Re: [RFC PATCH v3 06/37] bpf tools: Introduce 'bpf' library to tools

[Wangnan (F)]

å 2015/5/19 1:35, Alexei Starovoitov åé:
> On 5/17/15 3:56 AM, Wang Nan wrote:
> > This is the first patch of libbpf. The goal of libbpf is to create a
> > standard way for accessing eBPF object files. This patch creates
> > Makefile and Build for it, allows 'make' to build libbpf.a and
> > libbpf.so, 'make install' to put them into proper directories.
> > Most part of Makefile is borrowed from traceevent. Before building,
> > it checks the existance of libelf in Makefile, and deny to build if
> > not found. Instead of throw an error if libelf not found, the error
> > raises in a phony target "elfdep". This design is to ensure
> > 'make clean' still workable even if libelf is not found.
> >
> > Signed-off-by: Wang Nan <wangnan0@xxxxxxxxxx>
> > ---
> ...
> > +
> > +# Version of eBPF elf file
> > +FILE_VERSION = 1
>
> what that comment suppose to mean?
>
> > +# Makefiles suck: This macro sets a default value of $(2) for the
> > +# variable named by $(1), unless the variable has been set by
> > +# environment or command line. This is necessary for CC and AR
> > +# because make sets default values, so the simpler ?= approach
> > +# won't work as expected.
>
> what this for? copy-paste?
>
> > +# Allow setting CC and AR, or setting CROSS_COMPILE as a prefix.
> > +$(call allow-override,CC,$(CROSS_COMPILE)gcc)
> > +$(call allow-override,AR,$(CROSS_COMPILE)ar)
>
> was cross-compile tested or just copy-pasted?

Cross compiling is tested on aarch64.

> > +EXT = -std=gnu99
>
> I guess it was copy-pasted from libtraceevent, but please double
> check that it's actually needed.

Will remove.

> > +# Append required CFLAGS
> > +override CFLAGS += -fPIC
> > +override CFLAGS += $(INCLUDES)
> > +override CFLAGS += -D_GNU_SOURCE
>
> _GNU_SOURCE actually needed?
> Please sanitize the file.
>
> > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> > new file mode 100644
> > index 0000000..bebe99a
> > --- /dev/null
> > +++ b/tools/lib/bpf/libbpf.c
> > @@ -0,0 +1,15 @@
> > +/*
> > + * common eBPF ELF loading operations.
> > + *
> > + * Copyright (C) 2015, Wang Nan <wangnan0@xxxxxxxxxx>
> > + * Copyright (C) 2015, Huawei Inc.
>
> since it borrows heavily from samples/bpf/bpf_load.c, libbpf.h
> would be nice if you mention the source and/or copyright in the header.

Will change. Could you please provide copyright information so I can add 
it here?

> > + *
> > + * Released under the GPL v2. (and only v2, not any later version)
> > + */
>
> are you sure about this restriction? libtracevent is LGPL, for example.

Will change.

Thank you.


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