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futex: Flag conversion 

Futex has 3 sets of flags:

 - legacy futex op bits
 - futex2 flags
 - internal flags

Add a few helpers to convert from the API flags into the internal
flags.

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/20230921105247.722140574@noisy.programming.kicks-ass.net
This commit is contained in:
peterz@infradead.org 2023-09-21 12:45:08 +02:00 committed by Peter Zijlstra
parent d6d08d2479
commit 5694289ce1
3 changed files with 71 additions and 20 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

63
kernel/futex/futex.h
View File

@ -5,6 +5,7 @@
#include <linux/futex.h>
#include <linux/rtmutex.h>
#include <linux/sched/wake_q.h>
#include <linux/compat.h>
#ifdef CONFIG_PREEMPT_RT
#include <linux/rcuwait.h>
@ -16,8 +17,15 @@
* Futex flags used to encode options to functions and preserve them across
* restarts.
*/
#define FLAGS_SIZE_8 0x00
#define FLAGS_SIZE_16 0x01
#define FLAGS_SIZE_32 0x02
#define FLAGS_SIZE_64 0x03
#define FLAGS_SIZE_MASK 0x03
#ifdef CONFIG_MMU
# define FLAGS_SHARED 0x01
# define FLAGS_SHARED 0x10
#else
/*
* NOMMU does not have per process address space. Let the compiler optimize
@ -25,8 +33,57 @@
*/
# define FLAGS_SHARED 0x00
#endif
#define FLAGS_CLOCKRT 0x02
#define FLAGS_HAS_TIMEOUT 0x04
#define FLAGS_CLOCKRT 0x20
#define FLAGS_HAS_TIMEOUT 0x40
#define FLAGS_NUMA 0x80
/* FUTEX_ to FLAGS_ */
static inline unsigned int futex_to_flags(unsigned int op)
{
unsigned int flags = FLAGS_SIZE_32;
if (!(op & FUTEX_PRIVATE_FLAG))
flags |= FLAGS_SHARED;
if (op & FUTEX_CLOCK_REALTIME)
flags |= FLAGS_CLOCKRT;
return flags;
}
/* FUTEX2_ to FLAGS_ */
static inline unsigned int futex2_to_flags(unsigned int flags2)
{
unsigned int flags = flags2 & FUTEX2_SIZE_MASK;
if (!(flags2 & FUTEX2_PRIVATE))
flags |= FLAGS_SHARED;
if (flags2 & FUTEX2_NUMA)
flags |= FLAGS_NUMA;
return flags;
}
static inline unsigned int futex_size(unsigned int flags)
{
return 1 << (flags & FLAGS_SIZE_MASK);
}
static inline bool futex_flags_valid(unsigned int flags)
{
/* Only 64bit futexes for 64bit code */
if (!IS_ENABLED(CONFIG_64BIT) || in_compat_syscall()) {
if ((flags & FLAGS_SIZE_MASK) == FLAGS_SIZE_64)
return false;
}
/* Only 32bit futexes are implemented -- for now */
if ((flags & FLAGS_SIZE_MASK) != FLAGS_SIZE_32)
return false;
return true;
}
#ifdef CONFIG_FAIL_FUTEX
extern bool should_fail_futex(bool fshared);

24
kernel/futex/syscalls.c
View File

@ -1,6 +1,5 @@
// SPDX-License-Identifier: GPL-2.0-or-later
#include <linux/compat.h>
#include <linux/syscalls.h>
#include <linux/time_namespace.h>
@ -85,15 +84,12 @@ err_unlock:
long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout,
u32 __user *uaddr2, u32 val2, u32 val3)
{
unsigned int flags = futex_to_flags(op);
int cmd = op & FUTEX_CMD_MASK;
unsigned int flags = 0;
if (!(op & FUTEX_PRIVATE_FLAG))
flags |= FLAGS_SHARED;
if (op & FUTEX_CLOCK_REALTIME) {
flags |= FLAGS_CLOCKRT;
if (cmd != FUTEX_WAIT_BITSET && cmd != FUTEX_WAIT_REQUEUE_PI &&
if (flags & FLAGS_CLOCKRT) {
if (cmd != FUTEX_WAIT_BITSET &&
cmd != FUTEX_WAIT_REQUEUE_PI &&
cmd != FUTEX_LOCK_PI2)
return -ENOSYS;
}
@ -201,21 +197,19 @@ static int futex_parse_waitv(struct futex_vector *futexv,
unsigned int i;
for (i = 0; i < nr_futexes; i++) {
unsigned int flags;
if (copy_from_user(&aux, &uwaitv[i], sizeof(aux)))
return -EFAULT;
if ((aux.flags & ~FUTEX2_VALID_MASK) || aux.__reserved)
return -EINVAL;
if (!IS_ENABLED(CONFIG_64BIT) || in_compat_syscall()) {
if ((aux.flags & FUTEX2_SIZE_MASK) == FUTEX2_SIZE_U64)
return -EINVAL;
}
if ((aux.flags & FUTEX2_SIZE_MASK) != FUTEX2_SIZE_U32)
flags = futex2_to_flags(aux.flags);
if (!futex_flags_valid(flags))
return -EINVAL;
futexv[i].w.flags = aux.flags;
futexv[i].w.flags = flags;
futexv[i].w.val = aux.val;
futexv[i].w.uaddr = aux.uaddr;
futexv[i].q = futex_q_init;

4
kernel/futex/waitwake.c
View File

@ -419,11 +419,11 @@ static int futex_wait_multiple_setup(struct futex_vector *vs, int count, int *wo
*/
retry:
for (i = 0; i < count; i++) {
if ((vs[i].w.flags & FUTEX_PRIVATE_FLAG) && retry)
if (!(vs[i].w.flags & FLAGS_SHARED) && retry)
continue;
ret = get_futex_key(u64_to_user_ptr(vs[i].w.uaddr),
!(vs[i].w.flags & FUTEX_PRIVATE_FLAG),
vs[i].w.flags & FLAGS_SHARED,
&vs[i].q.key, FUTEX_READ);
if (unlikely(ret))