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linux_futex.c
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/* $NetBSD: linux_futex.c,v 1.7 2006/07/24 19:01:49 manu Exp $ */
/*-
* SPDX-License-Identifier: BSD-4-Clause
*
* Copyright (c) 2009-2016 Dmitry Chagin
* Copyright (c) 2005 Emmanuel Dreyfus
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by Emmanuel Dreyfus
* 4. The name of the author may not be used to endorse or promote
* products derived from this software without specific prior written
* permission.
*
* THIS SOFTWARE IS PROVIDED BY THE THE AUTHOR AND CONTRIBUTORS ``AS IS''
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#if 0
__KERNEL_RCSID(1, "$NetBSD: linux_futex.c,v 1.7 2006/07/24 19:01:49 manu Exp $");
#endif
#include "opt_compat.h"
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/imgact.h>
#include <sys/kernel.h>
#include <sys/ktr.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mutex.h>
#include <sys/priv.h>
#include <sys/proc.h>
#include <sys/queue.h>
#include <sys/sched.h>
#include <sys/sdt.h>
#include <sys/umtx.h>
#include <vm/vm_extern.h>
#ifdef COMPAT_LINUX32
#include <machine/../linux32/linux.h>
#include <machine/../linux32/linux32_proto.h>
#else
#include <machine/../linux/linux.h>
#include <machine/../linux/linux_proto.h>
#endif
#include <compat/linux/linux_dtrace.h>
#include <compat/linux/linux_emul.h>
#include <compat/linux/linux_futex.h>
#include <compat/linux/linux_timer.h>
#include <compat/linux/linux_util.h>
/* DTrace init */
LIN_SDT_PROVIDER_DECLARE(LINUX_DTRACE);
/**
* Futex part for the special DTrace module "locks".
*/
LIN_SDT_PROBE_DEFINE1(locks, futex_mtx, locked, "struct mtx *");
LIN_SDT_PROBE_DEFINE1(locks, futex_mtx, unlock, "struct mtx *");
/**
* Per futex probes.
*/
LIN_SDT_PROBE_DEFINE1(futex, futex, create, "struct sx *");
LIN_SDT_PROBE_DEFINE1(futex, futex, destroy, "struct sx *");
/**
* DTrace probes in this module.
*/
LIN_SDT_PROBE_DEFINE2(futex, futex_put, entry, "struct futex *",
"struct waiting_proc *");
LIN_SDT_PROBE_DEFINE3(futex, futex_put, destroy, "uint32_t *", "uint32_t",
"int");
LIN_SDT_PROBE_DEFINE3(futex, futex_put, unlock, "uint32_t *", "uint32_t",
"int");
LIN_SDT_PROBE_DEFINE0(futex, futex_put, return);
LIN_SDT_PROBE_DEFINE3(futex, futex_get0, entry, "uint32_t *", "struct futex **",
"uint32_t");
LIN_SDT_PROBE_DEFINE1(futex, futex_get0, umtx_key_get_error, "int");
LIN_SDT_PROBE_DEFINE3(futex, futex_get0, shared, "uint32_t *", "uint32_t",
"int");
LIN_SDT_PROBE_DEFINE1(futex, futex_get0, null, "uint32_t *");
LIN_SDT_PROBE_DEFINE3(futex, futex_get0, new, "uint32_t *", "uint32_t", "int");
LIN_SDT_PROBE_DEFINE1(futex, futex_get0, return, "int");
LIN_SDT_PROBE_DEFINE3(futex, futex_get, entry, "uint32_t *",
"struct waiting_proc **", "struct futex **");
LIN_SDT_PROBE_DEFINE0(futex, futex_get, error);
LIN_SDT_PROBE_DEFINE1(futex, futex_get, return, "int");
LIN_SDT_PROBE_DEFINE3(futex, futex_sleep, entry, "struct futex *",
"struct waiting_proc **", "struct timespec *");
LIN_SDT_PROBE_DEFINE5(futex, futex_sleep, requeue_error, "int", "uint32_t *",
"struct waiting_proc *", "uint32_t *", "uint32_t");
LIN_SDT_PROBE_DEFINE3(futex, futex_sleep, sleep_error, "int", "uint32_t *",
"struct waiting_proc *");
LIN_SDT_PROBE_DEFINE1(futex, futex_sleep, return, "int");
LIN_SDT_PROBE_DEFINE3(futex, futex_wake, entry, "struct futex *", "int",
