samples: bpf: don't run probes at the local make stage

Quentin reports that commit 07c3bbdb1a9b ("samples: bpf: print
a warning about headers_install") is producing the false
positive when make is invoked locally, from the samples/bpf/
directory.

When make is run locally it hits the "all" target, which
will recursively invoke make through the full build system.

Speed up the "local" run which doesn't actually build anything,
and avoid false positives by skipping all the probes if not in
kbuild environment (cover both the new warning and the BTF
probes).

Reported-by: Quentin Monnet <quentin.monnet@netronome.com>
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Quentin Monnet <quentin.monnet@netronome.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
index 4074a66a70ca9fad10d522a5a348546eb15fb617..9eb5d733f575d00f6bf0b7c1dbc0f7a311a084c1 100644 (file)
--- a/samples/bpf/Makefile
+++ b/samples/bpf/Makefile
@@ -206,6 +206,8 @@ HOSTCC = $(CROSS_COMPILE)gcc
 CLANG_ARCH_ARGS = -target $(ARCH)
 endif
 
+# Don't evaluate probes and warnings if we need to run make recursively
+ifneq ($(src),)
 HDR_PROBE := $(shell echo "\#include <linux/types.h>\n struct list_head { int a; }; int main() { return 0; }" | \
        $(HOSTCC) $(KBUILD_HOSTCFLAGS) -x c - -o /dev/null 2>/dev/null && \
        echo okay)
@@ -232,6 +234,7 @@ ifneq ($(and $(BTF_LLC_PROBE),$(BTF_PAHOLE_PROBE),$(BTF_OBJCOPY_PROBE)),)
        DWARF2BTF = y
 endif
 endif
+endif
 
 # Trick to allow make to be run from this directory
 all: