[PATCH 0/7] efi: Various tidy-ups and drop the default

[Simon Glass]

Hi Heinrich,

On Mon, 28 Jun 2021 at 09:20, Heinrich Schuchardt <xypron.glpk at gmx.de> wrote:
>
> On 6/28/21 4:18 PM, Simon Glass wrote:
> > Hi Tom, Mark,
> >
> > On Mon, 28 Jun 2021 at 07:37, Tom Rini <trini at konsulko.com> wrote:
> >>
> >> On Mon, Jun 28, 2021 at 10:38:50AM +0200, Mark Kettenis wrote:
> >>>> From: Simon Glass <sjg at chromium.org>
> >>>> Date: Sun, 27 Jun 2021 19:48:34 -0600
> >>>>
> >>>> It has come to light that EFI_LOADER adds an extraordinary amount of
> >>>> code to U-Boot. For example, with nokia_rx51 the size delta is about
> >>>> 90KB. About 170 boards explicitly disable the option, but is is clear
> >>>> that many more could, thus saving image size and boot time.
> >>>
> >>> EFI_LOADER used to be a lot smaller.  It is great to see that over the
> >>> years UEFI support has become more complete, but a lot of that new
> >>> code implements features that are not at all essential for just
> >>> booting an OS from storage.  If that growth leads to the suggestion to
> >>> disable EFI_LOADER completely by default, we're putting the cart
> >>> before the horse.
> >>
> >> Well, I see I forgot to prefix my patch with RFC, but I hadn't found
> >> EFI_LOADER being used in the wild on armv7, but wasn't sure about the
> >> BSD families.  I did see that Debian doesn't use it, and that Armbian
> >> doesn't even use it on aarch64.
> >>
> >>>> The current situation is affecting U-Boot's image as a svelt bootloader.
> >>>
> >>> Really?  I know UEFI has a bad reputation in the Open Source world,
> >>> and some of its Microsoft-isms are really annoying (yay UCS-2).  But
> >>> it works, it provides a standardized approach across several platforms
> >>> (ARMv7, AMRv8, RISC-V) and the industry seems to like it.  Personally
> >>> I'd wish the industry had standardized on Open Firmware instead, but
> >>> that ship sailed a long time ago...
> >>>
> >>> I find it hard to imagine that 90k is a serious amount of storage for
> >>> something that is going to include a multi-MB Linux kernel.  This
> >>> isn't code that lives in SPL or TPL where severe size restrictions
> >>> apply.
> >>
> >> In one of those cases where I need to pop back in to the other (Nokia
> >> N900 specific) thread and see if the big size reduction really was just
> >> disabling EFI_LOADER, it's perhaps just one of those "fun" things about
> >> Kconfig and anything other than "make oldconfig" for spotting new config
> >> options that default to enabled.
> >
> > Yes it will be interesting to see what you find there. My results on
> > nokia_rx51 were something like this:
> >
> > default
> >         arm: (for 1/1 boards) all +129370.0 bss +1136.0 data +7399.0
> > rodata +10989.0 text +109846.0
> >
> > without ebbr
> >        arm: (for 1/1 boards) all +38460.0 bss +1040.0 data +2375.0
> > rodata +5333.0 text +29712.0
> >
> > with various other things:
> > CONFIG_OF_LIBFDT_ASSUME_MASK=7
> > # CONFIG_OF_TRANSLATE is not set
> > # CONFIG_SIMPLE_BUS is not set
> > # CONFIG_TI_SYSC is not set
> > # CONFIG_CMD_FDT is not set
> >
> >        arm: (for 1/1 boards) all +19170.0 bss -16.0 data +360.0 rodata
> > +3274.0 text +15552.0
> >
> > (Mark, in the same email:)
> >>> FIT simply isn't fit for purpose (pun intended).  It only really works
> >>> for booting Linux, and forces people to combine u-boot, kernel,
> >>> initial ramdisk and other firmware components into a single image.
> >>> That is really undesirable as:
> >>> - This makes it sigificantly harder to update individual components of
> >>>   such an image.  Making it hard to update a kernel is obviously a
> >>>   serious security risk.
> >>> - This makes it impossible to build an OS install image that works om
> >>>   multiple boards/SoCs.
> >
> >
> > I would really like to understand this better. The whole thing is a
> > complete mystery to me.
> >
> > Firstly I have sometimes fiddled with booting other OSes using FIT. It
> > seemed OK. I can't see why it only works with Linux.
> >
> > Secondly, I don't expect that U-Boot itself would be in the FIT.
> >
> > Thirdly, do you really want the kernel and initrd to be separate? At
> > least in the systems I have used, they are built together, even having
> > the same name, e.g.:
> >
> > initrd.img-5.10.40-1rodete1-amd64
> > System.map-5.10.40-1rodete1-amd64
> > vmlinuz-5.10.28-1rodete2-amd64
>
> I have not hit any distro that builds FIT images. All install vmlinux
> and initrd as separate files.
>
> Why would you want to change that?