"uint32_t");
LIN_SDT_PROBE_DEFINE3(futex, futex_wake, iterate, "uint32_t",
"struct waiting_proc *", "uint32_t");
LIN_SDT_PROBE_DEFINE1(futex, futex_wake, wakeup, "struct waiting_proc *");
LIN_SDT_PROBE_DEFINE1(futex, futex_wake, return, "int");
LIN_SDT_PROBE_DEFINE4(futex, futex_requeue, entry, "struct futex *", "int",
"struct futex *", "int");
LIN_SDT_PROBE_DEFINE1(futex, futex_requeue, wakeup, "struct waiting_proc *");
LIN_SDT_PROBE_DEFINE3(futex, futex_requeue, requeue, "uint32_t *",
"struct waiting_proc *", "uint32_t");
LIN_SDT_PROBE_DEFINE1(futex, futex_requeue, return, "int");
LIN_SDT_PROBE_DEFINE4(futex, futex_wait, entry, "struct futex *",
"struct waiting_proc **", "struct timespec *", "uint32_t");
LIN_SDT_PROBE_DEFINE1(futex, futex_wait, sleep_error, "int");
LIN_SDT_PROBE_DEFINE1(futex, futex_wait, return, "int");
LIN_SDT_PROBE_DEFINE3(futex, futex_atomic_op, entry, "struct thread *",
"int", "uint32_t");
LIN_SDT_PROBE_DEFINE4(futex, futex_atomic_op, decoded_op, "int", "int", "int",
"int");
LIN_SDT_PROBE_DEFINE0(futex, futex_atomic_op, missing_access_check);
LIN_SDT_PROBE_DEFINE1(futex, futex_atomic_op, unimplemented_op, "int");
LIN_SDT_PROBE_DEFINE1(futex, futex_atomic_op, unimplemented_cmp, "int");
LIN_SDT_PROBE_DEFINE1(futex, futex_atomic_op, return, "int");
LIN_SDT_PROBE_DEFINE2(futex, linux_sys_futex, entry, "struct thread *",
"struct linux_sys_futex_args *");
LIN_SDT_PROBE_DEFINE0(futex, linux_sys_futex, unimplemented_clockswitch);
LIN_SDT_PROBE_DEFINE1(futex, linux_sys_futex, copyin_error, "int");
LIN_SDT_PROBE_DEFINE0(futex, linux_sys_futex, invalid_cmp_requeue_use);
LIN_SDT_PROBE_DEFINE3(futex, linux_sys_futex, debug_wait, "uint32_t *",
"uint32_t", "uint32_t");
LIN_SDT_PROBE_DEFINE4(futex, linux_sys_futex, debug_wait_value_neq,
"uint32_t *", "uint32_t", "int", "uint32_t");
LIN_SDT_PROBE_DEFINE3(futex, linux_sys_futex, debug_wake, "uint32_t *",
"uint32_t", "uint32_t");
LIN_SDT_PROBE_DEFINE5(futex, linux_sys_futex, debug_cmp_requeue, "uint32_t *",
"uint32_t", "uint32_t", "uint32_t *", "struct l_timespec *");
LIN_SDT_PROBE_DEFINE2(futex, linux_sys_futex, debug_cmp_requeue_value_neq,
"uint32_t", "int");
LIN_SDT_PROBE_DEFINE5(futex, linux_sys_futex, debug_wake_op, "uint32_t *",
"int", "uint32_t", "uint32_t *", "uint32_t");
LIN_SDT_PROBE_DEFINE0(futex, linux_sys_futex, unhandled_efault);
LIN_SDT_PROBE_DEFINE0(futex, linux_sys_futex, unimplemented_lock_pi);
LIN_SDT_PROBE_DEFINE0(futex, linux_sys_futex, unimplemented_unlock_pi);
LIN_SDT_PROBE_DEFINE0(futex, linux_sys_futex, unimplemented_trylock_pi);
LIN_SDT_PROBE_DEFINE0(futex, linux_sys_futex, deprecated_requeue);
LIN_SDT_PROBE_DEFINE0(futex, linux_sys_futex, unimplemented_wait_requeue_pi);
LIN_SDT_PROBE_DEFINE0(futex, linux_sys_futex, unimplemented_cmp_requeue_pi);
LIN_SDT_PROBE_DEFINE1(futex, linux_sys_futex, unknown_operation, "int");
LIN_SDT_PROBE_DEFINE1(futex, linux_sys_futex, return, "int");
LIN_SDT_PROBE_DEFINE2(futex, linux_set_robust_list, entry, "struct thread *",
"struct linux_set_robust_list_args *");
LIN_SDT_PROBE_DEFINE0(futex, linux_set_robust_list, size_error);
LIN_SDT_PROBE_DEFINE1(futex, linux_set_robust_list, return, "int");
LIN_SDT_PROBE_DEFINE2(futex, linux_get_robust_list, entry, "struct thread *",
"struct linux_get_robust_list_args *");
LIN_SDT_PROBE_DEFINE1(futex, linux_get_robust_list, copyout_error, "int");
