[<prev] [next>] [<thread-prev] [day] [month] [year] [list]
Message-ID: <20151123093812.GA28212@gmail.com>
Date: Mon, 23 Nov 2015 10:38:12 +0100
From: Ingo Molnar <mingo@...nel.org>
To: Dan Williams <dan.j.williams@...el.com>
Cc: Russell King - ARM Linux <linux@....linux.org.uk>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Kees Cook <keescook@...omium.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Catalin Marinas <catalin.marinas@....com>,
linux-nvdimm <linux-nvdimm@...1.01.org>,
Heiko Carstens <heiko.carstens@...ibm.com>,
Will Deacon <will.deacon@....com>,
Ingo Molnar <mingo@...hat.com>,
Benjamin Herrenschmidt <benh@...nel.crashing.org>,
"H. Peter Anvin" <hpa@...or.com>,
Martin Schwidefsky <schwidefsky@...ibm.com>,
Thomas Gleixner <tglx@...utronix.de>,
Andrew Morton <akpm@...ux-foundation.org>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [RFC PATCH] restrict /dev/mem to idle io memory ranges
* Dan Williams <dan.j.williams@...el.com> wrote:
> On Fri, Nov 20, 2015 at 12:12 PM, Russell King - ARM Linux
> <linux@....linux.org.uk> wrote:
> > On Fri, Nov 20, 2015 at 09:31:33AM -0800, Dan Williams wrote:
> >> This effectively promotes IORESOURCE_BUSY to IORESOURCE_EXCLUSIVE
> >> semantics by default. If userspace really believes it is safe to access
> >> the memory region it can also perform the extra step of disabling an
> >> active driver. This protects device address ranges with read side
> >> effects and otherwise directs userspace to use the driver.
> >
> > I'm happy with this as long as we retain the option to disable this
> > new behaviour.
> >
> > The reason being, when developing a driver, it is _very_ useful to
> > be able to poke around in the device's (and system memory) address
> > spaces with tools like devmem2 to work out what's going on when
> > things go wrong.
> >
> > To put it another way, I think it's a good idea to disable access to
> > these regions on production systems, but for driver development, we
> > want to retain the ability to poke around in physical address space
> > in any way we so desire.
> >
>
> Sounds ok to me, but I do think it's a good idea to default it to the
> same value as STRICT_DEVMEM. Perhaps:
>
> bool "Filter I/O access to /dev/mem" if EXPERT
> default STRICT_DEVMEM
Agreed, STRICT_DEVMEM=y should grandfather in this new (and very sensible)
restriction.
Thanks,
Ingo
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists