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 X-Spam-Level: X-Spam-Status: No, score=-7.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id BC61AC2BA1A for ; Tue, 7 Apr 2020 15:58:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8683C2076E for ; Tue, 7 Apr 2020 15:58:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1586275137; bh=ltIOImB02Z71XhE+ab4AZjqWho6FXnB/SdX/vjB8BxA=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=i50V5mzx/6KMf+knaFqMI7rsMQE8RYLC/agZ3Pn9TDNv89aAZ7fM96y4FSGJhs4p2 xYUMAZ4G+YlLatOcBMLUgFIG8hpbenwOK81WdSErutG/mHRFibMUlmE91kIqBh5cOY jOEoSF054IVHecDTIf54BnMVnfScgryPkT79XDFw= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727920AbgDGP64 (ORCPT ); Tue, 7 Apr 2020 11:58:56 -0400 Received: from mail.kernel.org ([198.145.29.99]:37648 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726937AbgDGP64 (ORCPT ); Tue, 7 Apr 2020 11:58:56 -0400 Received: from devnote2 (NE2965lan1.rev.em-net.ne.jp [210.141.244.193]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 0A1C92072A; Tue, 7 Apr 2020 15:58:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1586275135; bh=ltIOImB02Z71XhE+ab4AZjqWho6FXnB/SdX/vjB8BxA=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=dmp90ubmZP2czndVvQXWl03wmMM9mO/JPcATNHy2z9xFFl+W4sASxc89XShQvJ65d 4xBUn2UodHNybm6HuKbb4TjlB2WCP09XP22hvEsQ/aWcT7vXtKseuW/MtYicFijNS1 GJpAlD3EXfNGs7i9RmNFzytbek/t01G3FwTWAehI= Date: Wed, 8 Apr 2020 00:58:50 +0900 From: Masami Hiramatsu To: Zong Li Cc: palmer@dabbelt.com, paul.walmsley@sifive.com, aou@eecs.berkeley.edu, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v4 2/9] riscv: introduce interfaces to patch kernel code Message-Id: <20200408005850.5e1a7666013f080ff60020e2@kernel.org> In-Reply-To: References: X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.32; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Zong, On Tue, 7 Apr 2020 22:46:47 +0800 Zong Li wrote: > On strict kernel memory permission, we couldn't patch code without > writable permission. Preserve two holes in fixmap area, so we can map > the kernel code temporarily to fixmap area, then patch the instructions. > > We need two pages here because we support the compressed instruction, so > the instruction might be align to 2 bytes. When patching the 32-bit > length instruction which is 2 bytes alignment, it will across two pages. > > Introduce two interfaces to patch kernel code: > riscv_patch_text_nosync: > - patch code without synchronization, it's caller's responsibility to > synchronize all CPUs if needed. > riscv_patch_text: > - patch code and always synchronize with stop_machine() > > Signed-off-by: Zong Li > Suggested-by: Masami Hiramatsu > --- > arch/riscv/include/asm/fixmap.h | 2 + > arch/riscv/include/asm/patch.h | 12 ++++ > arch/riscv/kernel/Makefile | 4 +- > arch/riscv/kernel/patch.c | 120 ++++++++++++++++++++++++++++++++ > 4 files changed, 137 insertions(+), 1 deletion(-) > create mode 100644 arch/riscv/include/asm/patch.h > create mode 100644 arch/riscv/kernel/patch.c > > diff --git a/arch/riscv/include/asm/fixmap.h b/arch/riscv/include/asm/fixmap.h > index 42d2c42f3cc9..2368d49eb4ef 100644 > --- a/arch/riscv/include/asm/fixmap.h > +++ b/arch/riscv/include/asm/fixmap.h > @@ -27,6 +27,8 @@ enum fixed_addresses { > FIX_FDT = FIX_FDT_END + FIX_FDT_SIZE / PAGE_SIZE - 1, > FIX_PTE, > FIX_PMD, > + FIX_TEXT_POKE1, > + FIX_TEXT_POKE0, > FIX_EARLYCON_MEM_BASE, > __end_of_fixed_addresses > }; > diff --git a/arch/riscv/include/asm/patch.h b/arch/riscv/include/asm/patch.h > new file mode 100644 > index 000000000000..9a7d7346001e > --- /dev/null > +++ b/arch/riscv/include/asm/patch.h > @@ -0,0 +1,12 @@ > +/* SPDX-License-Identifier: GPL-2.0-only */ > +/* > + * Copyright (C) 2020 SiFive > + */ > + > +#ifndef _ASM_RISCV_PATCH_H > +#define _ASM_RISCV_PATCH_H > + > +int patch_text_nosync(void *addr, const void *insns, size_t len); > +int patch_text(void *addr, u32 insn); > + > +#endif /* _ASM_RISCV_PATCH_H */ > diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile > index f40205cb9a22..d189bd3d8501 100644 > --- a/arch/riscv/kernel/Makefile > +++ b/arch/riscv/kernel/Makefile > @@ -4,7 +4,8 @@ > # > > ifdef CONFIG_FTRACE > -CFLAGS_REMOVE_ftrace.o = -pg > +CFLAGS_REMOVE_ftrace.o = -pg > +CFLAGS_REMOVE_patch.o = -pg > endif > > extra-y += head.o > @@ -26,6 +27,7 @@ obj-y += traps.o > obj-y += riscv_ksyms.o > obj-y += stacktrace.o > obj-y += cacheinfo.o > +obj-y += patch.o > obj-$(CONFIG_MMU) += vdso.o vdso/ > > obj-$(CONFIG_RISCV_M_MODE) += clint.o > diff --git a/arch/riscv/kernel/patch.c b/arch/riscv/kernel/patch.c > new file mode 100644 > index 000000000000..5b4f0d37097f > --- /dev/null > +++ b/arch/riscv/kernel/patch.c > @@ -0,0 +1,120 @@ > +// SPDX-License-Identifier: GPL-2.0-only > +/* > + * Copyright (C) 2020 SiFive > + */ > + > +#include > +#include > +#include > +#include > +#include > +#include > +#include > + > +struct patch_insn_patch { > + void *addr; > + u32 insn; > + atomic_t cpu_count; > +}; > + > +#ifdef CONFIG_MMU > +static void *patch_map(void *addr, int fixmap) > +{ > + uintptr_t uintaddr = (uintptr_t) addr; > + struct page *page; > + > + if (core_kernel_text(uintaddr)) > + page = phys_to_page(__pa_symbol(addr)); > + else if (IS_ENABLED(CONFIG_STRICT_MODULE_RWX)) > + page = vmalloc_to_page(addr); > + else > + return addr; > + > + BUG_ON(!page); > + > + return (void *)set_fixmap_offset(fixmap, page_to_phys(page) + > + (uintaddr & ~PAGE_MASK)); > +} > +NOKPROBE_SYMBOL(patch_map); > + > +static void patch_unmap(int fixmap) > +{ > + clear_fixmap(fixmap); > +} > +NOKPROBE_SYMBOL(patch_unmap); > + Please leave a comment here about text_mutex, > +static int patch_insn_write(void *addr, const void *insn, size_t len) > +{ > + void *waddr = addr; > + bool across_pages = (((uintptr_t) addr & ~PAGE_MASK) + len) > PAGE_SIZE; > + int ret; Or use lockdep_assert_held(&text_mutex); here so that user can easily understand they have to lock the text_mutex before calling this. Thank you, > + > + if (across_pages) > + patch_map(addr + len, FIX_TEXT_POKE1); > + > + waddr = patch_map(addr, FIX_TEXT_POKE0); > + > + ret = probe_kernel_write(waddr, insn, len); > + > + patch_unmap(FIX_TEXT_POKE0); > + > + if (across_pages) > + patch_unmap(FIX_TEXT_POKE1); > + > + return ret; > +} > +NOKPROBE_SYMBOL(patch_insn_write); > +#else > +static int patch_insn_write(void *addr, const void *insn, size_t len) > +{ > + return probe_kernel_write(addr, insn, len); > +} > +NOKPROBE_SYMBOL(patch_insn_write); > +#endif /* CONFIG_MMU */ > + > +int patch_text_nosync(void *addr, const void *insns, size_t len) > +{ > + u32 *tp = addr; > + int ret; > + > + ret = patch_insn_write(tp, insns, len); > + > + if (!ret) > + flush_icache_range((uintptr_t) tp, (uintptr_t) tp + len); > + > + return ret; > +} > +NOKPROBE_SYMBOL(patch_text_nosync); > + > +static int patch_text_cb(void *data) > +{ > + struct patch_insn_patch *patch = data; > + int ret = 0; > + > + if (atomic_inc_return(&patch->cpu_count) == 1) { > + ret = > + patch_text_nosync(patch->addr, &patch->insn, > + GET_INSN_LENGTH(patch->insn)); > + atomic_inc(&patch->cpu_count); > + } else { > + while (atomic_read(&patch->cpu_count) <= num_online_cpus()) > + cpu_relax(); > + smp_mb(); > + } > + > + return ret; > +} > +NOKPROBE_SYMBOL(patch_text_cb); > + > +int patch_text(void *addr, u32 insn) > +{ > + struct patch_insn_patch patch = { > + .addr = addr, > + .insn = insn, > + .cpu_count = ATOMIC_INIT(0), > + }; > + > + return stop_machine_cpuslocked(patch_text_cb, > + &patch, cpu_online_mask); > +} > +NOKPROBE_SYMBOL(patch_text); > -- > 2.26.0 > -- Masami Hiramatsu