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Subject[PATCH v2] ANDROID: binder: remove 32-bit binder interface.
Date
From: Martijn Coenen <maco@google.com>

New devices launching with Android P need to use the 64-bit
binder interface, even on 32-bit SoCs [0].

This change removes the Kconfig option to select the 32-bit
binder interface. We don't think this will affect existing
userspace for the following reasons:
1) The latest Android common tree is 4.14, so we don't
believe any Android devices are on kernels >4.14.
2) Android devices launch on an LTS release and stick with
it, so we wouldn't expect devices running on <= 4.14 now
to upgrade to 4.17 or later. But even if they did, they'd
rebuild the world (kernel + userspace) anyway.
3) Other userspaces like 'anbox' are already using the
64-bit interface.

Note that this change doesn't remove the 32-bit UAPI
itself; the reason for that is that Android userspace
always uses the latest UAPI headers from upstream, and
userspace retains 32-bit support for devices that are
upgrading. This will be removed as well in 2-3 years,
at which point we can remove the code from the UAPI
as well.

Finally, this change introduces build errors on archs where
64-bit get_user/put_user is not supported, so make binder
unavailable on m68k (which wouldn't want it anyway).

[0]: https://android-review.googlesource.com/c/platform/build/+/595193

Signed-off-by: Martijn Coenen <maco@android.com>
---
Changes in v2:
- Dropped support for m68k to avoid build errors.

drivers/android/Kconfig | 15 +--------------
drivers/android/binder.c | 4 ----
2 files changed, 1 insertion(+), 18 deletions(-)

diff --git a/drivers/android/Kconfig b/drivers/android/Kconfig
index 7dce3795b887..ee4880bfdcdc 100644
--- a/drivers/android/Kconfig
+++ b/drivers/android/Kconfig
@@ -10,7 +10,7 @@ if ANDROID

config ANDROID_BINDER_IPC
bool "Android Binder IPC Driver"
- depends on MMU
+ depends on MMU && !M68K
default n
---help---
Binder is used in Android for both communication between processes,
@@ -32,19 +32,6 @@ config ANDROID_BINDER_DEVICES
created. Each binder device has its own context manager, and is
therefore logically separated from the other devices.

-config ANDROID_BINDER_IPC_32BIT
- bool "Use old (Android 4.4 and earlier) 32-bit binder API"
- depends on !64BIT && ANDROID_BINDER_IPC
- default y
- ---help---
- The Binder API has been changed to support both 32 and 64bit
- applications in a mixed environment.
-
- Enable this to support an old 32-bit Android user-space (v4.4 and
- earlier).
-
- Note that enabling this will break newer Android user-space.
-
config ANDROID_BINDER_IPC_SELFTEST
bool "Android Binder IPC Driver Selftest"
depends on ANDROID_BINDER_IPC
diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index e578eee31589..2ee9fb02dfb8 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -72,10 +72,6 @@
#include <linux/security.h>
#include <linux/spinlock.h>

-#ifdef CONFIG_ANDROID_BINDER_IPC_32BIT
-#define BINDER_IPC_32BIT 1
-#endif
-
#include <uapi/linux/android/binder.h>
#include "binder_alloc.h"
#include "binder_trace.h"
--
2.17.0.441.gb46fe60e1d-goog
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