set proctitle by overwriting argv

common/SConscript

@@ -6,7 +6,8 @@ common_libs = [
   'util.cc',
   'i2c.cc',
   'watchdog.cc',
-  'ratekeeper.cc'
+  'ratekeeper.cc',
+  'proc_title.cc'
 ]
 
 if arch != "Darwin":
@@ -28,12 +29,13 @@ if GetOption('extras'):
 
 # Cython bindings
 params_python = envCython.Program('params_pyx.so', 'params_pyx.pyx', LIBS=envCython['LIBS'] + [_common, 'zmq', 'json11'])
+proc_title_python = envCython.Program('proc_title_pyx.so', 'proc_title_pyx.pyx')
 
 SConscript([
   'transformations/SConscript',
 ])
 
 Import('transformations_python')
-common_python = [params_python, transformations_python]
+common_python = [params_python, proc_title_python, transformations_python]
 
 Export('common_python')

common/proc_title.cc

@@ -0,0 +1,62 @@
+#include <iostream>
+#include <cstdlib>
+#include <cstring>
+#include <vector>
+#include <string>
+
+extern char **environ;
+
+char* argv = nullptr;
+int len_argv;
+
+void _init(int argc, char* argv0) {
+  char *ptr = environ[0] - 1;
+  char *limit = ptr - 2048;
+
+  for ( int i = argc - 1; i >= 1; i-- ) {
+    ptr--;
+    while ( *ptr && ptr > limit ) {
+      ptr--;
+    }
+
+    *ptr = ' ';
+
+    if ( ptr <= limit ) {
+      return;
+    }
+  }
+
+  ptr = ptr - strlen(argv0);
+
+  if ( strncmp(ptr, argv0, strlen(argv0)) ) {
+    return;
+  }
+
+  argv = ptr;
+  len_argv = environ[0] - 1 - ptr;
+}
+
+void setProcTitle(char* new_title) {
+  if (argv == nullptr) {
+    return;
+  }
+
+  int new_title_len = strlen(new_title);
+
+  if ( new_title_len > len_argv ) {
+    new_title_len = len_argv - 1;
+  }
+
+  strncpy(argv, new_title, new_title_len);
+  memset(argv + new_title_len, 0, len_argv - new_title_len);
+
+  return;
+}
+
+std::string getProcTitle() {
+  if (argv == nullptr) {
+    return "";
+  }
+
+  return argv;
+}

common/proc_title_pyx.pyx

@@ -0,0 +1,31 @@
+# distutils: language = c++
+# cython: language_level = 3
+import sys
+
+from libcpp.string cimport string
+
+
+cdef extern from "common/proc_title.cc":
+  void setProcTitle(char*)
+  cdef string getProcTitle()
+  void _init(int, char*)
+
+
+cdef init():
+  argv = sys.orig_argv
+  argc = len(argv)
+  _init(argc, argv[0].encode())
+
+
+def set_proc_title(title):
+  if sys.platform not in ('linux'):
+    return
+  setProcTitle(title.encode())
+
+
+def get_proc_title():
+  if sys.platform not in ('linux'):
+    return 0
+  return getProcTitle().decode()
+
+init()

common/tests/test_proc_title.py

@@ -0,0 +1,59 @@
+import pytest
+import sys
+import subprocess
+
+import openpilot.common.proc_title_pyx as proc_title
+
+def _run(script: str):
+  result = subprocess.run(
+    [sys.executable],
+    input=script,
+    capture_output=True,
+    text=True,
+    shell=True,
+  )
+
+  return result.stdout
+
+
+@pytest.mark.skipif(sys.platform not in ('linux'), reason="only supported on linux")
+class TestProcTitle:
+  def test_set_proc_title(self):
+    title = 'test'
+    script = f'''
+from openpilot.common.proc_title_pyx import set_proc_title
+import os
+
+set_proc_title("{title}")
+print(os.getpid())
+print(os.popen("ps -x -o pid,command 2> /dev/null").read())
+'''
+    out = _run(script)
+    lines = [line for line in out.splitlines() if line]
+    test_pid = lines.pop(0)
+    pids = dict([line.strip().split(None, 1) for line in lines])
+    assert pids[test_pid] == title
+
+
+  def test_truncate_long_title(self):
+    title_len = 1000
+    script = f'''
+from openpilot.common.proc_title_pyx import set_proc_title
+import os
+
+set_proc_title(''.join(['a' for _ in range({title_len})]))
+print(os.getpid())
+print(os.popen("ps -x -o pid,command 2> /dev/null").read())
+'''
+    out = _run(script)
+    lines = [line for line in out.splitlines() if line]
+    test_pid = lines.pop(0)
+    pids = dict([line.strip().split(None, 1) for line in lines])
+    assert len(pids[test_pid]) < title_len
+
+
+  def test_set_and_get(self):
+    proc_title.set_proc_title('abc')
+    assert proc_title.get_proc_title() == 'abc'
+    proc_title.set_proc_title('again')
+    assert proc_title.get_proc_title() == 'again'