Em Tue, Feb 14, 2017 at 02:23:26PM +0100, Jiri Olsa escreveu:
> On Tue, Feb 14, 2017 at 09:50:20AM -0300, Arnaldo Carvalho de Melo wrote:
>
> SNIP
>
> >
> > What I think Ingo meant with dependency at the build system level is to
> > somehow state that if file A gets changed, then tool B must be rebuilt.
> >
> > Now that samples/bpf and tools/perf/ depend on tools/lib/bpf/ I _always_
> > build both, ditto for tools/objtool, that shares a different library
> > with tools/perf/, tools/lib/subcmd/:
> >
> > ENTRYPOINT make -C /git/linux/tools/perf O=/tmp/build/perf && \
> > rm -rf /tmp/build/perf/{.[^.]*,*} && \
> > make NO_LIBELF=1 -C /git/linux/tools/perf O=/tmp/build/perf && \
> > make -C /git/linux/tools/objtool O=/tmp/build/objtool && \
> > make -C /git/linux O=/tmp/build/linux allmodconfig && \
> > make -C /git/linux O=/tmp/build/linux headers_install && \
> > make -C /git/linux O=/tmp/build/linux samples/bpf/
> >
> > This is the default action for my
> > docker.io/acmel/linux-perf-tools-build-fedora:rawhide container.
> >
> > It is published, so a:
> >
> > docker pull docker.io/acmel/linux-perf-tools-build-fedora:rawhide
> >
> > And then run it before pushing things upstream would catch these kinds
> > of errors.
> >
> > But that would possibly disrupt too much people's workflow, that is why
> > using the Kbuild originated tools/build/ we have to somehow express that
> > when a change is made in a file then a tool that uses that file needs to
> > be rebuilt.
>
> we already have the check in the check-headers.sh script,
> an AFAICS there's no 'rebuild' option here.. just warn or fail
> because the headers update needs to be done manualy
... when needed. And that will only be detected if you try to build
tools using what is in tools/include/linux/bpf.h
Tools using tools/lib/bpf/ _must_ use what is in tools/include/.
So lemme see if my reasoning is right:
tools/lib/bpf/bpf.c has:
#include <linux/bpf.h>
Now, samples/bpf/ will build tools/lib/bpf/bpf.o:
# Libbpf dependencies
LIBBPF := ../../tools/lib/bpf/bpf.o
HOSTCFLAGS += -I$(objtree)/usr/include
HOSTCFLAGS += -I$(srctree)/tools/lib/
HOSTCFLAGS += -I$(srctree)/tools/testing/selftests/bpf/
HOSTCFLAGS += -I$(srctree)/tools/lib/ -I$(srctree)/tools/include
HOSTCFLAGS += -I$(srctree)/tools/perf
HOSTCFLAGS_bpf_load.o += -I$(objtree)/usr/include -Wno-unused-variable
So it will never include tools/include/uapi/linux/bpf.h, which it
should.
Because the workflow people working on sample/bpf/ is to first install
the new headers using a variation of:
make headers_install
So they will get the new bpf.h, not use tools/include/uapi/linux/bpf.h,
b00m.
They should use tools/include/uapi/linux/bpf.h, which is the one we know
builds well with tools/lib/bpf/bpf.c, since we tested it last time we
made the copy.
> > Makefile rules probably would be enough, but then it would have to be
> > done at the tools/build/ level and all tools using shared components
> > would have to use it to trigger the rebuild.
> we can move/invoke the check-headers.sh script in some upper dir
Most of the time I just ignore that warning, only when I find spare time
I go look if the changes in the kernel copy, i.e. upstream, should
trigger changes in the tools using its copy in tools/include/.
- Arnaldo
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