linux-kernel - [PATCH] objtool: fix CONFIG_STACK_VALIDATION warning for out-of-tree modules

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Date:   Wed, 15 Feb 2017 12:21:17 -0600
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     linux-kernel@...r.kernel.org, Marc MERLIN <marc@...lins.org>,
        Jessica Yu <jeyu@...hat.com>, Michal Marek <mmarek@...e.com>
Subject: [PATCH] objtool: fix CONFIG_STACK_VALIDATION warning for out-of-tree modules

When building a CONFIG_STACK_VALIDATION enabled kernel without the
libelf devel package installed, the Makefile prints a warning:

  "Cannot use CONFIG_STACK_VALIDATION, please install libelf-dev, libelf-devel or elfutils-libelf-devel"

But when building an out-of-tree module, the warning doesn't show.
Instead it tries to use objtool, and the build fails with:

  /bin/sh: ./tools/objtool/objtool: No such file or directory

Make sure the warning and the disabling of objtool occur in all cases,
by moving the CONFIG_STACK_VALIDATION checks outside the 'ifeq
($(KBUILD_EXTMOD),)' block in the Makefile.

Reported-by: Marc MERLIN <marc@...lins.org>
Suggested-by: Jessica Yu <jeyu@...hat.com>
Fixes: 3b27a0c85d70 ("objtool: Detect and warn if libelf is missing and don't break the build")
Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
---
 Makefile | 24 ++++++++++++------------
 1 file changed, 12 insertions(+), 12 deletions(-)

diff --git a/Makefile b/Makefile
index 8e223e0..bcf7036 100644
--- a/Makefile
+++ b/Makefile
@@ -908,6 +908,18 @@ mod_sign_cmd = true
 endif
 export mod_sign_cmd
 
+ifdef CONFIG_STACK_VALIDATION
+  has_libelf := $(call try-run,\
+		echo "int main() {}" | $(HOSTCC) -xc -o /dev/null -lelf -,1,0)
+  ifeq ($(has_libelf),1)
+    objtool_target := tools/objtool FORCE
+  else
+    $(warning "Cannot use CONFIG_STACK_VALIDATION, please install libelf-dev, libelf-devel or elfutils-libelf-devel")
+    SKIP_STACK_VALIDATION := 1
+    export SKIP_STACK_VALIDATION
+  endif
+endif
+
 
 ifeq ($(KBUILD_EXTMOD),)
 core-y		+= kernel/ certs/ mm/ fs/ ipc/ security/ crypto/ block/
@@ -1035,18 +1047,6 @@ prepare0: archprepare gcc-plugins
 # All the preparing..
 prepare: prepare0 prepare-objtool
 
-ifdef CONFIG_STACK_VALIDATION
-  has_libelf := $(call try-run,\
-		echo "int main() {}" | $(HOSTCC) -xc -o /dev/null -lelf -,1,0)
-  ifeq ($(has_libelf),1)
-    objtool_target := tools/objtool FORCE
-  else
-    $(warning "Cannot use CONFIG_STACK_VALIDATION, please install libelf-dev, libelf-devel or elfutils-libelf-devel")
-    SKIP_STACK_VALIDATION := 1
-    export SKIP_STACK_VALIDATION
-  endif
-endif
-
 PHONY += prepare-objtool
 prepare-objtool: $(objtool_target)
 
-- 
2.7.4