On Sat, Mar 15, 2014 at 05:45:51AM +0000, AKASHI Takahiro wrote:
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.
Signed-off-by: AKASHI Takahiro takahiro.akashi@linaro.org
Acked-by: Will Deacon will.deacon@arm.com
Will