Well there is no point in having two files if one will do. Also it
allows for a hash / signature check.

>
> >
> > Finally, for the firmware components, do you mean system firmware? If
> > so, I would expect it to be more convenient to distribute updates to
> > that separately, although I suppose they could be combined with the
> > kernel if the combinatorial explosion can be contained. What is the
> > problem, exactly? (If you mean peripheral firmware, I would expect
> > fwupd to handle that.)
> >
> > What exactly is impossible? Can you please be more specific?
> >
> > FIT is just a container. It seems to have been rejected by the EFI
> > crew at some point. Perhaps I just need to try to use it with one of
> > the distros out there, to actually understand what is going on here.
> > But any help is appreciated.
>
> FIT and EFI are orthogonal. A FIT image can contain an EFI binary. See
> CONFIG_BOOTM_EFI.

(I think that is a different topic; FIT can of course contain any image)

>
> >
> >>
> >>>> EFI_LOADER is required by EBBR, a new boot standard which aims to
> >>>> bring in UEFI protocols to U-Boot. But EBRR is not required for
> >>>> booting. U-Boot already provides support for FIT, the 'bootm' command
> >>>> and a suitable hand-off to Linux. EBRR has made the decision to create
> >>>> a parallel infrastructure, e.g. does not use FIT, nor U-Boot's signing
> >>>> infrastructure.
> >>>
> >>> EFI_LOADER is required to boot FreeBSD and OpenBSD on several
> >>> platforms as well as generic Linux distros.  For example
> >>> OpenBSD/armv7, OpenBSD/arm64 and OpenBSD/riscv64 all rely on
> >>> EFI_LOADER to boot and have done so for the last 4 years.  The fact
> >>> that ARM has embraced UEFI as an embedded boot standard and branded it
> >>> EBBR really isn't all that relevant.
> >>
> >> To be clear here, I like EFI_LOADER.  I too do wish some other
> >> technologies had become dominant for technical rather than inertia
> >> reasons, but here we are.  Having played around with it on aarch64,
> >> there are some pretty nice comes-along-with parts to it.
> >>
> >> What I hadn't seen, and am only a little skeptical of still, is how far
> >> backwards in generations it's going to be used on.  The general wish is
> >> that users nor off the shelf OS groups need to rebuild U-Boot for a
> >> given board, and instead it just works.  The number of new designs for
> >> 32bit parts is no where near the number of new designs for 64bit parts.
> >> So what we're seeing in U-Boot now is people updating support on their
> >> older designs, and not necessarily caring about using EFI_LOADER.
> >
> > In a reply to one of the patches in this series, Heinrich mentions a
> > few problems that need resolving (devices for partitions and file
> > handles). Both of those features should first be added to U-Boot, so
> > EFI can then use that support. In general, EFI has tried to work
> > beside driver model, creating its own parallel tables, etc.
>
> Could you, please, be a bit more specific. Please, indicate which data
> structures you would like to integrate into the driver model.

As a starting point, all the struct efi_device_path* things should be
generated on the fly from DM, rather than existing in parallel.

>
> EDK II shows that a driver model completely based on UEFI protocols is
> possible. As long as we don't follow that road we will have separate
> APIs for the UEFI world and U-Boot's internal use and we will have to
> keep track of objects that exist only in the one world or the other.
>
> What we definitively need is a better integration between probing and
> removing U-Boot devices and their representation in the UEFI world.

That is the crux of the problem. The approach taken by UEFI (of
duplicating everything) needs to change.

>
> Another area that might deserve attention is memory allocation.
> AllocatePool() consuming whole memory pages is quite a waste.
>
> > I have
> > tried to influence this at various points along the way, including at
> > the start and I'm happy to dig out those threads if it helps. But I
> > wasn't kidding. it really needs to be addressed. I would love to see
> > Linaro (for example) organise something here and take this on. I am
> > very happy to help.
>
> The starting point would be comparing the DM and UEFI object models and
> pointing out which objects can be mapped and which cannot.

In my book there are three categories:

- can
- cannot at present, but should be soon
- should not

Regards,
Simon