Backtrace when parsing firmware on the LVFS

[hughsie]

I've just been notified that a specific firmware on the LVFS causes PSPTool to crash with a backtrace:

File "/home/hughsie/Code/lvfs-website/plugins/amdpsp/__init__.py", line 42, in _run_psptool_on_blob
  psp = PSPTool(md.blob, verbose=True)
File "/home/hughsie/Code/lvfs-website/env/lib/python3.7/site-packages/psptool/psptool.py", line 38, in __init__
  self.blob = Blob(rom_bytes, len(rom_bytes), self)
File "/home/hughsie/Code/lvfs-website/env/lib/python3.7/site-packages/psptool/blob.py", line 58, in __init__
  self._parse_entry_table()
File "/home/hughsie/Code/lvfs-website/env/lib/python3.7/site-packages/psptool/blob.py", line 112, in _parse_entry_table
  directory = self[address:address + 16 * 8]
File "/home/hughsie/Code/lvfs-website/env/lib/python3.7/site-packages/psptool/utils.py", line 45, in __getitem__
  new_slice = self._offset_slice(item)
File "/home/hughsie/Code/lvfs-website/env/lib/python3.7/site-packages/psptool/utils.py", line 63, in _offset_slice
  assert (old_slice.start <= self.buffer_size)

The file to reproduce this problem is inside the archive found here https://fwupd.org/downloads/ab2c51b54fb69b70000922a8b672eba6e79e36c2-Lenovo-M625Q-SystemFirmware-M1WKT30A.cab -- just download that, decompress the archive then run psptool on M1WKT30A.ROM

[cwerling]

Thank you for this interesting bug, Richard! I found the bug and will push a fix soon. In case you are curious what happened here:

We are dealing with an 8 MB ROM here instead of a 16 MB ROM as usual. The latter are normally mapped into memory at 0xFF000000, i.e. the last 16 MB of memory in a 32 bit memory. That is why PSPTool has to mask all global addresses in the PSP Firmware File System with 0x00FFFFFF to obtain the actual offset in the ROM file.

Now this very special 8 MB ROM file must be mapped to the last 8 MB of memory, so naturally, we have to further mask all offsets with 0x00800000 to obtain the correct offset in the ROM file.

Cheers! :)

[cwerling]

pip install -U psptool 🎉
(https://pypi.org/project/psptool/2.1/)

[hughsie]

Many thanks!