staging: android: ashmem: Add support for 32bit ashmem calls in a 64bit kernel

Android's shared memory subsystem, Ashmem, does not support calls from a
32bit userspace in a 64 bit kernel. This patch adds support for syscalls
coming from a 32bit userspace in a 64bit kernel.

The patch has been successfully tested on ARMv8 AEM(64bit
platform model) and Versatile Express A9(32bit platform).

v2: Fix missing compat.h include.
Signed-off-by: Serban Constantinescu <serban.constantinescu@arm.com>
Acked-by: Arve Hjønnevåg <arve@android.com>
Acked-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/android/ashmem.c

@@ -702,6 +702,23 @@ static long ashmem_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 	return ret;
 }
 
+/* support of 32bit userspace on 64bit platforms */
+#ifdef CONFIG_COMPAT
+static long compat_ashmem_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
+{
+
+	switch (cmd) {
+	case COMPAT_ASHMEM_SET_SIZE:
+		cmd = ASHMEM_SET_SIZE;
+		break;
+	case COMPAT_ASHMEM_SET_PROT_MASK:
+		cmd = ASHMEM_SET_PROT_MASK;
+		break;
+	}
+	return ashmem_ioctl(file, cmd, arg);
+}
+#endif
+
 static const struct file_operations ashmem_fops = {
 	.owner = THIS_MODULE,
 	.open = ashmem_open,
@@ -710,7 +727,9 @@ static const struct file_operations ashmem_fops = {
 	.llseek = ashmem_llseek,
 	.mmap = ashmem_mmap,
 	.unlocked_ioctl = ashmem_ioctl,
-	.compat_ioctl = ashmem_ioctl,
+#ifdef CONFIG_COMPAT
+	.compat_ioctl = compat_ashmem_ioctl,
+#endif
 };
 
 static struct miscdevice ashmem_misc = {

drivers/staging/android/ashmem.h

@@ -14,6 +14,7 @@
 
 #include <linux/limits.h>
 #include <linux/ioctl.h>
+#include <linux/compat.h>
 
 #define ASHMEM_NAME_LEN		256
 
@@ -45,4 +46,10 @@ struct ashmem_pin {
 #define ASHMEM_GET_PIN_STATUS	_IO(__ASHMEMIOC, 9)
 #define ASHMEM_PURGE_ALL_CACHES	_IO(__ASHMEMIOC, 10)
 
+/* support of 32bit userspace on 64bit platforms */
+#ifdef CONFIG_COMPAT
+#define COMPAT_ASHMEM_SET_SIZE		_IOW(__ASHMEMIOC, 3, compat_size_t)
+#define COMPAT_ASHMEM_SET_PROT_MASK	_IOW(__ASHMEMIOC, 5, unsigned int)
+#endif
+
 #endif	/* _LINUX_ASHMEM_H */