From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wr1-f54.google.com (mail-wr1-f54.google.com [209.85.221.54]) by mx.groups.io with SMTP id smtpd.web11.40727.1673479296802907824 for ; Wed, 11 Jan 2023 15:21:37 -0800 Authentication-Results: mx.groups.io; dkim=pass header.i=@gmail.com header.s=20210112 header.b=TG/vypKl; spf=pass (domain: gmail.com, ip: 209.85.221.54, mailfrom: pedro.falcato@gmail.com) Received: by mail-wr1-f54.google.com with SMTP id v2so5519351wrw.10 for ; Wed, 11 Jan 2023 15:21:36 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=Ojkg60D3UDSMCQP5zMm8YFHR5PGQfRPRSm+bh1ITYb4=; b=TG/vypKlyh5TAnRQNhBZXS4UNSfx3khzxCRACv+TDjrXtU+wiOmITrC/pkGPxg8rKv Te9ssTnIKSc1nv9rnzw+qftU7kc8U7LWc2UVC9lbGbeG3Q89+xLFhqjdnSemWOgbgZiP iBbzwAxHAJpqGuIeZQh2doeEgJltFwu5LbEt4uvGDP+l5E82gB5O+2ffX4Os6iFPcaHH Ty52rSr4Utlskf+SdDMY88LUs62/Xt8Ga4bsFhG0i4rSIMhKpUjVVH4GBSljyBuYrxcl e/WQfyrWwb+9mMGNvKibhOQiDKdZc6GrqYxm3Vad5y2YfXCxOHaegoxOtzPQ/WfQ5GPs v1TA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=Ojkg60D3UDSMCQP5zMm8YFHR5PGQfRPRSm+bh1ITYb4=; b=qdxk6XcnX9ycZXa9eP3W+StM6kRRou4KHuHMn7xUvnKjTPu+sfdsjPpJJFdoI152Fr vVeH02zuSqhQ3X9Lxzp/ld5In1KPlX9UOHORqN8FTrswq+J8er6o5CS+fcbcorNQvW74 Qlh7k17JKHITJrYLW1EP/wfNkkDU18ArnKyLs1nDjSJfymAEGUhxKz15xKJzYJniFSsC QayTGDsdhHWZieCeeCHrKMoxgMmbIFpm4dYBb97WwBBN+jy+9dnq/QzQFQnFcQyKfiXD kYRcz6IJeU8HNNF/6aagoD2oN+1cMlTLt5mGIctXUEAXrrxI1+wqN8KQMXkWO7Dn2wuQ kISA== X-Gm-Message-State: AFqh2koxzCaiyuigxwlG2X2i6+GBgkRc94b5r3fMbyxw59JN0rvBNWW6 IRXRtCCONeLHGGyksSvo/RhCnlEBdekojQ== X-Google-Smtp-Source: AMrXdXvlNYU13WoL/q2URmoFSUF7iYHLo4E18j1ocLWuF2Q1NbZLApoKGcQQ0mHoAsYsDZmOkaHIuA== X-Received: by 2002:a5d:488b:0:b0:242:5ae0:5b41 with SMTP id g11-20020a5d488b000000b002425ae05b41mr48052818wrq.33.1673479294799; Wed, 11 Jan 2023 15:21:34 -0800 (PST) Return-Path: Received: from PC-PEDRO-ARCH.lan ([2001:8a0:7280:5801:9441:3dce:686c:bfc7]) by smtp.gmail.com with ESMTPSA id u5-20020adfdb85000000b002ba2646fd30sm17509821wri.36.2023.01.11.15.21.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 11 Jan 2023 15:21:34 -0800 (PST) From: "Pedro Falcato" To: devel@edk2.groups.io Cc: Pedro Falcato , =?UTF-8?q?Marvin=20H=C3=A4user?= Subject: [PATCH 1/1] Ext4Pkg: Add documentation surrounding ext4 directory entries Date: Wed, 11 Jan 2023 23:21:31 +0000 Message-Id: <20230111232131.244584-1-pedro.falcato@gmail.com> X-Mailer: git-send-email 2.39.0 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Cc: Marvin Häuser --- Features/Ext4Pkg/Ext4Dxe/Ext4Disk.h | 18 +++++++++++++++++- Features/Ext4Pkg/Ext4Dxe/Ext4Dxe.h | 3 +-- 2 files changed, 18 insertions(+), 3 deletions(-) diff --git a/Features/Ext4Pkg/Ext4Dxe/Ext4Disk.h b/Features/Ext4Pkg/Ext4Dxe/Ext4Disk.h index 4fd91a423324..2dad967e575d 100644 --- a/Features/Ext4Pkg/Ext4Dxe/Ext4Disk.h +++ b/Features/Ext4Pkg/Ext4Dxe/Ext4Disk.h @@ -397,12 +397,28 @@ typedef struct _Ext4Inode { UINT32 i_projid; } EXT4_INODE; +#define EXT4_NAME_MAX 255 + typedef struct { + // ext4 directory entries are layed out in the following fashion: + // offset 0x0: UINT32 inode number (if 0, unused entry, should skip.) + // offset 0x4: UINT16 rec_len: Dir entry's length. + // Note: rec_len >= name_len + EXT4_MIN_DIR_ENTRY_LEN and rec_len % 4 == 0. + // offset 0x6: UINT8 name_len: Dir entry's name's length + // offset 0x7: UINT8 file_type Dir entry's file type indicator + // offset 0x8: CHAR8 name[name_len]: Variable length character array; not null-terminated. + // + // Further note: 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. UINT32 inode; UINT16 rec_len; UINT8 name_len; UINT8 file_type; - CHAR8 name[255]; + CHAR8 name[EXT4_NAME_MAX]; } 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..81ba568c5947 100644 --- a/Features/Ext4Pkg/Ext4Dxe/Ext4Dxe.h +++ b/Features/Ext4Pkg/Ext4Dxe/Ext4Dxe.h @@ -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