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Sat, 14 Nov 2026 23:13:31 -0800 (PST) Received: from pve-server ([49.205.216.49]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-37956bad134sm27441185eec.27.2026.11.14.23.13.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 14 Nov 2026 23:13:30 -0800 (PST) From: Ritesh Harjani (IBM) To: Mike Rapoport , "Christophe Leroy (CS GROUP)" Cc: linux-kernel@vger.kernel.org, Alexandre Ghiti , Andrew Morton , =?utf-8?B?QmrDtnJuIFTDtnBlbA==?= , Catalin Marinas , "David S. Miller" , Dinh Nguyen , Donald Dutile , Eric Chanudet , Heiko Carstens , Helge Deller , Huacai Chen , Kent Overstreet , Liviu Dudau , Luis Chamberlain , Mark Rutland , Masami Hiramatsu , Michael Ellerman , Nadav Amit , Palmer Dabbelt , Peter Zijlstra , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , Rick Edgecombe , Russell King , Sam Ravnborg , Song Liu , Steven Rostedt , Thomas Bogendoerfer , Thomas Gleixner , Will Deacon , 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, Madhavan Srinivasan Subject: Re: [PATCH RESEND v8 11/16] powerpc: extend execmem_params for kprobes allocations In-Reply-To: Date: Sun, 15 Nov 2026 12:33:31 +0530 Message-ID: <4idi8tks.ritesh.list@gmail.com> References: <20240505160628.2323363-1-rppt@kernel.org> <20240505160628.2323363-12-rppt@kernel.org> <3f7af771-87a7-4ae7-9919-bc4c23bd31c9@kernel.org> X-Mailing-List: bpf@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Mike Rapoport writes: > Hi Christophe, > > On Fri, Nov 13, 2026 at 03:36:01PM +0100, Christophe Leroy (CS GROUP) wro= te: >> Hi Mike, >>=20 >> Looks like I missed this change ... >>=20 I didn't initially get what Christophe meant here. Then I came across this reply of from him[1]. So looks like somehow between v3 to v8, something got changed?=20 On powerpc book3s/32, vmalloc space is not executable. Only modules=20 space is executable. X/NX cannot be set on a per page basis, it can onl= y=20 be set on a 256 Mbytes segment basis. See commit c49643319715 ("powerpc/32s: Only leave NX unset on segments= =20 used for modules") and 6ca055322da8 ("powerpc/32s: Use dedicated segmen= t=20 for modules with STRICT_KERNEL_RWX") and 7bee31ad8e2f ("powerpc/32s: Fi= x=20 is_module_segment() when MODULES_VADDR is defined"). So if your intention is still to have an executable kprobes, then you=20 can't use vmalloc address space. [1]: https://lore.kernel.org/all/1cb41761-29d0-5d33-b7c1-0ca3acaa810d@csgro= up.eu/ >> Le 05/05/2024 =C3=A0 18:06, Mike Rapoport a =C3=A9crit=C2=A0: >> > From: "Mike Rapoport (IBM)" >> >=20 >> > powerpc overrides kprobes::alloc_insn_page() to remove writable >> > permissions when STRICT_MODULE_RWX is on. >> >=20 >> > Add definition of EXECMEM_KRPOBES to execmem_params to allow using the >> > generic kprobes::alloc_insn_page() with the desired permissions. >> >=20 >> > As powerpc uses breakpoint instructions to inject kprobes, it does not >> > need to constrain kprobe allocations to the modules area and can use t= he >> > entire vmalloc address space. >>=20 >> Using breakpoint means the segment must still be executable. >> On book3s/32 VMALLOC segment is not executable, while module segment is. >>=20 >> See commit 6ca055322da8 ("powerpc/32s: Use dedicated segment for modules >> with STRICT_KERNEL_RWX") >>=20 >> See report and fix at https://lore.kernel.org/all/ed03d290d440d579a81ae0= b7de5243721291d903.1794543909.git.ritesh.list@gmail.com/ > > I'll take a look, thanks! >=20=20 Thanks Mike for taking a look. Sorry, I should have ccd'd you there, I guess I missed it. However, the changes are these one here [2][3] [2]: https://lore.kernel.org/linuxppc-dev/82c4973addebd82923c460cb44221f5b7= 6146afe.1794572365.git.ritesh.list@gmail.com/ [3]: https://lore.kernel.org/linuxppc-dev/f75f2cf97f44375fd2c8820e0caeab703= cdb371c.1794572365.git.ritesh.list@gmail.com/ -ritesh