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=-8.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 4E9E5CA9EC7 for ; Sat, 2 Nov 2019 12:20:15 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 1C69A2080F for ; Sat, 2 Nov 2019 12:20:15 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="SzTT6nh/" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1C69A2080F Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender:Content-Type: Content-Transfer-Encoding:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:Date:Message-ID:References: To:Subject:From:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=+RQCqbPAISevEaivtBP3h+bRSw+5/DVj/p1Te6gIraY=; b=SzTT6nh/9cMZXK42MVw+CHPMW AGeW8t5/ZiiV3WX4HOalJyUTCObZhVo2hzxL77Pbbjiy2MjJhYltoLHwHAobsoN/Kl25b96HluIbB R2jiSSmdFW2xq+TM9BKHjv5j/zIHdrA25qYuR2CFM1SQJ7cwllfQXk82EckMQe9fTovBVHzXH5vF7 wgeuJXSr6tLM5o9ypEguXLz5SbovcRpEl6ebQ0un5qziUIgQ/0ami69wWR0CHnJwk4YgYZ1QxJ6w2 wUEiy4IEJ6vevyp1K+mQojFRwZTXcqIaAryMbJNR76jLjfG/qeCyOjCMIGEiIJ+j4W+BEgLrmWwFC w8NlSj57A==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1iQsO6-0000rF-Q5; Sat, 02 Nov 2019 12:20:14 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1iQsO3-0000qG-AN for linux-arm-kernel@lists.infradead.org; Sat, 02 Nov 2019 12:20:13 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 9B857328; Sat, 2 Nov 2019 05:20:09 -0700 (PDT) Received: from [10.162.0.144] (a075553-lin.blr.arm.com [10.162.0.144]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 076EC3F718; Sat, 2 Nov 2019 05:20:04 -0700 (PDT) From: Amit Daniel Kachhap Subject: Re: [PATCHv2 4/8] arm64: module/ftrace: intialize PLT at load time To: Mark Rutland , linux-arm-kernel@lists.infradead.org References: <20191029165832.33606-1-mark.rutland@arm.com> <20191029165832.33606-5-mark.rutland@arm.com> Message-ID: Date: Sat, 2 Nov 2019 17:50:02 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: <20191029165832.33606-5-mark.rutland@arm.com> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20191102_052011_450310_4F2BE7C0 X-CRM114-Status: GOOD ( 35.42 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: jthierry@redhat.com, linux-parisc@vger.kernel.org, peterz@infradead.org, catalin.marinas@arm.com, deller@gmx.de, jpoimboe@redhat.com, linux-kernel@vger.kernel.org, rostedt@goodmis.org, James.Bottomley@HansenPartnership.com, takahiro.akashi@linaro.org, will@kernel.org, mingo@redhat.com, james.morse@arm.com, jeyu@kernel.org, svens@stackframe.org, duwe@suse.de Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi, On 10/29/19 10:28 PM, Mark Rutland wrote: > Currently we lazily-initialize a module's ftrace PLT at runtime when we > install the first ftrace call. To do so we have to apply a number of > sanity checks, transiently mark the module text as RW, and perform an > IPI as part of handling Neoverse-N1 erratum #1542419. > > We only expect the ftrace trampoline to point at ftrace_caller() (AKA > FTRACE_ADDR), so let's simplify all of this by intializing the PLT at > module load time, before the module loader marks the module RO and > performs the intial I-cache maintenance for the module. > > Thus we can rely on the module having been correctly intialized, and can > simplify the runtime work necessary to install an ftrace call in a > module. This will also allow for the removal of module_disable_ro(). > > Tested by forcing ftrace_make_call() to use the module PLT, and then > loading up a module after setting up ftrace with: > > | echo ":mod:" > set_ftrace_filter; > | echo function > current_tracer; > | modprobe > > Since FTRACE_ADDR is only defined when CONFIG_DYNAMIC_FTRACE is > selected, we wrap its use along with most of module_init_ftrace_plt() > with ifdeffery rather than using IS_ENABLED(). > > Signed-off-by: Mark Rutland > Reviewed-by: Ard Biesheuvel > Cc: Catalin Marinas > Cc: James Morse > Cc: Peter Zijlstra > Cc: Will Deacon > --- > arch/arm64/kernel/ftrace.c | 55 ++++++++++++---------------------------------- > arch/arm64/kernel/module.c | 32 +++++++++++++++++---------- > 2 files changed, 35 insertions(+), 52 deletions(-) > > diff --git a/arch/arm64/kernel/ftrace.c b/arch/arm64/kernel/ftrace.c > index 06e56b470315..822718eafdb4 100644 > --- a/arch/arm64/kernel/ftrace.c > +++ b/arch/arm64/kernel/ftrace.c > @@ -73,10 +73,22 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) > > if (offset < -SZ_128M || offset >= SZ_128M) { > #ifdef CONFIG_ARM64_MODULE_PLTS > - struct plt_entry trampoline, *dst; > struct module *mod; > > /* > + * There is only one ftrace trampoline per module. For now, > + * this is not a problem since on arm64, all dynamic ftrace > + * invocations are routed via ftrace_caller(). This will need > + * to be revisited if support for multiple ftrace entry points > + * is added in the future, but for now, the pr_err() below > + * deals with a theoretical issue only. > + */ > + if (addr != FTRACE_ADDR) { > + pr_err("ftrace: far branches to multiple entry points unsupported inside a single module\n"); > + return -EINVAL; > + } > + > + /* > * On kernels that support module PLTs, the offset between the > * branch instruction and its target may legally exceed the > * range of an ordinary relative 'bl' opcode. In this case, we > @@ -93,46 +105,7 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) > if (WARN_ON(!mod)) > return -EINVAL; > > - /* > - * There is only one ftrace trampoline per module. For now, > - * this is not a problem since on arm64, all dynamic ftrace > - * invocations are routed via ftrace_caller(). This will need > - * to be revisited if support for multiple ftrace entry points > - * is added in the future, but for now, the pr_err() below > - * deals with a theoretical issue only. > - * > - * Note that PLTs are place relative, and plt_entries_equal() > - * checks whether they point to the same target. Here, we need > - * to check if the actual opcodes are in fact identical, > - * regardless of the offset in memory so use memcmp() instead. > - */ > - dst = mod->arch.ftrace_trampoline; > - trampoline = get_plt_entry(addr, dst); > - if (memcmp(dst, &trampoline, sizeof(trampoline))) { > - if (plt_entry_is_initialized(dst)) { > - pr_err("ftrace: far branches to multiple entry points unsupported inside a single module\n"); > - return -EINVAL; > - } > - > - /* point the trampoline to our ftrace entry point */ > - module_disable_ro(mod); > - *dst = trampoline; > - module_enable_ro(mod, true); > - > - /* > - * Ensure updated trampoline is visible to instruction > - * fetch before we patch in the branch. Although the > - * architecture doesn't require an IPI in this case, > - * Neoverse-N1 erratum #1542419 does require one > - * if the TLB maintenance in module_enable_ro() is > - * skipped due to rodata_enabled. It doesn't seem worth > - * it to make it conditional given that this is > - * certainly not a fast-path. > - */ > - flush_icache_range((unsigned long)&dst[0], > - (unsigned long)&dst[1]); > - } > - addr = (unsigned long)dst; > + addr = (unsigned long)mod->arch.ftrace_trampoline; > #else /* CONFIG_ARM64_MODULE_PLTS */ > return -EINVAL; > #endif /* CONFIG_ARM64_MODULE_PLTS */ > diff --git a/arch/arm64/kernel/module.c b/arch/arm64/kernel/module.c > index 763a86d52fef..5f5bc3b94da7 100644 > --- a/arch/arm64/kernel/module.c > +++ b/arch/arm64/kernel/module.c > @@ -9,6 +9,7 @@ > > #include > #include > +#include > #include > #include > #include > @@ -485,24 +486,33 @@ static const Elf_Shdr *find_section(const Elf_Ehdr *hdr, > return NULL; > } > > +int module_init_ftrace_plt(const Elf_Ehdr *hdr, > + const Elf_Shdr *sechdrs, > + struct module *mod) I think this function can be made static as it is not used anywhere. Thanks, Amit Daniel > +{ > +#if defined(CONFIG_ARM64_MODULE_PLTS) && defined(CONFIG_DYNAMIC_FTRACE) > + const Elf_Shdr *s; > + struct plt_entry *plt; > + > + s = find_section(hdr, sechdrs, ".text.ftrace_trampoline"); > + if (!s) > + return -ENOEXEC; > + > + plt = (void *)s->sh_addr; > + *plt = get_plt_entry(FTRACE_ADDR, plt); > + mod->arch.ftrace_trampoline = plt; > +#endif > + return 0; > +} > + > int module_finalize(const Elf_Ehdr *hdr, > const Elf_Shdr *sechdrs, > struct module *me) > { > const Elf_Shdr *s; > - > s = find_section(hdr, sechdrs, ".altinstructions"); > if (s) > apply_alternatives_module((void *)s->sh_addr, s->sh_size); > > -#ifdef CONFIG_ARM64_MODULE_PLTS > - if (IS_ENABLED(CONFIG_DYNAMIC_FTRACE)) { > - s = find_section(hdr, sechdrs, ".text.ftrace_trampoline"); > - if (!s) > - return -ENOEXEC; > - me->arch.ftrace_trampoline = (void *)s->sh_addr; > - } > -#endif > - > - return 0; > + return module_init_ftrace_plt(hdr, sechdrs, me); > } > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel