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

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Message-ID: <20170426144943.GG3780@atomide.com>
Date:   Wed, 26 Apr 2017 07:49:43 -0700
From:   Tony Lindgren <tony@...mide.com>
To:     Dave Gerlach <d-gerlach@...com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Arnd Bergmann <arnd@...db.de>,
        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

* Dave Gerlach <d-gerlach@...com> [170410 07:55]:
> 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.

Looks good to me:

Acked-by: Tony Lindgren <tony@...mide.com>