linux-kernel - Re: [PATCH] powerpc/watchpoint: Don't call dar_within

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Message-ID: <d2aad6ea-5b61-7321-13a6-5faef361c57d@c-s.fr>
Date:   Sat, 22 Feb 2020 11:26:08 +0000
From:   Christophe Leroy <christophe.leroy@....fr>
To:     Ravi Bangoria <ravi.bangoria@...ux.ibm.com>, mpe@...erman.id.au
Cc:     mikey@...ling.org, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] powerpc/watchpoint: Don't call dar_within_range() for
 Book3S



On 02/22/2020 08:20 AM, Ravi Bangoria wrote:
> DAR is set to the first byte of overlap between actual access and
> watched range at DSI on Book3S processor. But actual access range
> might or might not be within user asked range. So for Book3S, it
> must not call dar_within_range().
> 
> This revert portion of commit 39413ae00967 ("powerpc/hw_breakpoints:
> Rewrite 8xx breakpoints to allow any address range size.").
> 
> Before patch:
>    # ./tools/testing/selftests/powerpc/ptrace/perf-hwbreak
>    ...
>    TESTED: No overlap
>    FAILED: Partial overlap: 0 != 2
>    TESTED: Partial overlap
>    TESTED: No overlap
>    FAILED: Full overlap: 0 != 2
>    failure: perf_hwbreak
> 
> After patch:
>    TESTED: No overlap
>    TESTED: Partial overlap
>    TESTED: Partial overlap
>    TESTED: No overlap
>    TESTED: Full overlap
>    success: perf_hwbreak
> 
> Fixes: 39413ae00967 ("powerpc/hw_breakpoints: Rewrite 8xx breakpoints to allow any address range size.")

Oh, this seems to have been introduced by 27985b2a640e 
("powerpc/watchpoint: Don't ignore extraneous exceptions blindly").

I must have lost it through a rebase as we were doing our series 
approximately at the same time, sorry for that.

Reviewed-by: Christophe Leroy <christophe.leroy@....fr>

> Reported-by: Michael Ellerman <mpe@...erman.id.au>
> Signed-off-by: Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
> ---
>   arch/powerpc/kernel/hw_breakpoint.c | 12 +++++++-----
>   1 file changed, 7 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/powerpc/kernel/hw_breakpoint.c b/arch/powerpc/kernel/hw_breakpoint.c
> index 2462cd7c565c..d0854320bb50 100644
> --- a/arch/powerpc/kernel/hw_breakpoint.c
> +++ b/arch/powerpc/kernel/hw_breakpoint.c
> @@ -331,11 +331,13 @@ int hw_breakpoint_handler(struct die_args *args)
>   	}
>   
>   	info->type &= ~HW_BRK_TYPE_EXTRANEOUS_IRQ;
> -	if (!dar_within_range(regs->dar, info))
> -		info->type |= HW_BRK_TYPE_EXTRANEOUS_IRQ;
> -
> -	if (!IS_ENABLED(CONFIG_PPC_8xx) && !stepping_handler(regs, bp, info))
> -		goto out;
> +	if (IS_ENABLED(CONFIG_PPC_8xx)) {
> +		if (!dar_within_range(regs->dar, info))
> +			info->type |= HW_BRK_TYPE_EXTRANEOUS_IRQ;
> +	} else {
> +		if (!stepping_handler(regs, bp, info))
> +			goto out;
> +	}
>   
>   	/*
>   	 * As a policy, the callback is invoked in a 'trigger-after-execute'
>