linux-kernel - Re: [PATCH 0/2] tracing/wprobe: Fix to avoid inifinite watchpoint exception on arm64

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] [day] [month] [year] [list]

Message-Id: <20251117114624.5fc972e65edac5bb91caa4b2@kernel.org>
Date: Mon, 17 Nov 2025 11:46:24 +0900
From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
To: Will Deacon <will@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
 Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim
 <namhyung@...nel.org>, Steven Rostedt <rostedt@...dmis.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>,
 Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-trace-kernel@...r.kernel.org, Catalin Marinas
 <catalin.marinas@....com>, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 0/2] tracing/wprobe: Fix to avoid inifinite watchpoint
 exception on arm64

On Fri, 14 Nov 2025 16:17:06 +0000
Will Deacon <will@...nel.org> wrote:

> On Tue, Nov 04, 2025 at 10:37:35PM +0900, Masami Hiramatsu wrote:
> > Gently ping.
> > 
> > There is a bugfix (or strange behavior) on arm64 hw breakpoint but
> > to fix it cleanly, it should change the perf itself (but I'm not
> > sure why arm64 changes the behavior only for the default overflow
> > handlers.) Anyone knows it?
> 
> It's because GDB expects to handle the stepping itself when using the
> ptrace interface (with a custom overflow handler to deliver SIGTRAP).

Hmm, would you mean GDB for user program?
If so, it expects hw breakpoint is used by:
 - user-space ptrace (for GDB)
 - kernel-space perf (must be default overflow handler)

And not expects to be used by 

 - kernel-space custom overflow handler

This series is to handle the third use case.

Thank you,

-- 
Masami Hiramatsu (Google) <mhiramat@...nel.org>