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Provide protection against starvation of the ll/sc loops when accessing userpace.

Browse Source 
Casueword(9) on ll/sc architectures must be prepared for userspace
constantly modifying the same cache line as containing the CAS word,
and not loop infinitely.  Otherwise, rogue userspace livelocks the
kernel.

To fix the issue, change casueword(9) interface to return new value 1
indicating that either comparision or store failed, instead of relying
on the oldval == *oldvalp comparison.  The primitive no longer retries
the operation if it failed spuriously.  Modify callers of
casueword(9), all in kern_umtx.c, to handle retries, and react to
stops and requests to terminate between retries.

On x86, despite cmpxchg should not return spurious failures, we can
take advantage of the new interface and just return PSL.ZF.

Reviewed by:	andrew (arm64, previous version), markj
Tested by:	pho
Reported by:	https://xenbits.xen.org/xsa/advisory-295.txt
Sponsored by:	The FreeBSD Foundation
MFC after:	2 weeks
Differential revision:	https://reviews.freebsd.org/D20772
This commit is contained in:
Konstantin Belousov 2019-07-12 18:43:24 +00:00
parent e1be41acf7
commit 30b3018d48
11 changed files with 401 additions and 230 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
share/man/man9/casuword.9
View File

@ -1,4 +1,4 @@
.\" Copyright (c) 2014 The FreeBSD Foundation
.\" Copyright (c) 2014, 2019 The FreeBSD Foundation
.\" All rights reserved.
.\"
.\" Part of this documentation was written by
@ -28,7 +28,7 @@
.\"
.\" $FreeBSD$
.\"
.Dd October 21, 2014
.Dd April 19, 2019
.Dt CASU 9
.Os
.Sh NAME
@ -106,7 +106,9 @@ The
.Fn casueword
and
.Fn casueword32
functions return 0 on success and -1 on failure.
functions return 0 on success, -1 on failure to access memory,
and 1 when comparison or store failed.
The store can fail on load-linked/store-conditional architectures.
.Sh SEE ALSO
.Xr atomic 9 ,
.Xr fetch 9 ,

8
sys/amd64/amd64/support.S
View File

@ -811,6 +811,7 @@ ENTRY(casueword32_nosmap)
lock
#endif
cmpxchgl %ecx,(%rdi) /* new = %ecx */
setne %cl
/*
* The old value is in %eax. If the store succeeded it will be the
@ -828,6 +829,7 @@ ENTRY(casueword32_nosmap)
*/
movl %esi,(%rdx) /* oldp = %rdx */
POP_FRAME_POINTER
movzbl %cl, %eax
ret
END(casueword32_nosmap)
@ -847,6 +849,7 @@ ENTRY(casueword32_smap)
#endif
cmpxchgl %ecx,(%rdi) /* new = %ecx */
clac
setne %cl
/*
* The old value is in %eax. If the store succeeded it will be the
@ -864,6 +867,7 @@ ENTRY(casueword32_smap)
*/
movl %esi,(%rdx) /* oldp = %rdx */
POP_FRAME_POINTER
movzbl %cl, %eax
ret
END(casueword32_smap)
@ -886,6 +890,7 @@ ENTRY(casueword_nosmap)
lock
#endif
cmpxchgq %rcx,(%rdi) /* new = %rcx */
setne %cl
/*
* The old value is in %rax. If the store succeeded it will be the
@ -897,6 +902,7 @@ ENTRY(casueword_nosmap)
movq %rax,PCB_ONFAULT(%r8)
movq %rsi,(%rdx)
POP_FRAME_POINTER
movzbl %cl, %eax
ret
END(casueword_nosmap)
@ -916,6 +922,7 @@ ENTRY(casueword_smap)
#endif
cmpxchgq %rcx,(%rdi) /* new = %rcx */
clac
setne %cl
/*
* The old value is in %rax. If the store succeeded it will be the
@ -927,6 +934,7 @@ ENTRY(casueword_smap)
movq %rax,PCB_ONFAULT(%r8)
movq %rsi,(%rdx)
POP_FRAME_POINTER
movzbl %cl, %eax
ret
END(casueword_smap)

11
sys/arm/arm/fusu.S
View File

@ -63,7 +63,7 @@ EENTRY_NP(casueword32)
ldr r4, =(VM_MAXUSER_ADDRESS-3)
cmp r0, r4
mvncs r0, #0
bcs 2f
bcs 1f
GET_PCB(r6)
ldr r6, [r6]
@ -78,12 +78,10 @@ EENTRY_NP(casueword32)
str r4, [r6, #PCB_ONFAULT]
#if __ARM_ARCH >= 6
1:
mov r5, #1
ldrex r4, [r0]
cmp r4, r1
strexeq r5, r3, [r0]
cmpeq r5, #1
beq 1b
#else
ldrt r4, [r0]
cmp r4, r1
@ -92,7 +90,10 @@ EENTRY_NP(casueword32)
str r4, [r2]
mov r0, #0
str r0, [r6, #PCB_ONFAULT]
2:
#if __ARM_ARCH >= 6
mov r0, r5
#endif
1:
ldmfd sp!, {r4, r5, r6}
RET
EEND(casueword32)

