Fix relaunches on the Mac

chrome/browser/mac/relauncher.cc

+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "chrome/browser/mac/relauncher.h"
+
+#include <ApplicationServices/ApplicationServices.h>
+#include <dlfcn.h>
+#include <string.h>
+#include <sys/event.h>
+#include <sys/time.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include <string>
+#include <vector>
+
+#include "base/basictypes.h"
+#include "base/eintr_wrapper.h"
+#include "base/file_util.h"
+#include "base/logging.h"
+#include "base/mac/mac_util.h"
+#include "base/mac/scoped_cftyperef.h"
+#include "base/path_service.h"
+#include "base/process_util.h"
+#include "base/stringprintf.h"
+#include "base/sys_string_conversions.h"
+#include "chrome/common/chrome_switches.h"
+#include "content/common/content_paths.h"
+#include "content/common/content_switches.h"
+#include "content/common/main_function_params.h"
+
+namespace mac_relauncher {
+
+namespace {
+
+// The "magic" file descriptor that the relauncher process' write side of the
+// pipe shows up on. Chosen to avoid conflicting with stdin, stdout, and
+// stderr.
+const int kRelauncherSyncFD = 3;

[Robert Sesek, 2011/06/23 19:30:16]

I'm probably remembering incorrectly, but doesn't something already use fd #3?

[Mark Mentovai, 2011/06/23 20:23:03]

rsesek wrote:
Certainly nothing system-level. FD 3 would be closed by base::LaunchApp anyway
(see CloseSuperfluousFDs in base/process_util_posix.cc, noting that it only
skips STDIN_FILENO, STDOUT_FILENO, and STDERR_FILENO), and since we’re in
complete control of the FD mapping set we give it, there really isn’t anything
else that could be there.

I’ve changed this to STDERR_FILENO + 1 and added a COMPILE_ASSERT to make sure
it doesn’t wind up with the same value as one of the stdio FDs.

+
+// The argument separating arguments intended for the relauncher process from
+// those intended for the relaunched process. "---" is chosen instead of "--"
+// because CommandLine interprets "--" as meaning "end of switches", but
+// for many purposes, the relauncher process' CommandLine ought to interpret
+// arguments intended for the relaunched process, to get the correct settings
+// for such things as logging and the user-data-dir in case it impacts crash

[Robert Sesek, 2011/06/23 19:30:16]

s/impacts/affects

+// reporting.
+const char kRelauncherArgSeparator[] = "---";
+
+// When this argument is supplied to the relauncher process, it will launch
+// the relaunched process without bringing it to the foreground.
+const char kRelauncherBackgroundArg[] = "--background";
+
+// The beginning of the "process serial number" argument that Launch Services
+// sometimes inserts into command lines. A process serial number is only valid
+// for a single process, so any PSN arguments will be stripped from command
+// lines during relaunch to avoid confusion.
+const char kPSNArg[] = "-psn_";
+
+// Returns the "type" argument identifying a relauncher process
+// ("--type=relauncher").
+const std::string RelauncherTypeArg() {
+  return base::StringPrintf("--%s=%s",
+                            switches::kProcessType,
+                            switches::kRelauncherProcess);
+}
+
+}  // namespace
+
+bool RelaunchApp(const std::vector<std::string>& args) {
+  // Use the currently-running application's helper process. The automatic
+  // update feature is careful to leave the currently-running version alone,
+  // so this is safe even if the relaunch is the result of an update having
+  // been applied. In fact, it's safer than using the updated version of the
+  // helper process, because there's no guarantee that the updated version's
+  // relauncher implementation will be compatible with the running version's.
+  FilePath child_path;
+  if (!PathService::Get(content::CHILD_PROCESS_EXE, &child_path)) {
+    LOG(ERROR) << "No CHILD_PROCESS_EXE";
+    return false;
+  }
+
+  return RelaunchAppWithHelper(child_path.value(), args);
+}
+
+bool RelaunchAppWithHelper(const std::string& helper,
+                           const std::vector<std::string>& args) {
+  std::vector<std::string> relaunch_args;
+  relaunch_args.push_back(helper);
+  relaunch_args.push_back(RelauncherTypeArg());
+
+  // If this application isn't in the foreground, the relaunched one shouldn't
+  // be either.
+  if (!base::mac::AmIForeground()) {
+    relaunch_args.push_back(kRelauncherBackgroundArg);
+  }
+
+  relaunch_args.push_back(kRelauncherArgSeparator);
+
+  // When using the CommandLine interface, -psn_ may have been rewritten as
+  // --psn_. Look for both.
+  const char alt_psn_arg[] = "--psn_";
+  for (size_t index = 0; index < args.size(); ++index) {
+    // Strip any -psn_ arguments, as they apply to a specific process.
+    if (args[index].compare(0, strlen(kPSNArg), kPSNArg) != 0 &&
+        args[index].compare(0, strlen(alt_psn_arg), alt_psn_arg) != 0) {
+      relaunch_args.push_back(args[index]);
+    }
+  }
+
+  int pipe_fds[2];
+  if (HANDLE_EINTR(pipe(pipe_fds)) != 0) {
+    PLOG(ERROR) << "pipe";

[Robert Sesek, 2011/06/23 19:30:16]

errno?

