cmdline splitting fails for some processes

[tehybel]

Certain processes, such as Discord, modify their /proc/pid/cmdline file (?) to contain spaces instead of null bytes:

12:42 /proc/528292 $ cat cmdline | xxd                                                                                                    
00000000: 2f6f 7074 2f64 6973 636f 7264 2f44 6973  /opt/discord/Dis
00000010: 636f 7264 202d 2d74 7970 653d 7265 6e64  cord --type=rend
00000020: 6572 6572 202d 2d63 7261 7368 7061 642d  erer --crashpad-
00000030: 6861 6e64 6c65 722d 7069 643d 3532 3832  handler-pid=5282
00000040: 3139 202d 2d65 6e61 626c 652d 6372 6173  19 --enable-cras
00000050: 682d 7265 706f 7274 6572 3d62 3632 3039  h-reporter=b6209
00000060: 6135 342d 6565 6432 2d34 3134 382d 6138  a54-eed2-4148-a8
...
000002c0: 6572 7300                                ers.

Note that arguments here are separated by spaces, not null bytes. This means that splitting arguments fails inside def cmdline(self), and therefore matching by cmdlines ends up failing.

For context, I'm trying to modify the nice value of the Discord renderer process, specifically, with a rule such as:

{ "name": "Discord", "cmdlines": ["--type=renderer"], "type": "discord-renderer" }

Splitting by both spaces and null bytes fixes the issue in this case:

_cmdline = _cmdline.replace(b' ', b'\x00').split(b'\x00')

However do note that this will not handle the cases where there are spaces inside the arguments.