linux-kernel - Re: [PATCH 2/2] LoongArch: Extend the maximum number of watchpoints

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Message-ID: <42e64433f3255740292d428cf459959430fdc7e3.camel@xry111.site>
Date: Tue, 21 Jan 2025 21:46:17 +0800
From: Xi Ruoyao <xry111@...111.site>
To: WANG Xuerui <kernel@...0n.name>, Tiezhu Yang <yangtiezhu@...ngson.cn>, 
 Huacai Chen <chenhuacai@...nel.org>
Cc: loongarch@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] LoongArch: Extend the maximum number of watchpoints

On Tue, 2025-01-21 at 21:35 +0800, WANG Xuerui wrote:
> one cannot account for older (in fact, *every existing*) clients 
> expecting the old UAPI, hence providing a smaller buffer than struct 
> user_watch_state_v2. In which case the kernel will happily write 
> out-of-bounds if the client asks for the current watchpoint state. This 
> is not acceptable I'm afraid.

Yes, many distros support running the latest kernel with an old
userspace for hardware compatibility reason and the change will blow up
gdb on all those distros.  We need to do something smarter to retain the
backward compatibility.

-- 
Xi Ruoyao <xry111@...111.site>
School of Aerospace Science and Technology, Xidian University