[Mark Mentovai, 2011/06/23 20:23:03]

rsesek wrote:
PLOG does that, as discussed.

Allays I log de ERR.

+    return false;
+  }
+  file_util::ScopedFD pipe_read_fd(&pipe_fds[0]);
+  file_util::ScopedFD pipe_write_fd(&pipe_fds[1]);

[Robert Sesek, 2011/06/23 19:30:16]

Maybe note that the write pipe isn't used in this proc.

+
+  base::file_handle_mapping_vector fd_map;
+  fd_map.push_back(std::pair<int, int>(*pipe_write_fd, kRelauncherSyncFD));

[Robert Sesek, 2011/06/23 19:30:16]

std::make_pair()?

+
+  if (!base::LaunchApp(relaunch_args, fd_map, false, NULL)) {
+    LOG(ERROR) << "base::LaunchApp failed";
+    return false;
+  }
+
+  // The relauncher process is now starting up, or has started up. The
+  // original parent process continues.
+
+  pipe_write_fd.reset();  // close(pipe_fds[1]);
+
+  // Synchronize with the relauncher process.
+  char read_char;
+  int read_result = HANDLE_EINTR(read(*pipe_read_fd, &read_char, 1));
+  if (read_result != 1) {
+    if (read_result < 0) {
+      PLOG(ERROR) << "read";

[Robert Sesek, 2011/06/23 19:30:16]

errno?

+    } else {
+      LOG(ERROR) << "read: unexpected result " << read_result;
+    }
+    return false;
+  }
+
+  // Since a byte has been successfully read from the relauncher process, it's
+  // guaranteed to have set up its kqueue monitoring this process for exit.
+  // It's safe to exit now.
+  return true;
+}
+
+namespace {
+
+// In the relauncher process, performs the necessary synchronization steps
+// with the parent, by setting up a kqueue to watch for it to exit, writing

[Robert Sesek, 2011/06/23 19:30:16]

nit: don't need this first comma

+// a byte to the pipe, and then waiting for the exit notification on the
+// kqueue. If anything fails, this logs a message and returns immediately.
+// In those situations, it can be assumed that something went wrong with the
+// parent process and the best recovery approach is to attempt relaunch
+// anyway.
+void RelauncherSynchronizeWithParent() {
+  // file_util::ScopedFD needs something non-const to operate on.
+  int relauncher_sync_fd = kRelauncherSyncFD;
+  file_util::ScopedFD relauncher_sync_fd_closer(&relauncher_sync_fd);
+
+  int parent_pid = getppid();
+
+  // PID 1 identifies init. launchd, that is. launchd never starts the
+  // relauncher process directly, having this parent_pid means that the parent
+  // already exited and launchd "inherited" the relauncher as its child.
+  // There's no reason to synchronize with launchd.
+  if (parent_pid == 1) {
+    LOG(ERROR) << "unexpected parent_pid";
+    return;
+  }
+
+  // Set up a kqueue to monitor the parent process for exit.
+  int kq = kqueue();
+  if (kq < 0) {
+    PLOG(ERROR) << "kqueue";

[Robert Sesek, 2011/06/23 19:30:16]

errno?

+    return;
+  }
+  file_util::ScopedFD kq_closer(&kq);
+
+  struct kevent change = { 0 };
+  EV_SET(&change, parent_pid, EVFILT_PROC, EV_ADD, NOTE_EXIT, 0, NULL);
+  if (kevent(kq, &change, 1, NULL, 0, NULL) == -1) {
+    PLOG(ERROR) << "kevent (add)";

[Robert Sesek, 2011/06/23 19:30:16]

I feel like a broken record, but after that super sad canary... errno?

+    return;
+  }
+
+  // Write a '\0' character to the pipe.
+  if (HANDLE_EINTR(write(relauncher_sync_fd, "", 1)) != 1) {
+    PLOG(ERROR) << "write";
+    return;
+  }
+
+  // Up until now, the parent process was blocked in a read waiting for the
+  // write above to complete. The parent process is now free to exit. Wait for
+  // that to happen.
+  struct kevent event;
+  int events = kevent(kq, NULL, 0, &event, 1, NULL);
+  if (events != 1) {
+    if (events < 0) {
+      PLOG(ERROR) << "kevent (monitor)";
+    } else {
+      LOG(ERROR) << "kevent (monitor): unexpected result " << events;
+    }
+    return;
+  }
+
+  if (event.filter != EVFILT_PROC ||
+      event.fflags != NOTE_EXIT ||
+      event.ident != static_cast<uintptr_t>(parent_pid)) {
+    LOG(ERROR) << "kevent (monitor): unexpected event, filter " << event.filter
+               << ", fflags " << event.fflags << ", ident " << event.ident;
+    return;
+  }
+}
+
+}  // namespace
+
+int RelauncherMain(const MainFunctionParams& main_parameters) {
+  // CommandLine rearranges the order of the arguments returned by
+  // main_parameters.argv(), rendering it impossible to determine which
+  // arguments originally came before kRelauncherArgSeparator and which came
+  // after. It's crucial to distinguish between these because only those
+  // after the separator should be given to the relaunched process; it's also
+  // important to not treat the path to the relaunched process as a "loose"
+  // argument. NXArgc and NXArgv are pointers to the original argc and argv as
+  // passed to main(), so use those. The typical mechanism to do this is to
+  // provide "extern" declarations to access these, but they're only present
+  // in the crt1.o start file. This function will be linked into the framework
+  // dylib, having no direct access to anything in crt1.o. dlsym to the
+  // rescue.
+  const int* argcp = static_cast<const int*>(dlsym(RTLD_MAIN_ONLY, "NXArgc"));
+  if (!argcp) {
+    LOG(ERROR) << "dlsym NXArgc: " << dlerror();
+    return 1;
+  }
+  const int argc = *argcp;
+
+  const char* const** argvp =

