122 lines
5.6 KiB
C++
122 lines
5.6 KiB
C++
// Copyright (c) 2016 GitHub, Inc.
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// Use of this source code is governed by the MIT license that can be
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// found in the LICENSE file.
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#ifndef ATOM_BROWSER_RELAUNCHER_H_
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#define ATOM_BROWSER_RELAUNCHER_H_
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// relauncher implements main browser application relaunches across platforms.
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// When a browser wants to relaunch itself, it can't simply fork off a new
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// process and exec a new browser from within. That leaves open a window
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// during which two browser applications might be running concurrently. If
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// that happens, each will wind up with a distinct Dock icon, which is
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// especially bad if the user expected the Dock icon to be persistent by
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// choosing Keep in Dock from the icon's contextual menu.
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//
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// relauncher approaches this problem by introducing an intermediate
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// process (the "relauncher") in between the original browser ("parent") and
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// replacement browser ("relaunched"). The helper executable is used for the
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// relauncher process; because it's an LSUIElement, it doesn't get a Dock
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// icon and isn't visible as a running application at all. The parent will
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// start a relauncher process, giving it the "writer" side of a pipe that it
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// retains the "reader" end of. When the relauncher starts up, it will
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// establish a kqueue to wait for the parent to exit, and will then write to
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// the pipe. The parent, upon reading from the pipe, is free to exit. When the
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// relauncher is notified via its kqueue that the parent has exited, it
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// proceeds, launching the relaunched process. The handshake to synchronize
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// the parent with the relauncher is necessary to avoid races: the relauncher
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// needs to be sure that it's monitoring the parent and not some other process
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// in light of PID reuse, so the parent must remain alive long enough for the
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// relauncher to set up its kqueue.
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#include <string>
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#include <vector>
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#include "base/command_line.h"
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#if defined(OS_WIN)
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#include "base/process/process_handle.h"
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#endif
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namespace content {
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struct MainFunctionParams;
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}
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namespace relauncher {
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using CharType = base::CommandLine::CharType;
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using StringType = base::CommandLine::StringType;
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using StringVector = base::CommandLine::StringVector;
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// Relaunches the application using the helper application associated with the
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// currently running instance of Chrome in the parent browser process as the
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// executable for the relauncher process. |args| is an argv-style vector of
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// command line arguments of the form normally passed to execv. args[0] is
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// also the path to the relaunched process. Because the relauncher process
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// will ultimately launch the relaunched process via Launch Services, args[0]
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// may be either a pathname to an executable file or a pathname to an .app
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// bundle directory. The caller should exit soon after RelaunchApp returns
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// successfully. Returns true on success, although some failures can occur
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// after this function returns true if, for example, they occur within the
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// relauncher process. Returns false when the relaunch definitely failed.
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bool RelaunchApp(const StringVector& argv);
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// Identical to RelaunchApp, but uses |helper| as the path to the relauncher
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// process, and allows additional arguments to be supplied to the relauncher
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// process in relauncher_args. Unlike args[0], |helper| must be a pathname to
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// an executable file. The helper path given must be from the same version of
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// Chrome as the running parent browser process, as there are no guarantees
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// that the parent and relauncher processes from different versions will be
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// able to communicate with one another. This variant can be useful to
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// relaunch the same version of Chrome from another location, using that
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// location's helper.
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bool RelaunchAppWithHelper(const base::FilePath& helper,
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const StringVector& relauncher_args,
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const StringVector& args);
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// The entry point from ChromeMain into the relauncher process.
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int RelauncherMain(const content::MainFunctionParams& main_parameters);
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namespace internal {
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#if defined(OS_POSIX)
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// The "magic" file descriptor that the relauncher process' write side of the
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// pipe shows up on. Chosen to avoid conflicting with stdin, stdout, and
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// stderr.
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extern const int kRelauncherSyncFD;
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#endif
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// The "type" argument identifying a relauncher process ("--type=relauncher").
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extern const CharType* kRelauncherTypeArg;
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// The argument separating arguments intended for the relauncher process from
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// those intended for the relaunched process. "---" is chosen instead of "--"
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// because CommandLine interprets "--" as meaning "end of switches", but
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// for many purposes, the relauncher process' CommandLine ought to interpret
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// arguments intended for the relaunched process, to get the correct settings
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// for such things as logging and the user-data-dir in case it affects crash
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// reporting.
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extern const CharType* kRelauncherArgSeparator;
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#if defined(OS_WIN)
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StringType GetWaitEventName(base::ProcessId pid);
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StringType ArgvToCommandLineString(const StringVector& argv);
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#endif
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// In the relauncher process, performs the necessary synchronization steps
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// with the parent by setting up a kqueue to watch for it to exit, writing a
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// byte to the pipe, and then waiting for the exit notification on the kqueue.
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// If anything fails, this logs a message and returns immediately. In those
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// situations, it can be assumed that something went wrong with the parent
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// process and the best recovery approach is to attempt relaunch anyway.
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void RelauncherSynchronizeWithParent();
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int LaunchProgram(const StringVector& relauncher_args,
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const StringVector& argv);
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} // namespace internal
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} // namespace relauncher
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#endif // ATOM_BROWSER_RELAUNCHER_H_
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