12
sys/arm64/arm64/support.S
View File

@ -57,17 +57,17 @@ ENTRY(casueword32)
cmp x0, x4
b.cs fsu_fault_nopcb
adr x6, fsu_fault /* Load the fault handler */
mov w5, #1
SET_FAULT_HANDLER(x6, x4) /* And set it */
ENTER_USER_ACCESS(w6, x4)
1: ldxr w4, [x0] /* Load-exclusive the data */
cmp w4, w1 /* Compare */
b.ne 2f /* Not equal, exit */
stxr w5, w3, [x0] /* Store the new data */
cbnz w5, 1b /* Retry on failure */
2: EXIT_USER_ACCESS(w6)
SET_FAULT_HANDLER(xzr, x5) /* Reset the fault handler */
SET_FAULT_HANDLER(xzr, x6) /* Reset the fault handler */
str w4, [x2] /* Store the read data */
mov x0, #0 /* Success */
mov w0, w5 /* Result same as store status */
ret /* Return */
END(casueword32)
@ -79,17 +79,17 @@ ENTRY(casueword)
cmp x0, x4
b.cs fsu_fault_nopcb
adr x6, fsu_fault /* Load the fault handler */
mov w5, #1
SET_FAULT_HANDLER(x6, x4) /* And set it */
ENTER_USER_ACCESS(w6, x4)
1: ldxr x4, [x0] /* Load-exclusive the data */
cmp x4, x1 /* Compare */
b.ne 2f /* Not equal, exit */
stxr w5, x3, [x0] /* Store the new data */
cbnz w5, 1b /* Retry on failure */
2: EXIT_USER_ACCESS(w6)
SET_FAULT_HANDLER(xzr, x5) /* Reset the fault handler */
SET_FAULT_HANDLER(xzr, x6) /* Reset the fault handler */
str x4, [x2] /* Store the read data */
mov x0, #0 /* Success */
mov w0, w5 /* Result same as store status */
ret /* Return */
END(casueword)

8
sys/i386/i386/copyout.c
View File

@ -428,6 +428,7 @@ suword32(volatile void *base, int32_t word)
struct casueword_arg0 {
uint32_t oldval;
uint32_t newval;
int res;
};
static void
@ -436,7 +437,8 @@ casueword_slow0(vm_offset_t kva, void *arg)
struct casueword_arg0 *ca;
ca = arg;
atomic_fcmpset_int((u_int *)kva, &ca->oldval, ca->newval);
ca->res = 1 - atomic_fcmpset_int((u_int *)kva, &ca->oldval,
ca->newval);
}
int
@ -452,7 +454,7 @@ casueword32(volatile uint32_t *base, uint32_t oldval, uint32_t *oldvalp,
casueword_slow0, &ca);
if (res == 0) {
*oldvalp = ca.oldval;
return (0);
return (ca.res);
}
return (-1);
}
@ -469,7 +471,7 @@ casueword(volatile u_long *base, u_long oldval, u_long *oldvalp, u_long newval)
casueword_slow0, &ca);
if (res == 0) {
*oldvalp = ca.oldval;
return (0);
return (ca.res);
}
return (-1);
}

