Re: [PATCH RESEND v8 11/16] powerpc: extend execmem_params for kprobes allocations

From: Mike Rapoport <rppt@kernel.org>
To: "Christophe Leroy (CS GROUP)" <chleroy@kernel.org>
Cc: linux-kernel@vger.kernel.org,
	"Ritesh Harjani (IBM)" <ritesh.list@gmail.com>,
	"Alexandre Ghiti" <alexghiti@rivosinc.com>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Björn Töpel" <bjorn@kernel.org>,
	"Catalin Marinas" <catalin.marinas@arm.com>,
	"David S. Miller" <davem@davemloft.net>,
	"Dinh Nguyen" <dinguyen@kernel.org>,
	"Donald Dutile" <ddutile@redhat.com>,
	"Eric Chanudet" <echanude@redhat.com>,
	"Heiko Carstens" <hca@linux.ibm.com>,
	"Helge Deller" <deller@gmx.de>,
	"Huacai Chen" <chenhuacai@kernel.org>,
	"Kent Overstreet" <kent.overstreet@linux.dev>,
	"Liviu Dudau" <liviu@dudau.co.uk>,
	"Luis Chamberlain" <mcgrof@kernel.org>,
	"Mark Rutland" <mark.rutland@arm.com>,
	"Masami Hiramatsu" <mhiramat@kernel.org>,
	"Michael Ellerman" <mpe@ellerman.id.au>,
	"Nadav Amit" <nadav.amit@gmail.com>,
	"Palmer Dabbelt" <palmer@dabbelt.com>,
	"Peter Zijlstra" <peterz@infradead.org>,
	"Philippe Mathieu-Daudé" <philmd@linaro.org>,
	"Rick Edgecombe" <rick.p.edgecombe@intel.com>,
	"Russell King" <linux@armlinux.org.uk>,
	"Sam Ravnborg" <sam@ravnborg.org>, "Song Liu" <song@kernel.org>,
	"Steven Rostedt" <rostedt@goodmis.org>,
	"Thomas Bogendoerfer" <tsbogend@alpha.franken.de>,
	"Thomas Gleixner" <tglx@linutronix.de>,
	"Will Deacon" <will@kernel.org>,
	bpf@vger.kernel.org, linux-arch@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org, linux-mips@vger.kernel.org,
	linux-mm@kvack.org, linux-modules@vger.kernel.org,
	linux-parisc@vger.kernel.org, linux-riscv@lists.infradead.org,
	linux-s390@vger.kernel.org, linux-trace-kernel@vger.kernel.org,
	linuxppc-dev@lists.ozlabs.org, loongarch@lists.linux.dev,
	netdev@vger.kernel.org, sparclinux@vger.kernel.org,
	x86@kernel.org
Subject: Re: [PATCH RESEND v8 11/16] powerpc: extend execmem_params for kprobes allocations
Date: Sun, 15 Nov 2026 08:38:46 +0200	[thread overview]
Message-ID: <avlTdlK9ErlqVRYl@kernel.org> (raw)
In-Reply-To: <3f7af771-87a7-4ae7-9919-bc4c23bd31c9@kernel.org>

Hi Christophe,

On Fri, Nov 13, 2026 at 03:36:01PM +0100, Christophe Leroy (CS GROUP) wrote:
> Hi Mike,
> 
> Looks like I missed this change ...
> 
> Le 05/05/2024 à 18:06, Mike Rapoport a écrit :
> > From: "Mike Rapoport (IBM)" <rppt@kernel.org>
> > 
> > powerpc overrides kprobes::alloc_insn_page() to remove writable
> > permissions when STRICT_MODULE_RWX is on.
> > 
> > Add definition of EXECMEM_KRPOBES to execmem_params to allow using the
> > generic kprobes::alloc_insn_page() with the desired permissions.
> > 
> > As powerpc uses breakpoint instructions to inject kprobes, it does not
> > need to constrain kprobe allocations to the modules area and can use the
> > entire vmalloc address space.
> 
> Using breakpoint means the segment must still be executable.
> On book3s/32 VMALLOC segment is not executable, while module segment is.
> 
> See commit 6ca055322da8 ("powerpc/32s: Use dedicated segment for modules
> with STRICT_KERNEL_RWX")
> 
> See report and fix at https://lore.kernel.org/all/ed03d290d440d579a81ae0b7de5243721291d903.1794543909.git.ritesh.list@gmail.com/

I'll take a look, thanks!

> Christophe

-- 
Sincerely yours,
Mike.