Re: [PATCH v1 02/14] futex: Extend the FUTEX2 flags

On Mon, Jul 31, 2023 at 06:11:27PM +0200, Thomas Gleixner wrote:

On Fri, Jul 21 2023 at 12:22, Peter Zijlstra wrote:

quoted

+#define FUTEX2_8		0x00
+#define FUTEX2_16		0x01
 #define FUTEX2_32		0x02
-			/*	0x04 */
+#define FUTEX2_64		0x03
+#define FUTEX2_NUMA		0x04
 			/*	0x08 */
 			/*	0x10 */
 			/*	0x20 */

--- a/kernel/futex/syscalls.c
+++ b/kernel/futex/syscalls.c

@@ -183,7 +183,7 @@ SYSCALL_DEFINE6(futex, u32 __user *, uad
 	return do_futex(uaddr, op, val, tp, uaddr2, (unsigned long)utime, val3);
 }
 
-#define FUTEX2_MASK (FUTEX2_32 | FUTEX2_PRIVATE)
+#define FUTEX2_MASK (FUTEX2_64 | FUTEX2_PRIVATE)
 
 /**
  * futex_parse_waitv - Parse a waitv array from userspace

@@ -207,7 +207,12 @@ static int futex_parse_waitv(struct fute
 		if ((aux.flags & ~FUTEX2_MASK) || aux.__reserved)
 			return -EINVAL;

With the above aux.flags with FUTEX2_32 set will result in -EINVAL. I
don't think that's intentional.

FUTEX2_8     0
FUTEX2_16    1
FUTEX2_32    2
FUTEX2_64    3

Therefore FUTEX2_64, when used as a mask, includes then all.

Arnd suggested adding FUTEX2_SIZE_MASK or something. And I initially had
something like that, but pulled it for not wanting to pullute the uabi.

Can easily add back.