Bcc: feature request: specify additional include paths at runtime

[ahrens]

I'd like to be able to specify additional include paths at runtime. The use case is that I have a kernel module (zfs) whose header files are not all in /usr/src/linux-headers-4.15.0-19-generic/include. I'd like to be able to do the equivalent of -I/path/to/zfs/include, so that my bcc program can #include <sys/dbuf.h>, etc. My current workaround is to copy all the header files into the system path:

find /export/home/delphix/spl/include /export/home/delphix/zfs/include -name "*.h" | \
        xargs tar -cf -  | \
        tar --strip-components=5 -xf -

@brendangregg

[drzaeus77]

Have you tried passing -I/path/to/zfs/include to the cflags argument of bcc.BPF() constructor (assuming python use case)?

[ahrens]

@drzaeus77 Yes, thank you that totally works! I wasn't aware of that argument. I'm happy for this issue to be closed, or perhaps converted to a documentation issue.

[brendangregg]

I didn't know about it; sounds like we need docs.

[yonghong-song]

We use this in trace.py.
https://github.com/iovisor/bcc/blob/master/tools/trace_example.txt#L268-L271

[ahrens]

@yonghong-song this isn't exactly the same as what's done in trace.py. trace.py -I adds additional #include ... directives, but I need to change the include path by which we search for those includes. I can't simply use an absolute path for the few files that I include, because those files include other files, which are assumed to be available in the include path.

[yonghong-song]

Oh, yes. trace.py example is bad. In fb, we use this cflags option to pass addition -D<macro>=<value>s, e.g., queue size etc.

Agreed. that we need documentation to advertise this feature.

[ahrens]

@yonghong-song Cool. I opened a PR to add very basic documentation of this: https://github.com/iovisor/bcc/pull/1709