[RFC][PATCH] staging: Fix build issues with new binder API

[RFC][PATCH] staging: Fix build issues with new binder API

[John Stultz]

The new 64bit binder API causes build issues on 32bit ARM
due to the lack of 64bit __get_user_asm_* implementation.

Until that implementation is done, remove the choice for
32bit ARM, automatically enabling the old 32bit binder
protocol.

This can be reverted once a 64bit __get_user_asm_*
implementation is merged.

Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: Colin Cross <ccross@android.com>
Cc: Arve Hjønnevåg <arve@android.com>
Cc: Serban Constantinescu <serban.constantinescu@arm.com>
Cc: Android Kernel Team <kernel-team@android.com>
Reported-by: Arnd Bergmann <arnd.bergmann@linaro.org>
Signed-off-by: John Stultz <john.stultz@linaro.org>
---
 drivers/staging/android/Kconfig | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/staging/android/Kconfig b/drivers/staging/android/Kconfig
index 1c779ef..ab28d2b 100644
--- a/drivers/staging/android/Kconfig
+++ b/drivers/staging/android/Kconfig
@@ -21,7 +21,7 @@ config ANDROID_BINDER_IPC
 	  between said processes.
 
 config ANDROID_BINDER_IPC_32BIT
-	bool "Use old (Android 4.4 and earlier) 32-bit binder API"
+	bool
 	depends on !64BIT && ANDROID_BINDER_IPC
 	default y
 	---help---
-- 
1.8.3.2

Re: [RFC][PATCH] staging: Fix build issues with new binder API

[Greg KH]

On Wed, Feb 26, 2014 at 02:29:07PM -0800, John Stultz wrote:
> The new 64bit binder API causes build issues on 32bit ARM
> due to the lack of 64bit __get_user_asm_* implementation.

So no one ever tested this out on ARM?  Really, that seems odd...

Anyway, if you want this to always be on, that's fine with me, your
choice :)

Re: [RFC][PATCH] staging: Fix build issues with new binder API

[John Stultz]

On 02/26/2014 07:34 PM, Greg KH wrote:
> On Wed, Feb 26, 2014 at 02:29:07PM -0800, John Stultz wrote:
>> The new 64bit binder API causes build issues on 32bit ARM
>> due to the lack of 64bit __get_user_asm_* implementation.
> So no one ever tested this out on ARM?  Really, that seems odd...

Its my bad, I was focused on the 32bit legacy compatibility code in my
testing because the userspace I have only works with that.

Arve actually warned about this in one of his mails, but I mistakenly
thought it was an issue w/ 3.10 and earlier kernels and had since been
addressed.


> Anyway, if you want this to always be on, that's fine with me, your
> choice :)

I think its the best option for now, but wanted to send it out for
comment to see if anyone objected.

I'm about to head for a conference so I'll be offline until around
Monday. While at the conference I'm going to be working with folks to
see if we can't get the real solution (a __get_user_asm_64
implementation) sorted.  But if there are no objections, it might be
best to queue this for staging-next so folks don't hit the issue in the
meantime.

thanks
-john

Re: [RFC][PATCH] staging: Fix build issues with new binder API

[Greg KH]

On Thu, Feb 27, 2014 at 11:04:01AM -0800, John Stultz wrote:
> On 02/26/2014 07:34 PM, Greg KH wrote:
> > On Wed, Feb 26, 2014 at 02:29:07PM -0800, John Stultz wrote:
> >> The new 64bit binder API causes build issues on 32bit ARM
> >> due to the lack of 64bit __get_user_asm_* implementation.
> > So no one ever tested this out on ARM?  Really, that seems odd...
> 
> Its my bad, I was focused on the 32bit legacy compatibility code in my
> testing because the userspace I have only works with that.
> 
> Arve actually warned about this in one of his mails, but I mistakenly
> thought it was an issue w/ 3.10 and earlier kernels and had since been
> addressed.
> 
> 
> > Anyway, if you want this to always be on, that's fine with me, your
> > choice :)
> 
> I think its the best option for now, but wanted to send it out for
> comment to see if anyone objected.
> 
> I'm about to head for a conference so I'll be offline until around
> Monday. While at the conference I'm going to be working with folks to
> see if we can't get the real solution (a __get_user_asm_64
> implementation) sorted.  But if there are no objections, it might be
> best to queue this for staging-next so folks don't hit the issue in the
> meantime.

Yes, the "real" solution would be best, but I'll queue this up for now,
thanks.

greg k-h

Re: Fwd: [RFC][PATCH] staging: Fix build issues with new binder API

[Arnd Bergmann]

On Wednesday 26 February 2014, John Stultz wrote:
> The new 64bit binder API causes build issues on 32bit ARM
> due to the lack of 64bit __get_user_asm_* implementation.

It is impossible to implement this. Many have tried before.

> Until that implementation is done, remove the choice for
> 32bit ARM, automatically enabling the old 32bit binder
> protocol.
> 
> This can be reverted once a 64bit __get_user_asm_*
> implementation is merged.

I think the best solution is to use __copy_from_user for
the 64-bit access. You can wrap it in a helper function
if you want to speed up the native-word-size case.

	Arnd

Re: Fwd: [RFC][PATCH] staging: Fix build issues with new binder API

[John Stultz]

On 02/27/2014 11:15 AM, Arnd Bergmann wrote:
> On Wednesday 26 February 2014, John Stultz wrote:
>> The new 64bit binder API causes build issues on 32bit ARM
>> due to the lack of 64bit __get_user_asm_* implementation.
> It is impossible to implement this. Many have tried before.
>
>> Until that implementation is done, remove the choice for
>> 32bit ARM, automatically enabling the old 32bit binder
>> protocol.
>>
>> This can be reverted once a 64bit __get_user_asm_*
>> implementation is merged.
> I think the best solution is to use __copy_from_user for
> the 64-bit access. You can wrap it in a helper function
> if you want to speed up the native-word-size case.

Ah. Thanks for the context and the tip. Will try to get an appropriate
solution there then.

thanks
-john