[Buildroot] [bug] bootwrapper runs before linking initrd

[Buildroot] [bug] bootwrapper runs before linking initrd

[Hollis Blanchard]

I have a BR config that includes the following:
BR2_LINUX_KERNEL=y
BR2_TARGET_ROOTFS_INITRAMFS=y
BR2_TARGET_BOOT_WRAPPER_AARCH64=y

I expect that Buildroot will:

 1. build the kernel
 2. build rootfs.cpio
 3. link rootfs.cpio into the kernel as an initrd
 4. run boot-wrapper-aarch64 on the kernel+initrd

When I do a build, however, I can clearly see that step 4 happens before 
step 3. In fact, "Rebuilding kernel with initramfs" is the very last 
step of the build. "boot-wrapper-aarch64 Installing to images directory" 
happened much earlier.

(Side note: the error is far more catastrophic than a simple "couldn't 
find root filesystem" panic; it looks like big chunks of the kernel's 
data section are zeroed, so that kernel messages aren't even logged, to 
say nothing of no serial output. I don't know why this is.)

A workaround is to remember to manually "make 
boot-wrapper-aarch64-rebuild" after a regular build has completed.

What's the real solution? Thanks!

-- 
Hollis Blanchard
Mentor Graphics Emulation Division

[Buildroot] [bug] bootwrapper runs before linking initrd

[Thomas Petazzoni]

Hollis,

On Thu, 3 Sep 2015 15:00:49 -0700, Hollis Blanchard wrote:
> I have a BR config that includes the following:
> BR2_LINUX_KERNEL=y
> BR2_TARGET_ROOTFS_INITRAMFS=y
> BR2_TARGET_BOOT_WRAPPER_AARCH64=y

Yes, this is not working right now.

> I expect that Buildroot will:
> 
>  1. build the kernel
>  2. build rootfs.cpio
>  3. link rootfs.cpio into the kernel as an initrd
>  4. run boot-wrapper-aarch64 on the kernel+initrd
> 
> When I do a build, however, I can clearly see that step 4 happens before 
> step 3. In fact, "Rebuilding kernel with initramfs" is the very last 
> step of the build. "boot-wrapper-aarch64 Installing to images directory" 
> happened much earlier.
> 
> (Side note: the error is far more catastrophic than a simple "couldn't 
> find root filesystem" panic; it looks like big chunks of the kernel's 
> data section are zeroed, so that kernel messages aren't even logged, to 
> say nothing of no serial output. I don't know why this is.)
> 
> A workaround is to remember to manually "make 
> boot-wrapper-aarch64-rebuild" after a regular build has completed.
> 
> What's the real solution? Thanks!

See http://lists.busybox.net/pipermail/buildroot/2014-July/101052.html
for a possible solution. I remember we discussed this patch during the
Buildroot Summer camp, but I thought we had sent some comments for
Jeremy to improve the patch. But it seems it wasn't done. Arnout, do
you remember the conclusion of our discussion?

I must say I'm not thrilled by making such major changes to Buildroot
just for the sake of this very specific use-case. But we probably don't
have much choice.

Thomas
-- 
Thomas Petazzoni, CTO, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com

[Buildroot] [bug] bootwrapper runs before linking initrd

[Peter Korsgaard]

>>>>> "Thomas" == Thomas Petazzoni <thomas.petazzoni@free-electrons.com> writes:

Hi,

 > See http://lists.busybox.net/pipermail/buildroot/2014-July/101052.html
 > for a possible solution. I remember we discussed this patch during the
 > Buildroot Summer camp, but I thought we had sent some comments for
 > Jeremy to improve the patch. But it seems it wasn't done. Arnout, do
 > you remember the conclusion of our discussion?

 > I must say I'm not thrilled by making such major changes to Buildroot
 > just for the sake of this very specific use-case. But we probably don't
 > have much choice.

I don't know any details of this boot wrapper, but perhaps we could
change the package to only build the host tool and simply ask people to
write a post-image script to invoke it with the correct arguments once
the build is completely done, similar to what we do for other custom
"post processing" tasks?

