pointer to a bloblist in a register, with an extra register to point to a devicetree, for more complex data, if one is present in the bloblist. This should cover all cases (small memory footprint as well as complex data flow) and be easy enough to implement on all architectures.
The core bloblist code is relicensed to BSD-3-Clause in case it is useful in non-GPL projects but there is no requirement to use the same code.
This series includes tweaks to the bloblist implementation in U-Boot to make it more suitable for the task, including:
- Allocate tags explicitly in the enum
- Put the magic number first
- Define a process for adding tags
The emphasis is on enabling open communcation between binaries, not enabling passage of secret, undocumented data, although this is possible in a private environment.
This series is built on the OF_BOARD series It is available at u-boot-dm/pass-working or:
https://source.denx.de/u-boot/custodians/u-boot-dm/-/commit/073b5c156f222c69...
Simon Glass (31): Makefile: Correct TPL rule for OF_REAL kconfig: Add support for conditional values dm: core: Allow getting some basic stats stddef: Avoid warning with clang with offsetof() fdt: Drop SPL_BUILD macro bloblist: Put the magic number first bloblist: Rename the SPL tag bloblist: Drop unused tags bloblist: Use explicit numbering for the tags bloblist: Support allocating the bloblist bloblist: Use LOG_CATEGORY to simply logging bloblist: Use 'phase' consistently for bloblists bloblist: Refactor Kconfig to support alloc or fixed arm: qemu: Add an SPL build bloblist: Add functions to obtain base address and size passage: Support an incoming passage passage: Support a control devicetree passage: arm: Accept a passage from the previous phase passage: spl: Support adding the dtb to the passage bloblist passage: spl: Support passing the passage to U-Boot passage: Record where the devicetree came from passage: Report the devicetree source passage: Add a qemu test for ARM bloblist: doc: Bring in the API documentation bloblist: Relicense to allow BSD-3-Clause sandbox: Add a way of checking structs for standard passage passage: Add documentation passage: Add docs for spl_handoff x86: Move Intel GNVS file into the common include directory passage: Add checks for pre-existing blobs WIP: RFC: Add a gitlab test
.gitlab-ci.yml | 6 + MAINTAINERS | 10 + Makefile | 2 +- arch/arm/cpu/armv7/start.S | 7 +- arch/arm/dts/qemu-arm-u-boot.dtsi | 22 ++ arch/arm/lib/crt0.S | 4 + arch/arm/mach-qemu/Kconfig | 9 + arch/sandbox/cpu/spl.c | 2 +- arch/x86/cpu/apollolake/acpi.c | 2 +- arch/x86/cpu/broadwell/cpu_from_spl.c | 4 +- arch/x86/cpu/intel_common/acpi.c | 2 +- .../include/asm/arch-apollolake/global_nvs.h | 2 +- arch/x86/lib/spl.c | 2 +- arch/x86/lib/tpl.c | 2 +- board/emulation/qemu-arm/Kconfig | 23 +- board/emulation/qemu-arm/MAINTAINERS | 1 + board/emulation/qemu-arm/Makefile | 1 + board/emulation/qemu-arm/spl.c | 27 ++ board/google/chromebook_coral/coral.c | 2 +- board/sandbox/Makefile | 3 +- board/sandbox/stdpass_check.c | 107 ++++++ cmd/bdinfo.c | 2 + common/Kconfig | 161 ++++++++- common/bloblist.c | 124 +++++-- common/board_f.c | 48 ++- common/board_r.c | 18 + common/spl/spl.c | 74 +++- configs/qemu_arm_spl_defconfig | 78 +++++ doc/board/emulation/qemu-arm.rst | 38 +++ doc/develop/bloblist.rst | 28 +- doc/develop/index.rst | 1 + doc/develop/std_passage.rst | 319 ++++++++++++++++++ drivers/core/device.c | 11 + drivers/core/root.c | 7 + drivers/core/uclass.c | 13 + drivers/serial/serial-uclass.c | 3 +- dts/Kconfig | 12 + include/asm-generic/global_data.h | 35 ++ include/bloblist.h | 175 +++++++--- include/dm/device.h | 11 +- include/dm/root.h | 8 + include/dm/uclass-internal.h | 7 + include/fdtdec.h | 40 ++- include/handoff.h | 8 +- .../x86/include/asm => include}/intel_gnvs.h | 0 include/linux/kconfig.h | 18 + include/linux/stddef.h | 8 +- include/spl.h | 15 + include/stdpass/README | 4 + include/stdpass/tpm2_eventlog.h | 42 +++ include/stdpass/vboot_ctx.h | 267 +++++++++++++++ lib/asm-offsets.c | 5 + lib/fdtdec.c | 65 +++- scripts/config_whitelist.txt | 1 + test/bloblist.c | 21 +- test/dm/core.c | 41 +++ test/py/tests/test_passage.py | 11 + 57 files changed, 1798 insertions(+), 161 deletions(-) create mode 100644 arch/arm/dts/qemu-arm-u-boot.dtsi create mode 100644 board/emulation/qemu-arm/spl.c create mode 100644 board/sandbox/stdpass_check.c create mode 100644 configs/qemu_arm_spl_defconfig create mode 100644 doc/develop/std_passage.rst rename {arch/x86/include/asm => include}/intel_gnvs.h (100%) create mode 100644 include/stdpass/README create mode 100644 include/stdpass/tpm2_eventlog.h create mode 100644 include/stdpass/vboot_ctx.h create mode 100644 test/py/tests/test_passage.py
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-- François-Frédéric Ozog | Director Business Development T: +33.67221.6485 francois.ozog@linaro.org | Skype: ffozog