2020-01-20 13:09:36

by Toke Høiland-Jørgensen

Subject: [PATCH bpf-next v5 02/11] tools/bpf/runqslower: Fix override option for VMLINUX_BTF

From: Toke Høiland-Jørgensen <[email protected]>

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 <[email protected]>
---
tools/bpf/runqslower/Makefile | 19 ++++++++++---------
1 file changed, 10 insertions(+), 9 deletions(-)

diff --git a/tools/bpf/runqslower/Makefile b/tools/bpf/runqslower/Makefile
index cff2fbcd29a8..3242ab874ac0 100644
--- a/tools/bpf/runqslower/Makefile
+++ b/tools/bpf/runqslower/Makefile
@@ -10,13 +10,9 @@ 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")
-endif
+VMLINUX_BTF_PATHS := /sys/kernel/btf/vmlinux /boot/vmlinux-$(KERNEL_REL)
+VMLINUX_BTF_PATH := $(or $(VMLINUX_BTF),$(firstword \
+ $(wildcard $(VMLINUX_BTF_PATHS))))

abs_out := $(abspath $(OUTPUT))
ifeq ($(V),1)
@@ -67,9 +63,14 @@ $(OUTPUT):
$(call msg,MKDIR,$@)
$(Q)mkdir -p $(OUTPUT)

-$(OUTPUT)/vmlinux.h: $(VMLINUX_BTF) | $(OUTPUT) $(BPFTOOL)
+$(OUTPUT)/vmlinux.h: $(VMLINUX_BTF_PATH) | $(OUTPUT) $(BPFTOOL)
$(call msg,GEN,$@)
- $(Q)$(BPFTOOL) btf dump file $(VMLINUX_BTF) format c > $@
+ $(Q)if [ ! -e "$(VMLINUX_BTF_PATH)" ] ; then \
+ echo "Couldn't find kernel BTF; set VMLINUX_BTF to" \
+ "specify its location." >&2; \
+ exit 1;\
+ fi
+ $(Q)$(BPFTOOL) btf dump file $(VMLINUX_BTF_PATH) format c > $@

$(OUTPUT)/libbpf.a: | $(OUTPUT)
$(Q)$(MAKE) $(submake_extras) -C $(LIBBPF_SRC) \

2020-01-20 20:57:33

by Andrii Nakryiko

Subject: Re: [PATCH bpf-next v5 02/11] tools/bpf/runqslower: Fix override option for VMLINUX_BTF

On Mon, Jan 20, 2020 at 5:08 AM Toke Høiland-Jørgensen <[email protected]> wrote:
>
> From: Toke Høiland-Jørgensen <[email protected]>
>
> 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 <[email protected]>
> ---

Thanks!

Acked-by: Andrii Nakryiko <[email protected]>

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