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Merge branch 'for-next/futex' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux into for-next/core

hifive-unleashed-5.2
Will Deacon 2019-05-01 15:34:17 +01:00
parent 61cf61d81e 4275035197
commit 9431ac2bf6
4 changed files with 163 additions and 99 deletions
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3
Documentation/robust-futexes.txt
View File

@ -218,5 +218,4 @@ All other architectures should build just fine too - but they won't have
the new syscalls yet.
Architectures need to implement the new futex_atomic_cmpxchg_inatomic()
inline function before writing up the syscalls (that function returns
-ENOSYS right now).
inline function before writing up the syscalls.

63
arch/arm64/include/asm/futex.h
View File

@ -23,26 +23,34 @@
#include <asm/errno.h>
#define FUTEX_MAX_LOOPS 128 /* What's the largest number you can think of? */
#define __futex_atomic_op(insn, ret, oldval, uaddr, tmp, oparg) \
do { \
unsigned int loops = FUTEX_MAX_LOOPS; \
\
uaccess_enable(); \
asm volatile( \
" prfm pstl1strm, %2\n" \
"1: ldxr %w1, %2\n" \
insn "\n" \
"2: stlxr %w3, %w0, %2\n" \
" cbnz %w3, 1b\n" \
" dmb ish\n" \
"2: stlxr %w0, %w3, %2\n" \
" cbz %w0, 3f\n" \
" sub %w4, %w4, %w0\n" \
" cbnz %w4, 1b\n" \
" mov %w0, %w7\n" \
"3:\n" \
" dmb ish\n" \
" .pushsection .fixup,\"ax\"\n" \
" .align 2\n" \
"4: mov %w0, %w5\n" \
"4: mov %w0, %w6\n" \
" b 3b\n" \
" .popsection\n" \
_ASM_EXTABLE(1b, 4b) \
_ASM_EXTABLE(2b, 4b) \
: "=&r" (ret), "=&r" (oldval), "+Q" (*uaddr), "=&r" (tmp) \
: "r" (oparg), "Ir" (-EFAULT) \
: "=&r" (ret), "=&r" (oldval), "+Q" (*uaddr), "=&r" (tmp), \
"+r" (loops) \
: "r" (oparg), "Ir" (-EFAULT), "Ir" (-EAGAIN) \
: "memory"); \
uaccess_disable(); \
} while (0)
@ -50,30 +58,30 @@ do { \
static inline int
arch_futex_atomic_op_inuser(int op, int oparg, int *oval, u32 __user *_uaddr)
{
int oldval = 0, ret, tmp;
int oldval, ret, tmp;
u32 __user *uaddr = __uaccess_mask_ptr(_uaddr);
pagefault_disable();
switch (op) {
case FUTEX_OP_SET:
__futex_atomic_op("mov %w0, %w4",
__futex_atomic_op("mov %w3, %w5",
ret, oldval, uaddr, tmp, oparg);
break;
case FUTEX_OP_ADD:
__futex_atomic_op("add %w0, %w1, %w4",
__futex_atomic_op("add %w3, %w1, %w5",
ret, oldval, uaddr, tmp, oparg);
break;
case FUTEX_OP_OR:
__futex_atomic_op("orr %w0, %w1, %w4",
__futex_atomic_op("orr %w3, %w1, %w5",
ret, oldval, uaddr, tmp, oparg);
break;
case FUTEX_OP_ANDN:
__futex_atomic_op("and %w0, %w1, %w4",
__futex_atomic_op("and %w3, %w1, %w5",
ret, oldval, uaddr, tmp, ~oparg);
break;
case FUTEX_OP_XOR:
__futex_atomic_op("eor %w0, %w1, %w4",
__futex_atomic_op("eor %w3, %w1, %w5",
ret, oldval, uaddr, tmp, oparg);
break;
default:
@ -93,6 +101,7 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *_uaddr,
u32 oldval, u32 newval)
{
int ret = 0;
unsigned int loops = FUTEX_MAX_LOOPS;
u32 val, tmp;
u32 __user *uaddr;
@ -104,24 +113,30 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *_uaddr,
asm volatile("// futex_atomic_cmpxchg_inatomic\n"
" prfm pstl1strm, %2\n"
"1: ldxr %w1, %2\n"
" sub %w3, %w1, %w4\n"
" cbnz %w3, 3f\n"
"2: stlxr %w3, %w5, %2\n"
" cbnz %w3, 1b\n"
" dmb ish\n"
" sub %w3, %w1, %w5\n"
" cbnz %w3, 4f\n"
"2: stlxr %w3, %w6, %2\n"
" cbz %w3, 3f\n"
" sub %w4, %w4, %w3\n"
" cbnz %w4, 1b\n"
" mov %w0, %w8\n"
"3:\n"
" dmb ish\n"
"4:\n"
" .pushsection .fixup,\"ax\"\n"
"4: mov %w0, %w6\n"
" b 3b\n"
"5: mov %w0, %w7\n"
" b 4b\n"
" .popsection\n"
_ASM_EXTABLE(1b, 4b)
_ASM_EXTABLE(2b, 4b)
: "+r" (ret), "=&r" (val), "+Q" (*uaddr), "=&r" (tmp)
: "r" (oldval), "r" (newval), "Ir" (-EFAULT)
_ASM_EXTABLE(1b, 5b)
_ASM_EXTABLE(2b, 5b)
: "+r" (ret), "=&r" (val), "+Q" (*uaddr), "=&r" (tmp), "+r" (loops)
: "r" (oldval), "r" (newval), "Ir" (-EFAULT), "Ir" (-EAGAIN)
: "memory");
uaccess_disable();
*uval = val;
if (!ret)
*uval = val;
return ret;
}

