Re: [PATCH 1/2] riscv: stacktrace: use arch_stack_walk() in place of walk_stackframe

From: "Björn Töpel" <bjorn@kernel.org>
To: "Puranjay Mohan" <puranjay12@gmail.com>,
	"Paul Walmsley" <paul.walmsley@sifive.com>,
	"Palmer Dabbelt" <palmer@dabbelt.com>,
	"Albert Ou" <aou@eecs.berkeley.edu>,
	linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
	"Björn Töpel" <bjorn@rivosinc.com>
Cc: puranjay12@gmail.com
Subject: Re: [PATCH 1/2] riscv: stacktrace: use arch_stack_walk() in place of walk_stackframe
Date: Tue, 02 Apr 2024 15:19:29 +0200	[thread overview]
Message-ID: <87zfubrjfi.fsf@all.your.base.are.belong.to.us> (raw)
In-Reply-To: <20240328184020.34278-2-puranjay12@gmail.com>

Puranjay Mohan <puranjay12@gmail.com> writes:

> Currently, dump_backtrace(), __get_wchan(), and perf_callchain_kernel()
> directly call walk_stackframe(). Make then call arch_stack_walk() which
> is a wrapper around walk_stackframe() and make walk_stackframe() static.
>
> This allows making changes to walk_stackframe() without disturbing the
> users of arch_stack_walk() which is the exposed function.
>
> Signed-off-by: Puranjay Mohan <puranjay12@gmail.com>
> ---
>  arch/riscv/include/asm/stacktrace.h |  2 --
>  arch/riscv/kernel/perf_callchain.c  |  2 +-
>  arch/riscv/kernel/stacktrace.c      | 26 ++++++++++++++------------
>  3 files changed, 15 insertions(+), 15 deletions(-)
>
> diff --git a/arch/riscv/include/asm/stacktrace.h b/arch/riscv/include/asm/stacktrace.h
> index b1495a7e06ce6..32213e37c379f 100644
> --- a/arch/riscv/include/asm/stacktrace.h
> +++ b/arch/riscv/include/asm/stacktrace.h
> @@ -11,8 +11,6 @@ struct stackframe {
>  	unsigned long ra;
>  };
>  
> -extern void notrace walk_stackframe(struct task_struct *task, struct pt_regs *regs,
> -				    bool (*fn)(void *, unsigned long), void *arg);
>  extern void dump_backtrace(struct pt_regs *regs, struct task_struct *task,
>  			   const char *loglvl);
>  
> diff --git a/arch/riscv/kernel/perf_callchain.c b/arch/riscv/kernel/perf_callchain.c
> index 3348a61de7d99..c023e0b1eb814 100644
> --- a/arch/riscv/kernel/perf_callchain.c
> +++ b/arch/riscv/kernel/perf_callchain.c
> @@ -74,5 +74,5 @@ static bool fill_callchain(void *entry, unsigned long pc)
>  void perf_callchain_kernel(struct perf_callchain_entry_ctx *entry,
>  			   struct pt_regs *regs)
>  {
> -	walk_stackframe(NULL, regs, fill_callchain, entry);
> +	arch_stack_walk(fill_callchain, entry, NULL, regs);
>  }
> diff --git a/arch/riscv/kernel/stacktrace.c b/arch/riscv/kernel/stacktrace.c
> index 64a9c093aef93..e28f7b2e4b6a6 100644
> --- a/arch/riscv/kernel/stacktrace.c
> +++ b/arch/riscv/kernel/stacktrace.c
> @@ -18,8 +18,9 @@
>  
>  extern asmlinkage void ret_from_exception(void);
>  
> -void notrace walk_stackframe(struct task_struct *task, struct pt_regs *regs,
> -			     bool (*fn)(void *, unsigned long), void *arg)
> +static __always_inline void
> +walk_stackframe(struct task_struct *task, struct pt_regs *regs,
> +		bool (*fn)(void *, unsigned long), void *arg)

Really a nit, but please try to keep the return value/linkage/function
name on one line if possible.

>  {
>  	unsigned long fp, sp, pc;
>  	int level = 0;
> @@ -76,8 +77,9 @@ void notrace walk_stackframe(struct task_struct *task, struct pt_regs *regs,
>  
>  #else /* !CONFIG_FRAME_POINTER */
>  
> -void notrace walk_stackframe(struct task_struct *task,
> -	struct pt_regs *regs, bool (*fn)(void *, unsigned long), void *arg)
> +static __always_inline void
> +walk_stackframe(struct task_struct *task, struct pt_regs *regs,
> +		bool (*fn)(void *, unsigned long), void *arg)

...and here.

Björn