linux-kernel - [PATCH] kbuild: improve libelf detection

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Message-Id: <20210112190010.1582888-1-adelva@google.com>
Date:   Tue, 12 Jan 2021 19:00:10 +0000
From:   Alistair Delva <adelva@...gle.com>
To:     linux-kernel@...r.kernel.org
Cc:     kernel-team@...roid.com, linux-kbuild@...r.kernel.org,
        Masahiro Yamada <masahiroy@...nel.org>,
        Rolf Eike Beer <eb@...ix.com>
Subject: [PATCH] kbuild: improve libelf detection

When `pkg-config --libs' wasn't used or didn't return anything useful,
the test for libelf would fail even if the headers and libraries were
available to kbuild via KBUILD_HOSTCFLAGS and KBUILD_HOSTLDFLAGS.

This makes the check in the core Makefile match the check that is done
in tools/objtool/Makefile. Specifically, the C compiler is passed the
full KBUILD_HOSTCFLAGS and KBUILD_HOSTLDFLAGS, which may have set up
additional sysroot/include/library search paths to find libelf.

Cc: kernel-team@...roid.com
Cc: linux-kbuild@...r.kernel.org
Cc: Masahiro Yamada <masahiroy@...nel.org>
Cc: Rolf Eike Beer <eb@...ix.com>
Signed-off-by: Alistair Delva <adelva@...gle.com>
---
 Makefile | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/Makefile b/Makefile
index 9e73f82e0d86..3269e155fbe4 100644
--- a/Makefile
+++ b/Makefile
@@ -1074,8 +1074,9 @@ export mod_sign_cmd
 
 HOST_LIBELF_LIBS = $(shell pkg-config libelf --libs 2>/dev/null || echo -lelf)
 
-has_libelf = $(call try-run,\
-               echo "int main() {}" | $(HOSTCC) -xc -o /dev/null $(HOST_LIBELF_LIBS) -,1,0)
+has_libelf := $(call try-run,\
+                echo "int main() {}" | \
+                $(HOSTCC) $(KBUILD_HOSTCFLAGS) -xc -o /dev/null $(KBUILD_HOSTLDFLAGS) $(HOST_LIBELF_LIBS) -,1,0)
 
 ifdef CONFIG_STACK_VALIDATION
   ifeq ($(has_libelf),1)
-- 
2.29.2