diff --git a/common.py b/common.py
index 052aa1f..b515b89 100644
--- a/common.py
+++ b/common.py
@@ -135,10 +135,15 @@ around when you checkout between branches.
     parser.set_defaults(**defaults)
     return parser
 
-def print_cmd(cmd, cmd_file=None):
+def print_cmd(cmd, cmd_file=None, extra_env=None):
+    if extra_env is None:
+        extra_env = {}
+    newline_separator = ' \\\n'
     out = []
+    for key in extra_env:
+        out.extend(['{}={}'.format(shlex.quote(key), shlex.quote(extra_env[key])), newline_separator])
     for arg in cmd:
-        out.extend([shlex.quote(arg), ' \\\n'])
+        out.extend([shlex.quote(arg), newline_separator])
     out = ''.join(out)
     print(out)
     if cmd_file is not None:
@@ -148,7 +153,7 @@ def print_cmd(cmd, cmd_file=None):
         st = os.stat(cmd_file)
         os.chmod(cmd_file, st.st_mode | stat.S_IXUSR)
 
-def run_cmd(cmd, cmd_file=None, out_file=None, **kwargs):
+def run_cmd(cmd, cmd_file=None, out_file=None, extra_env=None, **kwargs):
     """
     Run a command. Write the command to stdout before running it.
 
@@ -159,19 +164,23 @@ def run_cmd(cmd, cmd_file=None, out_file=None, **kwargs):
     - cmd_file is not None, write the command to the given file
     - out_file is not None, write the stdout and stderr of the command to the given file
     """
-    if out_file:
+    if out_file is not None:
         stdout=subprocess.PIPE
         stderr=subprocess.STDOUT
     else:
         stdout=None
         stderr=None
-    print_cmd(cmd, cmd_file)
+    if extra_env is None:
+        extra_env = {}
+    env = os.environ.copy()
+    env.update(extra_env)
+    print_cmd(cmd, cmd_file, extra_env=extra_env)
     # Otherwise Ctrl + C gives:
     # - ugly Python stack trace for gem5 (QEMU takes over terminal and is fine).
     # - kills Python, and that then kills GDB: https://stackoverflow.com/questions/19807134/does-python-always-raise-an-exception-if-you-do-ctrlc-when-a-subprocess-is-exec
     signal.signal(signal.SIGINT, signal.SIG_IGN)
     # https://stackoverflow.com/questions/15535240/python-popen-write-to-stdout-and-log-file-simultaneously/52090802#52090802
-    with subprocess.Popen(cmd, stdout=stdout, stderr=stderr, **kwargs) as proc:
+    with subprocess.Popen(cmd, stdout=stdout, stderr=stderr, env=env, **kwargs) as proc:
         if out_file is not None:
             with open(out_file, 'bw') as logfile:
                 while True:
diff --git a/run b/run
index cb21f05..d5f4f76 100755
--- a/run
+++ b/run
@@ -163,7 +163,6 @@ args = common.setup(parser)
 kernel_cli_extra = 'console_msg_format=syslog nokaslr norandmaps panic=-1 printk.devkmsg=on printk.time=y'
 if args.kernel_cli_extra is not None:
     kernel_cli_extra += ' {}'.format(args.kernel_cli_extra)
-env = os.environ.copy()
 kernel_cli_extra_after_dash = ''
 extra_emulator_args = args.extra_emulator_args.copy()
 extra_qemu_args = []
@@ -200,6 +199,7 @@ if not args.graphic:
     extra_qemu_args.append('-nographic')
 if kernel_cli_extra_after_dash:
     kernel_cli_extra += " -{}".format(kernel_cli_extra_after_dash)
+extra_env = {}
 
 # A dummy value that is already turned on by default and does not produce large output,
 # just to prevent QEMU from emitting a warning that '' is not valid.
@@ -210,7 +210,7 @@ if args.gem5:
     gem5_exe_args = shlex.split(args.gem5_exe_args)
     if args.trace is not None:
         gem5_exe_args.append('--debug-flags={}'.format(args.trace))
-    env['M5_PATH'] = common.gem5_system_dir
+    extra_env['M5_PATH'] = common.gem5_system_dir
     cmd = (
         debug_vm +
         [
@@ -378,7 +378,7 @@ if debug_vm:
     out_file = None
 else:
     out_file = common.termout_file
-returncode = common.run_cmd(cmd, cmd_file=common.run_cmd_file, out_file=out_file, env=env)
+returncode = common.run_cmd(cmd, cmd_file=common.run_cmd_file, out_file=out_file, extra_env=extra_env)
 if returncode != 0:
     common.error('simulator exited with status != 0')
 # Check if guest panicked.