LIN_SDT_PROBE_DEFINE1(futex, linux_get_robust_list, return, "int");
LIN_SDT_PROBE_DEFINE3(futex, handle_futex_death, entry,
"struct linux_emuldata *", "uint32_t *", "unsigned int");
LIN_SDT_PROBE_DEFINE1(futex, handle_futex_death, copyin_error, "int");
LIN_SDT_PROBE_DEFINE1(futex, handle_futex_death, return, "int");
LIN_SDT_PROBE_DEFINE3(futex, fetch_robust_entry, entry,
"struct linux_robust_list **", "struct linux_robust_list **",
"unsigned int *");
LIN_SDT_PROBE_DEFINE1(futex, fetch_robust_entry, copyin_error, "int");
LIN_SDT_PROBE_DEFINE1(futex, fetch_robust_entry, return, "int");
LIN_SDT_PROBE_DEFINE2(futex, release_futexes, entry, "struct thread *",
"struct linux_emuldata *");
LIN_SDT_PROBE_DEFINE1(futex, release_futexes, copyin_error, "int");
LIN_SDT_PROBE_DEFINE0(futex, release_futexes, return);
struct futex;
struct waiting_proc {
uint32_t wp_flags;
struct futex *wp_futex;
TAILQ_ENTRY(waiting_proc) wp_list;
};
struct futex {
struct mtx f_lck;
uint32_t *f_uaddr; /* user-supplied value, for debug */
struct umtx_key f_key;
uint32_t f_refcount;
uint32_t f_bitset;
LIST_ENTRY(futex) f_list;
TAILQ_HEAD(lf_waiting_proc, waiting_proc) f_waiting_proc;
};
#define FUTEX_LOCK(f) mtx_lock(&(f)->f_lck)
#define FUTEX_LOCKED(f) mtx_owned(&(f)->f_lck)
#define FUTEX_UNLOCK(f) mtx_unlock(&(f)->f_lck)
#define FUTEX_INIT(f) do { \
mtx_init(&(f)->f_lck, "ftlk", NULL, \
MTX_DUPOK); \
LIN_SDT_PROBE1(futex, futex, create, \
&(f)->f_lck); \
} while (0)
#define FUTEX_DESTROY(f) do { \
LIN_SDT_PROBE1(futex, futex, destroy, \
&(f)->f_lck); \
mtx_destroy(&(f)->f_lck); \
} while (0)
#define FUTEX_ASSERT_LOCKED(f) mtx_assert(&(f)->f_lck, MA_OWNED)
#define FUTEX_ASSERT_UNLOCKED(f) mtx_assert(&(f)->f_lck, MA_NOTOWNED)
#define FUTEXES_LOCK do { \
mtx_lock(&futex_mtx); \
LIN_SDT_PROBE1(locks, futex_mtx, \
locked, &futex_mtx); \
} while (0)
#define FUTEXES_UNLOCK do { \
LIN_SDT_PROBE1(locks, futex_mtx, \
unlock, &futex_mtx); \
mtx_unlock(&futex_mtx); \
} while (0)
/* flags for futex_get() */
#define FUTEX_CREATE_WP 0x1 /* create waiting_proc */
#define FUTEX_DONTCREATE 0x2 /* don't create futex if not exists */
#define FUTEX_DONTEXISTS 0x4 /* return EINVAL if futex exists */
#define FUTEX_SHARED 0x8 /* shared futex */
#define FUTEX_DONTLOCK 0x10 /* don't lock futex */
/* wp_flags */
#define FUTEX_WP_REQUEUED 0x1 /* wp requeued - wp moved from wp_list
* of futex where thread sleep to wp_list
* of another futex.
*/
#define FUTEX_WP_REMOVED 0x2 /* wp is woken up and removed from futex
* wp_list to prevent double wakeup.
*/
static void futex_put(struct futex *, struct waiting_proc *);
static int futex_get0(uint32_t *, struct futex **f, uint32_t);
static int futex_get(uint32_t *, struct waiting_proc **, struct futex **,
uint32_t);
static int futex_sleep(struct futex *, struct waiting_proc *, struct timespec *);
static int futex_wake(struct futex *, int, uint32_t);
static int futex_requeue(struct futex *, int, struct futex *, int);
static int futex_copyin_timeout(int, struct l_timespec *, int,
struct timespec *);
static int futex_wait(struct futex *, struct waiting_proc *, struct timespec *,
uint32_t);
static void futex_lock(struct futex *);
static void futex_unlock(struct futex *);
static int futex_atomic_op(struct thread *, int, uint32_t *);
static int handle_futex_death(struct linux_emuldata *, uint32_t *,
unsigned int);
static int fetch_robust_entry(struct linux_robust_list **,
