Re: [PATCH v6 3/5] riscv: ptrace support for hardware break/watchpoints

From: Chen Pei <cp0613@linux.alibaba.com>
To: Himanshu Chauhan <himanshu.chauhan@oss.qualcomm.com>,
	linux-riscv@lists.infradead.org
Cc: qingfang.deng@linux.dev, alex@ghiti.fr, aou@eecs.berkeley.edu,
	palmer@dabbelt.com, pjw@kernel.org, shuah@kernel.org,
	linux-kernel@vger.kernel.org, thecharlesjenkins@gmail.com,
	jtaubepe@redhat.com
Subject: Re: [PATCH v6 3/5] riscv: ptrace support for hardware break/watchpoints
Date: Wed,  5 Aug 2026 21:22:52 +0800	[thread overview]
Message-ID: <20260805132256.918-1-cp0613@linux.alibaba.com> (raw)
In-Reply-To: <20260803134913.2013674-4-himanshu.chauhan@oss.qualcomm.com>

> +struct __riscv_hwdebug_state {
> +	unsigned long addr;
> +	unsigned long type;
> +	unsigned long len;
> +	unsigned long ctrl;
> +} __packed;

Hi Himanshu,

Two suggestions about the new UAPI structure added in this patch.

1) Consider __u64 instead of 'unsigned long': its size differs
   between rv32 and rv64, so the layout would not be stable across
   32-bit and 64-bit userspace (e.g. a future COMPAT path). __u64
   keeps the layout identical for both.

2) With all members the same width there is no interior padding, so
   __packed can be dropped.

The struct user_hwdebug_state above already uses fixed-width types;
defining this one the same way would be consistent.

Best regards,
Pei

-- 
Chen Pei <cp0613@linux.alibaba.com>

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