Re: [PATCH 5/6] ftrace/x86: Add separate function to save regs

[Steven Rostedt <rostedt@goodmis.org>]

On Tue, 2012-07-03 at 17:29 +0900, Masami Hiramatsu wrote:


> 
> > +	/* Restore flags */
> > +	pushq EFLAGS(%rsp)
> > +	popfq
> > +
> > +	MCOUNT_RESTORE_FRAME
> 
> Here, if MCOUNT_RESTORE_FRAME has skip too, I think you don't
> need to restore flags before restoring other registers, like
> below;
> 
> 	MCOUNT_RESTORE_FRAME 8
> 	popfq
> 
> And also, this will prevent to modify flags before return by
> addq in MCOUNT_RESTORE_FRAME.

Ah, because the addq will modify flags :-/

Grumble, I guess I should implement this, even though it will make it a
little more complex. I thought it was better to restore flags
explicitly, but that's not the case.

OK, I'll make the update. As MCOUNT_SAVE_FRAME has the skip, I guess
it's not so bad to have restore have it too.

-- Steve

> 
> > +
> > +	jmp ftrace_return
> > +ftrace_restore_flags:
> > +	popfq
> > +	jmp  ftrace_stub
> > +
> > +END(ftrace_regs_caller)
> > +
> 
> Thank you,
> 
>