[tip:perf/core] kbuild/recordmcount: Add RECORDMCOUNT_WARN to warn about mcount callers

[tip-bot for Steven Rostedt <srostedt@redhat.com>]

Commit-ID:  a3a8350ab2f588f3a7a08dc86658bf90773f9a52
Gitweb:     http://git.kernel.org/tip/a3a8350ab2f588f3a7a08dc86658bf90773f9a52
Author:     Steven Rostedt <srostedt@redhat.com>
AuthorDate: Tue, 12 Apr 2011 18:59:10 -0400
Committer:  Steven Rostedt <rostedt@goodmis.org>
CommitDate: Tue, 17 May 2011 10:41:49 -0400

kbuild/recordmcount: Add RECORDMCOUNT_WARN to warn about mcount callers

When mcount is called in a section that ftrace will not modify it into
a nop, we want to warn about this. But not warn about this always. Now
if the user builds the kernel with the option RECORDMCOUNT_WARN=1 then
the build will warn about mcount callers that are ignored and will just
waste execution time.

Acked-by: Michal Marek <mmarek@suse.cz>
Cc: linux-kbuild@vger.kernel.org
Link: http://lkml.kernel.org/r/20110421023738.714956282@goodmis.org
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 Makefile               |    1 +
 scripts/Makefile.build |    5 ++++-
 2 files changed, 5 insertions(+), 1 deletions(-)

diff --git a/Makefile b/Makefile
index 41ea6fb..e7d01ad 100644
--- a/Makefile
+++ b/Makefile
@@ -1268,6 +1268,7 @@ help:
 	@echo  '  make C=1   [targets] Check all c source with $$CHECK (sparse by default)'
 	@echo  '  make C=2   [targets] Force check of all c source with $$CHECK'
 	@echo  '  make W=1   [targets] Enable extra gcc checks'
+	@echo  '  make RECORDMCOUNT_WARN=1 [targets] Warn about ignored mcount sections'
 	@echo  ''
 	@echo  'Execute "make" or "make all" to build all targets marked with [*] '
 	@echo  'For further info see the ./README file'
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 7d3f903..6165622 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -244,13 +244,16 @@ endif
 
 ifdef CONFIG_FTRACE_MCOUNT_RECORD
 ifdef BUILD_C_RECORDMCOUNT
+ifeq ("$(origin RECORDMCOUNT_WARN)", "command line")
+  RECORDMCOUNT_FLAGS = -w
+endif
 # Due to recursion, we must skip empty.o.
 # The empty.o file is created in the make process in order to determine
 #  the target endianness and word size. It is made before all other C
 #  files, including recordmcount.
 sub_cmd_record_mcount =					\
 	if [ $(@) != "scripts/mod/empty.o" ]; then	\
-		$(objtree)/scripts/recordmcount "$(@)";	\
+		$(objtree)/scripts/recordmcount $(RECORDMCOUNT_FLAGS) "$(@)";	\
 	fi;
 recordmcount_source := $(srctree)/scripts/recordmcount.c \
 		    $(srctree)/scripts/recordmcount.h