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Subject[PATCH 5.10 055/103] selftests/bpf: Clarify build error if no vmlinux
From: Kamal Mostafa <>

commit 1a3449c19407a28f7019a887cdf0d6ba2444751a upstream.

If Makefile cannot find any of the vmlinux's in its VMLINUX_BTF_PATHS list,
it tries to run btftool incorrectly, with VMLINUX_BTF unset:

bpftool btf dump file $(VMLINUX_BTF) format c

Such that the keyword 'format' is misinterpreted as the path to vmlinux.
The resulting build error message is fairly cryptic:

GEN vmlinux.h
Error: failed to load BTF from format: No such file or directory

This patch makes the failure reason clearer by yielding this instead:

Makefile:...: *** Cannot find a vmlinux for VMLINUX_BTF at any of
"{paths}". Stop.

Fixes: acbd06206bbb ("selftests/bpf: Add vmlinux.h selftest exercising tracing of syscalls")
Signed-off-by: Kamal Mostafa <>
Signed-off-by: Andrii Nakryiko <>
Signed-off-by: Greg Kroah-Hartman <>

tools/testing/selftests/bpf/Makefile | 3 +++
1 file changed, 3 insertions(+)

--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -146,6 +146,9 @@ VMLINUX_BTF_PATHS ?= $(if $(O),$(O)/vmli
/sys/kernel/btf/vmlinux \
/boot/vmlinux-$(shell uname -r)
VMLINUX_BTF ?= $(abspath $(firstword $(wildcard $(VMLINUX_BTF_PATHS))))
+ifeq ($(VMLINUX_BTF),)
+$(error Cannot find a vmlinux for VMLINUX_BTF at any of "$(VMLINUX_BTF_PATHS)")


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