448
sys/kern/kern_umtx.c
View File

@ -690,8 +690,26 @@ umtxq_count_pi(struct umtx_key *key, struct umtx_q **first)
return (0);
}
/*
* Check for possible stops and suspensions while executing a umtx
* locking operation.
*
* The sleep argument controls whether the function can handle a stop
* request itself or it should return ERESTART and the request is
* proceed at the kernel/user boundary in ast.
*
* Typically, when retrying due to casueword(9) failure (rv == 1), we
* should handle the stop requests there, with exception of cases when
* the thread busied the umtx key, or when functions return
* immediately if umtxq_check_susp() returned non-zero. On the other
* hand, retrying the whole lock operation, we better not stop there
* but delegate the handling to ast.
*
* If the request is for thread termination P_SINGLE_EXIT, we cannot
* handle it at all, and simply return EINTR.
*/
static int
umtxq_check_susp(struct thread *td)
umtxq_check_susp(struct thread *td, bool sleep)
{
struct proc *p;
int error;
@ -710,7 +728,7 @@ umtxq_check_susp(struct thread *td)
if (p->p_flag & P_SINGLE_EXIT)
error = EINTR;
else
error = ERESTART;
error = sleep ? thread_suspend_check(0) : ERESTART;
}
PROC_UNLOCK(p);
return (error);
@ -1049,9 +1067,12 @@ do_lock_normal(struct thread *td, struct umutex *m, uint32_t flags,
id | UMUTEX_CONTESTED);
if (rv == -1)
return (EFAULT);
if (owner == UMUTEX_RB_OWNERDEAD)
if (rv == 0) {
MPASS(owner == UMUTEX_RB_OWNERDEAD);
return (EOWNERDEAD); /* success */
rv = umtxq_check_susp(td);
}
MPASS(rv == 1);
rv = umtxq_check_susp(td, false);
if (rv != 0)
return (rv);
continue;
@ -1070,13 +1091,16 @@ do_lock_normal(struct thread *td, struct umutex *m, uint32_t flags,
return (EFAULT);
/* The acquire succeeded. */
if (owner == UMUTEX_UNOWNED)
if (rv == 0) {
MPASS(owner == UMUTEX_UNOWNED);
return (0);
}
/*
* If no one owns it but it is contested try
* to acquire it.
*/
MPASS(rv == 1);
if (owner == UMUTEX_CONTESTED) {
rv = casueword32(&m->m_owner,
UMUTEX_CONTESTED, &owner,
@ -1084,13 +1108,15 @@ do_lock_normal(struct thread *td, struct umutex *m, uint32_t flags,
/* The address was invalid. */
if (rv == -1)
return (EFAULT);
if (owner == UMUTEX_CONTESTED)
if (rv == 0) {
MPASS(owner == UMUTEX_CONTESTED);
return (0);
rv = umtxq_check_susp(td);
if (rv != 0)
return (rv);
}
if (rv == 1) {
rv = umtxq_check_susp(td, false);
if (rv != 0)
return (rv);
}
/*
* If this failed the lock has
@ -1098,6 +1124,11 @@ do_lock_normal(struct thread *td, struct umutex *m, uint32_t flags,
*/
continue;
}
/* rv == 1 but not contested, likely store failure */
rv = umtxq_check_susp(td, false);
if (rv != 0)
return (rv);
}
if (mode == _UMUTEX_TRY)
@ -1128,14 +1159,21 @@ do_lock_normal(struct thread *td, struct umutex *m, uint32_t flags,
rv = casueword32(&m->m_owner, owner, &old,
owner | UMUTEX_CONTESTED);
/* The address was invalid. */
if (rv == -1) {
/* The address was invalid or casueword failed to store. */
if (rv == -1 || rv == 1) {
umtxq_lock(&uq->uq_key);
umtxq_remove(uq);
umtxq_unbusy(&uq->uq_key);
umtxq_unlock(&uq->uq_key);
umtx_key_release(&uq->uq_key);
return (EFAULT);
if (rv == -1)
return (EFAULT);
if (rv == 1) {
rv = umtxq_check_susp(td, false);
if (rv != 0)
return (rv);
}
continue;
}
/*
@ -1145,15 +1183,15 @@ do_lock_normal(struct thread *td, struct umutex *m, uint32_t flags,
*/
umtxq_lock(&uq->uq_key);
umtxq_unbusy(&uq->uq_key);
if (old == owner)
error = umtxq_sleep(uq, "umtxn", timeout == NULL ?
NULL : &timo);
MPASS(old == owner);
error = umtxq_sleep(uq, "umtxn", timeout == NULL ?
NULL : &timo);
umtxq_remove(uq);
umtxq_unlock(&uq->uq_key);
umtx_key_release(&uq->uq_key);
if (error == 0)
error = umtxq_check_susp(td);
error = umtxq_check_susp(td, false);
}
return (0);
@ -1170,6 +1208,8 @@ do_unlock_normal(struct thread *td, struct umutex *m, uint32_t flags, bool rb)
int error, count;
id = td->td_tid;
again:
/*
* Make sure we own this mtx.
*/
@ -1185,9 +1225,14 @@ do_unlock_normal(struct thread *td, struct umutex *m, uint32_t flags, bool rb)
error = casueword32(&m->m_owner, owner, &old, newlock);
if (error == -1)
return (EFAULT);
if (old == owner)
return (0);
owner = old;
if (error == 1) {
error = umtxq_check_susp(td, false);
if (error != 0)
return (error);
goto again;
}
MPASS(old == owner);
return (0);
}
/* We should only ever be in here for contested locks */
@ -1215,8 +1260,14 @@ do_unlock_normal(struct thread *td, struct umutex *m, uint32_t flags, bool rb)
umtx_key_release(&key);
if (error == -1)
return (EFAULT);
if (old != owner)
return (EINVAL);
if (error == 1) {
if (old != owner)
return (EINVAL);
error = umtxq_check_susp(td, false);
if (error != 0)
return (error);
goto again;
}
return (0);
}
@ -1233,6 +1284,7 @@ do_wake_umutex(struct thread *td, struct umutex *m)
int error;
int count;
again:
error = fueword32(&m->m_owner, &owner);