struct linux_robust_list **, unsigned int *);
static int
futex_copyin_timeout(int op, struct l_timespec *luts, int clockrt,
struct timespec *ts)
{
struct l_timespec lts;
struct timespec kts;
int error;
error = copyin(luts, <s, sizeof(lts));
if (error)
return (error);
error = linux_to_native_timespec(ts, <s);
if (error)
return (error);
if (clockrt) {
nanotime(&kts);
timespecsub(ts, &kts, ts);
} else if (op == LINUX_FUTEX_WAIT_BITSET) {
nanouptime(&kts);
timespecsub(ts, &kts, ts);
}
return (error);
}
static void
futex_put(struct futex *f, struct waiting_proc *wp)
{
LIN_SDT_PROBE2(futex, futex_put, entry, f, wp);
if (wp != NULL) {
if ((wp->wp_flags & FUTEX_WP_REMOVED) == 0)
TAILQ_REMOVE(&f->f_waiting_proc, wp, wp_list);
free(wp, M_FUTEX_WP);
}
FUTEXES_LOCK;
if (--f->f_refcount == 0) {
LIST_REMOVE(f, f_list);
FUTEXES_UNLOCK;
if (FUTEX_LOCKED(f))
futex_unlock(f);
LIN_SDT_PROBE3(futex, futex_put, destroy, f->f_uaddr,
f->f_refcount, f->f_key.shared);
LINUX_CTR3(sys_futex, "futex_put destroy uaddr %p ref %d "
"shared %d", f->f_uaddr, f->f_refcount, f->f_key.shared);
umtx_key_release(&f->f_key);
FUTEX_DESTROY(f);
free(f, M_FUTEX);
LIN_SDT_PROBE0(futex, futex_put, return);
return;
}
LIN_SDT_PROBE3(futex, futex_put, unlock, f->f_uaddr, f->f_refcount,
f->f_key.shared);
LINUX_CTR3(sys_futex, "futex_put uaddr %p ref %d shared %d",
f->f_uaddr, f->f_refcount, f->f_key.shared);
if (FUTEX_LOCKED(f))
futex_unlock(f);
FUTEXES_UNLOCK;
LIN_SDT_PROBE0(futex, futex_put, return);
}
static int
futex_get0(uint32_t *uaddr, struct futex **newf, uint32_t flags)
{
struct futex *f, *tmpf;
struct umtx_key key;
int error;
LIN_SDT_PROBE3(futex, futex_get0, entry, uaddr, newf, flags);
*newf = tmpf = NULL;
error = umtx_key_get(uaddr, TYPE_FUTEX, (flags & FUTEX_SHARED) ?
AUTO_SHARE : THREAD_SHARE, &key);
if (error) {
LIN_SDT_PROBE1(futex, futex_get0, umtx_key_get_error, error);
LIN_SDT_PROBE1(futex, futex_get0, return, error);
return (error);
}
retry:
FUTEXES_LOCK;
LIST_FOREACH(f, &futex_list, f_list) {
if (umtx_key_match(&f->f_key, &key)) {
if (tmpf != NULL) {
if (FUTEX_LOCKED(tmpf))
futex_unlock(tmpf);
FUTEX_DESTROY(tmpf);
free(tmpf, M_FUTEX);
}
if (flags & FUTEX_DONTEXISTS) {
FUTEXES_UNLOCK;
umtx_key_release(&key);
LIN_SDT_PROBE1(futex, futex_get0, return,
EINVAL);
return (EINVAL);
}
/*
* Increment refcount of the found futex to
* prevent it from deallocation before FUTEX_LOCK()
*/
++f->f_refcount;
FUTEXES_UNLOCK;
umtx_key_release(&key);
if ((flags & FUTEX_DONTLOCK) == 0)
futex_lock(f);
*newf = f;
LIN_SDT_PROBE3(futex, futex_get0, shared, uaddr,
f->f_refcount, f->f_key.shared);
LINUX_CTR3(sys_futex, "futex_get uaddr %p ref %d shared %d",
uaddr, f->f_refcount, f->f_key.shared);
LIN_SDT_PROBE1(futex, futex_get0, return, 0);
return (0);
}
}
if (flags & FUTEX_DONTCREATE) {
FUTEXES_UNLOCK;
umtx_key_release(&key);
LIN_SDT_PROBE1(futex, futex_get0, null, uaddr);
LINUX_CTR1(sys_futex, "futex_get uaddr %p null", uaddr);
LIN_SDT_PROBE1(futex, futex_get0, return, 0);
return (0);
}
if (tmpf == NULL) {
FUTEXES_UNLOCK;
tmpf = malloc(sizeof(*tmpf), M_FUTEX, M_WAITOK | M_ZERO);
tmpf->f_uaddr = uaddr;
tmpf->f_key = key;
tmpf->f_refcount = 1;
tmpf->f_bitset = FUTEX_BITSET_MATCH_ANY;
FUTEX_INIT(tmpf);
TAILQ_INIT(&tmpf->f_waiting_proc);
/*
* Lock the new futex before an insert into the futex_list
* to prevent futex usage by other.
