linux-kernel - Re: [PATCH v7 00/17] unwind_user: perf: x86: Deferred unwinding infrastructure

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <aBc2ZBlQTpybK3Z-@gmail.com>
Date: Sun, 4 May 2025 11:41:56 +0200
From: Ingo Molnar <mingo@...nel.org>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Josh Poimboeuf <jpoimboe@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>, x86@...nel.org,
	Jiri Olsa <jolsa@...nel.org>, Namhyung Kim <namhyung@...nel.org>
Subject: Re: [PATCH v7 00/17] unwind_user: perf: x86: Deferred unwinding
 infrastructure


* Steven Rostedt <rostedt@...dmis.org> wrote:

>       unwind_user: Add user space unwinding API
>       unwind_user: Add frame pointer support
>       unwind_user/x86: Enable frame pointer unwinding on x86
>       perf/x86: Rename and move get_segment_base() and make it global
>       unwind_user: Add compat mode frame pointer support
>       unwind_user/x86: Enable compat mode frame pointer unwinding on x86
>       unwind_user/deferred: Add unwind cache

What is the cost of 'caching' here? Will we double-buffer the tracing 
data before it reaches its single primary tooling user, with no use of 
any actual 'caching', which will be scenario in like 99.9% of the 
everyday usecases when this facility is used?

>       unwind_user/deferred: Add deferred unwinding interface
>       unwind_user/deferred: Make unwind deferral requests NMI-safe
>       perf: Remove get_perf_callchain() init_nr argument
>       perf: Have get_perf_callchain() return NULL if crosstask and user are set
>       perf: Simplify get_perf_callchain() user logic
>       perf: Skip user unwind if the task is a kernel thread.

Please don't leave periods in titles.

Thanks,

	Ingo