linux-kernel - Re: [PATCH v2 3/3] riscv/ftrace: cleanup ftrace_caller and ftrace_regs

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Date:   Thu, 17 Nov 2022 09:49:06 +0800
From:   Guo Ren <guoren@...nel.org>
To:     Song Shuai <suagrfillet@...il.com>
Cc:     rostedt@...dmis.org, mhiramat@...nel.org, mark.rutland@....com,
        paul.walmsley@...ive.com, palmer@...belt.com,
        aou@...s.berkeley.edu, linux-riscv@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/3] riscv/ftrace: cleanup ftrace_caller and ftrace_regs_caller

On Wed, Nov 16, 2022 at 11:13 AM Song Shuai <suagrfillet@...il.com> wrote:
>
> ftrace_caller and ftrace_regs_caller save their regs with the respective
> option of SAVE_ALL, then call the tracing function, especially graph_ops's
> ftrace_graph_func. So the ftrace_graph_[regs]_call labels aren't needed
> anymore if FTRACE_WITH_REGS is defined.
>
> If FTRACE_WITH_REGS isn't defined, the !FTRACE_WITH_REGS version
> ftrace_caller remains with the ftrace_graph_call. So the enable/disable
> helpers are revised for serving only this ftrace_graph_call.
>
> Signed-off-by: Song Shuai <suagrfillet@...il.com>
> ---
>  arch/riscv/kernel/ftrace.c     | 19 ++----------------
>  arch/riscv/kernel/mcount-dyn.S | 35 +++++++++++++++-------------------
>  2 files changed, 17 insertions(+), 37 deletions(-)
>
> diff --git a/arch/riscv/kernel/ftrace.c b/arch/riscv/kernel/ftrace.c
> index 148a5480076b..2f0bcedc6a2d 100644
> --- a/arch/riscv/kernel/ftrace.c
> +++ b/arch/riscv/kernel/ftrace.c
> @@ -211,30 +211,15 @@ void ftrace_graph_func(unsigned long ip, unsigned long parent_ip,
>  #else /* CONFIG_DYNAMIC_FTRACE_WITH_REGS */
>
>  extern void ftrace_graph_call(void);
> -extern void ftrace_graph_regs_call(void);
>  int ftrace_enable_ftrace_graph_caller(void)
>  {
> -       int ret;
> -
> -       ret = __ftrace_modify_call((unsigned long)&ftrace_graph_call,
> -                                   (unsigned long)&prepare_ftrace_return, true);
> -       if (ret)
> -               return ret;
> -
> -       return __ftrace_modify_call((unsigned long)&ftrace_graph_regs_call,
> +       return  __ftrace_modify_call((unsigned long)&ftrace_graph_call,
>                                     (unsigned long)&prepare_ftrace_return, true);
>  }
>
>  int ftrace_disable_ftrace_graph_caller(void)
>  {
> -       int ret;
> -
> -       ret = __ftrace_modify_call((unsigned long)&ftrace_graph_call,
> -                                   (unsigned long)&prepare_ftrace_return, false);
> -       if (ret)
> -               return ret;
> -
> -       return __ftrace_modify_call((unsigned long)&ftrace_graph_regs_call,
> +       return  __ftrace_modify_call((unsigned long)&ftrace_graph_call,
>                                     (unsigned long)&prepare_ftrace_return, false);
>  }
>  #endif /* CONFIG_DYNAMIC_FTRACE_WITH_REGS */
> diff --git a/arch/riscv/kernel/mcount-dyn.S b/arch/riscv/kernel/mcount-dyn.S
> index 2f0a280bd7a0..9e4097c6793d 100644
> --- a/arch/riscv/kernel/mcount-dyn.S
> +++ b/arch/riscv/kernel/mcount-dyn.S
> @@ -215,6 +215,7 @@
>         .endm
>  #endif /* CONFIG_DYNAMIC_FTRACE_WITH_REGS */
>
> +#ifndef CONFIG_DYNAMIC_FTRACE_WITH_REGS
>  ENTRY(ftrace_caller)
>         SAVE_ABI
>
> @@ -243,33 +244,27 @@ ftrace_graph_call:
>         ret
>  ENDPROC(ftrace_caller)
>
> -#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
> +#else /* CONFIG_DYNAMIC_FTRACE_WITH_REGS */
>  ENTRY(ftrace_regs_caller)
> -       SAVE_ALL
> -
> -       addi    a0, ra, -FENTRY_RA_OFFSET
> -       la      a1, function_trace_op
> -       REG_L   a2, 0(a1)
> -       REG_L   a1, PT_SIZE_ON_STACK(sp)
> -       mv      a3, sp
> +       SAVE_ALL 1
I think the patch is broken, we shouldn't split mcount-dyn.S
modification from the patch.

>
>  ftrace_regs_call:
>         .global ftrace_regs_call
>         call    ftrace_stub
>
> -#ifdef CONFIG_FUNCTION_GRAPH_TRACER
> -       addi    a0, sp, PT_RA
> -       REG_L   a1, PT_EPC(sp)
> -       addi    a1, a1, -FENTRY_RA_OFFSET
> -#ifdef HAVE_FUNCTION_GRAPH_FP_TEST
> -       mv      a2, s0
> -#endif
> -ftrace_graph_regs_call:
> -       .global ftrace_graph_regs_call
> -       call    ftrace_stub
> -#endif
>
> -       RESTORE_ALL
> +       RESTORE_ALL 1
>         ret
>  ENDPROC(ftrace_regs_caller)
> +
> +ENTRY(ftrace_caller)
> +       SAVE_ALL 0
> +
> +ftrace_call:
> +       .global ftrace_call
> +       call    ftrace_stub
> +
> +       RESTORE_ALL 0
> +       ret
> +ENDPROC(ftrace_caller)
>  #endif /* CONFIG_DYNAMIC_FTRACE_WITH_REGS */
> --
> 2.20.1
>


--
Best Regards
 Guo Ren