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ProcessForker.php
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ProcessForker.php
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<?php
/*
* This file is part of Psy Shell.
*
* (c) 2012-2023 Justin Hileman
*
* For the full copyright and license information, please view the LICENSE
* file that was distributed with this source code.
*/
namespace Psy\ExecutionLoop;
use Psy\Context;
use Psy\Exception\BreakException;
use Psy\Shell;
/**
* An execution loop listener that forks the process before executing code.
*
* This is awesome, as the session won't die prematurely if user input includes
* a fatal error, such as redeclaring a class or function.
*/
class ProcessForker extends AbstractListener
{
private ?int $savegame = null;
/** @var resource */
private $up;
private const PCNTL_FUNCTIONS = [
'pcntl_fork',
'pcntl_signal_dispatch',
'pcntl_signal',
'pcntl_waitpid',
'pcntl_wexitstatus',
];
private const POSIX_FUNCTIONS = [
'posix_getpid',
'posix_kill',
];
/**
* Process forker is supported if pcntl and posix extensions are available.
*/
public static function isSupported(): bool
{
return self::isPcntlSupported() && !self::disabledPcntlFunctions() && self::isPosixSupported() && !self::disabledPosixFunctions();
}
/**
* Verify that all required pcntl functions are, in fact, available.
*/
public static function isPcntlSupported(): bool
{
foreach (self::PCNTL_FUNCTIONS as $func) {
if (!\function_exists($func)) {
return false;
}
}
return true;
}
/**
* Check whether required pcntl functions are disabled.
*/
public static function disabledPcntlFunctions()
{
return self::checkDisabledFunctions(self::PCNTL_FUNCTIONS);
}
/**
* Verify that all required posix functions are, in fact, available.
*/
public static function isPosixSupported(): bool
{
foreach (self::POSIX_FUNCTIONS as $func) {
if (!\function_exists($func)) {
return false;
}
}
return true;
}
/**
* Check whether required posix functions are disabled.
*/
public static function disabledPosixFunctions()
{
return self::checkDisabledFunctions(self::POSIX_FUNCTIONS);
}
private static function checkDisabledFunctions(array $functions): array
{
return \array_values(\array_intersect($functions, \array_map('strtolower', \array_map('trim', \explode(',', \ini_get('disable_functions'))))));
}
/**
* Forks into a main and a loop process.
*
* The loop process will handle the evaluation of all instructions, then
* return its state via a socket upon completion.
*
* @param Shell $shell
*/
public function beforeRun(Shell $shell)
{
list($up, $down) = \stream_socket_pair(\STREAM_PF_UNIX, \STREAM_SOCK_STREAM, \STREAM_IPPROTO_IP);
if (!$up) {
throw new \RuntimeException('Unable to create socket pair');
}
$pid = \pcntl_fork();
if ($pid < 0) {
throw new \RuntimeException('Unable to start execution loop');
} elseif ($pid > 0) {
// This is the main thread. We'll just wait for a while.
// We won't be needing this one.
\fclose($up);
// Wait for a return value from the loop process.
$read = [$down];
$write = null;
$except = null;
do {
$n = @\stream_select($read, $write, $except, null);
if ($n === 0) {
throw new \RuntimeException('Process timed out waiting for execution loop');
}
if ($n === false) {
$err = \error_get_last();
if (!isset($err['message']) || \stripos($err['message'], 'interrupted system call') === false) {
$msg = $err['message'] ?
\sprintf('Error waiting for execution loop: %s', $err['message']) :
'Error waiting for execution loop';
throw new \RuntimeException($msg);
}
}
} while ($n < 1);
$content = \stream_get_contents($down);
\fclose($down);
if ($content) {
$shell->setScopeVariables(@\unserialize($content));
}
throw new BreakException('Exiting main thread');
}
// This is the child process. It's going to do all the work.
if (!@\cli_set_process_title('psysh (loop)')) {
// Fall back to `setproctitle` if that wasn't succesful.
if (\function_exists('setproctitle')) {
@\setproctitle('psysh (loop)');
}
}
// We won't be needing this one.
\fclose($down);
// Save this; we'll need to close it in `afterRun`
$this->up = $up;
}
/**
* Create a savegame at the start of each loop iteration.
*
* @param Shell $shell
*/
public function beforeLoop(Shell $shell)
{
$this->createSavegame();
}
/**
* Clean up old savegames at the end of each loop iteration.
*
* @param Shell $shell
*/
public function afterLoop(Shell $shell)
{
// if there's an old savegame hanging around, let's kill it.
if (isset($this->savegame)) {
\posix_kill($this->savegame, \SIGKILL);
\pcntl_signal_dispatch();
}
}
/**
* After the REPL session ends, send the scope variables back up to the main
* thread (if this is a child thread).
*
* @param Shell $shell
*/
public function afterRun(Shell $shell)
{
// We're a child thread. Send the scope variables back up to the main thread.
if (isset($this->up)) {
\fwrite($this->up, $this->serializeReturn($shell->getScopeVariables(false)));
\fclose($this->up);
\posix_kill(\posix_getpid(), \SIGKILL);
}
}
/**
* Create a savegame fork.
*
* The savegame contains the current execution state, and can be resumed in
* the event that the worker dies unexpectedly (for example, by encountering
* a PHP fatal error).
*/
private function createSavegame()
{
// the current process will become the savegame
$this->savegame = \posix_getpid();
$pid = \pcntl_fork();
if ($pid < 0) {
throw new \RuntimeException('Unable to create savegame fork');
} elseif ($pid > 0) {
// we're the savegame now... let's wait and see what happens
\pcntl_waitpid($pid, $status);
// worker exited cleanly, let's bail
if (!\pcntl_wexitstatus($status)) {
\posix_kill(\posix_getpid(), \SIGKILL);
}
// worker didn't exit cleanly, we'll need to have another go
$this->createSavegame();
}
}
/**
* Serialize all serializable return values.
*
* A naïve serialization will run into issues if there is a Closure or
* SimpleXMLElement (among other things) in scope when exiting the execution
* loop. We'll just ignore these unserializable classes, and serialize what
* we can.
*
* @param array $return
*/
private function serializeReturn(array $return): string
{
$serializable = [];
foreach ($return as $key => $value) {
// No need to return magic variables
if (Context::isSpecialVariableName($key)) {
continue;
}
// Resources and Closures don't error, but they don't serialize well either.
if (\is_resource($value) || $value instanceof \Closure) {
continue;
}
if (\version_compare(\PHP_VERSION, '8.1', '>=') && $value instanceof \UnitEnum) {
// Enums defined in the REPL session can't be unserialized.
$ref = new \ReflectionObject($value);
if (\strpos($ref->getFileName(), ": eval()'d code") !== false) {
continue;
}
}
try {
@\serialize($value);
$serializable[$key] = $value;
} catch (\Throwable $e) {
// we'll just ignore this one...
}
}
return @\serialize($serializable);
}
}

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