linux-kernel - Re: [PATCH v2 5/5] LoongArch: Abstract DYNAMIC_FTRACE_WITH

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Message-ID: <87h6t17sux.fsf@kylinos.cn>
Date:   Thu, 27 Apr 2023 14:16:06 +0800
From:   Enze Li <lienze@...inos.cn>
To:     Youling Tang <tangyouling@...ngson.cn>
Cc:     Huacai Chen <chenhuacai@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        WANG Xuerui <kernel@...0n.name>, linux-kernel@...r.kernel.org,
        linux-trace-kernel@...r.kernel.org, loongarch@...ts.linux.dev,
        loongson-kernel@...ts.loongnix.cn,
        Qing Zhang <zhangqing@...ngson.cn>
Subject: Re: [PATCH v2 5/5] LoongArch: Abstract DYNAMIC_FTRACE_WITH_ARGS
 accesses

On Thu, Apr 27 2023 at 10:12:32 AM +0800, Youling Tang wrote:

> From: Qing Zhang <zhangqing@...ngson.cn>
>
> 1. Adds new ftrace_regs_{get,set}_*() helpers which can be used to manipulate
> ftrace_regs. When CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS=y, these can always
> be used on any ftrace_regs, and when CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS=n
> these can be used when regs are available. A new ftrace_regs_has_args(fregs)
> helper is added which code can use to check when these are usable.
>
> 2. Prepare ftrace_regs_set_instruction_pointer support in advance.
>
> Signed-off-by: Qing Zhang <zhangqing@...ngson.cn>
> ---
>  arch/loongarch/include/asm/ftrace.h | 25 +++++++++++++++++++++++++
>  1 file changed, 25 insertions(+)
>
> diff --git a/arch/loongarch/include/asm/ftrace.h b/arch/loongarch/include/asm/ftrace.h
> index f789e680f633..30ee01243416 100644
> --- a/arch/loongarch/include/asm/ftrace.h
> +++ b/arch/loongarch/include/asm/ftrace.h
> @@ -54,6 +54,31 @@ static __always_inline struct pt_regs *arch_ftrace_get_regs(struct ftrace_regs *
>  	return &fregs->regs;
>  }
>  
> +static __always_inline void
> +ftrace_regs_set_instruction_pointer(struct ftrace_regs *fregs,
> +				    unsigned long ip)
> +{
> +	regs_set_return_value(&fregs->regs, ip);
> +}
> +
> +static __always_inline unsigned long
> +ftrace_regs_get_instruction_pointer(struct ftrace_regs *fregs)
> +{
> +	return instruction_pointer(&fregs->regs);
> +}
> +
> +#define ftrace_regs_get_argument(fregs, n) \
> +	regs_get_kernel_argument(&(fregs)->regs, n)
> +#define ftrace_regs_get_stack_pointer(fregs) \
> +	kernel_stack_pointer(&(fregs)->regs)
> +#define ftrace_regs_return_value(fregs) \
> +	regs_return_value(&(fregs)->regs)
> +#define ftrace_regs_set_return_value(fregs, ret) \

Hi Youling,

> +	regs_set_return_value(&(fregs)->regs, ret)
       ^^^^^^^^^^^^^^^^^^^^^^^^
I can not find the implementation of this function, am I missing
something?

> +#define ftrace_override_function_with_return(fregs) \
> +	override_function_with_return(&(fregs)->regs)
> +#define ftrace_regs_query_register_offset(name) \
                                                 ^^^^^^
There seems to be a missing function here.  Otherwise, the backslash
should be redundant.  Did I understand correctly?

Best Regards,
Enze

> +
>  #define ftrace_graph_func ftrace_graph_func
>  void ftrace_graph_func(unsigned long ip, unsigned long parent_ip,
>  		       struct ftrace_ops *op, struct ftrace_regs *fregs);