linux-kernel - Re: [PATCH] ARM/hw_breakpoint: modify dead code for breakpoint

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Date:   Fri, 11 Oct 2019 17:43:19 +0100
From:   Will Deacon <will@...nel.org>
To:     wangxu <wangxu72@...wei.com>
Cc:     mark.rutland@....com, linux@...linux.org.uk,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ARM/hw_breakpoint: modify dead code for
 breakpoint_handler()

On Wed, Oct 09, 2019 at 05:27:00PM +0800, wangxu wrote:
> From: Wang Xu <wangxu72@...wei.com>
> 
> In perf_event_alloc(), event->overflow_handler is initialized to a
> non-null value, which makes enable_single_step(bp, addr) in
> breakpoint_handler() never be executed.
> 
> As a matter of fact, the branch condition has been updated to
> is_default_overflow_handler().
> 
> Signed-off-by: Wang Xu <wangxu72@...wei.com>
> ---
>  arch/arm/kernel/hw_breakpoint.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm/kernel/hw_breakpoint.c b/arch/arm/kernel/hw_breakpoint.c
> index b0c195e..586a587 100644
> --- a/arch/arm/kernel/hw_breakpoint.c
> +++ b/arch/arm/kernel/hw_breakpoint.c
> @@ -822,7 +822,7 @@ static void breakpoint_handler(unsigned long unknown, struct pt_regs *regs)
>  			info->trigger = addr;
>  			pr_debug("breakpoint fired: address = 0x%x\n", addr);
>  			perf_bp_event(bp, regs);
> -			if (!bp->overflow_handler)
> +			if (is_default_overflow_handler(bp))
>  				enable_single_step(bp, addr);
>  			goto unlock;

Seems to match what we do on arm64, so:

Acked-by: Will Deacon <will@...nel.org>

You'll need to put this into rmk's patch system [1].

Will

[1] https://www.arm.linux.org.uk/developer/