if (error == -1)
return (EFAULT);
@ -1259,14 +1311,27 @@ do_wake_umutex(struct thread *td, struct umutex *m)
owner != UMUTEX_RB_NOTRECOV) {
error = casueword32(&m->m_owner, UMUTEX_CONTESTED, &owner,
UMUTEX_UNOWNED);
if (error == -1)
if (error == -1) {
error = EFAULT;
} else if (error == 1) {
umtxq_lock(&key);
umtxq_unbusy(&key);
umtxq_unlock(&key);
umtx_key_release(&key);
error = umtxq_check_susp(td, false);
if (error != 0)
return (error);
goto again;
}
}
umtxq_lock(&key);
if (error == 0 && count != 0 && ((owner & ~UMUTEX_CONTESTED) == 0 ||
owner == UMUTEX_RB_OWNERDEAD || owner == UMUTEX_RB_NOTRECOV))
if (error == 0 && count != 0) {
MPASS((owner & ~UMUTEX_CONTESTED) == 0 ||
owner == UMUTEX_RB_OWNERDEAD ||
owner == UMUTEX_RB_NOTRECOV);
umtxq_signal(&key, 1);
}
umtxq_unbusy(&key);
umtxq_unlock(&key);
umtx_key_release(&key);
@ -1314,49 +1379,32 @@ do_wake2_umutex(struct thread *td, struct umutex *m, uint32_t flags)
umtxq_busy(&key);
count = umtxq_count(&key);
umtxq_unlock(&key);
error = fueword32(&m->m_owner, &owner);
if (error == -1)
error = EFAULT;
/*
* Only repair contention bit if there is a waiter, this means the mutex
* is still being referenced by userland code, otherwise don't update
* any memory.
* Only repair contention bit if there is a waiter, this means
* the mutex is still being referenced by userland code,
* otherwise don't update any memory.
*/
if (count > 1) {
error = fueword32(&m->m_owner, &owner);
if (error == -1)
while (error == 0 && (owner & UMUTEX_CONTESTED) == 0 &&
(count > 1 || (count == 1 && (owner & ~UMUTEX_CONTESTED) != 0))) {
error = casueword32(&m->m_owner, owner, &old,
owner | UMUTEX_CONTESTED);
if (error == -1) {
error = EFAULT;
while (error == 0 && (owner & UMUTEX_CONTESTED) == 0) {
error = casueword32(&m->m_owner, owner, &old,
owner | UMUTEX_CONTESTED);
if (error == -1) {
error = EFAULT;
break;
}
if (old == owner)
break;
owner = old;
error = umtxq_check_susp(td);
if (error != 0)
break;
break;
}
} else if (count == 1) {
error = fueword32(&m->m_owner, &owner);
if (error == -1)
error = EFAULT;
while (error == 0 && (owner & ~UMUTEX_CONTESTED) != 0 &&
(owner & UMUTEX_CONTESTED) == 0) {
error = casueword32(&m->m_owner, owner, &old,
owner | UMUTEX_CONTESTED);
if (error == -1) {
error = EFAULT;
break;
}
if (old == owner)
break;
owner = old;
error = umtxq_check_susp(td);
if (error != 0)
break;
if (error == 0) {
MPASS(old == owner);
break;
}
owner = old;
error = umtxq_check_susp(td, false);
}
umtxq_lock(&key);
if (error == EFAULT) {
umtxq_signal(&key, INT_MAX);
@ -1842,9 +1890,9 @@ do_lock_pi(struct thread *td, struct umutex *m, uint32_t flags,
error = EFAULT;
break;
}
/* The acquire succeeded. */
if (owner == UMUTEX_UNOWNED) {
if (rv == 0) {
MPASS(owner == UMUTEX_UNOWNED);
error = 0;
break;
}
@ -1854,6 +1902,16 @@ do_lock_pi(struct thread *td, struct umutex *m, uint32_t flags,
break;
}
/*
* Avoid overwriting a possible error from sleep due
* to the pending signal with suspension check result.
*/
if (error == 0) {
error = umtxq_check_susp(td, true);
if (error != 0)
break;
}
/* If no one owns it but it is contested try to acquire it. */
if (owner == UMUTEX_CONTESTED || owner == UMUTEX_RB_OWNERDEAD) {
old_owner = owner;
@ -1864,36 +1922,40 @@ do_lock_pi(struct thread *td, struct umutex *m, uint32_t flags,
error = EFAULT;
break;
}
if (owner == old_owner) {
umtxq_lock(&uq->uq_key);
umtxq_busy(&uq->uq_key);
error = umtx_pi_claim(pi, td);
umtxq_unbusy(&uq->uq_key);
umtxq_unlock(&uq->uq_key);
if (error != 0) {
/*
* Since we're going to return an
* error, restore the m_owner to its
* previous, unowned state to avoid
* compounding the problem.
*/
(void)casuword32(&m->m_owner,
id | UMUTEX_CONTESTED,
old_owner);
if (rv == 1) {
if (error == 0) {
error = umtxq_check_susp(td, true);
if (error != 0)
return (error);
}
if (error == 0 &&
old_owner == UMUTEX_RB_OWNERDEAD)
error = EOWNERDEAD;
break;
/*
* If this failed the lock could
* changed, restart.
*/
continue;
}
error = umtxq_check_susp(td);
if (error != 0)
break;
/* If this failed the lock has changed, restart. */
continue;
MPASS(rv == 0);
MPASS(owner == old_owner);
umtxq_lock(&uq->uq_key);
umtxq_busy(&uq->uq_key);
error = umtx_pi_claim(pi, td);
umtxq_unbusy(&uq->uq_key);
umtxq_unlock(&uq->uq_key);
if (error != 0) {
/*
* Since we're going to return an
* error, restore the m_owner to its
* previous, unowned state to avoid
* compounding the problem.
*/
(void)casuword32(&m->m_owner,
id | UMUTEX_CONTESTED, old_owner);
}
if (error == 0 && old_owner == UMUTEX_RB_OWNERDEAD)
error = EOWNERDEAD;
break;
}
if ((owner & ~UMUTEX_CONTESTED) == id) {
@ -1932,27 +1994,32 @@ do_lock_pi(struct thread *td, struct umutex *m, uint32_t flags,
error = EFAULT;
break;
}
umtxq_lock(&uq->uq_key);
/*
* We set the contested bit, sleep. Otherwise the lock changed
* and we need to retry or we lost a race to the thread
* unlocking the umtx. Note that the UMUTEX_RB_OWNERDEAD
* value for owner is impossible there.
*/
if (old == owner) {
error = umtxq_sleep_pi(uq, pi,
owner & ~UMUTEX_CONTESTED,
"umtxpi", timeout == NULL ? NULL : &timo,
(flags & USYNC_PROCESS_SHARED) != 0);
if (rv == 1) {
umtxq_unbusy_unlocked(&uq->uq_key);
error = umtxq_check_susp(td, true);
if (error != 0)
continue;
} else {
umtxq_unbusy(&uq->uq_key);
umtxq_unlock(&uq->uq_key);
break;
/*
* The lock changed and we need to retry or we
* lost a race to the thread unlocking the
* umtx. Note that the UMUTEX_RB_OWNERDEAD
* value for owner is impossible there.
*/
continue;
}
error = umtxq_check_susp(td);
umtxq_lock(&uq->uq_key);
/* We set the contested bit, sleep. */
MPASS(old == owner);
error = umtxq_sleep_pi(uq, pi, owner & ~UMUTEX_CONTESTED,
"umtxpi", timeout == NULL ? NULL : &timo,
(flags & USYNC_PROCESS_SHARED) != 0);
if (error != 0)
continue;
error = umtxq_check_susp(td, false);
if (error != 0)
break;
}
@ -1978,6 +2045,8 @@ do_unlock_pi(struct thread *td, struct umutex *m, uint32_t flags, bool rb)
int count, error, pri;
id = td->td_tid;
usrloop:
/*
* Make sure we own this mtx.
*/
@ -1995,6 +2064,12 @@ do_unlock_pi(struct thread *td, struct umutex *m, uint32_t flags, bool rb)
error = casueword32(&m->m_owner, owner, &old, new_owner);
if (error == -1)
return (EFAULT);
if (error == 1) {
error = umtxq_check_susp(td, true);
if (error != 0)
return (error);
goto usrloop;
}
if (old == owner)
return (0);
owner = old;
@ -2074,15 +2149,20 @@ do_unlock_pi(struct thread *td, struct umutex *m, uint32_t flags, bool rb)
if (count > 1)
new_owner |= UMUTEX_CONTESTED;
again:
error = casueword32(&m->m_owner, owner, &old, new_owner);
if (error == 1) {
error = umtxq_check_susp(td, false);
if (error == 0)
goto again;
}
umtxq_unbusy_unlocked(&key);
umtx_key_release(&key);
if (error == -1)
return (EFAULT);
if (old != owner)
if (error == 0 && old != owner)
return (EINVAL);
return (0);
return (error);
}
/*
@ -2149,31 +2229,49 @@ do_lock_pp(struct thread *td, struct umutex *m, uint32_t flags,
error = EFAULT;
break;
}
if (owner == UMUTEX_CONTESTED) {
if (rv == 0) {
MPASS(owner == UMUTEX_CONTESTED);
error = 0;
break;
} else if (owner == UMUTEX_RB_OWNERDEAD) {
}
/* rv == 1 */
if (owner == UMUTEX_RB_OWNERDEAD) {
rv = casueword32(&m->m_owner, UMUTEX_RB_OWNERDEAD,
&owner, id | UMUTEX_CONTESTED);
if (rv == -1) {
error = EFAULT;
break;
}
if (owner == UMUTEX_RB_OWNERDEAD) {
if (rv == 0) {
MPASS(owner == UMUTEX_RB_OWNERDEAD);
error = EOWNERDEAD; /* success */
break;
}
error = 0;
/*
* rv == 1, only check for suspension if we
* did not already catched a signal. If we
* get an error from the check, the same
* condition is checked by the umtxq_sleep()
* call below, so we should obliterate the
* error to not skip the last loop iteration.
*/
if (error == 0) {
error = umtxq_check_susp(td, false);
if (error == 0) {
if (try != 0)
error = EBUSY;
else
continue;
}
error = 0;
}
} else if (owner == UMUTEX_RB_NOTRECOV) {
error = ENOTRECOVERABLE;
break;
}
if (try != 0) {
if (try != 0)
error = EBUSY;
break;
}
/*
* If we caught a signal, we have retried and now
@ -2668,11 +2766,12 @@ do_rw_rdlock(struct thread *td, struct urwlock *rwlock, long fflag,
umtx_key_release(&uq->uq_key);
return (EFAULT);
}
if (oldstate == state) {
if (rv == 0) {
MPASS(oldstate == state);
umtx_key_release(&uq->uq_key);
return (0);
}
error = umtxq_check_susp(td);
error = umtxq_check_susp(td, true);
if (error != 0)
break;
state = oldstate;
@ -2703,10 +2802,12 @@ do_rw_rdlock(struct thread *td, struct urwlock *rwlock, long fflag,
error = EFAULT;
break;
}
if (oldstate == state)
if (rv == 0) {
MPASS(oldstate == state);
goto sleep;
}
state = oldstate;
error = umtxq_check_susp(td);
error = umtxq_check_susp(td, false);
if (error != 0)
break;
}
@ -2718,7 +2819,7 @@ do_rw_rdlock(struct thread *td, struct urwlock *rwlock, long fflag,
/* state is changed while setting flags, restart */
if (!(state & wrflags)) {
umtxq_unbusy_unlocked(&uq->uq_key);
error = umtxq_check_susp(td);
error = umtxq_check_susp(td, true);
if (error != 0)
break;
continue;
@ -2781,10 +2882,12 @@ do_rw_rdlock(struct thread *td, struct urwlock *rwlock, long fflag,
error = EFAULT;
break;
}
if (oldstate == state)
if (rv == 0) {
MPASS(oldstate == state);
break;
}
state = oldstate;
error1 = umtxq_check_susp(td);
error1 = umtxq_check_susp(td, false);
if (error1 != 0) {
if (error == 0)
error = error1;
@ -2840,22 +2943,25 @@ do_rw_wrlock(struct thread *td, struct urwlock *rwlock, struct _umtx_time *timeo
umtx_key_release(&uq->uq_key);
return (EFAULT);
}
if (oldstate == state) {
if (rv == 0) {
MPASS(oldstate == state);
umtx_key_release(&uq->uq_key);
return (0);
}
state = oldstate;
error = umtxq_check_susp(td);
error = umtxq_check_susp(td, true);
if (error != 0)
