[PATCH 5/5] arm64: signal: Allow expansion of the signal frame

[Catalin Marinas]

On Thu, Jun 15, 2017 at 03:03:42PM +0100, Dave P Martin wrote:
> This patch defines an extra_context signal frame record that can be
> used to describe an expanded signal frame, and modifies the context
> block allocator and signal frame setup and parsing code to create,
> populate, parse and decode this block as necessary.
> 
> To avoid abuse by userspace, parse_user_sigframe() attempts to
> ensure that:
> 
>  * no more than one extra_context is accepted;
>  * the extra context data is a sensible size, and properly placed
>    and aligned.
> 
> The extra_context data is required to start at the first 16-byte
> aligned address immediately after the dummy terminator record
> following extra_context in rt_sigframe.__reserved[] (as ensured
> during signal delivery).  This serves as a sanity-check that the
> signal frame has not been moved or copied without taking the extra
> data into account.
> 
> Signed-off-by: Dave Martin <Dave.Martin at arm.com>

Reviewed-by: Catalin Marinas <catalin.marinas at arm.com>