Commit 5694289c authored by peterz@infradead.org's avatar peterz@infradead.org Committed by Peter Zijlstra
Browse files

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: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarThomas Gleixner <tglx@linutronix.de>
Reviewed-by: default avatarAndré Almeida <andrealmeid@igalia.com>
Link: https://lore.kernel.org/r/20230921105247.722140574@noisy.programming.kicks-ass.net
parent d6d08d24

kernel/futex/futex.h

+60 −3
Original line number Diff line number Diff line
@@ -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);

kernel/futex/syscalls.c

+9 −15
Original line number Diff line number Diff line 
// 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 @@ SYSCALL_DEFINE3(get_robust_list, int, pid, 
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;

kernel/futex/waitwake.c

+2 −2
Original line number Diff line number Diff line
@@ -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))