tracing: Add -mcount-nop option support (2f4df001) · Commits · 戴 / test

-mcount-nop gcc option generates the calls to the profiling functions as nops which allows to avoid patching mcount jump with NOP instructions initially. -mcount-nop gcc option will be activated if platform selects HAVE_NOP_MCOUNT and gcc actually supports it. In addition to that CC_USING_NOP_MCOUNT is defined and could be used by architectures to adapt ftrace patching behavior. Link: http://lkml.kernel.org/r/patch-3.thread-aa7b8d.git-e02ed2dc082b.your-ad-here.call-01533557518-ext-9465@work.hours Signed-off-by:

Vasily Gorbik <gor@linux.ibm.com> Signed-off-by:

Steven Rostedt (VMware) <rostedt@goodmis.org>

Makefile

+6 −0

Original line number	Diff line number	Diff line
		@@ -749,6 +749,12 @@ ifdef CONFIG_FTRACE_MCOUNT_RECORD
		CC_FLAGS_FTRACE += -mrecord-mcount
		export CC_USING_RECORD_MCOUNT := 1
		endif
		ifdef CONFIG_HAVE_NOP_MCOUNT
		ifeq ($(call cc-option-yn, -mnop-mcount),y)
		CC_FLAGS_FTRACE += -mnop-mcount
		CC_FLAGS_USING += -DCC_USING_NOP_MCOUNT
		endif
		endif
		endif
		ifdef CONFIG_HAVE_FENTRY
		ifeq ($(call cc-option-yn, -mfentry),y)

kernel/trace/Kconfig

+5 −0

Original line number	Diff line number	Diff line
		@@ -47,6 +47,11 @@ config HAVE_FENTRY
		help
		Arch supports the gcc options -pg with -mfentry

		config HAVE_NOP_MCOUNT
		bool
		help
		Arch supports the gcc options -pg with -mrecord-mcount and -nop-mcount

		config HAVE_C_RECORDMCOUNT
		bool
		help

kernel/trace/ftrace.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -2950,12 +2950,14 @@ static int ftrace_update_code(struct module mod, struct ftrace_page new_pgs)
		p = &pg->records[i];
		p->flags = rec_flags;

		#ifndef CC_USING_NOP_MCOUNT
		/*
		* Do the initial record conversion from mcount jump
		* to the NOP instructions.
		*/
		if (!ftrace_code_disable(mod, p))
		break;
		#endif

		update_cnt++;
		}

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