[tip:core/urgent] objtool: Upgrade libelf-devel warning to error for CONFIG_ORC_UNWINDER

[tip-bot for Josh Poimboeuf]

Commit-ID:  3dd40cb320fee7c23b574ab821ce140ccd1281c9
Gitweb:     https://git.kernel.org/tip/3dd40cb320fee7c23b574ab821ce140ccd1281c9
Author:     Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
AuthorDate: Tue, 3 Oct 2017 20:10:36 -0500
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Wed, 4 Oct 2017 08:02:18 +0200

objtool: Upgrade libelf-devel warning to error for CONFIG_ORC_UNWINDER

With CONFIG_ORC_UNWINDER, if the user doesn't have libelf-devel
installed, and they don't see the make warning, their ORC unwinder will
be silently broken.  Upgrade the warning to an error.

Reported-and-tested-by: Borislav Petkov <bp@xxxxxxxxx>
Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/d9dfc39fb8240998820f9efb233d283a1ee96084.1507079417.git.jpoimboe@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 Makefile | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/Makefile b/Makefile
index cf007a3..bc5c79e 100644
--- a/Makefile
+++ b/Makefile
@@ -933,7 +933,11 @@ ifdef CONFIG_STACK_VALIDATION
   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")
+    ifdef CONFIG_ORC_UNWINDER
+      $(error "Cannot generate ORC metadata for CONFIG_ORC_UNWINDER=y, please install libelf-dev, libelf-devel or elfutils-libelf-devel")
+    else
+      $(warning "Cannot use CONFIG_STACK_VALIDATION=y, please install libelf-dev, libelf-devel or elfutils-libelf-devel")
+    endif
     SKIP_STACK_VALIDATION := 1
     export SKIP_STACK_VALIDATION
   endif