*/
if ((flags & FUTEX_DONTLOCK) == 0)
futex_lock(tmpf);
goto retry;
}
LIST_INSERT_HEAD(&futex_list, tmpf, f_list);
FUTEXES_UNLOCK;
LIN_SDT_PROBE3(futex, futex_get0, new, uaddr, tmpf->f_refcount,
tmpf->f_key.shared);
LINUX_CTR3(sys_futex, "futex_get uaddr %p ref %d shared %d new",
uaddr, tmpf->f_refcount, tmpf->f_key.shared);
*newf = tmpf;
LIN_SDT_PROBE1(futex, futex_get0, return, 0);
return (0);
}
static int
futex_get(uint32_t *uaddr, struct waiting_proc **wp, struct futex **f,
uint32_t flags)
{
int error;
LIN_SDT_PROBE3(futex, futex_get, entry, uaddr, wp, f);
if (flags & FUTEX_CREATE_WP) {
*wp = malloc(sizeof(struct waiting_proc), M_FUTEX_WP, M_WAITOK);
(*wp)->wp_flags = 0;
}
error = futex_get0(uaddr, f, flags);
if (error) {
LIN_SDT_PROBE0(futex, futex_get, error);
if (flags & FUTEX_CREATE_WP)
free(*wp, M_FUTEX_WP);
LIN_SDT_PROBE1(futex, futex_get, return, error);
return (error);
}
if (flags & FUTEX_CREATE_WP) {
TAILQ_INSERT_HEAD(&(*f)->f_waiting_proc, *wp, wp_list);
(*wp)->wp_futex = *f;
}
LIN_SDT_PROBE1(futex, futex_get, return, error);
return (error);
}
static inline void
futex_lock(struct futex *f)
{
LINUX_CTR3(sys_futex, "futex_lock uaddr %p ref %d shared %d",
f->f_uaddr, f->f_refcount, f->f_key.shared);
FUTEX_ASSERT_UNLOCKED(f);
FUTEX_LOCK(f);
}
static inline void
futex_unlock(struct futex *f)
{
LINUX_CTR3(sys_futex, "futex_unlock uaddr %p ref %d shared %d",
f->f_uaddr, f->f_refcount, f->f_key.shared);
FUTEX_ASSERT_LOCKED(f);
FUTEX_UNLOCK(f);
}
static int
futex_sleep(struct futex *f, struct waiting_proc *wp, struct timespec *ts)
{
struct timespec uts;
sbintime_t sbt, prec, tmp;
time_t over;
int error;
FUTEX_ASSERT_LOCKED(f);
if (ts != NULL) {
uts = *ts;
if (uts.tv_sec > INT32_MAX / 2) {
over = uts.tv_sec - INT32_MAX / 2;
uts.tv_sec -= over;
}
tmp = tstosbt(uts);
if (TIMESEL(&sbt, tmp))
sbt += tc_tick_sbt;
sbt += tmp;
prec = tmp;
prec >>= tc_precexp;
} else {
sbt = 0;
prec = 0;
}
LIN_SDT_PROBE3(futex, futex_sleep, entry, f, wp, sbt);
LINUX_CTR4(sys_futex, "futex_sleep enter uaddr %p wp %p timo %ld ref %d",
f->f_uaddr, wp, sbt, f->f_refcount);
error = msleep_sbt(wp, &f->f_lck, PCATCH, "futex", sbt, prec, C_ABSOLUTE);
if (wp->wp_flags & FUTEX_WP_REQUEUED) {
KASSERT(f != wp->wp_futex, ("futex != wp_futex"));
if (error) {
LIN_SDT_PROBE5(futex, futex_sleep, requeue_error, error,
f->f_uaddr, wp, wp->wp_futex->f_uaddr,
wp->wp_futex->f_refcount);
}
LINUX_CTR5(sys_futex, "futex_sleep out error %d uaddr %p wp"
" %p requeued uaddr %p ref %d",
error, f->f_uaddr, wp, wp->wp_futex->f_uaddr,
wp->wp_futex->f_refcount);
futex_put(f, NULL);
f = wp->wp_futex;
futex_lock(f);
} else {
if (error) {
LIN_SDT_PROBE3(futex, futex_sleep, sleep_error, error,
f->f_uaddr, wp);
}
LINUX_CTR3(sys_futex, "futex_sleep out error %d uaddr %p wp %p",
error, f->f_uaddr, wp);
}
futex_put(f, wp);
LIN_SDT_PROBE1(futex, futex_sleep, return, error);
return (error);
}
static int
futex_wake(struct futex *f, int n, uint32_t bitset)
{
struct waiting_proc *wp, *wpt;
int count = 0;
LIN_SDT_PROBE3(futex, futex_wake, entry, f, n, bitset);
if (bitset == 0) {
LIN_SDT_PROBE1(futex, futex_wake, return, EINVAL);
return (EINVAL);
}
FUTEX_ASSERT_LOCKED(f);
TAILQ_FOREACH_SAFE(wp, &f->f_waiting_proc, wp_list, wpt) {
LIN_SDT_PROBE3(futex, futex_wake, iterate, f->f_uaddr, wp,
f->f_refcount);
LINUX_CTR3(sys_futex, "futex_wake uaddr %p wp %p ref %d",
f->f_uaddr, wp, f->f_refcount);
/*
* Unless we find a matching bit in
* the bitset, continue searching.
