samples/bpf build currently always fails if it can't generate
vmlinux.h from vmlinux, even when vmlinux.h is directly provided by
VMLINUX_H variable, which makes VMLINUX_H pointless.
Only fails when neither method works.

Fixes: 384b6b3bbf0d ("samples: bpf: Add vmlinux.h generation support")
Reported-by: CKI Project <cki-project@redhat.com>
Reported-by: Veronika Kabatova <vkabatov@redhat.com>
Signed-off-by: Jerome Marchand <jmarchan@redhat.com>
---
 samples/bpf/Makefile | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
index 38638845db9d..72bb85c18804 100644
--- a/samples/bpf/Makefile
+++ b/samples/bpf/Makefile
@@ -368,16 +368,15 @@ VMLINUX_BTF ?= $(abspath $(firstword $(wildcard $(VMLINUX_BTF_PATHS))))
 
 $(obj)/vmlinux.h: $(VMLINUX_BTF) $(BPFTOOL)
 ifeq ($(VMLINUX_H),)
+ifeq ($(VMLINUX_BTF),)
+	$(error Cannot find a vmlinux for VMLINUX_BTF at any of "$(VMLINUX_BTF_PATHS)",\
+		build the kernel or set VMLINUX_BTF or VMLINUX_H variable)
+endif
 	$(Q)$(BPFTOOL) btf dump file $(VMLINUX_BTF) format c > $@
 else
 	$(Q)cp "$(VMLINUX_H)" $@
 endif
 
-ifeq ($(VMLINUX_BTF),)
-	$(error Cannot find a vmlinux for VMLINUX_BTF at any of "$(VMLINUX_BTF_PATHS)",\
-		build the kernel or set VMLINUX_BTF variable)
-endif
-
 clean-files += vmlinux.h
 
 # Get Clang's default includes on this system, as opposed to those seen by
-- 
2.35.1

Hello:

This patch was applied to bpf/bpf-next.git (master)
by Andrii Nakryiko <andrii@kernel.org>:

On Sat,  7 May 2022 18:16:35 +0200 you wrote:
> samples/bpf build currently always fails if it can't generate
> vmlinux.h from vmlinux, even when vmlinux.h is directly provided by
> VMLINUX_H variable, which makes VMLINUX_H pointless.
> Only fails when neither method works.
> 
> Fixes: 384b6b3bbf0d ("samples: bpf: Add vmlinux.h generation support")
> Reported-by: CKI Project <cki-project@redhat.com>
> Reported-by: Veronika Kabatova <vkabatov@redhat.com>
> Signed-off-by: Jerome Marchand <jmarchan@redhat.com>
> 
> [...]

Here is the summary with links:
  - samples: bpf: Don't fail for a missing VMLINUX_BTF when VMLINUX_H is provided
    https://git.kernel.org/bpf/bpf-next/c/ec24704492d8

You are awesome, thank you!
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