linux-kernel - Re: [PATCH v2] misc: sram-exec: Use aligned fncpy instead of memcpy

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Date:   Wed, 17 May 2017 11:13:17 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Tony Lindgren <tony@...mide.com>
Cc:     Russell King - ARM Linux <linux@...linux.org.uk>,
        Dave Gerlach <d-gerlach@...com>, Arnd Bergmann <arnd@...db.de>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-omap@...r.kernel.org, Shawn Guo <shawnguo@...nel.org>,
        Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
        Keerthy J <j-keerthy@...com>
Subject: Re: [PATCH v2] misc: sram-exec: Use aligned fncpy instead of memcpy

On Tue, May 16, 2017 at 09:01:27AM -0700, Tony Lindgren wrote:
> * Russell King - ARM Linux <linux@...linux.org.uk> [170503 11:58]:
> > On Mon, Apr 10, 2017 at 09:52:47AM -0500, Dave Gerlach wrote:
> > > Currently the sram-exec functionality, which allows allocation of
> > > executable memory and provides an API to move code to it, is only
> > > selected in configs for the ARM architecture. Based on commit
> > > 5756e9dd0de6 ("ARM: 6640/1: Thumb-2: Symbol manipulation macros for
> > > function body copying") simply copying a C function pointer address
> > > using memcpy without consideration of alignment and Thumb is unsafe on
> > > ARM platforms.
> > > 
> > > The aforementioned patch introduces the fncpy macro which is a safe way
> > > to copy executable code on ARM platforms, so let's make use of that here
> > > rather than the unsafe plain memcpy that was previously used by
> > > sram_exec_copy. Now sram_exec_copy will move the code to "dst" and
> > > return an address that is guaranteed to be safely callable.
> > > 
> > > In the future, architectures hoping to make use of the sram-exec
> > > functionality must define an fncpy macro just as ARM has done to
> > > guarantee or check for safe copying to executable memory before allowing
> > > the arch to select CONFIG_SRAM_EXEC.
> > > 
> > > Signed-off-by: Dave Gerlach <d-gerlach@...com>
> > 
> > Looks a lot saner, thanks.  It's just a bit sad that we lose the type
> > checking.
> > 
> > Acked-by: Russell King <rmk+kernel@...linux.org.uk>
> 
> Looks like this is still pending so I'll add it into
> omap-for-v4.12/fixes so we can get this out of the way.

It's a "fix"?  Looked to be a 4.13 issue, sorry for the delay, otherwise
I would have queued it up earlier.

No objection for you to take this through your tree.

greg k-h