From patchwork Wed Oct 2 09:49:35 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: James Morse X-Patchwork-Id: 11170699 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 7A4FE14DB for ; Wed, 2 Oct 2019 09:50:51 +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 53D2521783 for ; Wed, 2 Oct 2019 09:50:51 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="t/pwLJS4" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 53D2521783 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+patchwork-linux-arm=patchwork.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-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-Id:Date:Subject:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=9k5zZwmby/nk2QRwQF+5BLxcZYd86Kv8DCEmJxsp3lU=; b=t/pwLJS45/QYum grLom81p4JXqoh3VDktB+qIJjkgxV1i9lLiqGcGaIun9G8vEOKj9psBZBnKHGE/CLliIXbRsmMqZw 6thOeTDKZdphzhL5NfAZ+o/6/HrkaSFKYkAPBcv8Ewr+hkQ3zb0uMBl2mAV+JT3qHBoKCNJTOjQyr TJG+nXklOkHaVPkOMwnsS6CYo3UVOLRQjeczOfR/2+SwdqaEh4kN53FGliIJ34pbFHNHgVAm9ROpU XdKl876wTTcSlqsAEvzrOScJxH1uSv7NLj7Jmvyu3+Yv4ak4nDx+2a8sCNAmgAfsx68AkgbtQmoXZ 4G+bQ5sh16NFFmcuLSwg==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.2 #3 (Red Hat Linux)) id 1iFbHT-0004DK-M9; Wed, 02 Oct 2019 09:50:47 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92.2 #3 (Red Hat Linux)) id 1iFbGd-0003ON-ST for linux-arm-kernel@lists.infradead.org; Wed, 02 Oct 2019 09:49:57 +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 68E2115AD; Wed, 2 Oct 2019 02:49:55 -0700 (PDT) Received: from eglon.cambridge.arm.com (eglon.cambridge.arm.com [10.1.196.105]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id D22CD3F739; Wed, 2 Oct 2019 02:49:54 -0700 (PDT) From: James Morse To: linux-arm-kernel@lists.infradead.org Subject: [PATCH 4/4] arm64: ftrace: Ensure synchronisation in PLT setup for Neoverse-N1 #1542419 Date: Wed, 2 Oct 2019 10:49:35 +0100 Message-Id: <20191002094935.48848-5-james.morse@arm.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20191002094935.48848-1-james.morse@arm.com> References: <20191002094935.48848-1-james.morse@arm.com> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20191002_024955_982429_0E410E43 X-CRM114-Status: GOOD ( 13.16 ) X-Spam-Score: 0.0 (/) X-Spam-Report: SpamAssassin version 3.4.2 on bombadil.infradead.org summary: Content analysis details: (0.0 points) pts rule name description ---- ---------------------- -------------------------------------------------- -0.0 SPF_PASS SPF: sender matches SPF record 0.0 SPF_HELO_NONE SPF: HELO does not publish an SPF Record 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: Catalin Marinas , Will Deacon Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org CPUs affected by Neoverse-N1 #1542419 may execute a stale instruction if it was recently modified. The affected sequence requires freshly written instructions to be executable before a branch to them is updated. There are very few places in the kernel that modify executable text, all but one come with sufficient synchronisation: * The module loader's flush_module_icache() calls flush_icache_range(), which does a kick_all_cpus_sync() * bpf_int_jit_compile() calls flush_icache_range(). * Kprobes calls aarch64_insn_patch_text(), which does its work in stop_machine(). * static keys and ftrace both patch between nops and branches to existing kernel code (not generated code). The affected sequence is the interaction between ftrace and modules. The module PLT is cleaned using __flush_icache_range() as the trampoline shouldn't be executable until we update the branch to it. Drop the double-underscore so that this path runs kick_all_cpus_sync() too. Signed-off-by: James Morse --- arch/arm64/kernel/ftrace.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/arch/arm64/kernel/ftrace.c b/arch/arm64/kernel/ftrace.c index 171773257974..06e56b470315 100644 --- a/arch/arm64/kernel/ftrace.c +++ b/arch/arm64/kernel/ftrace.c @@ -121,10 +121,16 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) /* * Ensure updated trampoline is visible to instruction - * fetch before we patch in the branch. + * 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]); + flush_icache_range((unsigned long)&dst[0], + (unsigned long)&dst[1]); } addr = (unsigned long)dst; #else /* CONFIG_ARM64_MODULE_PLTS */