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tracing: Add -mcount-nop option support

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-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>
This commit is contained in:
Vasily Gorbik
2018-08-06 15:17:46 +02:00
committed by Steven Rostedt (VMware)
parent 07d0408120
commit 2f4df0017b
3 changed files with 13 additions and 0 deletions
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6
Makefile
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@@ -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)