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Subject: Re: [PATCH v6 7/8] powerpc/watchpoint/ptrace: Introduce
 PPC_DEBUG_FEATURE_DATA_BP_ARCH_31
To:     Ravi Bangoria <ravi.bangoria@linux.ibm.com>, mpe@ellerman.id.au,
        christophe.leroy@c-s.fr
Cc:     mikey@neuling.org, jniethe5@gmail.com, pedromfc@linux.ibm.com,
        linux-kernel@vger.kernel.org, paulus@samba.org,
        rogealve@linux.ibm.com, naveen.n.rao@linux.vnet.ibm.com,
        linuxppc-dev@lists.ozlabs.org
References: <20200902042945.129369-1-ravi.bangoria@linux.ibm.com>
 <20200902042945.129369-8-ravi.bangoria@linux.ibm.com>
From:   Rogerio Alves <rcardoso@linux.ibm.com>
Message-ID: <6868995a-0b93-d93c-5151-486ed602ac81@linux.ibm.com>
Date:   Thu, 17 Sep 2020 10:26:14 -0300
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On 9/2/20 1:29 AM, Ravi Bangoria wrote:
> PPC_DEBUG_FEATURE_DATA_BP_ARCH_31 can be used to determine whether
> we are running on an ISA 3.1 compliant machine. Which is needed to
> determine DAR behaviour, 512 byte boundary limit etc. This was
> requested by Pedro Miraglia Franco de Carvalho for extending
> watchpoint features in gdb. Note that availability of 2nd DAWR is
> independent of this flag and should be checked using
> ppc_debug_info->num_data_bps.
> 
> Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Tested-by: Rogerio Alves <rcardoso@linux.ibm.com>
> ---
>   Documentation/powerpc/ptrace.rst          | 1 +
>   arch/powerpc/include/uapi/asm/ptrace.h    | 1 +
>   arch/powerpc/kernel/ptrace/ptrace-noadv.c | 2 ++
>   3 files changed, 4 insertions(+)
> 
> diff --git a/Documentation/powerpc/ptrace.rst b/Documentation/powerpc/ptrace.rst
> index 864d4b6dddd1..77725d69eb4a 100644
> --- a/Documentation/powerpc/ptrace.rst
> +++ b/Documentation/powerpc/ptrace.rst
> @@ -46,6 +46,7 @@ features will have bits indicating whether there is support for::
>     #define PPC_DEBUG_FEATURE_DATA_BP_RANGE		0x4
>     #define PPC_DEBUG_FEATURE_DATA_BP_MASK		0x8
>     #define PPC_DEBUG_FEATURE_DATA_BP_DAWR		0x10
> +  #define PPC_DEBUG_FEATURE_DATA_BP_ARCH_31		0x20
>   
>   2. PTRACE_SETHWDEBUG
>   
> diff --git a/arch/powerpc/include/uapi/asm/ptrace.h b/arch/powerpc/include/uapi/asm/ptrace.h
> index f5f1ccc740fc..7004cfea3f5f 100644
> --- a/arch/powerpc/include/uapi/asm/ptrace.h
> +++ b/arch/powerpc/include/uapi/asm/ptrace.h
> @@ -222,6 +222,7 @@ struct ppc_debug_info {
>   #define PPC_DEBUG_FEATURE_DATA_BP_RANGE		0x0000000000000004
>   #define PPC_DEBUG_FEATURE_DATA_BP_MASK		0x0000000000000008
>   #define PPC_DEBUG_FEATURE_DATA_BP_DAWR		0x0000000000000010
> +#define PPC_DEBUG_FEATURE_DATA_BP_ARCH_31	0x0000000000000020
>   
>   #ifndef __ASSEMBLY__
>   
> diff --git a/arch/powerpc/kernel/ptrace/ptrace-noadv.c b/arch/powerpc/kernel/ptrace/ptrace-noadv.c
> index 48c52426af80..aa36fcad36cd 100644
> --- a/arch/powerpc/kernel/ptrace/ptrace-noadv.c
> +++ b/arch/powerpc/kernel/ptrace/ptrace-noadv.c
> @@ -57,6 +57,8 @@ void ppc_gethwdinfo(struct ppc_debug_info *dbginfo)
>   	} else {
>   		dbginfo->features = 0;
>   	}
> +	if (cpu_has_feature(CPU_FTR_ARCH_31))
> +		dbginfo->features |= PPC_DEBUG_FEATURE_DATA_BP_ARCH_31;
>   }
>   
>   int ptrace_get_debugreg(struct task_struct *child, unsigned long addr,
>