Commit 6b6810c2 authored Nov 27, 2017 by Andi Kleen Committed by Greg Kroah-Hartman Feb 23, 2021

trace: Use -mcount-record for dynamic ftrace

commit 96f60dfa5819a065bfdd2f2ba0df7d9cbce7f4dd upstream.

gcc 5 supports a new -mcount-record option to generate ftrace
tables directly. This avoids the need to run record_mcount
manually.

Use this option when available.

So far doesn't use -mcount-nop, which also exists now.

This is needed to make ftrace work with LTO because the
normal record-mcount script doesn't run over the link
time output.

It should also improve build times slightly in the general
case.
Link: http://lkml.kernel.org/r/20171127213423.27218-12-andi@firstfloor.org



Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent d10795e3

scripts/Makefile.build

+6 −0

Original line number	Diff line number	Diff line
		@@ -222,6 +222,11 @@ cmd_modversions_c = \
		endif

		ifdef CONFIG_FTRACE_MCOUNT_RECORD
		# gcc 5 supports generating the mcount tables directly
		ifneq ($(call cc-option,-mrecord-mcount,y),y)
		KBUILD_CFLAGS += -mrecord-mcount
		else
		# else do it all manually
		ifdef BUILD_C_RECORDMCOUNT
		ifeq ("$(origin RECORDMCOUNT_WARN)", "command line")
		RECORDMCOUNT_FLAGS = -w
		@@ -264,6 +269,7 @@ endif
		ifdef CONFIG_GCOV_KERNEL
		objtool_args += --no-unreachable
		endif
		endif

		# 'OBJECT_FILES_NON_STANDARD := y': skip objtool checking for a directory
		# 'OBJECT_FILES_NON_STANDARD_foo.o := 'y': skip objtool checking for a file