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Offset Size Description
0x0 0x80 SHA-256 hash-table, verified by CRR
0x80 0x04 Magic "CRO0"
0x84 0x04 Name offset
0x88 0x04 Next loaded CRO pointer, set by RO during loading (Usually zero when the CRO is being loaded)
0x8C 0x04 Previous loaded CRO pointer, set by RO during loading
0x90 0x04 File size
0x94 0x18 Unknown
0xAC 0x04 "Segment offset", symbols are loaded relative to this. Probably filled by dynamic linker, set to 0xFFFFFFFF in file.
0xB0 0x04 Code offset
0xB4 0x04 Code size
0xB8 0x04 unk1 offset
0xBC 0x04 unk1 size
0xC0 0x04 Module Name offset
0xC4 0x04 Module Name size
0xC8 0x04 Segment Table offset
0xCC 0x04 Segment Table num (size = num*12)
0xD0 0x04 Export Table offset
0xD4 0x04 Export Table num (size = num * 8)
0xD8 0x04 unk3 offset
0xDC 0x04 unk3 num
0xE0 0x04 Export Strings offset
0xE4 0x04 Export Strings size
0xE8 0x04 Export Tree offset (fast lookups based on strlen)
0xEC 0x04 Export Tree num (size = num * 8)
0xF0 0x04 unk4 offset
0xF4 0x04 unk4 num
0xF8 0x04 Import Patches offset
0xFC 0x04 Import Patches num (size = num * 12)
0x100 0x04 Import Table 1 offset
0x104 0x04 Import Table 1 num (size = num * 8)
0x108 0x04 Import Table 2 offset
0x10C 0x04 Import Table 2 num (size = num * 8)
0x110 0x04 Import Table 3 offset
0x114 0x04 Import Table 3 num (size = num * 8)
0x118 0x04 Import Strings offset
0x11C 0x04 Import Strings size
0x120 0x04 unk8 offset
0x124 0x04 unk8 num
0x128 0x04 Relocation Patches offset
0x12C 0x04 Relocation Patches num (size = num * 12)
0x130 0x04 unk9 offset
0x134 0x04 unk9 num

Segment offset (4 bytes)

Bits Description
0-3 Segment index for table
4-31 Offset into segment

Segment Table entry (12 bytes)

Offset Size Description
0x0 0x4 Segment offset
0x4 0x4 Segment size
0x8 0x4 Segment id (0, 1, 2..)

Export Table entry (8 bytes)

Offset Size Description
0x0 0x4 Name offset
0x4 0x4 "Segment offset" for export

Import Table entry (8 bytes)

Offset Size Description
0x0 0x4 Name offset
0x4 0x4 Offset of the head of a linear list that contains the patches for this import

Patch entry (12 bytes)

Offset Size Description
0x0 0x4 "Segment offset" for output.
0x4 0x1 Patch type (0=nothing/ignore, 2=38=write u32 absolute (base+X), 3=write u32 relative (base+X-in_ptr), 10=THUMB branch, 28=ARM32 branch, 29=modify ARM32 branch offset, 42=write u32 relative (((signed int)base*2)/2+X-in_ptr), otherwise err)
0x5 0x1 Non-zero if last entry.
0x6 0x1 1 is written to last entry if all symbols loaded successfully.
0x7 0x1 Unknown
0x8 0x4 X (00's in file, probably set by dynamic linker)

ARM32 branch instruction is constructed as follows:

 If X > 0x2000000 or X < 0xFE000000, then skip.
 If (X&1) == 1 then write "b +4" (nop).
 Else write as normal.

CRO with extension .cro is used for "DLLs". CRS with extension .crs can be used for storing "DLL" symbols as well. The end of the file is aligned to a 0x1000-byte boundary with 0xCC bytes. CRO0 files are usually stored under "romfs:/cro/".

The first hash-table entry hashes the 0x100-byte header following the hash-table. The following hash-table entries hash the sections specified in the header.

When the RO module loads the entire CRO into process memory(mapped in the 0x00100000-0x04000000 region), it modifies the mapped CRO data. The magic field is also changed to "FIXD".

Upon loading, the RO module will look for symbol "__aeabi_atexit" or "nnroAeabiAtexit_".

For dumping symbols and loading a CRO into IDA, see [1].