From patchwork Thu Apr 21 11:35:29 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mark Rutland X-Patchwork-Id: 66380 Delivered-To: patch@linaro.org Received: by 10.140.93.198 with SMTP id d64csp88797qge; Thu, 21 Apr 2016 04:36:36 -0700 (PDT) X-Received: by 10.66.118.166 with SMTP id kn6mr19650938pab.33.1461238596360; Thu, 21 Apr 2016 04:36:36 -0700 (PDT) Return-Path: Received: from vger.kernel.org (vger.kernel.org. [209.132.180.67]) by mx.google.com with ESMTP id rz3si823814pac.196.2016.04.21.04.36.36; Thu, 21 Apr 2016 04:36:36 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-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 linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752324AbcDULgT (ORCPT + 29 others); Thu, 21 Apr 2016 07:36:19 -0400 Received: from foss.arm.com ([217.140.101.70]:54488 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752158AbcDULgQ (ORCPT ); Thu, 21 Apr 2016 07:36:16 -0400 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 3DA9F52B; Thu, 21 Apr 2016 04:34:58 -0700 (PDT) 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 5EA333F218; Thu, 21 Apr 2016 04:36:13 -0700 (PDT) From: Mark Rutland To: linux-efi@vger.kernel.org Cc: ard.biesheuvel@linaro.org, catalin.marinas@arm.com, hpa@zytor.com, leif.lindholm@linaro.org, linux@arm.linux.org.uk, mark.rutland@arm.com, matt@codeblueprint.co.uk, mingo@redhat.com, tglx@linutronix.de, will.deacon@arm.com, linux-kernel@vger.kernel.org Subject: [PATCHv2 5/5] efi/runtime-wrappers: detect FW irq flag corruption Date: Thu, 21 Apr 2016 12:35:29 +0100 Message-Id: <1461238529-12810-6-git-send-email-mark.rutland@arm.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1461238529-12810-1-git-send-email-mark.rutland@arm.com> References: <1461238529-12810-1-git-send-email-mark.rutland@arm.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The UEFI spec allows runtime services to be called with interrupts masked or unmasked, and if a runtime service function needs to mask interrupts, it must restore the mask to its original state before returning (i.e. from the PoV of the OS, this does not change across a call). Firmware should never unmask exceptions, as these may then be taken by the OS unexpectedly. Unfortunately, some firmware has been seen to unmask IRQs (and potentially other maskable exceptions) across runtime services calls, leaving irq flags corrupted after returning from a runtime services function call. This may be detected by the IRQ tracing code, but often goes unnoticed, leaving a potentially disastrous bug hidden. This patch detects when the irq flags are corrupted by an EFI runtime services call, logging the call and specific corruption to the console. While restoring the expected value of the flags is insufficient to avoid problems, we do so to avoid redundant warnings from elsewhere (e.g. IRQ tracing). Signed-off-by: Mark Rutland Cc: Matt Fleming Cc: linux-efi@vger.kernel.org Cc: linux-kernel@vger.kernel.org --- drivers/firmware/efi/runtime-wrappers.c | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) -- 1.9.1 Reviewed-by: Ard Biesheuvel diff --git a/drivers/firmware/efi/runtime-wrappers.c b/drivers/firmware/efi/runtime-wrappers.c index 1b9fa54..aeb65f2 100644 --- a/drivers/firmware/efi/runtime-wrappers.c +++ b/drivers/firmware/efi/runtime-wrappers.c @@ -16,8 +16,10 @@ #include #include +#include #include #include +#include #include @@ -25,8 +27,11 @@ #define efi_call_virt(f, args...) \ ({ \ efi_status_t __s; \ + unsigned long flags; \ arch_efi_call_virt_setup(); \ + local_save_flags(flags); \ __s = arch_efi_call_virt(f, args); \ + efi_call_virt_check_flags(flags, __stringify(f)); \ arch_efi_call_virt_teardown(); \ __s; \ }) @@ -35,12 +40,29 @@ #ifndef __efi_call_virt #define __efi_call_virt(f, args...) \ ({ \ + unsigned long flags; \ arch_efi_call_virt_setup(); \ + local_irq_save(flags); \ arch_efi_call_virt(f, args); \ + efi_call_virt_check_flags(flags, __stringify(f)); \ arch_efi_call_virt_teardown(); \ }) #endif +static void efi_call_virt_check_flags(unsigned long flags, const char *call) +{ + unsigned long cur_flags; + + local_save_flags(cur_flags); + if (!WARN_ON_ONCE(cur_flags != flags)) + return; + + add_taint(TAINT_FIRMWARE_WORKAROUND, LOCKDEP_NOW_UNRELIABLE); + pr_err_ratelimited(FW_BUG "IRQ flags corrupted (0x%08lx=>0x%08lx) by EFI %s\n", + flags, cur_flags, call); + local_irq_restore(flags); +} + /* * According to section 7.1 of the UEFI spec, Runtime Services are not fully * reentrant, and there are particular combinations of calls that need to be