linux-kernel - Re: [PATCH] ACPI / sysfs: Extend ACPI sysfs to provide access to boot error region

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Date:   Fri, 18 Aug 2017 01:30:47 +0100
From:   Alan Cox <gnomes@...rguk.ukuu.org.uk>
To:     "Luck, Tony" <tony.luck@...el.com>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Len Brown <lenb@...nel.org>, Boris Petkov <bp@...e.de>,
        Tyler Baicar <tbaicar@...eaurora.org>,
        Punit Agrawal <punit.agrawal@....com>,
        linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ACPI / sysfs: Extend ACPI sysfs to provide access to
 boot error region

On Thu, 17 Aug 2017 14:39:46 -0700
"Luck, Tony" <tony.luck@...el.com> wrote:

> From: Tony Luck <tony.luck@...el.com>
> 
> The ACPI sysfs interface provides a way to read each ACPI table from
> userspace via entries in /sys/firmware/acpi/tables/
> 
> The BERT table simply provides the size and address of the error
> record in BIOS reserved memory and users may want access to this
> 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
> file in a new directory /sys/firmware/acpi/tables/data/BERT

Should this not also have a capability check. Assuming file permissions
are sufficient for grabbing a chunk of system memory holding error
info doesn't seem too scary but it's at odds with a lot of other cases ?

Alan