-- 
Bye, Peter Korsgaard

[Buildroot] [bug] bootwrapper runs before linking initrd

[Thomas Petazzoni]

Dear Peter Korsgaard,

On Fri, 04 Sep 2015 11:51:33 +0200, Peter Korsgaard wrote:

>  > I must say I'm not thrilled by making such major changes to Buildroot
>  > just for the sake of this very specific use-case. But we probably don't
>  > have much choice.
> 
> I don't know any details of this boot wrapper, but perhaps we could
> change the package to only build the host tool and simply ask people to
> write a post-image script to invoke it with the correct arguments once
> the build is completely done, similar to what we do for other custom
> "post processing" tasks?

Doesn't work: the kernel image is *linked* into the boot wrapper. So
really, it's not just a post-processing tool, you need the kernel image
to build the wrapper.

Best regards,

Thomas
-- 
Thomas Petazzoni, CTO, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com

[Buildroot] [bug] bootwrapper runs before linking initrd

[Arnout Vandecappelle]

[Adding Jeremy Kerr in CC - he's the author of
http://patchwork.ozlabs.org/patch/366549/ ]

On 04-09-15 10:54, Thomas Petazzoni wrote:
> Hollis,
> 
> On Thu, 3 Sep 2015 15:00:49 -0700, Hollis Blanchard wrote:
>> I have a BR config that includes the following:
>> BR2_LINUX_KERNEL=y
>> BR2_TARGET_ROOTFS_INITRAMFS=y
>> BR2_TARGET_BOOT_WRAPPER_AARCH64=y
> 
> Yes, this is not working right now.
[snip]
>> What's the real solution? Thanks!
> 
> See http://lists.busybox.net/pipermail/buildroot/2014-July/101052.html
> for a possible solution. I remember we discussed this patch during the
> Buildroot Summer camp, but I thought we had sent some comments for
> Jeremy to improve the patch. But it seems it wasn't done. Arnout, do
> you remember the conclusion of our discussion?

 I did send it:

http://lists.busybox.net/pipermail/buildroot/2015-July/132686.html

(mailmain/pipermail threading sucks)

 TL;DR:

 It was a long discussion, mainly because it doesn't really solve the problem
(which BTW is mainly in the approach we take for linux-with-initramfs - that's
just a huge hack).

 That said, we basically agree with the approach. So if you're stilling willing
to do it, please post a full series including the change to
boot-wrapper-aarch64, taking into account the comments below. We've marked this
patch as Changes Requested in patchwork.


 _However_, I may have an idea for an alternative approach that confines the
hack to boot-wrapper-aarch64 itself. The following may work:

boot-wrapper-aarch64-rebuild-with-initramfs: linux-rebuild-with-initramfs
	$(TARGET_MAKE_ENV) $(MAKE) -C $(BOOT_WRAPPER_AARCH64_SRCDIR)
	cp $(BOOT_WRAPPER_AARCH64_SRCDIR)/linux-system.axf $(BINARIES_DIR)

ROOTFS_INITRAMFS_POST_TARGETS += boot-wrapper-aarch64-rebuild-with-initramfs


I.e., rerun the build and install commands as part of the rootfs-initramfs build
step. Note that no conditions are needed, since this target will anyway only
come into play when rootfs-initramfs is built.

 Can someone give that a try and post a patch?

 Regards,
 Arnout

> 
> I must say I'm not thrilled by making such major changes to Buildroot
> just for the sake of this very specific use-case. But we probably don't
> have much choice.
> 
> Thomas
> 


-- 
Arnout Vandecappelle                          arnout at mind be
Senior Embedded Software Architect            +32-16-286500
Essensium/Mind                                http://www.mind.be
G.Geenslaan 9, 3001 Leuven, Belgium           BE 872 984 063 RPR Leuven
LinkedIn profile: http://www.linkedin.com/in/arnoutvandecappelle
GPG fingerprint:  7493 020B C7E3 8618 8DEC 222C 82EB F404 F9AC 0DDF