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

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Date:   Thu, 18 May 2017 10:09:41 -0500
From:   Dave Gerlach <d-gerlach@...com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC:     Arnd Bergmann <arnd@...db.de>, Tony Lindgren <tony@...mide.com>,
        Russell King <linux@....linux.org.uk>,
        <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 05/18/2017 10:01 AM, Greg Kroah-Hartman wrote:
> 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>
>> Acked-by: Russell King <rmk+kernel@...linux.org.uk>
>> Reviewed-by: Alexandre Belloni <alexandre.belloni@...e-electrons.com>
>> Acked-by: Tony Lindgren <tony@...mide.com>
>
> Can you rebase this and resend as it doesn't apply to the tree right now
> :(
>

Resent as v3 based on v4.12-rc1 and with Acks from v2 added, thanks.

Regards,
Dave

> thanks,
>
> greg k-h
>