8
include/asm-generic/futex.h
View File

@ -23,7 +23,9 @@
*
* Return:
* 0 - On success
* <0 - On error
* -EFAULT - User access resulted in a page fault
* -EAGAIN - Atomic operation was unable to complete due to contention
* -ENOSYS - Operation not supported
*/
static inline int
arch_futex_atomic_op_inuser(int op, u32 oparg, int *oval, u32 __user *uaddr)
@ -85,7 +87,9 @@ out_pagefault_enable:
*
* Return:
* 0 - On success
* <0 - On error
* -EFAULT - User access resulted in a page fault
* -EAGAIN - Atomic operation was unable to complete due to contention
* -ENOSYS - Function not implemented (only if !HAVE_FUTEX_CMPXCHG)
*/
static inline int
futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,

188
kernel/futex.c
View File

@ -1311,13 +1311,15 @@ static int lookup_pi_state(u32 __user *uaddr, u32 uval,
static int lock_pi_update_atomic(u32 __user *uaddr, u32 uval, u32 newval)
{
int err;
u32 uninitialized_var(curval);
if (unlikely(should_fail_futex(true)))
return -EFAULT;
if (unlikely(cmpxchg_futex_value_locked(&curval, uaddr, uval, newval)))
return -EFAULT;
err = cmpxchg_futex_value_locked(&curval, uaddr, uval, newval);
if (unlikely(err))
return err;
/* If user space value changed, let the caller retry */
return curval != uval ? -EAGAIN : 0;
@ -1502,10 +1504,8 @@ static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_pi_state *pi_
if (unlikely(should_fail_futex(true)))
ret = -EFAULT;
if (cmpxchg_futex_value_locked(&curval, uaddr, uval, newval)) {
ret = -EFAULT;
} else if (curval != uval) {
ret = cmpxchg_futex_value_locked(&curval, uaddr, uval, newval);
if (!ret && (curval != uval)) {
/*
* If a unconditional UNLOCK_PI operation (user space did not
* try the TID->0 transition) raced with a waiter setting the
@ -1700,32 +1700,32 @@ retry_private:
double_lock_hb(hb1, hb2);
op_ret = futex_atomic_op_inuser(op, uaddr2);
if (unlikely(op_ret < 0)) {
double_unlock_hb(hb1, hb2);
#ifndef CONFIG_MMU
/*
* we don't get EFAULT from MMU faults if we don't have an MMU,
* but we might get them from range checking
*/
ret = op_ret;
goto out_put_keys;
#endif
if (unlikely(op_ret != -EFAULT)) {
if (!IS_ENABLED(CONFIG_MMU) ||
unlikely(op_ret != -EFAULT && op_ret != -EAGAIN)) {
/*
* we don't get EFAULT from MMU faults if we don't have
* an MMU, but we might get them from range checking
*/
ret = op_ret;
goto out_put_keys;
}
ret = fault_in_user_writeable(uaddr2);
if (ret)
goto out_put_keys;
if (op_ret == -EFAULT) {
ret = fault_in_user_writeable(uaddr2);
if (ret)
goto out_put_keys;
}
if (!(flags & FLAGS_SHARED))
if (!(flags & FLAGS_SHARED)) {
cond_resched();
goto retry_private;
}
put_futex_key(&key2);
put_futex_key(&key1);
cond_resched();
goto retry;
}
@ -2350,7 +2350,7 @@ static int fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q,
u32 uval, uninitialized_var(curval), newval;
