MachMessageDeadline WIP

util/mach/mach_message.cc

Index: util/mach/mach_message.cc
diff --git a/util/mach/mach_message.cc b/util/mach/mach_message.cc
new file mode 100644
index 0000000000000000000000000000000000000000..035d8677bc02fe463c8db5765c8a3f76c14f8bf9
--- /dev/null
+++ b/util/mach/mach_message.cc
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+// Copyright 2014 The Crashpad Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "util/mach/mach_message.h"
+
+#include <limits>
+
+#include "base/basictypes.h"
+#include "util/misc/clock.h"
+
+namespace crashpad {
+
+namespace {
+
+const int kNanosecondsPerMillisecond = 1E6;
+
+// TimerRunning() determines whether |deadline| has passed. If |deadline| is
+// kMachMessageWaitIndefinitely, |*timeout_options| is set to
+// MACH_MSG_OPTION_NONE, |*remaining_ms| is set to MACH_MSG_TIMEOUT_NONE, and
+// this function returns true. When used with mach_msg(), this will cause
+// indefinite waiting. In any other case, |*timeout_options| is set to
+// MACH_SEND_TIMEOUT | MACH_RCV_TIMEOUT, so mach_msg() will enforce a timeout
+// specified by |*remaining_ms|. If |deadline| is in the future, |*remaining_ms|
+// is set to the number of milliseconds remaining, which will always be a
+// positive value, and this function returns true. If |deadline| is
+// kMachMessageNonblocking (indicating that no timer is in effect),
+// |*remaining_ms| is set to zero and this function returns true. Otherwise,
+// this function sets |*remaining_ms| to zero and returns false.
+bool TimerRunning(uint64_t deadline,
+                  mach_msg_timeout_t* remaining_ms,
+                  mach_msg_option_t* timeout_options) {
+  if (deadline == kMachMessageWaitIndefinitely) {
+    *remaining_ms = MACH_MSG_TIMEOUT_NONE;
+    *timeout_options = MACH_MSG_OPTION_NONE;
+    return true;
+  }
+
+  *timeout_options = MACH_SEND_TIMEOUT | MACH_RCV_TIMEOUT;
+
+  if (deadline == kMachMessageNonblocking) {
+    *remaining_ms = 0;
+    return true;
+  }
+
+  uint64_t now = ClockMonotonicNanoseconds();
+
+  if (now >= deadline) {
+    *remaining_ms = 0;
+  } else {
+    uint64_t remaining = deadline - now;
+
+    // Round to the nearest millisecond, taking care not to overflow.
+    const int kHalfMillisecondInNanoseconds = kNanosecondsPerMillisecond / 2;
+    if (remaining <=
+        std::numeric_limits<uint64_t>::max() - kHalfMillisecondInNanoseconds) {
+      *remaining_ms = (remaining + kHalfMillisecondInNanoseconds) /
+                      kNanosecondsPerMillisecond;
+    } else {
+      *remaining_ms = remaining / kNanosecondsPerMillisecond;
+    }
+  }
+
+  return *remaining_ms != 0;
+}
+
+// This is an internal implementation detail of MachMessageWithDeadline(). It
+// determines whether |deadline| has expired, and what timeout value and
+// timeout-related options to pass to mach_msg() based on the value of
+// |deadline|. mach_msg() will only be called if TimerRunning() returns true or
+// if run_even_if_expired is true.
+mach_msg_return_t MachMessageWithDeadlineInternal(mach_msg_header_t* message,
+                                                  mach_msg_option_t options,
+                                                  mach_msg_size_t receive_size,
+                                                  mach_port_name_t receive_port,
+                                                  MachMessageDeadline deadline,
+                                                  mach_port_name_t notify_port,
+                                                  bool run_even_if_expired) {
+  mach_msg_timeout_t remaining_ms;
+  mach_msg_option_t timeout_options;
+  if (!TimerRunning(deadline, &remaining_ms, &timeout_options) &&
+      !run_even_if_expired) {
+    // Simulate the timed-out return values from mach_msg().
+    if (options & MACH_SEND_MSG) {
+      return MACH_SEND_TIMED_OUT;
+    }
+    if (options & MACH_RCV_MSG) {
+      return MACH_RCV_TIMED_OUT;
+    }
+    return MACH_MSG_SUCCESS;
+  }
+
+  // Turn off the passed-in timeout bits and replace them with the ones from
+  // TimerRunning(). Get the send_size value from message->msgh_size if sending
+  // a message.
