Re: [PATCH v10 06/11] arm64: Make profile_pc() use arch_stack_walk()

Mark Rutland
2021-10-27T13:32:21Z

On Thu, Oct 14, 2021 at 09:58:42PM -0500, madvenka@linux.microsoft.com wrote:
> From: "Madhavan T. Venkataraman" <madvenka@linux.microsoft.com>
>
> Currently, profile_pc() in ARM64 code walks the stack using
> start_backtrace() and unwind_frame(). Make it use arch_stack_walk()
> instead. This makes maintenance easier.
>
> Signed-off-by: Madhavan T. Venkataraman <madvenka@linux.microsoft.com>
> ---
> arch/arm64/kernel/time.c | 22 +++++++++++++---------
> 1 file changed, 13 insertions(+), 9 deletions(-)
>
> diff --git a/arch/arm64/kernel/time.c b/arch/arm64/kernel/time.c
> index eebbc8d7123e..671b3038a772 100644
> --- a/arch/arm64/kernel/time.c
> +++ b/arch/arm64/kernel/time.c
> @@ -32,22 +32,26 @@
> #include <asm/stacktrace.h>
> #include <asm/paravirt.h>
>
> +static bool profile_pc_cb(void *arg, unsigned long pc)
> +{
> + unsigned long *prof_pc = arg;
> +
> + if (in_lock_functions(pc))
> + return true;
> + *prof_pc = pc;
> + return false;
> +}
> +
> unsigned long profile_pc(struct pt_regs *regs)
> {
> - struct stackframe frame;
> + unsigned long prof_pc = 0;
>
> if (!in_lock_functions(regs->pc))
> return regs->pc;

This can go -- the first call to profile_pc_cb() will use regs->pc.

With that gone, and the include updates to use <linux/stacktrace.h>:

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

Mark.

> - start_backtrace(&frame, regs->regs[29], regs->pc);
> -
> - do {
> - int ret = unwind_frame(NULL, &frame);
> - if (ret < 0)
> - return 0;
> - } while (in_lock_functions(frame.pc));
> + arch_stack_walk(profile_pc_cb, &prof_pc, current, regs);
>
> - return frame.pc;
> + return prof_pc;
> }
> EXPORT_SYMBOL(profile_pc);
>
> --
> 2.25.1
>