[PATCH] arm: Hook up SYNC_CORE functionality for sys_membarrier()

[mathieu.desnoyers@efficios.com (Mathieu Desnoyers)]

----- On Jun 19, 2018, at 8:58 AM, Will Deacon will.deacon at arm.com wrote:

> Hi Mathieu,
> 
> On Tue, Jun 19, 2018 at 08:50:02AM -0400, Mathieu Desnoyers wrote:
>> ----- On Jun 19, 2018, at 8:22 AM, Will Deacon will.deacon at arm.com wrote:
>> 
>> > Exception return implies context synchronization, so we can hook up the
>> > SYNC_CORE option to sys_membarrier() simply by selecting the Kconfig option,
>> > just like we've done for arm64 already.
>> > 
>> > Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
>> > Cc: Orion Hodson <oth@google.com>
>> > Signed-off-by: Will Deacon <will.deacon@arm.com>
>> > ---
>> > arch/arm/Kconfig | 1 +
>> > 1 file changed, 1 insertion(+)
>> > 
>> > diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
>> > index 54eeb8d00bc6..b0ac18547370 100644
>> > --- a/arch/arm/Kconfig
>> > +++ b/arch/arm/Kconfig
>> > @@ -9,6 +9,7 @@ config ARM
>> > 	select ARCH_HAS_ELF_RANDOMIZE
>> > 	select ARCH_HAS_FORTIFY_SOURCE
>> > 	select ARCH_HAS_KCOV
>> > +	select ARCH_HAS_MEMBARRIER_SYNC_CORE
>> 
>> In addition to this, we added this comment in arch/arm64/kernel/entry.S:
>> 
>> +       /*
>> +        * ARCH_HAS_MEMBARRIER_SYNC_CORE rely on eret context synchronization
>> +        * when returning from IPI handler, and when returning to user-space.
>> +        */
>> 
>> So I would expect a similar comment in arch/arm/kernel/entry-header.S, within
>> svc_exit and svc_exit_via_fiq:
>> 
>>         /*
>>          * ARCH_HAS_MEMBARRIER_SYNC_CORE rely on [insn] context synchronization
>>          * when returning from IPI handler, and when returning to user-space.
>>          */
> 
> Bah, you know I hate that comment ;) I should update arch-support.txt,
> though. Diff below.

It works for me with this update, thanks!

Mathieu

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com