diff --git a/src/__phutil_library_map__.php b/src/__phutil_library_map__.php
--- a/src/__phutil_library_map__.php
+++ b/src/__phutil_library_map__.php
@@ -363,6 +363,8 @@
     'PhutilPostmarkFuture' => 'future/postmark/PhutilPostmarkFuture.php',
     'PhutilPregsprintfTestCase' => 'xsprintf/__tests__/PhutilPregsprintfTestCase.php',
     'PhutilProcessGroupDaemon' => 'daemon/torture/PhutilProcessGroupDaemon.php',
+    'PhutilProcessQuery' => 'filesystem/PhutilProcessQuery.php',
+    'PhutilProcessRef' => 'filesystem/PhutilProcessRef.php',
     'PhutilProseDiff' => 'utils/PhutilProseDiff.php',
     'PhutilProseDiffTestCase' => 'utils/__tests__/PhutilProseDiffTestCase.php',
     'PhutilProseDifferenceEngine' => 'utils/PhutilProseDifferenceEngine.php',
@@ -1027,6 +1029,8 @@
     'PhutilPostmarkFuture' => 'FutureProxy',
     'PhutilPregsprintfTestCase' => 'PhutilTestCase',
     'PhutilProcessGroupDaemon' => 'PhutilTortureTestDaemon',
+    'PhutilProcessQuery' => 'Phobject',
+    'PhutilProcessRef' => 'Phobject',
     'PhutilProseDiff' => 'Phobject',
     'PhutilProseDiffTestCase' => 'PhutilTestCase',
     'PhutilProseDifferenceEngine' => 'Phobject',
diff --git a/src/filesystem/PhutilProcessQuery.php b/src/filesystem/PhutilProcessQuery.php
new file mode 100644
--- /dev/null
+++ b/src/filesystem/PhutilProcessQuery.php
@@ -0,0 +1,83 @@
+<?php
+
+final class PhutilProcessQuery
+  extends Phobject {
+
+  private $isOverseer;
+  private $instances;
+
+  public function withIsOverseer($is_overseer) {
+    $this->isOverseer = $is_overseer;
+    return $this;
+  }
+
+  public function withInstances(array $instances) {
+    $this->instances = $instances;
+    return $this;
+  }
+
+  public function execute() {
+    if (phutil_is_windows()) {
+      throw new Exception(
+        pht(
+          'Querying system processes is not currently supported on '.
+          'Windows.'));
+    }
+
+    // TODO: See T12827. This formulation likely does not work properly on
+    // Solaris.
+
+    list($processes) = execx('ps -o pid,command -a -x -w -w -w');
+    $processes = phutil_split_lines($processes, false);
+
+    $refs = array();
+    foreach ($processes as $process) {
+      $parts = preg_split('/\s+/', trim($process), 2);
+      list($pid, $command) = $parts;
+
+      $ref = id(new PhutilProcessRef())
+        ->setPID((int)$pid)
+        ->setCommand($command);
+
+      // If this process is a "phd-daemon" process, mark it as a daemon
+      // overseer.
+      $is_overseer = (bool)preg_match('/\bphd-daemon\b/', $command);
+      $ref->setIsOverseer($is_overseer);
+
+      // If this is an overseer and the command has a "-l" ("Label") argument,
+      // the argument contains the "PHABRICATOR_INSTANCE" value for the daemon.
+      // Parse it out and annotate the process.
+      $instance = null;
+      if ($ref->getIsOverseer()) {
+        $matches = null;
+        if (preg_match('/-l (\S+)/', $command, $matches)) {
+          $instance = $matches[1];
+        }
+      }
+
+      $ref->setInstance($instance);
+
+      $refs[] = $ref;
+    }
+
+    if ($this->isOverseer !== null) {
+      foreach ($refs as $key => $ref) {
+        if ($ref->getIsOverseer() !== $this->isOverseer) {
+          unset($refs[$key]);
+        }
+      }
+    }
+
+    if ($this->instances) {
+      $instances_map = array_fuse($this->instances);
+      foreach ($refs as $key => $ref) {
+        if (!isset($instances_map[$ref->getInstance()])) {
+          unset($refs[$key]);
+        }
+      }
+    }
+
+    return array_values($refs);
+  }
+
+}
diff --git a/src/filesystem/PhutilProcessRef.php b/src/filesystem/PhutilProcessRef.php
new file mode 100644
--- /dev/null
+++ b/src/filesystem/PhutilProcessRef.php
@@ -0,0 +1,47 @@
+<?php
+
+final class PhutilProcessRef
+  extends Phobject {
+
+  private $pid;
+  private $command;
+  private $isOverseer;
+  private $instance;
+
+  public function setPID($pid) {
+    $this->pid = $pid;
+    return $this;
+  }
+
+  public function getPID() {
+    return $this->pid;
+  }
+
+  public function setCommand($command) {
+    $this->command = $command;
+    return $this;
+  }
+
+  public function getCommand() {
+    return $this->command;
+  }
+
+  public function setIsOverseer($is_overseer) {
+    $this->isOverseer = $is_overseer;
+    return $this;
+  }
+
+  public function getIsOverseer() {
+    return $this->isOverseer;
+  }
+
+  public function setInstance($instance) {
+    $this->instance = $instance;
+    return $this;
+  }
+
+  public function getInstance() {
+    return $this->instance;
+  }
+
+}