query about supported arch for bpftune

[sudipm-mukherjee]

Hi,
Sorry if I have missed it in the docs somewhere. But is bpftune only supports x86_64 and aarch64 ?

I can see at https://buildd.debian.org/status/package.php?p=bpftune that all others builds are failing. i386 has built in the past but it now fails with the HEAD of bpftune repo now. So, if you confirm that bpftune only supports x86_64 and aarch64 then I will mark it accordingly in the Debian package.

[06kellyjac]

bpftune/include/bpftune/bpftune.bpf.h

Lines 38 to 42 in 5966387

	#if defined(__TARGET_ARCH_x86)
	#include <bpftune/vmlinux_x86_64.h>
	#elif defined(__TARGET_ARCH_arm64)
	#include <bpftune/vmlinux_aarch64.h>
	#endif

bpftune/src/Makefile

Lines 20 to 23 in 5966387

	ARCH ?= $(shell uname -m)
	SRCARCH ?= $(shell uname -m | sed -e s/i.86/x86/ -e s/x86_64/x86/ \
	-e /arm64/!s/arm.*/arm/ -e s/sa110/arm/ \
	-e s/aarch64.*/arm64/ )

I'd be good to have it documented in the README or something, but my guess is yes. (Not part of the dev team)

[sudipm-mukherjee]

Yes, but again at the same time I am seeing 8ed522c which means that it worked on i386 at one point of time (which I can also see on Debian, the previous package built for i386).

So, if the dev team has now decided to remove i386 support, then it should be documented please.

[alan-maguire]

hi, it's not really a decision on i386 support; it's more a practical problem. More detail than you probably need but anyway:

To build bpftune we need a vmlinux.h which is generated by bpftool btf dump file /sys/kernel/btf/vmlinux ; this is basically the definition of all kernel data structures and it is useful for tuners since they often need access to kernel internals.

However, the problem is within an rpmbuild environment sysfs paths like /sys/kernel/btf are not available, so we have pre-generated vmlinux.h files. Currently only for x86_64/aarch64, but we could add more.

I guess the question is if there is a way to do that generation of vmlinux.h within the build setup you use? If there was we could try and figure out a method to do that within bpftune builds and it might open up other architectures. If there are examples of other bpf projects that handle this (and work across mutliple architectures) they may provide some ideas here.

Ideally I'd love to have an approach that did away with the hard-coded vmlinux.h files and opened up more architectures but I'm not sure how to achieve that to be honest. Thanks!

[sudipm-mukherjee]

I am not sure of rpmbuild environment. But for Debian, I should be able to use the package linux-bpf-dev and that should give me the vmlinux.h for all arch which I should be able to use while building the package.

https://packages.debian.org/search?suite=sid&mode=filename&searchon=contents&keywords=vmlinux.h

[alan-maguire]

Also see #158 ; changes were made to support using /usr/include/$(ARCH)-linux-gnu/linux/bpf/vmlinux.h. It's possible the ARCH variable is being set incorrectly for some arches, or maybe the package isn't installed; do we need to add it to the spec file explicitly to ensure it is installed in the pkg build enviornment perhaps?

[alan-maguire]

would it be possible to recheck builds now that #193 has been merged into main? thank you!

[alan-maguire]

@sudipm-mukherjee I think that the i386 issues should be fixed; if you get a chance to re-test with latest main branch that would be great. thank you!

[sudipm-mukherjee]

@sudipm-mukherjee I think that the i386 issues should be fixed; if you get a chance to re-test with latest main branch that would be great. thank you!

Hi @alan-maguire, sorry missed it before. I will test it tomorrow morning.

[alan-maguire]

fantastic, thank you!