From patchwork Wed Jan 18 17:21:29 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mark Rutland X-Patchwork-Id: 91818 Delivered-To: patch@linaro.org Received: by 10.182.3.34 with SMTP id 2csp965631obz; Wed, 18 Jan 2017 09:32:05 -0800 (PST) X-Received: by 10.98.217.209 with SMTP id b78mr5003195pfl.53.1484760725603; Wed, 18 Jan 2017 09:32:05 -0800 (PST) Return-Path: Received: from vger.kernel.org (vger.kernel.org. [209.132.180.67]) by mx.google.com with ESMTP id h91si846589pld.68.2017.01.18.09.32.05; Wed, 18 Jan 2017 09:32:05 -0800 (PST) Received-SPF: pass (google.com: best guess record for domain of stable-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of stable-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=stable-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751692AbdARRcE (ORCPT + 3 others); Wed, 18 Jan 2017 12:32:04 -0500 Received: from foss.arm.com ([217.140.101.70]:59522 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751610AbdARRcE (ORCPT ); Wed, 18 Jan 2017 12:32:04 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 43EBD707; Wed, 18 Jan 2017 09:22:34 -0800 (PST) Received: from leverpostej.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 417873F318; Wed, 18 Jan 2017 09:22:33 -0800 (PST) From: Mark Rutland To: linux-arm-kernel@lsits.infradead.org Cc: msalter@redhat.com, Mark Rutland , Catalin Marinas , Will Deacon , stable@vger.kernel.org Subject: [PATCH] arm64: avoid returning from bad_mode Date: Wed, 18 Jan 2017 17:21:29 +0000 Message-Id: <1484760089-30146-1-git-send-email-mark.rutland@arm.com> X-Mailer: git-send-email 1.9.1 Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org Generally, taking an unexpected exception should be a fatal event, and bad_mode is intended to cater for this. However, it should be possible to contain unexpected synchronous exceptions from EL0 without bringing the kernel down, by sending a SIGILL to the task. We tried to apply this approach in commit 9955ac47f4ba1c95 ("arm64: don't kill the kernel on a bad esr from el0"), by sending a signal for any bad_mode call resulting from an EL0 exception. However, this also applies to other unexpected exceptions, such as SError and FIQ. The entry paths for these exceptions branch to bad_mode without configuring the link register, and have no kernel_exit. Thus, if we take one of these exceptions from EL0, bad_mode will eventually return to the original user link register value. This patch fixes this by introducing a new bad_el0_sync handler to cater for the recoverable case, and restoring bad_mode to its original state, whereby it calls panic() and never returns. The recoverable case branches to bad_el0_sync with a bl, and returns to userspace via the usual ret_to_user mechanism. Signed-off-by: Mark Rutland Fixes: 9955ac47f4ba1c95 ("arm64: don't kill the kernel on a bad esr from el0") Reported-by: Mark Salter Cc: Catalin Marinas Cc: Will Deacon Cc: stable@vger.kernel.org --- arch/arm64/kernel/entry.S | 2 +- arch/arm64/kernel/traps.c | 28 ++++++++++++++++++++++++---- 2 files changed, 25 insertions(+), 5 deletions(-) -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 923841f..43512d4 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -683,7 +683,7 @@ el0_inv: mov x0, sp mov x1, #BAD_SYNC mov x2, x25 - bl bad_mode + bl bad_el0_sync b ret_to_user ENDPROC(el0_sync) diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c index 5b830be..659b2e6 100644 --- a/arch/arm64/kernel/traps.c +++ b/arch/arm64/kernel/traps.c @@ -604,17 +604,34 @@ const char *esr_get_class_string(u32 esr) } /* - * bad_mode handles the impossible case in the exception vector. + * bad_mode handles the impossible case in the exception vector. This is always + * fatal. */ asmlinkage void bad_mode(struct pt_regs *regs, int reason, unsigned int esr) { - siginfo_t info; - void __user *pc = (void __user *)instruction_pointer(regs); console_verbose(); pr_crit("Bad mode in %s handler detected on CPU%d, code 0x%08x -- %s\n", handler[reason], smp_processor_id(), esr, esr_get_class_string(esr)); + + die("Oops - bad mode", regs, 0); + local_irq_disable(); + panic("bad mode"); +} + +/* + * bad_el0_sync handles unexpected, but potentially recoverable synchronous + * exceptions taken from EL0. Unlike bad_mode, this returns. + */ +asmlinkage void bad_el0_sync(struct pt_regs *regs, int reason, unsigned int esr) +{ + siginfo_t info; + void __user *pc = (void __user *)instruction_pointer(regs); + console_verbose(); + + pr_crit("Bad EL0 synchronous exception detected on CPU%d, code 0x%08x -- %s\n", + smp_processor_id(), esr, esr_get_class_string(esr)); __show_regs(regs); info.si_signo = SIGILL; @@ -622,7 +639,10 @@ asmlinkage void bad_mode(struct pt_regs *regs, int reason, unsigned int esr) info.si_code = ILL_ILLOPC; info.si_addr = pc; - arm64_notify_die("Oops - bad mode", regs, &info, 0); + current->thread.fault_address = 0; + current->thread.fault_code = 0; + + force_sig_info(info.si_signo, &info, current); } void __pte_error(const char *file, int line, unsigned long val)