break;
}
if (error) {
if (!(state & (URWLOCK_WRITE_OWNER|URWLOCK_WRITE_WAITERS)) &&
if ((state & (URWLOCK_WRITE_OWNER |
URWLOCK_WRITE_WAITERS)) == 0 &&
blocked_readers != 0) {
umtxq_lock(&uq->uq_key);
umtxq_busy(&uq->uq_key);
umtxq_signal_queue(&uq->uq_key, INT_MAX, UMTX_SHARED_QUEUE);
umtxq_signal_queue(&uq->uq_key, INT_MAX,
UMTX_SHARED_QUEUE);
umtxq_unbusy(&uq->uq_key);
umtxq_unlock(&uq->uq_key);
}
@ -2885,10 +2991,12 @@ do_rw_wrlock(struct thread *td, struct urwlock *rwlock, struct _umtx_time *timeo
error = EFAULT;
break;
}
if (oldstate == state)
if (rv == 0) {
MPASS(oldstate == state);
goto sleep;
}
state = oldstate;
error = umtxq_check_susp(td);
error = umtxq_check_susp(td, false);
if (error != 0)
break;
}
@ -2900,7 +3008,7 @@ do_rw_wrlock(struct thread *td, struct urwlock *rwlock, struct _umtx_time *timeo
if ((state & URWLOCK_WRITE_OWNER) == 0 &&
URWLOCK_READER_COUNT(state) == 0) {
umtxq_unbusy_unlocked(&uq->uq_key);
error = umtxq_check_susp(td);
error = umtxq_check_susp(td, false);
if (error != 0)
break;
continue;
@ -2958,10 +3066,12 @@ do_rw_wrlock(struct thread *td, struct urwlock *rwlock, struct _umtx_time *timeo
error = EFAULT;
break;
}
if (oldstate == state)
if (rv == 0) {
MPASS(oldstate == state);
break;
}
state = oldstate;
error1 = umtxq_check_susp(td);
error1 = umtxq_check_susp(td, false);
/*
* We are leaving the URWLOCK_WRITE_WAITERS
* behind, but this should not harm the
@ -3021,13 +3131,13 @@ do_rw_unlock(struct thread *td, struct urwlock *rwlock)
error = EFAULT;
goto out;
}
if (oldstate != state) {
if (rv == 1) {
state = oldstate;
if (!(oldstate & URWLOCK_WRITE_OWNER)) {
error = EPERM;
goto out;
}
error = umtxq_check_susp(td);
error = umtxq_check_susp(td, true);
if (error != 0)
goto out;
} else
@ -3041,13 +3151,13 @@ do_rw_unlock(struct thread *td, struct urwlock *rwlock)
error = EFAULT;
goto out;
}
if (oldstate != state) {
if (rv == 1) {
state = oldstate;
if (URWLOCK_READER_COUNT(oldstate) == 0) {
error = EPERM;
goto out;
}
error = umtxq_check_susp(td);
error = umtxq_check_susp(td, true);
if (error != 0)
goto out;
} else
@ -3097,7 +3207,7 @@ do_sem_wait(struct thread *td, struct _usem *sem, struct _umtx_time *timeout)
struct abs_timeout timo;
struct umtx_q *uq;
uint32_t flags, count, count1;
int error, rv;
int error, rv, rv1;
uq = td->td_umtxq;
error = fueword32(&sem->_flags, &flags);
@ -3110,20 +3220,30 @@ do_sem_wait(struct thread *td, struct _usem *sem, struct _umtx_time *timeout)
if (timeout != NULL)
abs_timeout_init2(&timo, timeout);
again:
umtxq_lock(&uq->uq_key);
umtxq_busy(&uq->uq_key);
umtxq_insert(uq);
umtxq_unlock(&uq->uq_key);
rv = casueword32(&sem->_has_waiters, 0, &count1, 1);
if (rv == 0)
rv = fueword32(&sem->_count, &count);
if (rv == -1 || count != 0) {
rv1 = fueword32(&sem->_count, &count);
if (rv == -1 || (rv == 0 && (rv1 == -1 || count != 0)) || rv == 1) {
umtxq_lock(&uq->uq_key);
umtxq_unbusy(&uq->uq_key);
umtxq_remove(uq);
umtxq_unlock(&uq->uq_key);
umtx_key_release(&uq->uq_key);
return (rv == -1 ? EFAULT : 0);
if (rv == 1) {
rv = umtxq_check_susp(td, true);
if (rv == 0)
goto again;
error = rv;
goto out;
}
if (rv == 0)
rv = rv1;
error = rv == -1 ? EFAULT : 0;
goto out;
}
umtxq_lock(&uq->uq_key);
umtxq_unbusy(&uq->uq_key);
@ -3140,6 +3260,7 @@ do_sem_wait(struct thread *td, struct _usem *sem, struct _umtx_time *timeout)
error = EINTR;
}
umtxq_unlock(&uq->uq_key);
out:
umtx_key_release(&uq->uq_key);
return (error);
}
@ -3201,6 +3322,7 @@ do_sem2_wait(struct thread *td, struct _usem2 *sem, struct _umtx_time *timeout)
if (timeout != NULL)
abs_timeout_init2(&timo, timeout);
again:
umtxq_lock(&uq->uq_key);
umtxq_busy(&uq->uq_key);
umtxq_insert(uq);
@ -3226,16 +3348,19 @@ do_sem2_wait(struct thread *td, struct _usem2 *sem, struct _umtx_time *timeout)
if (count == USEM_HAS_WAITERS)
break;
rv = casueword32(&sem->_count, 0, &count, USEM_HAS_WAITERS);
if (rv == -1) {
umtxq_lock(&uq->uq_key);
umtxq_unbusy(&uq->uq_key);
umtxq_remove(uq);
umtxq_unlock(&uq->uq_key);
umtx_key_release(&uq->uq_key);
return (EFAULT);
}
if (count == 0)
if (rv == 0)
break;
umtxq_lock(&uq->uq_key);
umtxq_unbusy(&uq->uq_key);
umtxq_remove(uq);
umtxq_unlock(&uq->uq_key);
umtx_key_release(&uq->uq_key);
if (rv == -1)
return (EFAULT);
rv = umtxq_check_susp(td, true);
if (rv != 0)
return (rv);
goto again;
}
umtxq_lock(&uq->uq_key);
umtxq_unbusy(&uq->uq_key);
@ -3288,11 +3413,20 @@ do_sem2_wake(struct thread *td, struct _usem2 *sem)
if (cnt == 1) {
umtxq_unlock(&key);
rv = fueword32(&sem->_count, &count);
while (rv != -1 && count & USEM_HAS_WAITERS)
while (rv != -1 && count & USEM_HAS_WAITERS) {
rv = casueword32(&sem->_count, count, &count,
count & ~USEM_HAS_WAITERS);
if (rv == 1) {
rv = umtxq_check_susp(td, true);
if (rv != 0)
break;
}
}
if (rv == -1)
error = EFAULT;
else if (rv > 0) {
error = rv;
}
umtxq_lock(&key);
}

