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Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.97.1 #2 (Red Hat Linux)) id 1rwJsN-0000000AXAk-0b8k; Mon, 15 Apr 2024 10:47:52 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id C563430040C; Mon, 15 Apr 2024 12:47:50 +0200 (CEST) Date: Mon, 15 Apr 2024 12:47:50 +0200 From: Peter Zijlstra To: Mike Rapoport Cc: linux-kernel@vger.kernel.org, Andrew Morton , Andy Lutomirski , Arnd Bergmann , Catalin Marinas , Christoph Hellwig , Helge Deller , Lorenzo Stoakes , Luis Chamberlain , Mark Rutland , Masami Hiramatsu , Mathieu Desnoyers , Michael Ellerman , Palmer Dabbelt , Russell King , Song Liu , Steven Rostedt , Thomas Gleixner , Uladzislau Rezki , Will Deacon , bpf@vger.kernel.org, linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-modules@vger.kernel.org, linux-parisc@vger.kernel.org, linux-riscv@lists.infradead.org, linux-trace-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, x86@kernel.org Subject: Re: [RFC PATCH 6/7] execmem: add support for cache of large ROX pages Message-ID: <20240415104750.GJ40213@noisy.programming.kicks-ass.net> References: <20240411160526.2093408-1-rppt@kernel.org> <20240411160526.2093408-7-rppt@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240411160526.2093408-7-rppt@kernel.org> X-Rspamd-Queue-Id: 9689A1C0008 X-Rspam-User: X-Rspamd-Server: rspam11 X-Stat-Signature: 9kysi1w5nic9owqu5e3d3eqf38qom1e9 X-HE-Tag: 1713178085-843681 X-HE-Meta: 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 7W6zDp4L slRhoUfwpQQK4Yj0BKjlDMCwINYM+HPJSfxnQaiqGSyqaLj375lDdl8HihlzVQWEgbUX9prRiqwldHTnNjW8wUt2MpSefNR8+3TYXBPBiJ8az3fOe8oNOmg7PoIJv0tk04hWNFaw4EKCZeCM= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Apr 11, 2024 at 07:05:25PM +0300, Mike Rapoport wrote: > To populate the cache, a writable large page is allocated from vmalloc with > VM_ALLOW_HUGE_VMAP, filled with invalid instructions and then remapped as > ROX. > +static void execmem_invalidate(void *ptr, size_t size, bool writable) > +{ > + if (execmem_info->invalidate) > + execmem_info->invalidate(ptr, size, writable); > + else > + memset(ptr, 0, size); > +} +static void execmem_invalidate(void *ptr, size_t size, bool writeable) +{ + /* fill memory with INT3 instructions */ + if (writeable) + memset(ptr, 0xcc, size); + else + text_poke_set(ptr, 0xcc, size); +} Thing is, 0xcc (aka INT3_INSN_OPCODE) is not an invalid instruction. It raises #BP not #UD.