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Subject: Re: [PATCH v5 5/8] powerpc/watchpoint: Fix exception handling for
 CONFIG_HAVE_HW_BREAKPOINT=N
To:     Christophe Leroy <christophe.leroy@csgroup.eu>,
        christophe.leroy@c-s.fr
Cc:     mpe@ellerman.id.au, mikey@neuling.org, paulus@samba.org,
        naveen.n.rao@linux.vnet.ibm.com, pedromfc@linux.ibm.com,
        rogealve@linux.ibm.com, jniethe5@gmail.com,
        linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org,
        Ravi Bangoria <ravi.bangoria@linux.ibm.com>
References: <20200825043617.1073634-1-ravi.bangoria@linux.ibm.com>
 <20200825043617.1073634-6-ravi.bangoria@linux.ibm.com>
 <91d34b89-603a-fddc-ea0f-53a79b287eed@csgroup.eu>
From:   Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Message-ID: <1e706137-3de9-a713-5a86-48fbc5e6f740@linux.ibm.com>
Date:   Tue, 25 Aug 2020 16:37:57 +0530
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Hi Christophe,

>> diff --git a/arch/powerpc/kernel/ptrace/ptrace-noadv.c b/arch/powerpc/kernel/ptrace/ptrace-noadv.c
>> index 57a0ab822334..866597b407bc 100644
>> --- a/arch/powerpc/kernel/ptrace/ptrace-noadv.c
>> +++ b/arch/powerpc/kernel/ptrace/ptrace-noadv.c
>> @@ -286,11 +286,16 @@ long ppc_del_hwdebug(struct task_struct *child, long data)
>>       }
>>       return ret;
>>   #else /* CONFIG_HAVE_HW_BREAKPOINT */
>> +    if (child->thread.hw_brk[data - 1].flags & HW_BRK_FLAG_DISABLED)
> 
> I think child->thread.hw_brk[data - 1].flags & HW_BRK_FLAG_DISABLED should go around additionnal ()

Not sure I follow.

> 
>> +        goto del;
>> +
>>       if (child->thread.hw_brk[data - 1].address == 0)
>>           return -ENOENT;
> 
> What about replacing the above if by:
>      if (!(child->thread.hw_brk[data - 1].flags) & HW_BRK_FLAG_DISABLED) &&
>          child->thread.hw_brk[data - 1].address == 0)
>          return -ENOENT;
okay.. that's more compact.

But more importantly, what I wanted to know is whether CONFIG_HAVE_HW_BREAKPOINT
is set or not in production/distro builds for 8xx. Because I see it's not set in
8xx defconfigs.

Thanks,
Ravi