Re: [PATCH v7 5/7] arm64: ftrace: Add dynamic ftrace support

[Will Deacon]

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@xxxxxxxxxx>

  Acked-by: Will Deacon <will.deacon@xxxxxxx>

Will
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/