Re: [PATCH v11 04/11] tracing: wprobe: Add watchpoint probe event based on hardware breakpoint

[Masami Hiramatsu (Google) <mhiramat@kernel.org>]

On Mon, 3 Aug 2026 09:03:56 +0200
Peter Zijlstra <peterz@infradead.org> wrote:

> On Sun, Aug 02, 2026 at 05:19:10PM +0900, Masami Hiramatsu (Google) wrote:
> > From: Masami Hiramatsu (Google) <mhiramat@kernel.org>
> > 
> > Add a new probe event for the hardware breakpoint called wprobe-event.
> > This wprobe allows user to trace (watch) the memory access at the
> > specified memory address.
> 
> s/the memory/the kernel memory/

Indeed.

> 
> > The new syntax is;
> > 
> >  w[:[GROUP/]EVENT] [r|w|rw]@[ADDR|SYM][:SIZE] [FETCH_ARGs]
> > 
> > User also can use $addr to fetch the accessed address and $value to fetch
> > the accessed memory value (shorthand for '+0($addr)'). No other variables
> > are supported.
> 
> This seems limited to kernel addresses only? Should not also userspace
> addresses be supported?

Hmm, for x86, yes, since it causes a trap after executing (all page fault
are handled). But other architecture like arm64 may not be able to support
it because it needs to enable watchpoint after major page fault.
At this step, I would like to limit it just for kernel memory.

Thank you,

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