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

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  Re: [PATCH v2] misc: sram-exec: Use aligned fncpy instead of memcpy Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-05-18 17:10 +0200
    Re: [PATCH v2] misc: sram-exec: Use aligned fncpy instead of memcpy Dave Gerlach <d-gerlach@ti.com> - 2017-05-18 17:20 +0200

#1644659 — Re: [PATCH v2] misc: sram-exec: Use aligned fncpy instead of memcpy

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@ti.com>
> Acked-by: Russell King <rmk+kernel@armlinux.org.uk>
> Reviewed-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
> Acked-by: Tony Lindgren <tony@atomide.com>

Can you rebase this and resend as it doesn't apply to the tree right now
:(

thanks,

greg k-h

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#1644669

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@ti.com>
>> Acked-by: Russell King <rmk+kernel@armlinux.org.uk>
>> Reviewed-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
>> Acked-by: Tony Lindgren <tony@atomide.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
>

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