linux-kernel - Re: [PATCH] arm64: hw_breakpoint: Save privilege of access control via ptrace

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Date: Thu, 20 Jun 2024 11:08:07 +0200
From: Oleg Nesterov <oleg@...hat.com>
To: Tiezhu Yang <yangtiezhu@...ngson.cn>
Cc: Will Deacon <will@...nel.org>, Mark Rutland <mark.rutland@....com>,
	Catalin Marinas <catalin.marinas@....com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	linux-arm-kernel@...ts.infradead.org,
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arm64: hw_breakpoint: Save privilege of access control
 via ptrace

On 06/20, Tiezhu Yang wrote:
>
> On 06/19/2024 11:15 PM, Oleg Nesterov wrote:
> >>--- a/include/uapi/linux/perf_event.h
> >>+++ b/include/uapi/linux/perf_event.h
> >>@@ -467,6 +467,7 @@ struct perf_event_attr {
> >> 		__u32		wakeup_watermark; /* bytes before wakeup   */
> >> 	};
> >>
> >>+	__u8			bp_priv;
> >> 	__u32			bp_type;
> >
> >Is it safe to add the new member in the middle of uapi struct?
> >This will break userspace...
>
> Let me put the new member "bp_priv" at the end of uapi struct
> perf_event_attr in the next version if you are OK with it.

And add PERF_ATTR_SIZE_VER9 ?

Well, you can safely ignore me, you should ask the maintainers ;)

But to me the very idea of arm64-specific and "kernel only" member in
perf_event_attr looks a bit strange.

Oleg.