Build failure on Ubuntu: `/usr/include/linux/errno.h:1:10: fatal error: 'asm/errno.h' file not found`

[fnordahl]

$ make
[PROBE]      building /home/ubuntu/src/retis/retis/src/core/probe/kernel/bpf ...
[PROBE]      building /home/ubuntu/src/retis/retis/src/core/probe/user/bpf ...
In file included from usdt.bpf.c:3:
In file included from /home/ubuntu/src/retis/retis/src/.out/bpf/usdt.bpf.h:6:
/usr/include/linux/errno.h:1:10: fatal error: 'asm/errno.h' file not found
    1 | #include <asm/errno.h>
      |          ^~~~~~~~~~~~~
1 error generated.
make[1]: *** [/home/ubuntu/src/retis/ebpf.mk:17: .out/usdt.bpf.o] Error 1
make: *** [Makefile:162: /home/ubuntu/src/retis/retis/src/core/probe/user/bpf] Error 2

Adding /usr/include/$(ARCH)-linux-gnu to the include path appears to fix the issue.

[atenart]

Thanks for the report!

The issue is Ubuntu provides an header, linux/errno.h, which includes another header that cannot be found. This is because asm/errno.h lives under /usr/include/asm-generic while GCC looks to /usr/include/asm. This is an Ubuntu specific problem.

In our CI we fix this by adding the following symlink, ln -s /usr/include/asm-generic /usr/include/asm, although it seems installing gcc-multilib also fixes this for some reason (haven't dig into that).

[fnordahl]

So none of those options would work in a locked down build environment. Whether or not this is a distribution level bug it does not help anyone in need of building retis.

As a compromise, would you accept a PR that allows passing additional INCLUDES from environment or make command line?

[atenart]

So none of those options would work in a locked down build environment. Whether or not this is a distribution level bug it does not help anyone in need of building retis.

I'm not following, there are prerequisites for building most projects. The build environment requires those and they should be installed prior to the build step. It seems the proper way to provide asm/errno.h is to install gcc-multilib on Ubuntu systems, what would make this specific among all build dependencies? Maybe this could be added to our doc though.

(As a side note for context the above requirement is for building USDT probes as the header provided by libbpf includes linux/errno.h which in turns includes asm/errno.h).

[fnordahl]

gcc-multilib is meant for cross-compiling purposes and depends of compilers for all kinds of esoteric architectures, so it does not feel like a correct dependency for retis.

The file needed is right there in the system already, all we need is to point at the correct directory named after the target triplet of the system.

[atenart]

The file needed is right there in the system already, all we need is to point at the correct directory named after the target triplet of the system.

Looking at different options and trying to understand the root cause I learnt compilers support environment variables to configure the set of include paths. Here we need to fixup the eBPF build stage, which uses clang: CPATH can be used to add extra include paths. I successfully tested that. It's worth noting GCC supports the exact same variable, if we ever add support for it.

I think that fixes the build issue reported here in a good way (toolchain level). How does that sound? We can document this in our documentation in the Ubuntu section.

[atenart]

The file needed is right there in the system already, all we need is to point at the correct directory named after the target triplet of the system.

Looking at different options and trying to understand the root cause I learnt compilers support environment variables to configure the set of include paths. Here we need to fixup the eBPF build stage, which uses clang: CPATH can be used to add extra include paths. I successfully tested that. It's worth noting GCC supports the exact same variable, if we ever add support for it.

I think that fixes the build issue reported here in a good way (toolchain level). How does that sound? We can document this in our documentation in the Ubuntu section.

@fnordahl did you have a chance to have a look at the above?