Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
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
+71
-20
+60
-3
kernel/futex/futex.h
+60
-3
kernel/futex/futex.h
···
5
5
#include <linux/futex.h>
6
6
#include <linux/rtmutex.h>
7
7
#include <linux/sched/wake_q.h>
8
+
#include <linux/compat.h>
8
9
9
10
#ifdef CONFIG_PREEMPT_RT
10
11
#include <linux/rcuwait.h>
···
17
16
* Futex flags used to encode options to functions and preserve them across
18
17
* restarts.
19
18
*/
19
+
#define FLAGS_SIZE_8 0x00
20
+
#define FLAGS_SIZE_16 0x01
21
+
#define FLAGS_SIZE_32 0x02
22
+
#define FLAGS_SIZE_64 0x03
23
+
24
+
#define FLAGS_SIZE_MASK 0x03
25
+
20
26
#ifdef CONFIG_MMU
21
-
# define FLAGS_SHARED 0x01
27
+
# define FLAGS_SHARED 0x10
22
28
#else
23
29
/*
24
30
* NOMMU does not have per process address space. Let the compiler optimize
···
33
25
*/
34
26
# define FLAGS_SHARED 0x00
35
27
#endif
36
-
#define FLAGS_CLOCKRT 0x02
37
-
#define FLAGS_HAS_TIMEOUT 0x04
28
+
#define FLAGS_CLOCKRT 0x20
29
+
#define FLAGS_HAS_TIMEOUT 0x40
30
+
#define FLAGS_NUMA 0x80
31
+
32
+
/* FUTEX_ to FLAGS_ */
33
+
static inline unsigned int futex_to_flags(unsigned int op)
34
+
{
35
+
unsigned int flags = FLAGS_SIZE_32;
36
+
37
+
if (!(op & FUTEX_PRIVATE_FLAG))
38
+
flags |= FLAGS_SHARED;
39
+
40
+
if (op & FUTEX_CLOCK_REALTIME)
41
+
flags |= FLAGS_CLOCKRT;
42
+
43
+
return flags;
44
+
}
45
+
46
+
/* FUTEX2_ to FLAGS_ */
47
+
static inline unsigned int futex2_to_flags(unsigned int flags2)
48
+
{
49
+
unsigned int flags = flags2 & FUTEX2_SIZE_MASK;
50
+
51
+
if (!(flags2 & FUTEX2_PRIVATE))
52
+
flags |= FLAGS_SHARED;
53
+
54
+
if (flags2 & FUTEX2_NUMA)
55
+
flags |= FLAGS_NUMA;
56
+
57
+
return flags;
58
+
}
59
+
60
+
static inline unsigned int futex_size(unsigned int flags)
61
+
{
62
+
return 1 << (flags & FLAGS_SIZE_MASK);
63
+
}
64
+
65
+
static inline bool futex_flags_valid(unsigned int flags)
66
+
{
67
+
/* Only 64bit futexes for 64bit code */
68
+
if (!IS_ENABLED(CONFIG_64BIT) || in_compat_syscall()) {
69
+
if ((flags & FLAGS_SIZE_MASK) == FLAGS_SIZE_64)
70
+
return false;
71
+
}
72
+
73
+
/* Only 32bit futexes are implemented -- for now */
74
+
if ((flags & FLAGS_SIZE_MASK) != FLAGS_SIZE_32)
75
+
return false;
76
+
77
+
return true;
78
+
}
38
79
39
80
#ifdef CONFIG_FAIL_FUTEX
40
81
extern bool should_fail_futex(bool fshared);
+9
-15
kernel/futex/syscalls.c
+9
-15
kernel/futex/syscalls.c
···
1
1
// SPDX-License-Identifier: GPL-2.0-or-later
2
2
3
-
#include <linux/compat.h>
4
3
#include <linux/syscalls.h>
5
4
#include <linux/time_namespace.h>
6
5
···
84
85
long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout,
85
86
u32 __user *uaddr2, u32 val2, u32 val3)
86
87
{
88
+
unsigned int flags = futex_to_flags(op);
87
89
int cmd = op & FUTEX_CMD_MASK;
88
-
unsigned int flags = 0;
89
90
90
-
if (!(op & FUTEX_PRIVATE_FLAG))
91
-
flags |= FLAGS_SHARED;
92
-
93
-
if (op & FUTEX_CLOCK_REALTIME) {
94
-
flags |= FLAGS_CLOCKRT;
95
-
if (cmd != FUTEX_WAIT_BITSET && cmd != FUTEX_WAIT_REQUEUE_PI &&
91
+
if (flags & FLAGS_CLOCKRT) {
92
+
if (cmd != FUTEX_WAIT_BITSET &&
93
+
cmd != FUTEX_WAIT_REQUEUE_PI &&
96
94
cmd != FUTEX_LOCK_PI2)
97
95
return -ENOSYS;
98
96
}
···
197
201
unsigned int i;
198
202
199
203
for (i = 0; i < nr_futexes; i++) {
204
+
unsigned int flags;
205
+
200
206
if (copy_from_user(&aux, &uwaitv[i], sizeof(aux)))
201
207
return -EFAULT;
202
208
203
209
if ((aux.flags & ~FUTEX2_VALID_MASK) || aux.__reserved)
204
210
return -EINVAL;
205
211
206
-
if (!IS_ENABLED(CONFIG_64BIT) || in_compat_syscall()) {
207
-
if ((aux.flags & FUTEX2_SIZE_MASK) == FUTEX2_SIZE_U64)
208
-
return -EINVAL;
209
-
}
210
-
211
-
if ((aux.flags & FUTEX2_SIZE_MASK) != FUTEX2_SIZE_U32)
212
+
flags = futex2_to_flags(aux.flags);
213
+
if (!futex_flags_valid(flags))
212
214
return -EINVAL;
213
215
214
-
futexv[i].w.flags = aux.flags;
216
+
futexv[i].w.flags = flags;
215
217
futexv[i].w.val = aux.val;
216
218
futexv[i].w.uaddr = aux.uaddr;
217
219
futexv[i].q = futex_q_init;
+2
-2
kernel/futex/waitwake.c
+2
-2
kernel/futex/waitwake.c
···
419
419
*/
420
420
retry:
421
421
for (i = 0; i < count; i++) {
422
-
if ((vs[i].w.flags & FUTEX_PRIVATE_FLAG) && retry)
422
+
if (!(vs[i].w.flags & FLAGS_SHARED) && retry)
423
423
continue;
424
424
425
425
ret = get_futex_key(u64_to_user_ptr(vs[i].w.uaddr),
426
-
!(vs[i].w.flags & FUTEX_PRIVATE_FLAG),
426
+
vs[i].w.flags & FLAGS_SHARED,
427
427
&vs[i].q.key, FUTEX_READ);
428
428
429
429
if (unlikely(ret))