From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3E075E7D0BC for ; Fri, 22 Sep 2023 01:25:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229741AbjIVBZN (ORCPT ); Thu, 21 Sep 2023 21:25:13 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41260 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229452AbjIVBZM (ORCPT ); Thu, 21 Sep 2023 21:25:12 -0400 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B0A3FCE; Thu, 21 Sep 2023 18:25:05 -0700 (PDT) Received: from kwepemd100003.china.huawei.com (unknown [172.30.72.57]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4RsDyL3LlJzVl4r; Fri, 22 Sep 2023 09:22:02 +0800 (CST) Received: from [10.67.111.192] (10.67.111.192) by kwepemd100003.china.huawei.com (7.221.188.180) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.2.1258.23; Fri, 22 Sep 2023 09:25:02 +0800 Message-ID: <8e31490d-1a7b-7bf8-6a72-23e8955e2ecb@huawei.com> Date: Fri, 22 Sep 2023 09:25:01 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.9.0 Subject: Re: [PATCH bpf-next v5 2/3] arm64: patching: Add aarch64_insn_set() Content-Language: en-US To: Puranjay Mohan , , , , , , , , , , , References: <20230908144320.2474-1-puranjay12@gmail.com> <20230908144320.2474-3-puranjay12@gmail.com> <2095a591-8f3e-318c-a390-a43a653ce6d5@huaweicloud.com> From: Xu Kuohai In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.67.111.192] X-ClientProxiedBy: dggems703-chm.china.huawei.com (10.3.19.180) To kwepemd100003.china.huawei.com (7.221.188.180) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 9/21/2023 10:50 PM, Puranjay Mohan wrote: > Xu Kuohai writes: > >> On 9/8/2023 10:43 PM, Puranjay Mohan wrote: >>> The BPF JIT needs to write invalid instructions to RX regions of memory >>> to invalidate removed BPF programs. This needs a function like memset() >>> that can work with RX memory. >>> >>> Implement aarch64_insn_set() which is similar to text_poke_set() of x86. >>> >>> Signed-off-by: Puranjay Mohan >>> --- >>> arch/arm64/include/asm/patching.h | 1 + >>> arch/arm64/kernel/patching.c | 40 +++++++++++++++++++++++++++++++ >>> 2 files changed, 41 insertions(+) >>> >>> diff --git a/arch/arm64/include/asm/patching.h b/arch/arm64/include/asm/patching.h >>> index f78a0409cbdb..551933338739 100644 >>> --- a/arch/arm64/include/asm/patching.h >>> +++ b/arch/arm64/include/asm/patching.h >>> @@ -8,6 +8,7 @@ int aarch64_insn_read(void *addr, u32 *insnp); >>> int aarch64_insn_write(void *addr, u32 insn); >>> >>> int aarch64_insn_write_literal_u64(void *addr, u64 val); >>> +int aarch64_insn_set(void *dst, const u32 insn, size_t len); >>> void *aarch64_insn_copy(void *dst, const void *src, size_t len); >>> >>> int aarch64_insn_patch_text_nosync(void *addr, u32 insn); >>> diff --git a/arch/arm64/kernel/patching.c b/arch/arm64/kernel/patching.c >>> index 243d6ae8d2d8..63d9e0e77806 100644 >>> --- a/arch/arm64/kernel/patching.c >>> +++ b/arch/arm64/kernel/patching.c >>> @@ -146,6 +146,46 @@ noinstr void *aarch64_insn_copy(void *dst, const void *src, size_t len) >>> return dst; >>> } >>> >>> +/** >>> + * aarch64_insn_set - memset for RX memory regions. >>> + * @dst: address to modify >>> + * @c: value to set >> >> insn > > Thanks for catching. > >>> + * @len: length of memory region. >>> + * >>> + * Useful for JITs to fill regions of RX memory with illegal instructions. >>> + */ >>> +noinstr int aarch64_insn_set(void *dst, const u32 insn, size_t len) >> >> const is unnecessary >> > > Will remove in next version. > >>> +{ >>> + unsigned long flags; >>> + size_t patched = 0; >>> + size_t size; >>> + void *waddr; >>> + void *ptr; >>> + >>> + /* A64 instructions must be word aligned */ >>> + if ((uintptr_t)dst & 0x3) >>> + return -EINVAL; >>> + >>> + raw_spin_lock_irqsave(&patch_lock, flags); >>> + >>> + while (patched < len) { >>> + ptr = dst + patched; >>> + size = min_t(size_t, PAGE_SIZE - offset_in_page(ptr), >>> + len - patched); >>> + >>> + waddr = patch_map(ptr, FIX_TEXT_POKE0); >>> + memset32(waddr, insn, size / 4); >>> + patch_unmap(FIX_TEXT_POKE0); >>> + >>> + patched += size; >>> + } >>> + raw_spin_unlock_irqrestore(&patch_lock, flags); >>> + >>> + caches_clean_inval_pou((uintptr_t)dst, (uintptr_t)dst + len); >>> + >>> + return 0; >>> +} >>> + >> >> this function shares most of the code with aarch64_insn_copy(), how about >> extracting the shared code to a separate function? > > I was thinking of writing it like the text_poke api of x86. Where you > can provide a function as an argument to work on a memory area. > Essentially, it will look like: > > typedef int text_poke_f(void *dst, const void *src, size_t len); > > static void *aarch64_insn_poke(text_poke_f func, void *addr, const void *src, size_t len) > > We can call this function with a wrapper of `copy_to_kernel_nofault` for copy > and with a wrapper of memset32 for setting. > > Do you think this is a good approach? > Sounds great, thanks. >> >>> int __kprobes aarch64_insn_patch_text_nosync(void *addr, u32 insn) >>> { >>> u32 *tp = addr; > > Thanks, > Puranjay