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From: "Toke Høiland-Jørgensen" <toke@redhat.com>
To: Andrii Nakryiko <andrii.nakryiko@gmail.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 <kuba@kernel.org>,
	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 v3 02/11] tools/bpf/runqslower: Fix override option for VMLINUX_BTF
Date: Fri, 17 Jan 2020 10:44:52 +0100
Message-ID: <87wo9qquwb.fsf@toke.dk> (raw)
In-Reply-To: <CAEf4Bzbz47nFh4tPBn2PTi3+YiYpMDxymgf36P=ZjbuBPoCrZg@mail.gmail.com>

Andrii Nakryiko <andrii.nakryiko@gmail.com> writes:

> On Thu, Jan 16, 2020 at 5:23 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.
>>
>> Fix this by including the value of VMLINUX_BTF in the expansion, and only
>> emitting the error message if the *result* is empty. Also permit running
>> 'make clean' even though no VMLINUX_BTF is set.
>>
>> Fixes: 9c01546d26d2 ("tools/bpf: Add runqslower tool to tools/bpf")
>> Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
>> ---
>>  tools/bpf/runqslower/Makefile |   18 ++++++++++--------
>>  1 file changed, 10 insertions(+), 8 deletions(-)
>>
>> diff --git a/tools/bpf/runqslower/Makefile b/tools/bpf/runqslower/Makefile
>> index cff2fbcd29a8..89fb7cd30f1a 100644
>> --- a/tools/bpf/runqslower/Makefile
>> +++ b/tools/bpf/runqslower/Makefile
>> @@ -10,12 +10,14 @@ CFLAGS := -g -Wall
>>
>>  # Try to detect best kernel BTF source
>>  KERNEL_REL := $(shell uname -r)
>> -ifneq ("$(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")
>> +VMLINUX_BTF_PATHS := $(VMLINUX_BTF) /sys/kernel/btf/vmlinux /boot/vmlinux-$(KERNEL_REL)
>> +VMLINUX_BTF_PATH := $(firstword $(wildcard $(VMLINUX_BTF_PATHS)))
>
> If user specifies VMLINUX_BTF pointing to non-existing file, but the
> system has /sys/kernel/btf/vmlinux, the latter will still be used,
> which is a very surprising behavior.

Hmm, yeah, good point.

> Also MAKECMDGOALS feels like a fragile hack to me. How about we move
> this VMLINUX_BTF guessing (without $(error)) into vmlinux.h rule
> itself and use shell if conditional after it to check for file
> existance and print nice error. That way we'll be checking VMLINUX_BTF
> only when it's really needed.

OK, sure, can do.

-Toke


  reply index

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-16 13:22 [PATCH bpf-next v3 00/11] tools: Use consistent libbpf include paths everywhere Toke Høiland-Jørgensen
2020-01-16 13:22 ` [PATCH bpf-next v3 01/11] samples/bpf: Don't try to remove user's homedir on clean Toke Høiland-Jørgensen
2020-01-16 13:22 ` [PATCH bpf-next v3 02/11] tools/bpf/runqslower: Fix override option for VMLINUX_BTF Toke Høiland-Jørgensen
2020-01-16 18:54   ` Andrii Nakryiko
2020-01-17  9:44     ` Toke Høiland-Jørgensen [this message]
2020-01-16 13:22 ` [PATCH bpf-next v3 03/11] selftests: Pass VMLINUX_BTF to runqslower Makefile Toke Høiland-Jørgensen
2020-01-16 18:56   ` Andrii Nakryiko
2020-01-16 13:22 ` [PATCH bpf-next v3 04/11] tools/runqslower: Use consistent include paths for libbpf Toke Høiland-Jørgensen
2020-01-16 21:56   ` Andrii Nakryiko
2020-01-17  9:46     ` Toke Høiland-Jørgensen
2020-01-16 13:22 ` [PATCH bpf-next v3 05/11] selftests: " Toke Høiland-Jørgensen
2020-01-16 21:57   ` Andrii Nakryiko
2020-01-16 13:22 ` [PATCH bpf-next v3 06/11] bpftool: " Toke Høiland-Jørgensen
2020-01-16 22:21   ` Andrii Nakryiko
2020-01-16 13:22 ` [PATCH bpf-next v3 07/11] perf: " Toke Høiland-Jørgensen
2020-01-16 22:22   ` Andrii Nakryiko
2020-01-16 13:22 ` [PATCH bpf-next v3 08/11] samples/bpf: " Toke Høiland-Jørgensen
2020-01-16 22:23   ` Andrii Nakryiko
2020-01-16 13:22 ` [PATCH bpf-next v3 09/11] selftests: Remove tools/lib/bpf from include path Toke Høiland-Jørgensen
2020-01-16 22:41   ` Andrii Nakryiko
2020-01-16 23:05     ` Andrii Nakryiko
2020-01-17  9:50       ` Toke Høiland-Jørgensen
2020-01-17  9:49     ` Toke Høiland-Jørgensen
2020-01-16 13:22 ` [PATCH bpf-next v3 10/11] tools/runqslower: " Toke Høiland-Jørgensen
2020-01-16 22:44   ` Andrii Nakryiko
2020-01-16 13:22 ` [PATCH bpf-next v3 11/11] libbpf: Fix include of bpf_helpers.h when libbpf is installed on system Toke Høiland-Jørgensen
2020-01-16 22:43   ` Andrii Nakryiko
2020-01-17  4:14 ` [PATCH bpf-next v3 00/11] tools: Use consistent libbpf include paths everywhere Alexei Starovoitov
2020-01-17  8:57   ` Jesper Dangaard Brouer
2020-01-17  9:58     ` Toke Høiland-Jørgensen

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