arm64: ftrace: Add dynamic ftrace support

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This patch allows "dynamic ftrace" if CONFIG_DYNAMIC_FTRACE is enabled.
Here we can turn on and off tracing dynamically per-function base.

On arm64, this is done by patching single branch instruction to _mcount()
inserted by gcc -pg option. The branch is replaced to NOP initially at
kernel start up, and later on, NOP to branch to ftrace_caller() when
enabled or branch to NOP when disabled.
Please note that ftrace_caller() is a counterpart of _mcount() in case of
'static' ftrace.

More details on architecture specific requirements are described in
Documentation/trace/ftrace-design.txt.

Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>

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This commit is contained in:

AKASHI Takahiro 2014-04-30 10:54:34 +01:00 • committed by Will Deacon

parent 819e50e25d

commit bd7d38dbdf

4 changed files with 171 additions and 0 deletions

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1

arch/arm64/Kconfig

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15

arch/arm64/include/asm/ftrace.h

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43

arch/arm64/kernel/entry-ftrace.S

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112

arch/arm64/kernel/ftrace.c

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