[PATCH 5.10 055/103] selftests/bpf: Clarify build error if no vmlinux

Greg Kroah-Hartman
2021-01-15T12:46:43Z

From: Kamal Mostafa <kamal@canonical.com>

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 <kamal@canonical.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20201215182011.15755-1-kamal@canonical.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
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)")
+endif

DEFAULT_BPFTOOL := $(SCRATCH_DIR)/sbin/bpftool