tree edad0afa91c1774cfaba6319b319d65db244123d
parent 819e50e25d0ce8a75f5cba815416a6a8573655c4
author AKASHI Takahiro <takahiro.akashi@linaro.org> 1398851674 +0100
committer Will Deacon <will.deacon@arm.com> 1401350913 +0100

arm64: ftrace: Add dynamic ftrace support

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>