linux-kernel - [PATCH 4.4 24/35] tracing: Avoid calling cc-option -mrecord-mcount for every Makefile

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Date:   Mon, 22 Feb 2021 13:36:20 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Andi Kleen <ak@...ux.intel.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        "Steven Rostedt (VMware)" <rostedt@...dmis.org>
Subject: [PATCH 4.4 24/35] tracing: Avoid calling cc-option -mrecord-mcount for every Makefile

From: Vasily Gorbik <gor@...ux.ibm.com>

commit 07d0408120216b60625c9a5b8012d1c3a907984d upstream.

Currently if CONFIG_FTRACE_MCOUNT_RECORD is enabled -mrecord-mcount
compiler flag support is tested for every Makefile.

Top 4 cc-option usages:
    511 -mrecord-mcount
     11  -fno-stack-protector
      9 -Wno-override-init
      2 -fsched-pressure

To address that move cc-option from scripts/Makefile.build to top Makefile
and export CC_USING_RECORD_MCOUNT to be used in original place.

While doing that also add -mrecord-mcount to CC_FLAGS_FTRACE (if gcc
actually supports it).

Link: http://lkml.kernel.org/r/patch-2.thread-aa7b8d.git-de935bace15a.your-ad-here.call-01533557518-ext-9465@work.hours

Acked-by: Andi Kleen <ak@...ux.intel.com>
Signed-off-by: Vasily Gorbik <gor@...ux.ibm.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 Makefile               |    7 +++++++
 scripts/Makefile.build |    9 +++------
 2 files changed, 10 insertions(+), 6 deletions(-)

--- a/Makefile
+++ b/Makefile
@@ -760,6 +760,13 @@ ifdef CONFIG_FUNCTION_TRACER
 ifndef CC_FLAGS_FTRACE
 CC_FLAGS_FTRACE := -pg
 endif
+ifdef CONFIG_FTRACE_MCOUNT_RECORD
+  # gcc 5 supports generating the mcount tables directly
+  ifeq ($(call cc-option-yn,-mrecord-mcount),y)
+    CC_FLAGS_FTRACE	+= -mrecord-mcount
+    export CC_USING_RECORD_MCOUNT := 1
+  endif
+endif
 export CC_FLAGS_FTRACE
 ifdef CONFIG_HAVE_FENTRY
 CC_USING_FENTRY	:= $(call cc-option, -mfentry -DCC_USING_FENTRY)
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -221,11 +221,8 @@ cmd_modversions_c =								\
 endif
 
 ifdef CONFIG_FTRACE_MCOUNT_RECORD
-# gcc 5 supports generating the mcount tables directly
-ifneq ($(call cc-option,-mrecord-mcount,y),y)
-KBUILD_CFLAGS += -mrecord-mcount
-else
-# else do it all manually
+ifndef CC_USING_RECORD_MCOUNT
+# compiler will not generate __mcount_loc use recordmcount or recordmcount.pl
 ifdef BUILD_C_RECORDMCOUNT
 ifeq ("$(origin RECORDMCOUNT_WARN)", "command line")
   RECORDMCOUNT_FLAGS = -w
@@ -254,7 +251,7 @@ cmd_record_mcount =						\
 	     "$(CC_FLAGS_FTRACE)" ]; then			\
 		$(sub_cmd_record_mcount)			\
 	fi;
-endif # -record-mcount
+endif # CC_USING_RECORD_MCOUNT
 endif
 
 define rule_cc_o_c