diff options
| -rw-r--r-- | include/uapi/asm-generic/ioctl.h | 10 | ||||
| -rw-r--r-- | include/uapi/linux/userfaultfd.h | 6 |
2 files changed, 15 insertions, 1 deletions
diff --git a/include/uapi/asm-generic/ioctl.h b/include/uapi/asm-generic/ioctl.h index 7e7c11b52143..749b32fe5623 100644 --- a/include/uapi/asm-generic/ioctl.h +++ b/include/uapi/asm-generic/ioctl.h @@ -48,6 +48,9 @@ /* * Direction bits, which any architecture can choose to override * before including this file. + * + * NOTE: _IOC_WRITE means userland is writing and kernel is + * reading. _IOC_READ means userland is reading and kernel is writing. */ #ifndef _IOC_NONE @@ -72,7 +75,12 @@ #define _IOC_TYPECHECK(t) (sizeof(t)) #endif -/* used to create numbers */ +/* + * Used to create numbers. + * + * NOTE: _IOW means userland is writing and kernel is reading. _IOR + * means userland is reading and kernel is writing. + */ #define _IO(type,nr) _IOC(_IOC_NONE,(type),(nr),0) #define _IOR(type,nr,size) _IOC(_IOC_READ,(type),(nr),(_IOC_TYPECHECK(size))) #define _IOW(type,nr,size) _IOC(_IOC_WRITE,(type),(nr),(_IOC_TYPECHECK(size))) diff --git a/include/uapi/linux/userfaultfd.h b/include/uapi/linux/userfaultfd.h index 9057d7af3ae1..94046b8aa6ad 100644 --- a/include/uapi/linux/userfaultfd.h +++ b/include/uapi/linux/userfaultfd.h @@ -11,6 +11,12 @@ #include <linux/types.h> +/* + * If the UFFDIO_API is upgraded someday, the UFFDIO_UNREGISTER and + * UFFDIO_WAKE ioctls should be defined as _IOW and not as _IOR. In + * userfaultfd.h we assumed the kernel was reading (instead _IOC_READ + * means the userland is reading). + */ #define UFFD_API ((__u64)0xAA) /* * After implementing the respective features it will become: |