This is a collection of notes which should help anyone looking at the PS2 BIOS. The goal is to fully document the public interface so that a free (GPL) replacement BIOS can be developed for use in emulators such as PCSX2. Where source code examples are given, these refer to the fps2bios source code and not to any original Sony code. The information contained in here has been collected from a number of sources but the main sources are the PCSX2 source code which documents the machine hardware and the open source ps2sdk found at ps2dev.org.

The PS2 BIOS is a collection of files packed into a single file. A file called ROMDIR contains the name and size of each file in the archive. The first file in the archive is called RESET and contains …ver más…

It does this by modifying the import table and changing the j $31 to a j imm instruction where imm is the relative address of the exported function.

The LOADCORE code that actually does the linking is in fix_imports() and is shown below: int fix_imports(struct import *imp, struct export *exp){ func *ef; struct func_stub *fs; int count=0;

for (ef=exp->func; *ef; ef++){ count++; //count number of exported functions } for (fs=imp->func; fs->jr_ra; fs++) { int ordinal = fs->addiu0 & 0xFFFF; if (ordinal < count) { fs->jr_ra=(((u32)exp->func[ordinal]>>2) & 0x3FFFFFF) | INS_J; } else { fs->jr_ra=INS_JR_RA; } } imp->flags |=FLAG_IMPORT_QUEUED; return 0;
}

Module loading

The first 2 modules loaded are SYSMEM and LOADCORE. After these have been successfully loaded, the remaining modules are loaded in the order specified in iopload.c. The IRX dynamic linking mechanism is very simple and does not account for forward references, so this list must be carefully ordered. Details of the individual modules follow.

The Exception Manager (EXCEPMAN – version 1.1)

The exception manager is the 3rd module loaded and as the name suggests is responsible for managing the exception handling code. It does not actually implement any of the exception