struct task_struct *oldowner, *newowner;
u32 newtid;
int ret;
int ret, err = 0;
lockdep_assert_held(q->lock_ptr);
@ -2421,14 +2421,17 @@ retry:
if (!pi_state->owner)
newtid |= FUTEX_OWNER_DIED;
if (get_futex_value_locked(&uval, uaddr))
goto handle_fault;
err = get_futex_value_locked(&uval, uaddr);
if (err)
goto handle_err;
for (;;) {
newval = (uval & FUTEX_OWNER_DIED) | newtid;
if (cmpxchg_futex_value_locked(&curval, uaddr, uval, newval))
goto handle_fault;
err = cmpxchg_futex_value_locked(&curval, uaddr, uval, newval);
if (err)
goto handle_err;
if (curval == uval)
break;
uval = curval;
@ -2456,23 +2459,37 @@ retry:
return 0;
/*
* To handle the page fault we need to drop the locks here. That gives
* the other task (either the highest priority waiter itself or the
* task which stole the rtmutex) the chance to try the fixup of the
* pi_state. So once we are back from handling the fault we need to
* check the pi_state after reacquiring the locks and before trying to
* do another fixup. When the fixup has been done already we simply
* return.
* In order to reschedule or handle a page fault, we need to drop the
* locks here. In the case of a fault, this gives the other task
* (either the highest priority waiter itself or the task which stole
* the rtmutex) the chance to try the fixup of the pi_state. So once we
* are back from handling the fault we need to check the pi_state after
* reacquiring the locks and before trying to do another fixup. When
* the fixup has been done already we simply return.
*
* Note: we hold both hb->lock and pi_mutex->wait_lock. We can safely
* drop hb->lock since the caller owns the hb -> futex_q relation.
* Dropping the pi_mutex->wait_lock requires the state revalidate.
*/
handle_fault:
handle_err:
raw_spin_unlock_irq(&pi_state->pi_mutex.wait_lock);
spin_unlock(q->lock_ptr);
ret = fault_in_user_writeable(uaddr);
switch (err) {
case -EFAULT:
ret = fault_in_user_writeable(uaddr);
break;
case -EAGAIN:
cond_resched();
ret = 0;
break;
default:
WARN_ON_ONCE(1);
ret = err;
break;
}
spin_lock(q->lock_ptr);
raw_spin_lock_irq(&pi_state->pi_mutex.wait_lock);
@ -3041,10 +3058,8 @@ retry:
* A unconditional UNLOCK_PI op raced against a waiter
* setting the FUTEX_WAITERS bit. Try again.
*/
if (ret == -EAGAIN) {
put_futex_key(&key);
goto retry;
}
if (ret == -EAGAIN)
goto pi_retry;
/*
* wake_futex_pi has detected invalid state. Tell user
* space.
@ -3059,9 +3074,19 @@ retry:
* preserve the WAITERS bit not the OWNER_DIED one. We are the
* owner.
*/
if (cmpxchg_futex_value_locked(&curval, uaddr, uval, 0)) {
if ((ret = cmpxchg_futex_value_locked(&curval, uaddr, uval, 0))) {
spin_unlock(&hb->lock);
goto pi_faulted;
switch (ret) {
case -EFAULT:
goto pi_faulted;
case -EAGAIN:
goto pi_retry;
default:
WARN_ON_ONCE(1);
goto out_putkey;
}
}
/*
@ -3075,6 +3100,11 @@ out_putkey:
put_futex_key(&key);
