[RFC PATCH 2/3] arm64: stacktrace: Factor out backtrace initialisation

[Mark Rutland]

On Fri, Apr 20, 2018 at 11:46:18AM +0100, Dave Martin wrote:
> Some common code is required by each stacktrace user to initialised
> struct stackframe before the first call to unwind_frame().
> 
> In preparation for adding to the common code, this patch factors it
> out into a separate function start_backtrace(), and modifies the
> stacktrace callers appropriately.
> 
> No functional change.
> 
> Signed-off-by: Dave Martin <Dave.Martin at arm.com>

Looks like a nice cleanup.

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

Mark.

> ---
>  arch/arm64/include/asm/stacktrace.h | 11 +++++++++++
>  arch/arm64/kernel/process.c         |  6 +-----
>  arch/arm64/kernel/time.c            |  6 +-----
>  arch/arm64/kernel/traps.c           | 21 ++++++++-------------
>  4 files changed, 21 insertions(+), 23 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/stacktrace.h b/arch/arm64/include/asm/stacktrace.h
> index 63c0379..c9bef22 100644
> --- a/arch/arm64/include/asm/stacktrace.h
> +++ b/arch/arm64/include/asm/stacktrace.h
> @@ -94,4 +94,15 @@ static inline bool on_accessible_stack(struct task_struct const *tsk,
>  	return false;
>  }
>  
> +static inline void start_backtrace(struct stackframe *frame,
> +			    struct task_struct const *tsk,
> +			    unsigned long fp, unsigned long pc)
> +{
> +	frame->fp = fp;
> +	frame->pc = pc;
> +#ifdef CONFIG_FUNCTION_GRAPH_TRACER
> +	frame.graph = tsk->curr_ret_stack;
> +#endif
> +}
> +
>  #endif	/* __ASM_STACKTRACE_H */
> diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
> index f08a2ed..59b418c 100644
> --- a/arch/arm64/kernel/process.c
> +++ b/arch/arm64/kernel/process.c
> @@ -452,11 +452,7 @@ unsigned long get_wchan(struct task_struct *p)
>  	if (!stack_page)
>  		return 0;
>  
> -	frame.fp = thread_saved_fp(p);
> -	frame.pc = thread_saved_pc(p);
> -#ifdef CONFIG_FUNCTION_GRAPH_TRACER
> -	frame.graph = p->curr_ret_stack;
> -#endif
> +	start_backtrace(&frame, p, thread_saved_fp(p), thread_saved_pc(p));
>  	do {
>  		if (unwind_frame(p, &frame))
>  			goto out;
> diff --git a/arch/arm64/kernel/time.c b/arch/arm64/kernel/time.c
> index f258636..83f08c7 100644
> --- a/arch/arm64/kernel/time.c
> +++ b/arch/arm64/kernel/time.c
> @@ -49,11 +49,7 @@ unsigned long profile_pc(struct pt_regs *regs)
>  	if (!in_lock_functions(regs->pc))
>  		return regs->pc;
>  
> -	frame.fp = regs->regs[29];
> -	frame.pc = regs->pc;
> -#ifdef CONFIG_FUNCTION_GRAPH_TRACER
> -	frame.graph = current->curr_ret_stack;
> -#endif
> +	start_backtrace(&frame, current, regs->regs[29], regs->pc);
>  	do {
>  		int ret = unwind_frame(NULL, &frame);
>  		if (ret < 0)
> diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
> index ba964da..3910af4 100644
> --- a/arch/arm64/kernel/traps.c
> +++ b/arch/arm64/kernel/traps.c
> @@ -111,19 +111,14 @@ void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
>  	if (!try_get_task_stack(tsk))
>  		return;
>  
> -	if (tsk == current) {
> -		frame.fp = (unsigned long)__builtin_frame_address(0);
> -		frame.pc = (unsigned long)dump_backtrace;
> -	} else {
> -		/*
> -		 * task blocked in __switch_to
> -		 */
> -		frame.fp = thread_saved_fp(tsk);
> -		frame.pc = thread_saved_pc(tsk);
> -	}
> -#ifdef CONFIG_FUNCTION_GRAPH_TRACER
> -	frame.graph = tsk->curr_ret_stack;
> -#endif
> +	if (tsk == current)
> +		start_backtrace(&frame, tsk,
> +				(unsigned long)__builtin_frame_address(0),
> +				(unsigned long)dump_backtrace);
> +	else /* task blocked in __switch_to */
> +		start_backtrace(&frame, tsk,
> +				thread_saved_fp(tsk),
> +				thread_saved_pc(tsk));
>  
>  	skip = !!regs;
>  	printk("Call trace:\n");
> -- 
> 2.1.4
>