Re: [PATCH v1 02/14] futex: Extend the FUTEX2 flags
From: Peter Zijlstra <peterz@infradead.org>
Date: 2023-07-31 19:20:39
Also in:
linux-arch, linux-mm, lkml
On Mon, Jul 31, 2023 at 07:42:11PM +0200, Thomas Gleixner wrote:
Aargh. This is really nasty to make FUTEX2_64 0x3 and abuse it to test the flags for validity. Intuitive and obvious is something else.
Like so then?
--- a/include/uapi/linux/futex.h
+++ b/include/uapi/linux/futex.h@@ -57,6 +57,8 @@ /* 0x40 */ #define FUTEX2_PRIVATE FUTEX_PRIVATE_FLAG +#define FUTEX2_SIZE_MASK 0x03 + /* do not use */ #define FUTEX_32 FUTEX2_32 /* historical accident :-( */ --- 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_64 | FUTEX2_PRIVATE) +#define FUTEX2_MASK (FUTEX2_SIZE_MASK | FUTEX2_PRIVATE) /** * futex_parse_waitv - Parse a waitv array from userspace
@@ -208,11 +208,11 @@ static int futex_parse_waitv(struct fute return -EINVAL; if (!IS_ENABLED(CONFIG_64BIT) || in_compat_syscall()) { - if ((aux.flags & FUTEX2_64) == FUTEX2_64) + if ((aux.flags & FUTEX2_SIZE_MASK) == FUTEX2_64) return -EINVAL; } - if ((aux.flags & FUTEX2_64) != FUTEX2_32) + if ((aux.flags & FUTEX2_SIZE_MASK) != FUTEX2_32) return -EINVAL; futexv[i].w.flags = aux.flags;