Apologies for the duplicate send of these patches, small mistake using git
send-email *.patch ;)
Please only consider the patches that start with [PATCH N/3].
On Wed, Jan 11, 2023 at 11:59 PM Pedro Falcato via groups.io <pedro.falcato=
gmail....@groups.io> wrote:
> Several questions have popped up regarding the ext4 directory entry
> layout and contents off-list. Attempt to clarify these issues by adding
> some explanatory comments.
>
> Signed-off-by: Pedro Falcato <pedro.falc...@gmail.com>
> Cc: Marvin Häuser <mhaeu...@posteo.de>
> ---
> Features/Ext4Pkg/Ext4Dxe/Ext4Disk.h | 21 +++++++++++++++++++--
> Features/Ext4Pkg/Ext4Dxe/Ext4Dxe.h | 5 ++---
> 2 files changed, 21 insertions(+), 5 deletions(-)
>
> diff --git a/Features/Ext4Pkg/Ext4Dxe/Ext4Disk.h
> b/Features/Ext4Pkg/Ext4Dxe/Ext4Disk.h
> index 4fd91a423324..d0a455d0e572 100644
> --- a/Features/Ext4Pkg/Ext4Dxe/Ext4Disk.h
> +++ b/Features/Ext4Pkg/Ext4Dxe/Ext4Disk.h
> @@ -1,7 +1,7 @@
> /** @file
> Raw filesystem data structures
>
> - Copyright (c) 2021 Pedro Falcato All rights reserved.
> + Copyright (c) 2021 - 2023 Pedro Falcato All rights reserved.
> SPDX-License-Identifier: BSD-2-Clause-Patent
>
> Layout of an EXT2/3/4 filesystem:
> @@ -397,12 +397,29 @@ typedef struct _Ext4Inode {
> UINT32 i_projid;
> } EXT4_INODE;
>
> +#define EXT4_NAME_MAX 255
> +
> typedef struct {
> + // offset 0x0: inode number (if 0, unused entry, should skip.)
> UINT32 inode;
> + // offset 0x4: Directory entry's length.
> + // Note: rec_len >= name_len + EXT4_MIN_DIR_ENTRY_LEN and
> rec_len % 4 == 0.
> UINT16 rec_len;
> + // offset 0x6: Directory entry's name's length
> UINT8 name_len;
> + // offset 0x7: Directory entry's file type indicator
> UINT8 file_type;
> - CHAR8 name[255];
> + // offset 0x8: name[name_len]: Variable length character array; not
> null-terminated.
> + CHAR8 name[EXT4_NAME_MAX];
> + // Further notes on names:
> + // 1) We use EXT4_NAME_MAX here instead of flexible arrays for ease of
> use around the driver.
> + //
> + // 2) ext4 directories are defined, as the documentation puts it, as:
> + // "a directory is more or less a flat file that maps an arbitrary byte
> string
> + // (usually ASCII) to an inode number on the filesystem". So, they are
> not
> + // necessarily encoded with ASCII, UTF-8, or any of the sort. We must
> treat it
> + // as a bag of bytes. When interacting with EFI interfaces themselves
> (which expect UCS-2)
> + // we skip any directory entry that is not valid UTF-8.
> } EXT4_DIR_ENTRY;
>
> #define EXT4_MIN_DIR_ENTRY_LEN 8
> diff --git a/Features/Ext4Pkg/Ext4Dxe/Ext4Dxe.h
> b/Features/Ext4Pkg/Ext4Dxe/Ext4Dxe.h
> index adf3c13f6ea9..466e49523030 100644
> --- a/Features/Ext4Pkg/Ext4Dxe/Ext4Dxe.h
> +++ b/Features/Ext4Pkg/Ext4Dxe/Ext4Dxe.h
> @@ -1,7 +1,7 @@
> /** @file
> Common header for the driver
>
> - Copyright (c) 2021 - 2022 Pedro Falcato All rights reserved.
> + Copyright (c) 2021 - 2023 Pedro Falcato All rights reserved.
> SPDX-License-Identifier: BSD-2-Clause-Patent
> **/
>
> @@ -31,8 +31,7 @@
>
> #include "Ext4Disk.h"
>
> -#define SYMLOOP_MAX 8
> -#define EXT4_NAME_MAX 255
> +#define SYMLOOP_MAX 8
> //
> // We need to specify path length limit for security purposes, to prevent
> possible
> // overflows and dead-loop conditions. Originally this limit is absent in
> FS design,
> --
> 2.39.0
>
>
>
>
>
>
>
--
Pedro
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