From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752624AbdHOVQA (ORCPT ); Tue, 15 Aug 2017 17:16:00 -0400 Received: from mga01.intel.com ([192.55.52.88]:10175 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752437AbdHOVP6 (ORCPT ); Tue, 15 Aug 2017 17:15:58 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.41,379,1498546800"; d="scan'208";a="1162968456" Date: Tue, 15 Aug 2017 14:15:57 -0700 From: "Luck, Tony" To: Punit Agrawal Cc: "Rafael J. Wysocki" , Len Brown , Boris Petkov , Tyler Baicar , linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] ACPI/APEI: Add BERT data driver Message-ID: <20170815211556.nnnnbtlvorgc3ijh@intel.com> References: <20170814165613.25561-1-tony.luck@intel.com> <87k225p1v5.fsf@e105922-lin.cambridge.arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87k225p1v5.fsf@e105922-lin.cambridge.arm.com> User-Agent: NeoMutt/20170113 (1.7.2) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Aug 15, 2017 at 11:22:06AM +0100, Punit Agrawal wrote: > There is already a bert driver which prints the error record. Would it > make sense to integrate the character device there instead of creating a > new driver? Like this? The source code is smaller. But it doesn't offer the option to unload the driver and unmap the BERT data region after you have retrieved the error record. Either looks plausible to me (but I'm hardly a disinterested party). Votes? -Tony >>From cbeabf2d83fe91eebd960cd5cc1b61faaeed1441 Mon Sep 17 00:00:00 2001 From: Tony Luck Date: Tue, 15 Aug 2017 13:48:28 -0700 Subject: [PATCH] ACPI: APEI: Extend BERT driver to provide a character device to access data The BERT table simply provides the size and address of the error record in BIOS reserved memory. Currently this driver decodes the record to the console log. But other users of BERT may want to access the full binary record. In an earlier age we might have used /dev/mem to retrieve this error record, but many systems disable /dev/mem for security reasons. Extend this driver to provide read-only access to the data via a character special device "/dev/bert-data". Cc: Len Brown Cc: Boris Petkov Cc: Tyler Baicar Cc: Punit Agrawal Cc: linux-acpi@vger.kernel.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Tony Luck v2: (suggested by Punit Agrawal) don't make a whole new driver, merge this functionality into the existing BERT driver. --- drivers/acpi/apei/bert.c | 45 ++++++++++++++++++++++++++++++++++++++++++--- 1 file changed, 42 insertions(+), 3 deletions(-) diff --git a/drivers/acpi/apei/bert.c b/drivers/acpi/apei/bert.c index 12771fcf0417..9bc39b1bffde 100644 --- a/drivers/acpi/apei/bert.c +++ b/drivers/acpi/apei/bert.c @@ -26,12 +26,16 @@ #include #include #include +#include +#include #include "apei-internal.h" #undef pr_fmt #define pr_fmt(fmt) "BERT: " fmt +static __iomem void *bert_data; +static unsigned int region_len; static int bert_disable; static void __init bert_print_all(struct acpi_bert_region *region, @@ -95,12 +99,45 @@ static int __init bert_check_table(struct acpi_table_bert *bert_tab) return 0; } +static int bert_chrdev_open(struct inode *inode, struct file *file) +{ + if (file->f_flags & (O_WRONLY | O_RDWR)) + return -EPERM; + inode->i_size = region_len; + return 0; +} + +static ssize_t bert_chrdev_read(struct file *filp, char __user *ubuf, + size_t usize, loff_t *off) +{ + if (*off > region_len) + return -EINVAL; + if (*off + usize > region_len) + usize = region_len - *off; + if (copy_to_user(ubuf, bert_data + *off, usize)) + return -EFAULT; + *off += usize; + return usize; +} + +static const struct file_operations bert_chrdev_ops = { + .open = bert_chrdev_open, + .read = bert_chrdev_read, + .llseek = default_llseek, +}; + +static struct miscdevice bert_chrdev_device = { + .minor = MISC_DYNAMIC_MINOR, + .name = "bert-data", + .fops = &bert_chrdev_ops, + .mode = 0444, +}; + static int __init bert_init(void) { - struct apei_resources bert_resources; struct acpi_bert_region *boot_error_region; + struct apei_resources bert_resources; struct acpi_table_bert *bert_tab; - unsigned int region_len; acpi_status status; int rc = 0; @@ -139,7 +176,9 @@ static int __init bert_init(void) boot_error_region = ioremap_cache(bert_tab->address, region_len); if (boot_error_region) { bert_print_all(boot_error_region, region_len); - iounmap(boot_error_region); + bert_data = boot_error_region; + if (misc_register(&bert_chrdev_device)) + iounmap(boot_error_region); } else { rc = -ENOMEM; } -- 2.11.0