*/
if (!(wp->wp_futex->f_bitset & bitset))
continue;
wp->wp_flags |= FUTEX_WP_REMOVED;
TAILQ_REMOVE(&f->f_waiting_proc, wp, wp_list);
LIN_SDT_PROBE1(futex, futex_wake, wakeup, wp);
wakeup_one(wp);
if (++count == n)
break;
}
LIN_SDT_PROBE1(futex, futex_wake, return, count);
return (count);
}
static int
futex_requeue(struct futex *f, int nrwake, struct futex *f2,
int nrrequeue)
{
struct waiting_proc *wp, *wpt;
int count = 0;
LIN_SDT_PROBE4(futex, futex_requeue, entry, f, nrwake, f2, nrrequeue);
FUTEX_ASSERT_LOCKED(f);
FUTEX_ASSERT_LOCKED(f2);
TAILQ_FOREACH_SAFE(wp, &f->f_waiting_proc, wp_list, wpt) {
if (++count <= nrwake) {
LINUX_CTR2(sys_futex, "futex_req_wake uaddr %p wp %p",
f->f_uaddr, wp);
wp->wp_flags |= FUTEX_WP_REMOVED;
TAILQ_REMOVE(&f->f_waiting_proc, wp, wp_list);
LIN_SDT_PROBE1(futex, futex_requeue, wakeup, wp);
wakeup_one(wp);
} else {
LIN_SDT_PROBE3(futex, futex_requeue, requeue,
f->f_uaddr, wp, f2->f_uaddr);
LINUX_CTR3(sys_futex, "futex_requeue uaddr %p wp %p to %p",
f->f_uaddr, wp, f2->f_uaddr);
wp->wp_flags |= FUTEX_WP_REQUEUED;
/* Move wp to wp_list of f2 futex */
TAILQ_REMOVE(&f->f_waiting_proc, wp, wp_list);
TAILQ_INSERT_HEAD(&f2->f_waiting_proc, wp, wp_list);
/*
* Thread which sleeps on wp after waking should
* acquire f2 lock, so increment refcount of f2 to
* prevent it from premature deallocation.
*/
wp->wp_futex = f2;
FUTEXES_LOCK;
++f2->f_refcount;
FUTEXES_UNLOCK;
if (count - nrwake >= nrrequeue)
break;
}
}
LIN_SDT_PROBE1(futex, futex_requeue, return, count);
return (count);
}
static int
futex_wait(struct futex *f, struct waiting_proc *wp, struct timespec *ts,
uint32_t bitset)
{
int error;
LIN_SDT_PROBE4(futex, futex_wait, entry, f, wp, ts, bitset);
if (bitset == 0) {
LIN_SDT_PROBE1(futex, futex_wait, return, EINVAL);
futex_put(f, wp);
return (EINVAL);
}
f->f_bitset = bitset;
error = futex_sleep(f, wp, ts);
if (error)
LIN_SDT_PROBE1(futex, futex_wait, sleep_error, error);
if (error == EWOULDBLOCK)
error = ETIMEDOUT;
LIN_SDT_PROBE1(futex, futex_wait, return, error);
return (error);
}
static int
futex_atomic_op(struct thread *td, int encoded_op, uint32_t *uaddr)
{
int op = (encoded_op >> 28) & 7;
int cmp = (encoded_op >> 24) & 15;
int oparg = (encoded_op << 8) >> 20;
int cmparg = (encoded_op << 20) >> 20;
int oldval = 0, ret;
LIN_SDT_PROBE3(futex, futex_atomic_op, entry, td, encoded_op, uaddr);
if (encoded_op & (FUTEX_OP_OPARG_SHIFT << 28))
oparg = 1 << oparg;
LIN_SDT_PROBE4(futex, futex_atomic_op, decoded_op, op, cmp, oparg,
cmparg);
/* XXX: Linux verifies access here and returns EFAULT */
LIN_SDT_PROBE0(futex, futex_atomic_op, missing_access_check);
switch (op) {
case FUTEX_OP_SET:
ret = futex_xchgl(oparg, uaddr, &oldval);
break;
case FUTEX_OP_ADD:
ret = futex_addl(oparg, uaddr, &oldval);
break;
case FUTEX_OP_OR:
ret = futex_orl(oparg, uaddr, &oldval);
break;
case FUTEX_OP_ANDN:
ret = futex_andl(~oparg, uaddr, &oldval);
break;
case FUTEX_OP_XOR:
ret = futex_xorl(oparg, uaddr, &oldval);
break;
default:
LIN_SDT_PROBE1(futex, futex_atomic_op, unimplemented_op, op);
ret = -ENOSYS;
break;
}
if (ret) {
LIN_SDT_PROBE1(futex, futex_atomic_op, return, ret);
return (ret);
}
switch (cmp) {
case FUTEX_OP_CMP_EQ:
ret = (oldval == cmparg);
break;
case FUTEX_OP_CMP_NE:
ret = (oldval != cmparg);
break;
case FUTEX_OP_CMP_LT:
ret = (oldval < cmparg);
break;
case FUTEX_OP_CMP_GE:
ret = (oldval >= cmparg);
break;
case FUTEX_OP_CMP_LE:
ret = (oldval <= cmparg);
break;
case FUTEX_OP_CMP_GT:
ret = (oldval > cmparg);
break;
default:
LIN_SDT_PROBE1(futex, futex_atomic_op, unimplemented_cmp, cmp);
ret = -ENOSYS;
}
LIN_SDT_PROBE1(futex, futex_atomic_op, return, ret);
return (ret);
}
int
linux_sys_futex(struct thread *td, struct linux_sys_futex_args *args)
{
int clockrt, nrwake, nrrequeue, op_ret, ret;
struct linux_pemuldata *pem;
struct waiting_proc *wp;
struct futex *f, *f2;
struct timespec uts, *ts;
int error, save;
uint32_t flags, val;
LIN_SDT_PROBE2(futex, linux_sys_futex, entry, td, args);
if (args->op & LINUX_FUTEX_PRIVATE_FLAG) {
flags = 0;
args->op &= ~LINUX_FUTEX_PRIVATE_FLAG;
} else
flags = FUTEX_SHARED;
/*
* Currently support for switching between CLOCK_MONOTONIC and
* CLOCK_REALTIME is not present. However Linux forbids the use of
* FUTEX_CLOCK_REALTIME with any op except FUTEX_WAIT_BITSET and
* FUTEX_WAIT_REQUEUE_PI.
