linux-kernel - Re: [PATCH] uprobes: replace deprecated kmap_atomic() with kmap_local

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Message-ID: <04f2e194-5148-47b6-97ff-835f9561bd36@suse.de>
Date: Thu, 5 Feb 2026 12:19:12 +0100
From: Carlos López <clopez@...e.de>
To: Peter Zijlstra <peterz@...radead.org>
Cc: linux-trace-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
 Masami Hiramatsu <mhiramat@...nel.org>, Oleg Nesterov <oleg@...hat.com>,
 Ingo Molnar <mingo@...hat.com>, Arnaldo Carvalho de Melo <acme@...nel.org>,
 Namhyung Kim <namhyung@...nel.org>, Mark Rutland <mark.rutland@....com>,
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
 Jiri Olsa <jolsa@...nel.org>, Ian Rogers <irogers@...gle.com>,
 Adrian Hunter <adrian.hunter@...el.com>, James Clark
 <james.clark@...aro.org>, "open list:UPROBES" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] uprobes: replace deprecated kmap_atomic() with
 kmap_local_page()

Hi,

On 2/5/26 12:12 PM, Peter Zijlstra wrote:
> On Thu, Feb 05, 2026 at 11:57:25AM +0100, Carlos López wrote:
>> kmap_atomic() has been deprecated for a few years, and kmap_local_page()
>> should be used instead, so replace it. Since the uprobes code relied on
>> kmap_atomic() disabling page faults to access user pages, add the
>> required calls to keep the existing behavior.
> 
> Are those pagefault_disable()s really needed here, or is this just
> cargo-culting?

The subsystem experts can correct me, but it seems to me this code is
primarily accessing user memory, e.g. is_trap_at_addr() ->
get_user_pages() -> uprobe_copy_from_page().