28
sys/mips/mips/support.S
View File

@ -336,19 +336,15 @@ XLEAF(casueword)
GET_CPU_PCPU(v1)
PTR_L v1, PC_CURPCB(v1)
PTR_S v0, U_PCB_ONFAULT(v1)
1:
li v0, 1
move t0, a3
ll t1, 0(a0)
bne a1, t1, 2f
bne a1, t1, 1f
nop
sc t0, 0(a0) # store word
beqz t0, 1b
nop
j 3f
li v0, 0
2:
li v0, -1
3:
xori v0, t0, 1
1:
PTR_S zero, U_PCB_ONFAULT(v1)
jr ra
sw t1, 0(a2) # unconditionally store old word
@ -363,19 +359,15 @@ XLEAF(casueword)
GET_CPU_PCPU(v1)
PTR_L v1, PC_CURPCB(v1)
PTR_S v0, U_PCB_ONFAULT(v1)
1:
li v0, 1
move t0, a3
lld t1, 0(a0)
bne a1, t1, 2f
bne a1, t1, 1f
nop
scd t0, 0(a0) # store double word
beqz t0, 1b
nop
j 3f
li v0, 0
2:
li v0, -1
3:
xori v0, t0, 1
1:
PTR_S zero, U_PCB_ONFAULT(v1)
jr ra
sd t1, 0(a2) # unconditionally store old word

46
sys/powerpc/powerpc/copyinout.c
View File

@ -433,6 +433,7 @@ casueword32(volatile uint32_t *addr, uint32_t old, uint32_t *oldvalp,
pmap_t pm;
jmp_buf env;
uint32_t *p, val;
int res;
td = curthread;
pm = &td->td_proc->p_vmspace->vm_pmap;
@ -449,24 +450,26 @@ casueword32(volatile uint32_t *addr, uint32_t old, uint32_t *oldvalp,
return (-1);
}
res = 0;
__asm __volatile (
"1:\tlwarx %0, 0, %2\n\t" /* load old value */
"cmplw %3, %0\n\t" /* compare */
"bne 2f\n\t" /* exit if not equal */
"stwcx. %4, 0, %2\n\t" /* attempt to store */
"bne- 1b\n\t" /* spin if failed */
"b 3f\n\t" /* we've succeeded */
"lwarx %0, 0, %3\n\t" /* load old value */
"cmplw %4, %0\n\t" /* compare */
"bne 1f\n\t" /* exit if not equal */
"stwcx. %5, 0, %3\n\t" /* attempt to store */
"bne- 1f\n\t" /* if failed */
"b 2f\n\t" /* we've succeeded */
"1:\n\t"
"stwcx. %0, 0, %4\n\t" /* clear reservation (74xx) */
"li %2, 1\n\t"
"2:\n\t"
"stwcx. %0, 0, %2\n\t" /* clear reservation (74xx) */
"3:\n\t"
: "=&r" (val), "=m" (*p)
: "=&r" (val), "=m" (*p), "=&r" (res)
: "r" (p), "r" (old), "r" (new), "m" (*p)
: "cr0", "memory");
td->td_pcb->pcb_onfault = NULL;
*oldvalp = val;
return (0);
return (res);
}
#ifndef __powerpc64__
@ -485,6 +488,7 @@ casueword(volatile u_long *addr, u_long old, u_long *oldvalp, u_long new)
pmap_t pm;
jmp_buf env;
u_long *p, val;
int res;
td = curthread;
pm = &td->td_proc->p_vmspace->vm_pmap;
@ -501,23 +505,25 @@ casueword(volatile u_long *addr, u_long old, u_long *oldvalp, u_long new)
return (-1);
}
res = 0;
__asm __volatile (
"1:\tldarx %0, 0, %2\n\t" /* load old value */
"cmpld %3, %0\n\t" /* compare */
"bne 2f\n\t" /* exit if not equal */
"stdcx. %4, 0, %2\n\t" /* attempt to store */
"bne- 1b\n\t" /* spin if failed */
"b 3f\n\t" /* we've succeeded */
"ldarx %0, 0, %3\n\t" /* load old value */
"cmpld %4, %0\n\t" /* compare */
"bne 1f\n\t" /* exit if not equal */
"stdcx. %5, 0, %3\n\t" /* attempt to store */
"bne- 1f\n\t" /* if failed */
"b 2f\n\t" /* we've succeeded */
"1:\n\t"
"stdcx. %0, 0, %3\n\t" /* clear reservation (74xx) */
"li %2, 1\n\t"
"2:\n\t"
"stdcx. %0, 0, %2\n\t" /* clear reservation (74xx) */
"3:\n\t"
: "=&r" (val), "=m" (*p)
: "=&r" (val), "=m" (*p), "=&r" (res)
: "r" (p), "r" (old), "r" (new), "m" (*p)
: "cr0", "memory");
td->td_pcb->pcb_onfault = NULL;
*oldvalp = val;
return (0);
return (res);
}
#endif

