Re: [PATCH 08/10] bpf samples: Add utils.[ch] for using BPF

[Wangnan (F)]

On 2015/12/18 15:04, Wangnan (F) wrote:
> On 2015/12/18 14:19, Alexei Starovoitov wrote:
> > On Fri, Dec 18, 2015 at 09:47:11AM +0800, Wangnan (F) wrote:
> > > This is a limitation in tools/lib/bpf/libbpf.h, which has a #include
> > > <linux/err.h>
> > > in its header.
> > >
> > > libbpf.h requires this include because its API uses ERR_PTR() to encode
> > > error code.
> > > For example, when calling bpf_object__open(), caller should use 
> > > IS_ERR() to
> > > check its
> > > return value instead of compare with NULL, and use PTR_ERR() to retrive
> > > error number.
> > >
> > > However, linux/err.h is not a part of uapi. To make libbpf work, one 
> > > has to
> > > create its
> > > own err.h.
[SNIP]
> > > What about moving them into include/uapi/linux/filter.h ? Then
> > > normal user programs like those in samples/bpf can access
> > > them easier.
> > we don't want to add these macros to uapi.
> > Why not to add it to
> > tools/include/linux/filter.h
> > instead?
>
> What I want to do in this patchset is not only removing original libbpf.c
> and bpf_load.c. In fact I want libbpf in tools/lib/bpf becomes a public
> available library for other userspace tools (tc for example). Switching
> samples/bpf into libbpf is the first step of this goal. From doing this
> I found and fixed some limitation, like those missed BPF map operations.
> Making libbpf.h and bpf.h available for normal userspace programs is also
> important.
>
> Having the above goal, I think you can understand why improving 
> tools/include
> is not a good idea. You don't want to force a normal userspace program 
> setup
> a similar header environment for using libbpf. It is relatively a small
> library. So it would be good if bpf.h and libbpf.h only depend on what 
> can
> be found in uapi.

I suddenly realized that only linux/err.h causes problem. Those macros from
filter.h are never accessed by libbpf. So we can drop those filter.h by 
making
samples/bpf include from tools/include. However we still need a wrapper in
libbpf to avoid including linux/err.h.

Thank you.

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/