Re: [PATCH 1/9] LoongArch/ftrace: Add basic support

[Steven Rostedt]

On Sat, 20 Aug 2022 09:38:21 +0800
Jinyang He <hejinyang@xxxxxxxxxxx> wrote:

> I think we have implemented CONFIG_FTRACE_WITH_ARGS in dynamic ftrace
> in the [Patch3/9]. 

Sorry, I must have missed it.

> But, for non dynamic ftrace, it is hardly to
> implement it. Because the LoongArch compiler gcc treats mount as a

Don't bother implementing it for non-dynamic. I would just add a:

config HAVE_FTRACE_WITH_ARGS if DYNAMIC_FTRACE

and be done with it.

> really call, like 'call _mcount(__builtin_return_address(0))'. That
> means, they decrease stack, save args to callee saved regs and may
> do some optimization before calling mcount. It is difficult to find the
> original args and apply changes from tracers.

Right, there's no point in implementing it for non dynamic. Like I said,
non-dynamic is just a stepping stone for getting dynamic working. Once you
have dynamic working, it's up to you to throw out the non-dynamic. It's not
useful for anything other than porting to a new architecture or for
academic purposes.

-- Steve