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fix(fatfs): Fixed fatfsparse.py parsing of FAT boot sector

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The fatfsparse.py script was too strict in parsing the FAT boot sector, causing it to fail in
certain cases. This commit fixes the issue by making the parsing less strict and allowing for more
flexibility in the boot sector format.

This change improves the reliability and compatibility of the fatfsparse.py script, ensuring that it
can correctly parse a wider range of FAT boot sectors.

Docs updated
This commit is contained in:
radek.tandler
2023-11-02 11:33:47 +01:00
parent 0e69fcb8ac
commit a640626b76
4 changed files with 21 additions and 13 deletions
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17
components/fatfs/fatfs_utils/boot_sector.py
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@@ -1,9 +1,9 @@
# SPDX-FileCopyrightText: 2021-2022 Espressif Systems (Shanghai) CO LTD
# SPDX-FileCopyrightText: 2021-2023 Espressif Systems (Shanghai) CO LTD
# SPDX-License-Identifier: Apache-2.0
from inspect import getmembers, isroutine
from typing import Optional
from construct import Const, Int8ul, Int16ul, Int32ul, PaddedString, Struct, core
from construct import Bytes, Const, Int8ul, Int16ul, Int32ul, PaddedString, Padding, Struct, core
from .exceptions import InconsistentFATAttributes, NotInitialized
from .fatfs_state import BootSectorState
@@ -29,8 +29,7 @@ class BootSector:
BOOT_HEADER_SIZE = 512
BOOT_SECTOR_HEADER = Struct(
# this value reflects BS_jmpBoot used for ESP32 boot sector (any other accepted)
'BS_jmpBoot' / Const(b'\xeb\xfe\x90'),
'BS_jmpBoot' / Bytes(3),
'BS_OEMName' / PaddedString(MAX_OEM_NAME_SIZE, SHORT_NAMES_ENCODING),
'BPB_BytsPerSec' / Int16ul,
'BPB_SecPerClus' / Int8ul,
@@ -45,12 +44,12 @@ class BootSector:
'BPB_HiddSec' / Int32ul,
'BPB_TotSec32' / Int32ul, # zero if the FAT type is 12/16, otherwise number of sectors
'BS_DrvNum' / Const(b'\x80'),
'BS_Reserved1' / Const(EMPTY_BYTE),
'BS_Reserved1' / Padding(1),
'BS_BootSig' / Const(b'\x29'),
'BS_VolID' / Int32ul,
'BS_VolLab' / PaddedString(MAX_VOL_LAB_SIZE, SHORT_NAMES_ENCODING),
'BS_FilSysType' / PaddedString(MAX_FS_TYPE_SIZE, SHORT_NAMES_ENCODING),
'BS_EMPTY' / Const(448 * EMPTY_BYTE),
'BS_EMPTY' / Padding(448),
'Signature_word' / Const(FATDefaults.SIGNATURE_WORD)
)
assert BOOT_SECTOR_HEADER.sizeof() == BOOT_HEADER_SIZE
@@ -73,7 +72,8 @@ class BootSector:
* EMPTY_BYTE)
self.boot_sector_state.binary_image = (
BootSector.BOOT_SECTOR_HEADER.build(
dict(BS_OEMName=pad_string(boot_sector_state.oem_name, size=BootSector.MAX_OEM_NAME_SIZE),
dict(BS_jmpBoot=(b'\xeb\xfe\x90'),
BS_OEMName=pad_string(boot_sector_state.oem_name, size=BootSector.MAX_OEM_NAME_SIZE),
BPB_BytsPerSec=boot_sector_state.sector_size,
BPB_SecPerClus=boot_sector_state.sectors_per_cluster,
BPB_RsvdSecCnt=boot_sector_state.reserved_sectors_cnt,
@@ -91,8 +91,7 @@ class BootSector:
BS_VolLab=pad_string(boot_sector_state.volume_label,
size=BootSector.MAX_VOL_LAB_SIZE),
BS_FilSysType=pad_string(boot_sector_state.file_sys_type,
size=BootSector.MAX_FS_TYPE_SIZE)
)
size=BootSector.MAX_FS_TYPE_SIZE))
) + pad_header + fat_tables_content + root_dir_content + data_content
)