Re: [PATCH dwarves v2] dwarf_loader: Fix skipped encoding of function BTF on 32-bit systems

[Tony Ambardar <tony.ambardar@gmail.com>]

On Fri, May 09, 2025 at 10:33:50AM +0200, Alexis Lothoré wrote:
> On Fri May 9, 2025 at 7:21 AM CEST, Tony Ambardar wrote:
> > Hi Alexis,
> >
> > On Thu, May 08, 2025 at 11:38:06AM +0200, Alexis Lothoré wrote:
> >> Hello,
> 
> [...]
> 
> > Nice! I notice bootlin has worked on several BPF testing contributions,
> > and was wondering if your build is some new standard buildroot/yocto
> > config tailored for BPF testing, and what archs it might support? Reason
> > for asking is I have a large stack of WIP patches for enabling use of
> > test_progs across 64/32-bit archs and cross-compilation, and I'm keen to
> > see other examples of configs, root images, etc. (especially for 32-bit)
> > At the moment I'm targeting 32-bit armhf support to make progress..
> 
> No,  that's really a custom, minimal setup that I am using, based on
> buildroot. My workflow is roughly the following:
> - use buildroot to download an arm64 toolchain and build a minimal rootfs.
>   No specific defconfig used, it is a configuration from scratch, with
>   additional tools for development and debugging
> - configure a kernel for arm64 testing:
> $ cat tools/testing/selftest/bpf/{config,config.vm,config.aarch64} >
> .config
> - use the toolchain downloaded by buildroot to build the kernel
> - build the selftests with the same toolchain (so I am cross-building those
>   directly from my host, I am not really using vmtest)
> - run all of those in qemu, and run the selftests directly with test_progs
>   in there

Understood, and thanks for the details. I basically do the same, with only a
couple of differences intended to ease adding armhf as a bpf-ci target
eventually:

 - use the Ubuntu arm cross-toolchain to build on x86_64
 - use mkrootfs tools from bpf-ci to make a Debian Bookworm rootfs

Take care,
Tony

> 
> Alexis
> 
> -- 
> Alexis Lothoré, Bootlin
> Embedded Linux and Kernel engineering
> https://bootlin.com
>