linux-kernel - Re: [PATCH 07/15] powerpc/watchpoint: Get watchpoint count dynamically while disabling them

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Date:   Tue, 17 Mar 2020 11:32:26 +0100
From:   Christophe Leroy <christophe.leroy@....fr>
To:     Ravi Bangoria <ravi.bangoria@...ux.ibm.com>, mpe@...erman.id.au,
        mikey@...ling.org
Cc:     apopple@...ux.ibm.com, paulus@...ba.org, npiggin@...il.com,
        naveen.n.rao@...ux.vnet.ibm.com, peterz@...radead.org,
        jolsa@...nel.org, oleg@...hat.com, fweisbec@...il.com,
        mingo@...nel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 07/15] powerpc/watchpoint: Get watchpoint count
 dynamically while disabling them



Le 09/03/2020 à 09:57, Ravi Bangoria a écrit :
> Instead of disabling only one watchpooint, get num of available
> watchpoints dynamically and disable all of them.
> 
> Signed-off-by: Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
> ---
>   arch/powerpc/include/asm/hw_breakpoint.h | 15 +++++++--------
>   1 file changed, 7 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/hw_breakpoint.h b/arch/powerpc/include/asm/hw_breakpoint.h
> index 980ac7d9f267..ec61e2b7195c 100644
> --- a/arch/powerpc/include/asm/hw_breakpoint.h
> +++ b/arch/powerpc/include/asm/hw_breakpoint.h
> @@ -75,14 +75,13 @@ extern void ptrace_triggered(struct perf_event *bp,
>   			struct perf_sample_data *data, struct pt_regs *regs);
>   static inline void hw_breakpoint_disable(void)
>   {
> -	struct arch_hw_breakpoint brk;
> -
> -	brk.address = 0;
> -	brk.type = 0;
> -	brk.len = 0;
> -	brk.hw_len = 0;
> -	if (ppc_breakpoint_available())
> -		__set_breakpoint(&brk, 0);
> +	int i;
> +	struct arch_hw_breakpoint null_brk = {0};
> +
> +	if (ppc_breakpoint_available()) {

I think this test should go into nr_wp_slots() which should return zero 
when no breakpoint is available. This would simplify at least here and 
patch 4

Christophe

> +		for (i = 0; i < nr_wp_slots(); i++)
> +			__set_breakpoint(&null_brk, i);
> +	}
>   }
>   extern void thread_change_pc(struct task_struct *tsk, struct pt_regs *regs);
>   int hw_breakpoint_handler(struct die_args *args);
>