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tools/efs_parser: fix offset decision for directories lookup #18

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61168bd
tools/efs_parser: move magic and cookie values to global scope
Joursoir Aug 7, 2025
6d4f2a9
tools/efs_parser: fix offset decision for directories lookup
Joursoir Aug 7, 2025
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30 changes: 17 additions & 13 deletions tools/efs_parser.py
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Original file line number Diff line number Diff line change
Expand Up @@ -3,10 +3,15 @@
from struct import unpack
import zlib

EFS_MAGIC = b"\xAA\x55\xAA\x55"
PSP_COOKIE = b"$PSP"
PSPL2_COOKIE = b"$PL2"
PSP2_COOKIE = b"2PSP"
BHD_COOKIE = b"$BHD"
BHDL2_COOKIE = b"$BL2"
BHD2_COOKIE = b"2BHD"

def extract_efs(rom):
efs_magic = b"\xAA\x55\xAA\x55"

efs_offsets = [
0x020000,
0x820000,
Expand All @@ -17,22 +22,21 @@ def extract_efs(rom):
]

for offset in efs_offsets:
if rom[offset:offset+4] == efs_magic:
if rom[offset:offset+4] == EFS_MAGIC:
return rom[offset:offset+0x4B]

def parse_efs(efs):
print("Parsing EFS")
efs_magic = b"\xAA\x55\xAA\x55"

if efs[0x0:0x4] != efs_magic:
if efs[0x0:0x4] != EFS_MAGIC:
print(f"Invalid EFS magic {efs[0:4]}")
exit()


dir_offsets = []
for offset in range(0x14, 0x30, 4):
for offset in range(0x10, 0x30, 4):
ptr = int.from_bytes(efs[offset:offset+4], "little")
if ptr != 0x00000000 and ptr != 0xFFFFFFFE:
if ptr != 0x00000000 and ptr != 0xFFFFFFFE and ptr != 0xFFFFFFFF:
dir_offsets.append(ptr)

print(f"# EFS entries: {len(dir_offsets)}")
Expand All @@ -45,13 +49,13 @@ def parse_efs(efs):
def parse_dir(rom, offset):
magic = rom[offset:offset+4]

if magic == b"$PSP":
if magic == PSP_COOKIE:
parse_psp_dir(rom, offset)
pass
elif magic == b"2PSP" or magic == b"2BHD":
elif magic == PSP2_COOKIE or magic == BHD2_COOKIE:
parse_psp_combodir(rom, offset)
pass
elif magic == b"$BHD":
elif magic == BHD_COOKIE:
parse_bios_dir(rom, offset)
pass
else:
Expand All @@ -66,7 +70,7 @@ def parse_psp_dir(rom, offset):
psp_hdr = rom[offset:offset+0x10]

psp_magic = psp_hdr[0:4]
if psp_magic != b"$PSP" and psp_magic != b"$PL2":
if psp_magic != PSP_COOKIE and psp_magic != PSPL2_COOKIE:
print(f"Invalid magic {psp_magic} when parsing PSP directory")
exit()

Expand Down Expand Up @@ -149,7 +153,7 @@ def parse_psp_combodir(rom, offset):
psp_hdr = rom[offset:offset+0x20]

psp_magic = psp_hdr[0:4]
if psp_magic != b"2PSP" and psp_magic != b"2BHD":
if psp_magic != PSP2_COOKIE and psp_magic != BHD2_COOKIE:
print(f"Invalid magic {psp_magic} when parsing PSP directory")
exit()

Expand Down Expand Up @@ -214,7 +218,7 @@ def parse_bios_dir(rom, offset):
bios_hdr = rom[offset:offset+0x10]

bios_magic = bios_hdr[0x0:0x4]
if bios_magic != b"$BHD" and bios_magic != b"$BL2":
if bios_magic != BHD_COOKIE and bios_magic != BHDL2_COOKIE:
print(f"Invalid magic {bios_magic} when parsing BIOS directory")
exit()

Expand Down