[PATCH bpf-next v2 02/10] tools/bpf/runqslower: Fix override option for VMLINUX_BTF - Toke Høiland-Jørgensen

From: "Toke Høiland-Jørgensen" <toke@redhat.com>
To: Alexei Starovoitov <ast@kernel.org>
Cc: 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>,
	netdev@vger.kernel.org, bpf@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-rdma@vger.kernel.org,
	linux-kselftest@vger.kernel.org,
	clang-built-linux@googlegroups.com
Subject: [PATCH bpf-next v2 02/10] tools/bpf/runqslower: Fix override option for VMLINUX_BTF
Date: Wed, 15 Jan 2020 15:12:50 +0100	[thread overview]
Message-ID: <157909757089.1192265.9038866294345740126.stgit@toke.dk> (raw)
In-Reply-To: <157909756858.1192265.6657542187065456112.stgit@toke.dk>

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 only doing auto-detection if no override is set. And while
we're at it, also look for a vmlinux file in the current kernel build dir
if none if found on the running kernel.

Fixes: 9c01546d26d2 ("tools/bpf: Add runqslower tool to tools/bpf")
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
---
 tools/bpf/runqslower/Makefile |   16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/tools/bpf/runqslower/Makefile b/tools/bpf/runqslower/Makefile
index cff2fbcd29a8..fb93ce2bf2fe 100644
--- a/tools/bpf/runqslower/Makefile
+++ b/tools/bpf/runqslower/Makefile
@@ -10,12 +10,16 @@ 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")
+ifeq ("$(VMLINUX_BTF)","")
+  ifneq ("$(wildcard /sys/kernel/btf/vmlinux)","")
+  VMLINUX_BTF := /sys/kernel/btf/vmlinux
+  else ifneq ("$(wildcard /boot/vmlinux-$(KERNEL_REL))","")
+  VMLINUX_BTF := /boot/vmlinux-$(KERNEL_REL)
+  else ifneq ("$(wildcard $(abspath ../../../vmlinux))","")
+  VMLINUX_BTF := $(abspath ../../../vmlinux)
+  else
+  $(error "Can't detect kernel BTF, use VMLINUX_BTF to specify it explicitly")
+  endif
 endif
 
 abs_out := $(abspath $(OUTPUT))

