linux-kernel - Re: [PATCH v4 28/39] unwind_user/deferred: Add deferred unwinding interface

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: <20250122134420.GR7145@noisy.programming.kicks-ass.net>
Date: Wed, 22 Jan 2025 14:44:20 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Josh Poimboeuf <jpoimboe@...nel.org>
Cc: x86@...nel.org, Steven Rostedt <rostedt@...dmis.org>,
	Ingo Molnar <mingo@...nel.org>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	linux-kernel@...r.kernel.org, Indu Bhagat <indu.bhagat@...cle.com>,
	Mark Rutland <mark.rutland@....com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Jiri Olsa <jolsa@...nel.org>, Namhyung Kim <namhyung@...nel.org>,
	Ian Rogers <irogers@...gle.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	linux-perf-users@...r.kernel.org, Mark Brown <broonie@...nel.org>,
	linux-toolchains@...r.kernel.org, Jordan Rome <jordalgo@...a.com>,
	Sam James <sam@...too.org>, linux-trace-kernel@...r.kernel.org,
	Andrii Nakryiko <andrii.nakryiko@...il.com>,
	Jens Remus <jremus@...ux.ibm.com>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Florian Weimer <fweimer@...hat.com>,
	Andy Lutomirski <luto@...nel.org>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Weinan Liu <wnliu@...gle.com>
Subject: Re: [PATCH v4 28/39] unwind_user/deferred: Add deferred unwinding
 interface

On Tue, Jan 21, 2025 at 06:31:20PM -0800, Josh Poimboeuf wrote:

> +/* entry-from-user counter */
> +static DEFINE_PER_CPU(u64, unwind_ctx_ctr);

AFAICT from the below, this thing does *not* count entry-from-user. It
might count a subset, but I need to stare longer.

> +/*
> + * Read the task context cookie, first initializing it if this is the first
> + * call to get_cookie() since the most recent entry from user.
> + */
> +static u64 get_cookie(struct unwind_task_info *info)
> +{
> +	u64 ctx_ctr;
> +	u64 cookie;
> +	u64 cpu;
> +
> +	guard(irqsave)();
> +
> +	cookie = info->cookie;
> +	if (cookie)
> +		return cookie;
> +
> +
> +	cpu = raw_smp_processor_id();
> +	ctx_ctr = __this_cpu_inc_return(unwind_ctx_ctr);
> +	info->cookie = ctx_to_cookie(cpu, ctx_ctr);
> +
> +	return cookie;
> +
> +}
> +
> +static void unwind_deferred_task_work(struct callback_head *head)
> +{

> +	cookie = get_cookie(info);

> +}
> +

> +int unwind_deferred_request(struct unwind_work *work, u64 *cookie)
> +{

> +	*cookie = get_cookie(info);

> +}