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      1 // Copyright 2014 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #include <errno.h>
      6 #include <linux/futex.h>
      7 #include <sys/syscall.h>
      8 #include <sys/time.h>
      9 #include <unistd.h>
     10 
     11 #include "components/nacl/loader/nonsfi/irt_interfaces.h"
     12 #include "components/nacl/loader/nonsfi/irt_util.h"
     13 #include "native_client/src/trusted/service_runtime/include/sys/time.h"
     14 
     15 namespace nacl {
     16 namespace nonsfi {
     17 namespace {
     18 
     19 // Converts a pair of NaCl's timespec of absolute time and host's timespec of
     20 // the current time to host's timespec of the relative time between them.
     21 // Note that assuming tv_nsec for the both input structs are non-negative,
     22 // the returned reltime's tv_nsec is also always non-negative.
     23 // (I.e., for -0.1 sec, {tv_sec: -1, tv_nsec: 900000000} will be returned).
     24 void NaClAbsTimeToRelTime(const struct nacl_abi_timespec& nacl_abstime,
     25                           const struct timespec& now,
     26                           struct timespec* reltime) {
     27   reltime->tv_sec = nacl_abstime.tv_sec - now.tv_sec;
     28   reltime->tv_nsec = nacl_abstime.tv_nsec - now.tv_nsec;
     29   if (reltime->tv_nsec < 0) {
     30     reltime->tv_sec -= 1;
     31     reltime->tv_nsec += 1000000000;
     32   }
     33 }
     34 
     35 int IrtFutexWaitAbs(volatile int* addr, int value,
     36                     const struct nacl_abi_timespec* abstime) {
     37   struct timespec timeout;
     38   struct timespec* timeout_ptr = NULL;
     39   if (abstime) {
     40     // futex syscall takes relative timeout, but the ABI for IRT's
     41     // futex_wait_abs is absolute timeout. So, here we convert it.
     42     struct timespec now;
     43     if (clock_gettime(CLOCK_REALTIME, &now))
     44       return errno;
     45     NaClAbsTimeToRelTime(*abstime, now, &timeout);
     46 
     47     // Linux's FUTEX_WAIT returns EINVAL for negative timeout, but an absolute
     48     // time that is in the past is a valid argument to irt_futex_wait_abs(),
     49     // and a caller expects ETIMEDOUT.
     50     // Here check only tv_sec since we assume time_t is signed. See also
     51     // the comment for NaClAbsTimeToRelTime.
     52     if (timeout.tv_sec < 0)
     53       return ETIMEDOUT;
     54     timeout_ptr = &timeout;
     55   }
     56   return CheckError(
     57       syscall(SYS_futex, addr, FUTEX_WAIT_PRIVATE, value, timeout_ptr, 0, 0));
     58 }
     59 
     60 int IrtFutexWake(volatile int* addr, int nwake, int* count) {
     61   return CheckErrorWithResult(
     62       syscall(SYS_futex, addr, FUTEX_WAKE_PRIVATE, nwake, 0, 0, 0), count);
     63 }
     64 
     65 }  // namespace
     66 
     67 // For futex_wait_abs, the argument type should be nacl_abi_timespec. However,
     68 // the definition uses its host type, struct timespec. So, here we need to cast
     69 // it.
     70 const nacl_irt_futex kIrtFutex = {
     71   reinterpret_cast<int(*)(volatile int*, int, const struct timespec*)>(
     72       IrtFutexWaitAbs),
     73   IrtFutexWake,
     74 };
     75 
     76 }  // namespace nonsfi
     77 }  // namespace nacl
     78