diff options
| author | peterz@infradead.org <peterz@infradead.org> | 2023-09-21 12:45:06 +0200 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2023-09-21 19:22:04 +0200 |
| commit | 4923954bbc4a760e0b2210e0cb5733726ac2e2e9 (patch) | |
| tree | dc148ad41454f6eb031a9d569b81f6bb40badaa0 | |
| parent | asm-generic: ticket-lock: Optimize arch_spin_value_unlocked() (diff) | |
| download | linux-4923954bbc4a760e0b2210e0cb5733726ac2e2e9.tar.xz linux-4923954bbc4a760e0b2210e0cb5733726ac2e2e9.zip | |
futex: Clarify FUTEX2 flags
sys_futex_waitv() is part of the futex2 series (the first and only so
far) of syscalls and has a flags field per futex (as opposed to flags
being encoded in the futex op).
This new flags field has a new namespace, which unfortunately isn't
super explicit. Notably it currently takes FUTEX_32 and
FUTEX_PRIVATE_FLAG.
Introduce the FUTEX2 namespace to clarify this
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: André Almeida <andrealmeid@igalia.com>
Link: https://lore.kernel.org/r/20230921105247.507327749@noisy.programming.kicks-ass.net
| -rw-r--r-- | include/uapi/linux/futex.h | 16 | ||||
| -rw-r--r-- | kernel/futex/syscalls.c | 7 |
2 files changed, 16 insertions, 7 deletions
diff --git a/include/uapi/linux/futex.h b/include/uapi/linux/futex.h index 71a5df8d2689..21d4eff41162 100644 --- a/include/uapi/linux/futex.h +++ b/include/uapi/linux/futex.h @@ -44,10 +44,20 @@ FUTEX_PRIVATE_FLAG) /* - * Flags to specify the bit length of the futex word for futex2 syscalls. - * Currently, only 32 is supported. + * Flags for futex2 syscalls. */ -#define FUTEX_32 2 + /* 0x00 */ + /* 0x01 */ +#define FUTEX2_SIZE_U32 0x02 + /* 0x04 */ + /* 0x08 */ + /* 0x10 */ + /* 0x20 */ + /* 0x40 */ +#define FUTEX2_PRIVATE FUTEX_PRIVATE_FLAG + +/* do not use */ +#define FUTEX_32 FUTEX2_SIZE_U32 /* historical accident :-( */ /* * Max numbers of elements in a futex_waitv array diff --git a/kernel/futex/syscalls.c b/kernel/futex/syscalls.c index a8074079b09e..ff696b0e2e5c 100644 --- a/kernel/futex/syscalls.c +++ b/kernel/futex/syscalls.c @@ -183,8 +183,7 @@ SYSCALL_DEFINE6(futex, u32 __user *, uaddr, int, op, u32, val, return do_futex(uaddr, op, val, tp, uaddr2, (unsigned long)utime, val3); } -/* Mask of available flags for each futex in futex_waitv list */ -#define FUTEXV_WAITER_MASK (FUTEX_32 | FUTEX_PRIVATE_FLAG) +#define FUTEX2_VALID_MASK (FUTEX2_SIZE_U32 | FUTEX2_PRIVATE) /** * futex_parse_waitv - Parse a waitv array from userspace @@ -205,10 +204,10 @@ static int futex_parse_waitv(struct futex_vector *futexv, if (copy_from_user(&aux, &uwaitv[i], sizeof(aux))) return -EFAULT; - if ((aux.flags & ~FUTEXV_WAITER_MASK) || aux.__reserved) + if ((aux.flags & ~FUTEX2_VALID_MASK) || aux.__reserved) return -EINVAL; - if (!(aux.flags & FUTEX_32)) + if (!(aux.flags & FUTEX2_SIZE_U32)) return -EINVAL; futexv[i].w.flags = aux.flags; |