[OE-core] RFC: grub-efi native tools

[Darren Hart]

On 11/22/2011 11:36 PM, Koen Kooi wrote:
> 
> Op 23 nov. 2011, om 08:01 heeft Darren Hart het volgende geschreven:
> 
>> While working towards supporting efi boot in live images, I have been
>> refactoring bootimg.bbclass, syslinux.bbclass, and adding recipes and
>> classes for grub-efi.
>>
>> I'd like the seasoned OE experts' opinions on a question of
>> implementation. grub-efi seems to require a final step after the normal
>> build to assemble the efi image, specifically:
>>
>> grub-mkimage -p / -d ./grub-core/ -O i386-efi -o ./bootia32.efi \
>>             boot linux fat serial part_msdos normal
>>
>> grub-mkimage is a tool built during the grub-efi do_compile step, so it
>> needs to be native in order to run the above command. So I'm left with a
>> few options:
>>
>> 1) Use BBCLASSEXTEND="native" and make grub-efi depend on
>>   grub-efi-native so the native grub-mkimage is available.
>>   - I'm not sure how to avoid a circular dependency there,
>>     other than making an explicit grub-efi-native_1.99.bb.
> 
> One way:
> 
> DEPENDS = "grub-efi-native"
> DEPENDS_virtclass-native = ""

Ah, nice. I presume I can also zero out a function for the virtclass-native?

do_compile_append() {
	... non-native stuff ...
}

do_compile_append_virtclass-native() {
	:
}

> 
> But the proper way is IMAGE_DEPENDS = "grub-efi-native" in the image classes that need it.

Hrm, but the MACHINE is what will determine if it's needed. Specifically
if MACHINE_FEATURES contains "efi" and PREFERREF_EFI_LOADER (or some
such) is set to "grub-efi", then it's needed.


> 
> 
>>   - No component of the grub-efi build needs to be installed
>>     on the target rootfs - so perhaps the the target arch version
>>     isn't needed at all...
> 
> BBCLASSEXTEND is quite cheap.
> 
>> 2) Only build grub-efi-native.
>>   - The above grub-mkimage command fails with some incorrect elf format
>>     error messages on the grub kernel.img file. A similar error was
>>     reported on the grub mailing list when compiling with cygwin.
>>     Some work may be required to fix GRUB here.
>>   - Installing output of -native recipes onto the target seems to be a
>>     bit at odds with the existing mechanisms (it doesn't find
>>     bootia32.efi when placed in ${STAGING_LIBDIR}/grub by a -native
>>     build, for example).
>>
>> 3) Tweak the build so that only the grub-* utilities are built natively.
>>   - The Linux kernel build does this for some of the internal
>>     tooling required for the build (Kconfig, etc.).
>>   - If we did want to install the tools on the target, we wouldn't have
>>     the target arch binaries available. Perhaps both could be built.
>>
>> So there are a number of ways to go about this. If someone can leverage
>> some experience with OE to indicate which of these would be met with the
>> least resistance, both in terms of implementation as well as upstream
>> acceptance, I would appreciate it.
> 
> Have a look at u-boot-mkimage, there's a native and target version available.
> 

That looked really promising. Poring over the grub make system not only
made my eyes bleed, but also yielded no means to build only the util
directory. I'm hesitant to add a dependency that require GRUB be
configured and built twice - definitely goes against the goal of
improving build time.

I'll send a note to the grub guys and see if they have a solution.

Thanks Koen, very helpful stuff.

-- 
Darren Hart
Intel Open Source Technology Center
Yocto Project - Linux Kernel