26
sys/riscv/riscv/support.S
View File

@ -60,14 +60,15 @@ ENTRY(casueword32)
la a6, fsu_fault /* Load the fault handler */
SET_FAULT_HANDLER(a6, a4) /* And set it */
ENTER_USER_ACCESS(a4)
1: lr.w a4, 0(a0) /* Load-exclusive the data */
bne a4, a1, 2f /* If not equal then exit */
lr.w a4, 0(a0) /* Load-exclusive the data */
bne a4, a1, 1f /* If not equal then exit */
sc.w a5, a3, 0(a0) /* Store the new data */
bnez a5, 1b /* Retry on failure */
2: EXIT_USER_ACCESS(a5)
SET_FAULT_HANDLER(x0, a5) /* Reset the fault handler */
beqz a5, 2f /* Success */
1: li a5, 1 /* Normalize failure result */
2: EXIT_USER_ACCESS(a6)
SET_FAULT_HANDLER(x0, a6) /* Reset the fault handler */
sw a4, 0(a2) /* Store the read data */
li a0, 0 /* Success */
mv a0, a5 /* Success indicator */
ret /* Return */
END(casueword32)
@ -80,14 +81,15 @@ ENTRY(casueword)
la a6, fsu_fault /* Load the fault handler */
SET_FAULT_HANDLER(a6, a4) /* And set it */
ENTER_USER_ACCESS(a4)
1: lr.d a4, 0(a0) /* Load-exclusive the data */
bne a4, a1, 2f /* If not equal then exit */
lr.d a4, 0(a0) /* Load-exclusive the data */
bne a4, a1, 1f /* If not equal then exit */
sc.d a5, a3, 0(a0) /* Store the new data */
bnez a5, 1b /* Retry on failure */
2: EXIT_USER_ACCESS(a5)
SET_FAULT_HANDLER(x0, a5) /* Reset the fault handler */
beqz a5, 2f /* Success */
1: li a5, 1 /* Normalize failure result */
2: EXIT_USER_ACCESS(a6)
SET_FAULT_HANDLER(x0, a6) /* Reset the fault handler */
sd a4, 0(a2) /* Store the read data */
li a0, 0 /* Success */
mv a0, a5 /* Success indicator */
ret /* Return */
END(casueword)

11
sys/sparc64/sparc64/support.S
View File

@ -403,28 +403,27 @@ fs_nofault_begin:
.set susword, suword16
.set suword, suword64
.globl casuword32, casuword, fuptr, suptr
.set casuword, casuword64
.globl casuword32_int, casuword64_int, fuptr, suptr
.set fuptr, fuword64
.set suptr, suword64
/*
* int32_t casuword32(volatile int32_t *p, int32_t e, int32_t s)
*/
ENTRY(casuword32)
ENTRY(casuword32_int)
casa [%o0] ASI_AIUP, %o1, %o2
retl
mov %o2, %o0
END(casuword32)
END(casuword32_int)
/*
* int64_t casuword64(volatile int64_t *p, int64_t e, int64_t s)
*/
ENTRY(casuword64)
ENTRY(casuword64_int)
casxa [%o0] ASI_AIUP, %o1, %o2
retl
mov %o2, %o0
END(casuword64)
END(casuword64_int)
/*
* int fuword8(const void *base)

25
sys/sparc64/sparc64/vm_machdep.c
View File

@ -462,3 +462,28 @@ sf_buf_unmap(struct sf_buf *sf)
pmap_qremove(sf->kva, 1);
return (1);
}
uint32_t casuword32_int(volatile uint32_t *base, uint32_t oldval,
uint32_t newval);
uint32_t
casuword32(volatile uint32_t *base, uint32_t oldval, uint32_t newval)
{
uint32_t ret;
ret = casuword32_int(base, oldval, newval);
if (ret != -1)
ret = ret != oldval;
return (ret);
}
u_long casuword64_int(volatile u_long *p, u_long oldval, u_long newval);
u_long
casuword(volatile u_long *p, u_long oldval, u_long newval)
{
u_long ret;
ret = casuword64_int(p, oldval, newval);
if (ret != -1L)
ret = ret != oldval;
return (ret);
}