*/
clockrt = args->op & LINUX_FUTEX_CLOCK_REALTIME;
args->op = args->op & ~LINUX_FUTEX_CLOCK_REALTIME;
if (clockrt && args->op != LINUX_FUTEX_WAIT_BITSET &&
args->op != LINUX_FUTEX_WAIT_REQUEUE_PI) {
LIN_SDT_PROBE0(futex, linux_sys_futex,
unimplemented_clockswitch);
LIN_SDT_PROBE1(futex, linux_sys_futex, return, ENOSYS);
return (ENOSYS);
}
error = 0;
f = f2 = NULL;
switch (args->op) {
case LINUX_FUTEX_WAIT:
args->val3 = FUTEX_BITSET_MATCH_ANY;
/* FALLTHROUGH */
case LINUX_FUTEX_WAIT_BITSET:
LIN_SDT_PROBE3(futex, linux_sys_futex, debug_wait, args->uaddr,
args->val, args->val3);
LINUX_CTR3(sys_futex, "WAIT uaddr %p val 0x%x bitset 0x%x",
args->uaddr, args->val, args->val3);
if (args->timeout != NULL) {
error = futex_copyin_timeout(args->op, args->timeout,
clockrt, &uts);
if (error) {
LIN_SDT_PROBE1(futex, linux_sys_futex, copyin_error,
error);
LIN_SDT_PROBE1(futex, linux_sys_futex, return, error);
return (error);
}
ts = &uts;
} else
ts = NULL;
retry0:
error = futex_get(args->uaddr, &wp, &f,
flags | FUTEX_CREATE_WP);
if (error) {
LIN_SDT_PROBE1(futex, linux_sys_futex, return, error);
return (error);
}
error = copyin_nofault(args->uaddr, &val, sizeof(val));
if (error) {
futex_put(f, wp);
error = copyin(args->uaddr, &val, sizeof(val));
if (error == 0)
goto retry0;
LIN_SDT_PROBE1(futex, linux_sys_futex, copyin_error,
error);
LINUX_CTR1(sys_futex, "WAIT copyin failed %d",
error);
LIN_SDT_PROBE1(futex, linux_sys_futex, return, error);
return (error);
}
if (val != args->val) {
LIN_SDT_PROBE4(futex, linux_sys_futex,
debug_wait_value_neq, args->uaddr, args->val, val,
args->val3);
LINUX_CTR3(sys_futex,
"WAIT uaddr %p val 0x%x != uval 0x%x",
args->uaddr, args->val, val);
futex_put(f, wp);
LIN_SDT_PROBE1(futex, linux_sys_futex, return,
EWOULDBLOCK);
return (EWOULDBLOCK);
}
error = futex_wait(f, wp, ts, args->val3);
break;
case LINUX_FUTEX_WAKE:
args->val3 = FUTEX_BITSET_MATCH_ANY;
/* FALLTHROUGH */
case LINUX_FUTEX_WAKE_BITSET:
LIN_SDT_PROBE3(futex, linux_sys_futex, debug_wake, args->uaddr,
args->val, args->val3);
LINUX_CTR3(sys_futex, "WAKE uaddr %p nrwake 0x%x bitset 0x%x",
args->uaddr, args->val, args->val3);
error = futex_get(args->uaddr, NULL, &f,
flags | FUTEX_DONTCREATE);
if (error) {
LIN_SDT_PROBE1(futex, linux_sys_futex, return, error);
return (error);
}
if (f == NULL) {
td->td_retval[0] = 0;
LIN_SDT_PROBE1(futex, linux_sys_futex, return, error);
return (error);
}
td->td_retval[0] = futex_wake(f, args->val, args->val3);
futex_put(f, NULL);
break;
case LINUX_FUTEX_CMP_REQUEUE:
LIN_SDT_PROBE5(futex, linux_sys_futex, debug_cmp_requeue,
args->uaddr, args->val, args->val3, args->uaddr2,
args->timeout);
LINUX_CTR5(sys_futex, "CMP_REQUEUE uaddr %p "
"nrwake 0x%x uval 0x%x uaddr2 %p nrequeue 0x%x",
args->uaddr, args->val, args->val3, args->uaddr2,
args->timeout);
/*
* Linux allows this, we would not, it is an incorrect
* usage of declared ABI, so return EINVAL.
