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

From: Dave Martin <Dave.Martin@arm.com>
To: Mark Rutland <mark.rutland@arm.com>
Cc: catalin.marinas@arm.com, tengfeif@codeaurora.org,
	will.deacon@arm.com, james.morse@arm.com,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 2/3] arm64: stacktrace: Factor out backtrace initialisation
Date: Fri, 21 Jun 2019 16:50:48 +0100	[thread overview]
Message-ID: <20190621155047.GE2790@e103592.cambridge.arm.com> (raw)
In-Reply-To: <20190606125402.10229-3-mark.rutland@arm.com>

On Thu, Jun 06, 2019 at 01:54:01PM +0100, Mark Rutland wrote:
> From: Dave Martin <Dave.Martin@arm.com>
> 
> Some common code is required by each stacktrace user to initialise
> 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@arm.com>
> Signed-off-by: Mark Rutland <mark.rutland@arm.com>

Ack (from memory you just added the CONFIG_FUNCTION_GRAPH_TRACER stuff,
the lack of which was causing build failures in my original version).

Have you added any new calls to start_backtrace() here?

Cheers
---Dave

> ---
>  arch/arm64/include/asm/stacktrace.h | 10 ++++++++++
>  arch/arm64/kernel/process.c         |  6 +-----
>  arch/arm64/kernel/time.c            |  6 +-----
>  arch/arm64/kernel/traps.c           | 13 ++++++-------
>  4 files changed, 18 insertions(+), 17 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/stacktrace.h b/arch/arm64/include/asm/stacktrace.h
> index 4dd569592e65..18f90bf1385c 100644
> --- a/arch/arm64/include/asm/stacktrace.h
> +++ b/arch/arm64/include/asm/stacktrace.h
> @@ -142,4 +142,14 @@ static inline bool on_accessible_stack(const struct task_struct *tsk,
>  	return false;
>  }
>  
> +static inline void start_backtrace(struct stackframe *frame,
> +				   unsigned long fp, unsigned long pc)
> +{
> +	frame->fp = fp;
> +	frame->pc = pc;
> +#ifdef CONFIG_FUNCTION_GRAPH_TRACER
> +	frame->graph = 0;
> +#endif
> +}
> +
>  #endif	/* __ASM_STACKTRACE_H */
> diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
> index 3767fb21a5b8..122d88fccd13 100644
> --- a/arch/arm64/kernel/process.c
> +++ b/arch/arm64/kernel/process.c
> @@ -509,11 +509,7 @@ 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 = 0;
> -#endif
> +	start_backtrace(&frame, 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 a777ae90044d..aa3489f3a452 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 = 0;
> -#endif
> +	start_backtrace(&frame, 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 ade32046f3fe..8053bbed8776 100644
> --- a/arch/arm64/kernel/traps.c
> +++ b/arch/arm64/kernel/traps.c
> @@ -119,18 +119,17 @@ void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
>  		return;
>  
>  	if (tsk == current) {
> -		frame.fp = (unsigned long)__builtin_frame_address(0);
> -		frame.pc = (unsigned long)dump_backtrace;
> +		start_backtrace(&frame,
> +				(unsigned long)__builtin_frame_address(0),
> +				(unsigned long)dump_backtrace);
>  	} else {
>  		/*
>  		 * task blocked in __switch_to
>  		 */
> -		frame.fp = thread_saved_fp(tsk);
> -		frame.pc = thread_saved_pc(tsk);
> +		start_backtrace(&frame,
> +				thread_saved_fp(tsk),
> +				thread_saved_pc(tsk));
>  	}
> -#ifdef CONFIG_FUNCTION_GRAPH_TRACER
> -	frame.graph = 0;
> -#endif
>  
>  	printk("Call trace:\n");
>  	do {
> -- 
> 2.11.0
> 
> 
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