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

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Date: Thu, 20 Jun 2024 17:50:45 +0800
From: Tiezhu Yang <yangtiezhu@...ngson.cn>
To: Oleg Nesterov <oleg@...hat.com>
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 06/20/2024 05:08 PM, Oleg Nesterov wrote:
> 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 ?

Yes, thank you.

> 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.

I noticed that there is a similar arm64-specific change in
commit 09519ec3b19e ("perf: Add perf_event_attr::config3")
according to the commit message, and it will be used for
LoongArch later if this change is accepted.

Thanks,
Tiezhu