+  return mach_msg(
+      message,
+      (options & ~(MACH_SEND_TIMEOUT | MACH_RCV_TIMEOUT)) | timeout_options,
+      options & MACH_SEND_MSG ? message->msgh_size : 0,
+      receive_size,
+      receive_port,
+      remaining_ms,
+      notify_port);
+}
+
+}  // namespace
+
+MachMessageDeadline MachMessageDeadlineFromTimeout(
+    mach_msg_timeout_t timeout_ms) {
+  if (timeout_ms == 0) {
+    return kMachMessageNonblocking;
+  }
+
+  return ClockMonotonicNanoseconds() +
+         implicit_cast<uint64_t>(timeout_ms) * kNanosecondsPerMillisecond;
+}
+
+mach_msg_return_t MachMessageWithDeadline(mach_msg_header_t* message,
+                                          mach_msg_option_t options,
+                                          mach_msg_size_t receive_size,
+                                          mach_port_name_t receive_port,
+                                          MachMessageDeadline deadline,
+                                          mach_port_name_t notify_port,
+                                          bool run_even_if_expired) {
+  // mach_msg() actaully does return MACH_MSG_SUCCESS when not asked to send or
+  // receive anything. See 10.9.5 xnu-1504.15.3/osfmk/ipc/mach_msg.c
+  // mach_msg_overwrite_trap().
+  mach_msg_return_t mr = MACH_MSG_SUCCESS;
+
+  // Break up the send and receive into separate operations, so that the timeout
+  // can be recomputed from the deadline for each. Otherwise, the computed
+  // timeout will apply individually to the send and then to the receive, and
+  // the desired deadline could be exceeded.
+  //
+  // During sends, always set MACH_SEND_INTERRUPT, and during receives, always
+  // set MACH_RCV_INTERRUPT. If the caller didn’t specify these options, the
+  // calls will be retried with a recomputed deadline. If these bits weren’t
+  // set, the libsyscall wrapper (10.9.5
+  // xnu-2422.115.4/libsyscall/mach/mach_msg.c mach_msg() would restart
+  // interrupted calls with the original timeout value computed from the
+  // deadline, which would no longer correspond to the actual deadline. If the
+  // caller did specify these bits, don’t restart anything, because the caller
+  // wants to be notified of any interrupted calls.
+
+  if (options & MACH_SEND_MSG) {
+    do {
+      mr = MachMessageWithDeadlineInternal(
+          message,
+          (options & ~MACH_RCV_MSG) | MACH_SEND_INTERRUPT,
+          0,
+          MACH_PORT_NULL,
+          deadline,
+          notify_port,
+          run_even_if_expired);
+    } while (mr == MACH_SEND_INTERRUPTED && !(options & MACH_SEND_INTERRUPT));
+
+    if (mr != MACH_MSG_SUCCESS) {
+      return mr;
+    }
+  }
+
+  if (options & MACH_RCV_MSG) {
+    do {
+      mr = MachMessageWithDeadlineInternal(
+          message,
+          (options & ~MACH_SEND_MSG) | MACH_RCV_INTERRUPT,
+          receive_size,
+          receive_port,
+          deadline,
+          notify_port,
+          run_even_if_expired);
+    } while (mr == MACH_RCV_INTERRUPTED && !(options & MACH_RCV_INTERRUPT));
+  }
+
+  return mr;
+}
+
+void PrepareMIGReplyFromRequest(const mach_msg_header_t* in_header,
+                                mach_msg_header_t* out_header) {
+  out_header->msgh_bits =
+      MACH_MSGH_BITS(MACH_MSGH_BITS_REMOTE(in_header->msgh_bits), 0);
+  out_header->msgh_remote_port = in_header->msgh_remote_port;
+  out_header->msgh_size = sizeof(mig_reply_error_t);
+  out_header->msgh_local_port = MACH_PORT_NULL;
+  out_header->msgh_id = in_header->msgh_id + 100;
+  reinterpret_cast<mig_reply_error_t*>(out_header)->NDR = NDR_record;
+
+  // MIG-generated dispatch routines don’t do this, but they should.
+  out_header->msgh_reserved = 0;
+}
+
+void SetMIGReplyError(mach_msg_header_t* out_header, kern_return_t error) {
+  reinterpret_cast<mig_reply_error_t*>(out_header)->RetCode = error;
+}
+
+const mach_msg_trailer_t* MachMessageTrailerFromHeader(
+    const mach_msg_header_t* header) {
+  vm_address_t header_address = reinterpret_cast<vm_address_t>(header);
+  vm_address_t trailer_address = header_address + round_msg(header->msgh_size);
+  return reinterpret_cast<const mach_msg_trailer_t*>(trailer_address);
+}
+
+}  // namespace crashpad