--- /dev/null
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+#ifndef _LINUX_FUTEX_H
+#define _LINUX_FUTEX_H
+
+
+#include <linux/types.h>
+
+/* Second argument to futex syscall */
+
+
+#define FUTEX_WAIT 0
+#define FUTEX_WAKE 1
+#define FUTEX_FD 2
+#define FUTEX_REQUEUE 3
+#define FUTEX_CMP_REQUEUE 4
+#define FUTEX_WAKE_OP 5
+#define FUTEX_LOCK_PI 6
+#define FUTEX_UNLOCK_PI 7
+#define FUTEX_TRYLOCK_PI 8
+#define FUTEX_WAIT_BITSET 9
+#define FUTEX_WAKE_BITSET 10
+#define FUTEX_WAIT_REQUEUE_PI 11
+#define FUTEX_CMP_REQUEUE_PI 12
+
+#define FUTEX_PRIVATE_FLAG 128
+#define FUTEX_CLOCK_REALTIME 256
+#define FUTEX_CMD_MASK ~(FUTEX_PRIVATE_FLAG | FUTEX_CLOCK_REALTIME)
+
+#define FUTEX_WAIT_PRIVATE (FUTEX_WAIT | FUTEX_PRIVATE_FLAG)
+#define FUTEX_WAKE_PRIVATE (FUTEX_WAKE | FUTEX_PRIVATE_FLAG)
+#define FUTEX_REQUEUE_PRIVATE (FUTEX_REQUEUE | FUTEX_PRIVATE_FLAG)
+#define FUTEX_CMP_REQUEUE_PRIVATE (FUTEX_CMP_REQUEUE | FUTEX_PRIVATE_FLAG)
+#define FUTEX_WAKE_OP_PRIVATE (FUTEX_WAKE_OP | FUTEX_PRIVATE_FLAG)
+#define FUTEX_LOCK_PI_PRIVATE (FUTEX_LOCK_PI | FUTEX_PRIVATE_FLAG)
+#define FUTEX_UNLOCK_PI_PRIVATE (FUTEX_UNLOCK_PI | FUTEX_PRIVATE_FLAG)
+#define FUTEX_TRYLOCK_PI_PRIVATE (FUTEX_TRYLOCK_PI | FUTEX_PRIVATE_FLAG)
+#define FUTEX_WAIT_BITSET_PRIVATE (FUTEX_WAIT_BITSET | FUTEX_PRIVATE_FLAG)
+#define FUTEX_WAKE_BITSET_PRIVATE (FUTEX_WAKE_BITSET | FUTEX_PRIVATE_FLAG)
+#define FUTEX_WAIT_REQUEUE_PI_PRIVATE (FUTEX_WAIT_REQUEUE_PI | \
+ FUTEX_PRIVATE_FLAG)
+#define FUTEX_CMP_REQUEUE_PI_PRIVATE (FUTEX_CMP_REQUEUE_PI | \
+ FUTEX_PRIVATE_FLAG)
+
+/*
+ * Support for robust futexes: the kernel cleans up held futexes at
+ * thread exit time.
+ */
+
+/*
+ * Per-lock list entry - embedded in user-space locks, somewhere close
+ * to the futex field. (Note: user-space uses a double-linked list to
+ * achieve O(1) list add and remove, but the kernel only needs to know
+ * about the forward link)
+ *
+ * NOTE: this structure is part of the syscall ABI, and must not be
+ * changed.
+ */
+struct robust_list {
+ struct robust_list *next;
+};
+
+/*
+ * Per-thread list head:
+ *
+ * NOTE: this structure is part of the syscall ABI, and must only be
+ * changed if the change is first communicated with the glibc folks.
+ * (When an incompatible change is done, we'll increase the structure
+ * size, which glibc will detect)
+ */
+struct robust_list_head {
+ /*
+ * The head of the list. Points back to itself if empty:
+ */
+ struct robust_list list;
+
+ /*
+ * This relative offset is set by user-space, it gives the kernel
+ * the relative position of the futex field to examine. This way
+ * we keep userspace flexible, to freely shape its data-structure,
+ * without hardcoding any particular offset into the kernel:
+ */
+ long futex_offset;
+
+ /*
+ * The death of the thread may race with userspace setting
+ * up a lock's links. So to handle this race, userspace first
+ * sets this field to the address of the to-be-taken lock,
+ * then does the lock acquire, and then adds itself to the
+ * list, and then clears this field. Hence the kernel will
+ * always have full knowledge of all locks that the thread
+ * _might_ have taken. We check the owner TID in any case,
+ * so only truly owned locks will be handled.
+ */
+ struct robust_list *list_op_pending;
+};
+
+/*
+ * Are there any waiters for this robust futex:
+ */
+#define FUTEX_WAITERS 0x80000000
+
+/*
+ * The kernel signals via this bit that a thread holding a futex
+ * has exited without unlocking the futex. The kernel also does
+ * a FUTEX_WAKE on such futexes, after setting the bit, to wake
+ * up any possible waiters:
+ */
+#define FUTEX_OWNER_DIED 0x40000000
+
+/*
+ * The rest of the robust-futex field is for the TID:
+ */
+#define FUTEX_TID_MASK 0x3fffffff
+
+/*
+ * This limit protects against a deliberately circular list.
+ * (Not worth introducing an rlimit for it)
+ */
+#define ROBUST_LIST_LIMIT 2048
+
+/*
+ * bitset with all bits set for the FUTEX_xxx_BITSET OPs to request a
+ * match of any bit.
+ */
+#define FUTEX_BITSET_MATCH_ANY 0xffffffff
+
+
+#define FUTEX_OP_SET 0 /* *(int *)UADDR2 = OPARG; */
+#define FUTEX_OP_ADD 1 /* *(int *)UADDR2 += OPARG; */
+#define FUTEX_OP_OR 2 /* *(int *)UADDR2 |= OPARG; */
+#define FUTEX_OP_ANDN 3 /* *(int *)UADDR2 &= ~OPARG; */
+#define FUTEX_OP_XOR 4 /* *(int *)UADDR2 ^= OPARG; */
+
+#define FUTEX_OP_OPARG_SHIFT 8 /* Use (1 << OPARG) instead of OPARG. */
+
+#define FUTEX_OP_CMP_EQ 0 /* if (oldval == CMPARG) wake */
+#define FUTEX_OP_CMP_NE 1 /* if (oldval != CMPARG) wake */
+#define FUTEX_OP_CMP_LT 2 /* if (oldval < CMPARG) wake */
+#define FUTEX_OP_CMP_LE 3 /* if (oldval <= CMPARG) wake */
+#define FUTEX_OP_CMP_GT 4 /* if (oldval > CMPARG) wake */
+#define FUTEX_OP_CMP_GE 5 /* if (oldval >= CMPARG) wake */
+
+/* FUTEX_WAKE_OP will perform atomically
+ int oldval = *(int *)UADDR2;
+ *(int *)UADDR2 = oldval OP OPARG;
+ if (oldval CMP CMPARG)
+ wake UADDR2; */
+
+#define FUTEX_OP(op, oparg, cmp, cmparg) \
+ (((op & 0xf) << 28) | ((cmp & 0xf) << 24) \
+ | ((oparg & 0xfff) << 12) | (cmparg & 0xfff))
+
+#endif /* _LINUX_FUTEX_H */
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