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

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Date: Thu, 20 Jun 2024 12:31:36 +0100
From: James Clark <james.clark@....com>
To: Oleg Nesterov <oleg@...hat.com>, 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 20/06/2024 11:36, Oleg Nesterov wrote:
> Again, I can't really comment, I know almost nothing about perf, but
> 
> On 06/20, Tiezhu Yang wrote:
>>
>> On 06/20/2024 05:08 PM, Oleg Nesterov wrote:
>>>
>>> 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")
> 
> but this is another thing even if I have no idea what .config3 means.
> 
> If nothing else, what do you think, say, tools/perf can do with ->bp_priv?

Yeah, including the tools side change in the same series might help to
explain. It's not obvious what the end goal is from the commit message.

Thanks
James

> 
> What should sys_perf_event_open() do if bp_priv != 0 comes from user space?
> 
> Nevermind, please forget, I leave this to you and maintainers.
> 
> Oleg.
> 
>