On Friday, October 18, 2019 4:39:10 AM EDT Florian Weimer wrote:
> * Steve Grubb:
> > I am in the process of building a new version of suricata, an IDS
> > program that watches network traffic. It has a new module that uses eBPF
> > for high speed network packet categorization. When building, it uses the
> > following command:
> >
> > /usr/bin/clang -Wall -Iinclude -O2 \
> >
> > -I/usr/include/x86_64-linux-gnu/ \
> > -D__KERNEL__ -D__ASM_SYSREG_H \
> > -target bpf -S -emit-llvm xdp_lb.c -o xdp_lb.ll
> >
> > It eventually includes /usr/include/features.h which in turn includes
> > /usr/include/gnu/stubs.h. That file has this code:
> >
> > #if !defined __x86_64__
> > # include <gnu/stubs-32.h>
> > #endif
> >
> > I don't think __x86_64__ is defined as the program is aimed at eBPF in
> > the kernel. In rawhide, we no longer have glibc-devel(x86-32) to allow
> > this to resolve. However, I think that the assumption of not having
> > __x86_64__ defined means we are targeting i686 is wrong. What should I do?
> > Do we not support eBPF programs on Fedora?
>
> We certainly do not support building eBPF programs against glibc
> headers. There is no eBPF port of glibc, after all.
Suricata made it through the Debian/Ubuntu build systems. So, that leaves me
trying to figure out how push this through ours since other distros did it. I
have a feeling that it is not using the 32 bit headers at all. It's the
!defined __86_64__ test that causes the file to be pulled in.
> You need to figure out why the program includes glibc headers, and avoid
> doing that. It's like any other cross-compilation in this regard.
It's because eBPF programs are written to access the linux kernel internals.
This means it needs to pull in kernel headers to define data structures. The
full chain of includes that leads to the problem is this:
/usr/lib64/ccache/clang -Wall -Iinclude -O2 \
-I/usr/include/x86_64-linux-gnu/ \
-D__KERNEL__ -D__ASM_SYSREG_H \
-target bpf -S -emit-llvm xdp_lb.c -o xdp_lb.ll
In file included from xdp_lb.c:26:
In file included from /usr/include/linux/if_tunnel.h:6:
In file included from /usr/include/linux/if.h:28:
In file included from /usr/include/sys/socket.h:22:
In file included from /usr/include/features.h:474:
/usr/include/gnu/stubs.h:7:11: fatal error: 'gnu/stubs-32.h' file not found
# include <gnu/stubs-32.h>
^~~~~~~~~~~~~~~~
1 error generated.
Not sure how to proceed. I suspect this will be a bigger problem as more
people start to take advantage of the eBPF facility.
-Steve
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