return ret;
pi_retry:
put_futex_key(&key);
cond_resched();
goto retry;
pi_faulted:
put_futex_key(&key);
@ -3435,6 +3465,7 @@ err_unlock:
static int handle_futex_death(u32 __user *uaddr, struct task_struct *curr, int pi)
{
u32 uval, uninitialized_var(nval), mval;
int err;
/* Futex address must be 32bit aligned */
if ((((unsigned long)uaddr) % sizeof(*uaddr)) != 0)
@ -3444,42 +3475,57 @@ retry:
if (get_user(uval, uaddr))
return -1;
if ((uval & FUTEX_TID_MASK) == task_pid_vnr(curr)) {
/*
* Ok, this dying thread is truly holding a futex
* of interest. Set the OWNER_DIED bit atomically
* via cmpxchg, and if the value had FUTEX_WAITERS
* set, wake up a waiter (if any). (We have to do a
* futex_wake() even if OWNER_DIED is already set -
* to handle the rare but possible case of recursive
* thread-death.) The rest of the cleanup is done in
* userspace.
*/
mval = (uval & FUTEX_WAITERS) | FUTEX_OWNER_DIED;
/*
* We are not holding a lock here, but we want to have
* the pagefault_disable/enable() protection because
* we want to handle the fault gracefully. If the
* access fails we try to fault in the futex with R/W
* verification via get_user_pages. get_user() above
* does not guarantee R/W access. If that fails we
* give up and leave the futex locked.
*/
if (cmpxchg_futex_value_locked(&nval, uaddr, uval, mval)) {
if ((uval & FUTEX_TID_MASK) != task_pid_vnr(curr))
return 0;
/*
* Ok, this dying thread is truly holding a futex
* of interest. Set the OWNER_DIED bit atomically
* via cmpxchg, and if the value had FUTEX_WAITERS
* set, wake up a waiter (if any). (We have to do a
* futex_wake() even if OWNER_DIED is already set -
* to handle the rare but possible case of recursive
* thread-death.) The rest of the cleanup is done in
* userspace.
*/
mval = (uval & FUTEX_WAITERS) | FUTEX_OWNER_DIED;
/*
* We are not holding a lock here, but we want to have
* the pagefault_disable/enable() protection because
* we want to handle the fault gracefully. If the
* access fails we try to fault in the futex with R/W
* verification via get_user_pages. get_user() above
* does not guarantee R/W access. If that fails we
* give up and leave the futex locked.
*/
if ((err = cmpxchg_futex_value_locked(&nval, uaddr, uval, mval))) {
switch (err) {
case -EFAULT:
if (fault_in_user_writeable(uaddr))
return -1;
goto retry;
}
if (nval != uval)
case -EAGAIN:
cond_resched();
goto retry;
/*
* Wake robust non-PI futexes here. The wakeup of
* PI futexes happens in exit_pi_state():
*/
if (!pi && (uval & FUTEX_WAITERS))
futex_wake(uaddr, 1, 1, FUTEX_BITSET_MATCH_ANY);
default:
WARN_ON_ONCE(1);
return err;
}
}
if (nval != uval)
goto retry;
/*
* Wake robust non-PI futexes here. The wakeup of
* PI futexes happens in exit_pi_state():
*/
if (!pi && (uval & FUTEX_WAITERS))
futex_wake(uaddr, 1, 1, FUTEX_BITSET_MATCH_ANY);
return 0;
}