Re: [PATCH 1/2] riscv: ftrace: Fix the comments about the number of ftrace instruction

[Li Huafei]

On 2022/4/26 14:22, Guo Ren wrote:
> On Tue, Apr 26, 2022 at 9:59 AM Li Huafei <lihuafei1@xxxxxxxxxx> wrote:
> > When DYNAMIC_FTRACE is enabled, we put four instructions in front of the
> > function for ftrace use, not five.
> >
> > Signed-off-by: Li Huafei <lihuafei1@xxxxxxxxxx>
> > ---
> >   arch/riscv/kernel/ftrace.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/arch/riscv/kernel/ftrace.c b/arch/riscv/kernel/ftrace.c
> > index 4716f4cdc038..63f457650fa4 100644
> > --- a/arch/riscv/kernel/ftrace.c
> > +++ b/arch/riscv/kernel/ftrace.c
> > @@ -73,7 +73,7 @@ static int __ftrace_modify_call(unsigned long hook_pos, unsigned long target,
> >   }
> >
> >   /*
> > - * Put 5 instructions with 16 bytes at the front of function within
> > + * Put 4 instructions with 16 bytes at the front of function within
> Yeah, 5 instructions are for mcount, -fpatchable-function-entry=8
> cause 8 16bit instructions.
I misunderstood, thanks for the clarification.
> Fixes: afc76b8b8011 ("riscv: Using PATCHABLE_FUNCTION_ENTRY instead of MCOUNT")
There is no functional fix here, do we need to add the fix tag?
> I recommend just delete "4 instructions with"
> - * Put 5 instructions with 16 bytes at the front of function within
> - * patchable function entry nops' area.
> + * Put 16 bytes at the front of the function within the patchable
> + * function entry nops' area.

I agree and will use this modification for the next version, thanks!


Huafei
> >    * patchable function entry nops' area.
> >    *
> >    * 0: REG_S  ra, -SZREG(sp)
> > --
> > 2.17.1