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From: Andrii Nakryiko <andrii.nakryiko@gmail.com>
To: "Toke Høiland-Jørgensen" <toke@redhat.com>
Cc: Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
	Yonghong Song <yhs@fb.com>, Andrii Nakryiko <andriin@fb.com>,
	Doug Ledford <dledford@redhat.com>,
	Jason Gunthorpe <jgg@ziepe.ca>,
	"David S. Miller" <davem@davemloft.net>,
	Jakub Kicinski <jakub.kicinski@netronome.com>,
	Jesper Dangaard Brouer <brouer@redhat.com>,
	John Fastabend <john.fastabend@gmail.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@redhat.com>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Jiri Olsa <jolsa@redhat.com>, Namhyung Kim <namhyung@kernel.org>,
	Shuah Khan <shuah@kernel.org>,
	Networking <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>,
	open list <linux-kernel@vger.kernel.org>,
	linux-rdma@vger.kernel.org,
	"open list:KERNEL SELFTEST FRAMEWORK" 
	<linux-kselftest@vger.kernel.org>,
	clang-built-linux@googlegroups.com
Subject: Re: [PATCH bpf-next v2 02/10] tools/bpf/runqslower: Fix override option for VMLINUX_BTF
Date: Thu, 16 Jan 2020 09:14:47 -0800
Message-ID: <CAEf4BzYLycZb+DBkao-jt+5sGgi3vbmzQ4Ogq9eRXZ+Jvew-ZA@mail.gmail.com> (raw)
In-Reply-To: <87a76nu5yo.fsf@toke.dk>

On Thu, Jan 16, 2020 at 1:05 AM Toke Høiland-Jørgensen <toke@redhat.com> wrote:
>
> Andrii Nakryiko <andrii.nakryiko@gmail.com> writes:
>
> > On Wed, Jan 15, 2020 at 2:06 PM Toke Høiland-Jørgensen <toke@redhat.com> wrote:
> >>
> >> Andrii Nakryiko <andrii.nakryiko@gmail.com> writes:
> >>
> >> > On Wed, Jan 15, 2020 at 6:13 AM Toke Høiland-Jørgensen <toke@redhat.com> wrote:
> >> >>
> >> >> From: Toke Høiland-Jørgensen <toke@redhat.com>
> >> >>
> >> >> The runqslower tool refuses to build without a file to read vmlinux BTF
> >> >> from. The build fails with an error message to override the location by
> >> >> setting the VMLINUX_BTF variable if autodetection fails. However, the
> >> >> Makefile doesn't actually work with that override - the error message is
> >> >> still emitted.
> >> >
> >> > Do you have example command with VMLINUX_BTF override that didn't work
> >> > (and what error message was emitted)?
> >>
> >> Before this patch:
> >>
> >> $ cd ~/build/linux/tools/bpf/runqslower
> >> $ make
> >> Makefile:18: *** "Can't detect kernel BTF, use VMLINUX_BTF to specify it explicitly".  Stop.
> >>
> >> $ make VMLINUX_BTF=~/build/linux/vmlinux
> >> Makefile:18: *** "Can't detect kernel BTF, use VMLINUX_BTF to specify it explicitly".  Stop.
> >
> > Ok, so this is strange. Try make clean and run with V=1, it might help
> > to debug this. This could happen if ~/build/linux/vmlinux doesn't
> > exist, but I assume you double-checked that. It works for me just fine
> > (Makefile won't do VMLINUX_BTF := assignment, if it's defined through
> > make invocation, so your change should be a no-op in that regard):
> >
> > $ make clean
> > $ make VMLINUX_BTF=~/linux-build/default/vmlinux V=1
> > ...
> > .output/sbin/bpftool btf dump file ~/linux-build/default/vmlinux
> > format c > .output/vmlinux.h
> > ...
> >
> > Wonder what your output looks like?
>
> $ make clean
> Makefile:18: *** "Can't detect kernel BTF, use VMLINUX_BTF to specify it explicitly".  Stop.
> $ make VMLINUX_BTF=~/build/linux/vmlinux V=1
> Makefile:18: *** "Can't detect kernel BTF, use VMLINUX_BTF to specify it explicitly".  Stop.
>
> Take another look at the relevant part of the makefile:
>
>   ifneq ("$(wildcard /sys/kernel/btf/vmlinux)","")
>   VMLINUX_BTF := /sys/kernel/btf/vmlinux
>   else ifneq ("$(wildcard /boot/vmlinux-$(KERNEL_REL))","")
>   VMLINUX_BTF := /boot/vmlinux-$(KERNEL_REL)
>   else
>   $(error "Can't detect kernel BTF, use VMLINUX_BTF to specify it explicitly")
>   endif
>
> That if/else doesn't actually consider the value of VMLINUX_BTF; so the
> override only works if one of the files being considered by the
> auto-detection actually exists... :)

Ah, right, unconditional $(error), completely missed that few times, thanks!

>
> -Toke
>

  reply index

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-15 14:12 [PATCH bpf-next v2 00/10] tools: Use consistent libbpf include paths everywhere Toke Høiland-Jørgensen
2020-01-15 14:12 ` [PATCH bpf-next v2 01/10] samples/bpf: Don't try to remove user's homedir on clean Toke Høiland-Jørgensen
2020-01-15 15:21   ` Jesper Dangaard Brouer
2020-01-15 14:12 ` [PATCH bpf-next v2 02/10] tools/bpf/runqslower: Fix override option for VMLINUX_BTF Toke Høiland-Jørgensen
2020-01-15 16:59   ` Andrii Nakryiko
2020-01-15 22:06     ` Toke Høiland-Jørgensen
2020-01-15 22:31       ` Andrii Nakryiko
2020-01-16  9:05         ` Toke Høiland-Jørgensen
2020-01-16 17:14           ` Andrii Nakryiko [this message]
2020-01-15 14:12 ` [PATCH bpf-next v2 03/10] tools/runqslower: Use consistent include paths for libbpf Toke Høiland-Jørgensen
2020-01-15 14:12 ` [PATCH bpf-next v2 04/10] selftests: " Toke Høiland-Jørgensen
2020-01-15 14:12 ` [PATCH bpf-next v2 05/10] bpftool: " Toke Høiland-Jørgensen
2020-01-15 17:44   ` Andrii Nakryiko
2020-01-15 14:12 ` [PATCH bpf-next v2 06/10] perf: " Toke Høiland-Jørgensen
2020-01-15 14:12 ` [PATCH bpf-next v2 07/10] samples/bpf: " Toke Høiland-Jørgensen
2020-01-15 15:18   ` Jesper Dangaard Brouer
2020-01-15 15:41     ` Toke Høiland-Jørgensen
2020-01-15 14:12 ` [PATCH bpf-next v2 08/10] libbpf: Fix include of bpf_helpers.h when libbpf is installed on system Toke Høiland-Jørgensen
2020-01-15 14:12 ` [PATCH bpf-next v2 09/10] selftests: Remove tools/lib/bpf from include path Toke Høiland-Jørgensen
2020-01-15 17:22   ` Andrii Nakryiko
2020-01-15 14:12 ` [PATCH bpf-next v2 10/10] tools/runqslower: " Toke Høiland-Jørgensen
2020-01-15 18:06 ` [PATCH bpf-next v2 00/10] tools: Use consistent libbpf include paths everywhere Andrii Nakryiko
2020-01-15 22:10   ` Toke Høiland-Jørgensen
2020-01-15 21:19 ` Alexei Starovoitov
2020-01-15 22:09   ` Toke Høiland-Jørgensen

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