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Commit 2f4df001 authored by Vasily Gorbik's avatar Vasily Gorbik Committed by Steven Rostedt (VMware)
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tracing: Add -mcount-nop option support 

-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: default avatarVasily Gorbik <gor@linux.ibm.com>
Signed-off-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
parent 07d04081

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++;

		}