[Robert Sesek, 2011/06/23 19:30:16]

http://cdecl.ridiculousfish.com/?q=const+char*+const**+argvp

[Mark Mentovai, 2011/06/23 20:23:03]

rsesek wrote:
Awesome, I got it right without even breaking a sweat.

I did change argc to not be const, though, because it was incongruous with my
treatment of argv.

+      static_cast<const char* const**>(dlsym(RTLD_MAIN_ONLY, "NXArgv"));
+  if (!argvp) {
+    LOG(ERROR) << "dlsym NXArgv: " << dlerror();
+    return 1;
+  }
+  const char* const* argv = *argvp;
+
+  if (argc < 4 || RelauncherTypeArg() != argv[1]) {
+    LOG(ERROR) << "relauncher process invoked with unexpected arguments";
+    return 1;
+  }
+
+  RelauncherSynchronizeWithParent();
+
+  // The capacity for relaunch_args is 4 less than argc, because it
+  // won't contain the argv[0] of the relauncher process, the
+  // RelauncherTypeArg() at argv[1], kRelauncherArgSeparator, or the
+  // executable path of the process to be launched.
+  base::mac::ScopedCFTypeRef<CFMutableArrayRef> relaunch_args(
+      CFArrayCreateMutable(NULL, argc - 4, &kCFTypeArrayCallBacks));
+  if (!relaunch_args) {
+    LOG(ERROR) << "CFArrayCreateMutable";
+    return 1;
+  }
+
+  // Figure out what to execute, what arguments to pass it, and whether to
+  // start it in the background.
+  bool background = false;
+  bool in_relaunch_args = false;
+  bool seen_relaunch_executable = false;
+  std::string relaunch_executable;
+  const std::string relauncher_arg_separator(kRelauncherArgSeparator);
+  for (int argv_index = 2; argv_index < argc; ++argv_index) {
+    const std::string arg(argv[argv_index]);
+
+    // Strip any -psn_ arguments, as they apply to a specific process.
+    if (arg.compare(0, strlen(kPSNArg), kPSNArg) == 0) {
+      continue;
+    }
+
+    if (!in_relaunch_args) {
+      if (arg == relauncher_arg_separator) {
+        in_relaunch_args = true;
+      } else if (arg == kRelauncherBackgroundArg) {
+        background = true;
+      }
+    } else {
+      if (!seen_relaunch_executable) {
+        // The first argument after kRelauncherBackgroundArg is the path to
+        // the executable file or .app bundle directory. The Launch Services
+        // interface wants this separate from the rest of the arguments. In
+        // the relaunched process, this path will still be visible at argv[0].
+        relaunch_executable.assign(arg);
+        seen_relaunch_executable = true;
+      } else {
+        base::mac::ScopedCFTypeRef<CFStringRef> arg_cf(
+            base::SysUTF8ToCFStringRef(arg));
+        if (!arg_cf) {
+          LOG(ERROR) << "base::SysUTF8ToCFStringRef failed for " << arg;
+          return 1;
+        }
+        CFArrayAppendValue(relaunch_args, arg_cf);
+      }
+    }
+  }
+
+  if (!seen_relaunch_executable) {
+    LOG(ERROR) << "nothing to relaunch";
+    return 1;
+  }
+
+  FSRef app_fsref;
+  if (!base::mac::FSRefFromPath(relaunch_executable, &app_fsref)) {
+    LOG(ERROR) << "base::mac::FSRefFromPath failed for " << relaunch_executable;
+    return 1;
+  }
+
+  LSApplicationParameters ls_parameters = {
+    0,  // version
+    kLSLaunchDefaults | kLSLaunchAndDisplayErrors | kLSLaunchNewInstance |
+        (background ? kLSLaunchDontSwitch : 0),
+    &app_fsref,
+    NULL,  // asyncLaunchRefCon
+    NULL,  // environment
+    relaunch_args,
+    NULL   // initialEvent
+  };
+
+  OSStatus err = LSOpenApplication(&ls_parameters, NULL);
+  if (err != noErr) {
+    LOG(ERROR) << "LSOpenApplication: " << err;
+    return 1;
+  }
+
+  return 0;
+}
+
+}  // namespace mac_relauncher