linux-kernel - Re: [PATCH v11 2/5] arm64: Rename unwinder functions

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Message-ID: <YaY+gMPSQMx1M5Pj@FVFF77S0Q05N>
Date:   Tue, 30 Nov 2021 15:08:48 +0000
From:   Mark Rutland <mark.rutland@....com>
To:     madvenka@...ux.microsoft.com
Cc:     broonie@...nel.org, jpoimboe@...hat.com, ardb@...nel.org,
        nobuta.keiya@...itsu.com, sjitindarsingh@...il.com,
        catalin.marinas@....com, will@...nel.org, jmorris@...ei.org,
        linux-arm-kernel@...ts.infradead.org,
        live-patching@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v11 2/5] arm64: Rename unwinder functions

On Tue, Nov 23, 2021 at 01:37:20PM -0600, madvenka@...ux.microsoft.com wrote:
> From: "Madhavan T. Venkataraman" <madvenka@...ux.microsoft.com>
> 
> Rename unwinder functions for consistency and better naming.
> 
> 	- Rename start_backtrace() to unwind_start().
> 	- Rename unwind_frame() to unwind_next().
> 	- Rename walk_stackframe() to unwind().

Super trivial, but could we s/unwind_start/unwind_init/ ? That makes it
slightly clearer that it's not performing an unwind step.

Otherwise, this looks good to me.

For the rename:

Acked-by: Mark Rutland <mark.rutland@....com>

It's be nice if we could also clean up 'struct stackframe' into 'struct
unwind_state', but that can be a follow-up, and this is fine as it is, modulo
the super trivial comment above.

Thanks,
Mark.

> 
> Signed-off-by: Madhavan T. Venkataraman <madvenka@...ux.microsoft.com>
> ---
>  arch/arm64/kernel/stacktrace.c | 28 ++++++++++++++--------------
>  1 file changed, 14 insertions(+), 14 deletions(-)
> 
> diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c
> index 7217c4f63ef7..918852cd2681 100644
> --- a/arch/arm64/kernel/stacktrace.c
> +++ b/arch/arm64/kernel/stacktrace.c
> @@ -33,8 +33,8 @@
>   */
>  
>  
> -static void start_backtrace(struct stackframe *frame, unsigned long fp,
> -			    unsigned long pc)
> +static void unwind_start(struct stackframe *frame, unsigned long fp,
> +			 unsigned long pc)
>  {
>  	frame->fp = fp;
>  	frame->pc = pc;
> @@ -45,7 +45,7 @@ static void start_backtrace(struct stackframe *frame, unsigned long fp,
>  	/*
>  	 * Prime the first unwind.
>  	 *
> -	 * In unwind_frame() we'll check that the FP points to a valid stack,
> +	 * In unwind_next() we'll check that the FP points to a valid stack,
>  	 * which can't be STACK_TYPE_UNKNOWN, and the first unwind will be
>  	 * treated as a transition to whichever stack that happens to be. The
>  	 * prev_fp value won't be used, but we set it to 0 such that it is
> @@ -63,8 +63,8 @@ static void start_backtrace(struct stackframe *frame, unsigned long fp,
>   * records (e.g. a cycle), determined based on the location and fp value of A
>   * and the location (but not the fp value) of B.
>   */
> -static int notrace unwind_frame(struct task_struct *tsk,
> -				struct stackframe *frame)
> +static int notrace unwind_next(struct task_struct *tsk,
> +			       struct stackframe *frame)
>  {
>  	unsigned long fp = frame->fp;
>  	struct stack_info info;
> @@ -104,7 +104,7 @@ static int notrace unwind_frame(struct task_struct *tsk,
>  
>  	/*
>  	 * Record this frame record's values and location. The prev_fp and
> -	 * prev_type are only meaningful to the next unwind_frame() invocation.
> +	 * prev_type are only meaningful to the next unwind_next() invocation.
>  	 */
>  	frame->fp = READ_ONCE_NOCHECK(*(unsigned long *)(fp));
>  	frame->pc = READ_ONCE_NOCHECK(*(unsigned long *)(fp + 8));
> @@ -137,27 +137,27 @@ static int notrace unwind_frame(struct task_struct *tsk,
>  
>  	return 0;
>  }
> -NOKPROBE_SYMBOL(unwind_frame);
> +NOKPROBE_SYMBOL(unwind_next);
>  
> -static void notrace walk_stackframe(struct task_struct *tsk,
> -				    unsigned long fp, unsigned long pc,
> -				    bool (*fn)(void *, unsigned long), void *data)
> +static void notrace unwind(struct task_struct *tsk,
> +			   unsigned long fp, unsigned long pc,
> +			   bool (*fn)(void *, unsigned long), void *data)
>  {
>  	struct stackframe frame;
>  
> -	start_backtrace(&frame, fp, pc);
> +	unwind_start(&frame, fp, pc);
>  
>  	while (1) {
>  		int ret;
>  
>  		if (!fn(data, frame.pc))
>  			break;
> -		ret = unwind_frame(tsk, &frame);
> +		ret = unwind_next(tsk, &frame);
>  		if (ret < 0)
>  			break;
>  	}
>  }
> -NOKPROBE_SYMBOL(walk_stackframe);
> +NOKPROBE_SYMBOL(unwind);
>  
>  static bool dump_backtrace_entry(void *arg, unsigned long where)
>  {
> @@ -210,5 +210,5 @@ noinline notrace void arch_stack_walk(stack_trace_consume_fn consume_entry,
>  		fp = thread_saved_fp(task);
>  		pc = thread_saved_pc(task);
>  	}
> -	walk_stackframe(task, fp, pc, consume_entry, cookie);
> +	unwind(task, fp, pc, consume_entry, cookie);
>  }
> -- 
> 2.25.1
>