*/
if (args->uaddr == args->uaddr2) {
LIN_SDT_PROBE0(futex, linux_sys_futex,
invalid_cmp_requeue_use);
LIN_SDT_PROBE1(futex, linux_sys_futex, return, EINVAL);
return (EINVAL);
}
nrrequeue = (int)(unsigned long)args->timeout;
nrwake = args->val;
/*
* Sanity check to prevent signed integer overflow,
* see Linux CVE-2018-6927
*/
if (nrwake < 0 || nrrequeue < 0)
return (EINVAL);
retry1:
error = futex_get(args->uaddr, NULL, &f, flags | FUTEX_DONTLOCK);
if (error) {
LIN_SDT_PROBE1(futex, linux_sys_futex, return, error);
return (error);
}
/*
* To avoid deadlocks return EINVAL if second futex
* exists at this time.
*
* Glibc fall back to FUTEX_WAKE in case of any error
* returned by FUTEX_CMP_REQUEUE.
*/
error = futex_get(args->uaddr2, NULL, &f2,
flags | FUTEX_DONTEXISTS | FUTEX_DONTLOCK);
if (error) {
futex_put(f, NULL);
LIN_SDT_PROBE1(futex, linux_sys_futex, return, error);
return (error);
}
futex_lock(f);
futex_lock(f2);
error = copyin_nofault(args->uaddr, &val, sizeof(val));
if (error) {
futex_put(f2, NULL);
futex_put(f, NULL);
error = copyin(args->uaddr, &val, sizeof(val));
if (error == 0)
goto retry1;
LIN_SDT_PROBE1(futex, linux_sys_futex, copyin_error,
error);
LINUX_CTR1(sys_futex, "CMP_REQUEUE copyin failed %d",
error);
LIN_SDT_PROBE1(futex, linux_sys_futex, return, error);
return (error);
}
if (val != args->val3) {
LIN_SDT_PROBE2(futex, linux_sys_futex,
debug_cmp_requeue_value_neq, args->val, val);
LINUX_CTR2(sys_futex, "CMP_REQUEUE val 0x%x != uval 0x%x",
args->val, val);
futex_put(f2, NULL);
futex_put(f, NULL);
LIN_SDT_PROBE1(futex, linux_sys_futex, return, EAGAIN);
return (EAGAIN);
}
td->td_retval[0] = futex_requeue(f, nrwake, f2, nrrequeue);
futex_put(f2, NULL);
futex_put(f, NULL);
break;
case LINUX_FUTEX_WAKE_OP:
LIN_SDT_PROBE5(futex, linux_sys_futex, debug_wake_op,
args->uaddr, args->op, args->val, args->uaddr2, args->val3);
LINUX_CTR5(sys_futex, "WAKE_OP "
"uaddr %p nrwake 0x%x uaddr2 %p op 0x%x nrwake2 0x%x",
args->uaddr, args->val, args->uaddr2, args->val3,
args->timeout);
if (args->uaddr == args->uaddr2) {
LIN_SDT_PROBE1(futex, linux_sys_futex, return, EINVAL);
return (EINVAL);
}
retry2:
error = futex_get(args->uaddr, NULL, &f, flags | FUTEX_DONTLOCK);
if (error) {
LIN_SDT_PROBE1(futex, linux_sys_futex, return, error);
return (error);
}
error = futex_get(args->uaddr2, NULL, &f2, flags | FUTEX_DONTLOCK);
if (error) {
futex_put(f, NULL);
LIN_SDT_PROBE1(futex, linux_sys_futex, return, error);
return (error);
}
futex_lock(f);
futex_lock(f2);
/*
* This function returns positive number as results and
* negative as errors
*/
save = vm_fault_disable_pagefaults();
op_ret = futex_atomic_op(td, args->val3, args->uaddr2);
vm_fault_enable_pagefaults(save);
LINUX_CTR2(sys_futex, "WAKE_OP atomic_op uaddr %p ret 0x%x",
args->uaddr, op_ret);
if (op_ret < 0) {
if (f2 != NULL)
futex_put(f2, NULL);
futex_put(f, NULL);
error = copyin(args->uaddr2, &val, sizeof(val));
if (error == 0)
goto retry2;
LIN_SDT_PROBE1(futex, linux_sys_futex, return, error);
return (error);
}
ret = futex_wake(f, args->val, args->val3);