xfs: Symbolic links support

- Necessary hooks for reading symlinks are implemented

- Added support for local symlinks

- Added support for extent based symlinks

- This patch completes #17791

Change-Id: If6847974562b21f751097df357326f4643eff757
Reviewed-on: https://review.haiku-os.org/c/haiku/+/5621
Tested-by: Commit checker robot <no-reply+buildbot@haiku-os.org>
Reviewed-by: Adrien Destugues <pulkomandy@pulkomandy.tk>

src/add-ons/kernel/file_systems/xfs/Jamfile

@@ -32,6 +32,7 @@ local xfsSources =
 	Node.cpp
 	ShortAttribute.cpp
 	ShortDirectory.cpp
+	Symlink.cpp
 	Volume.cpp
 	xfs.cpp
 	;

src/add-ons/kernel/file_systems/xfs/Symlink.cpp

@@ -0,0 +1,141 @@
+/*
+ * Copyright 2022, Raghav Sharma, raghavself28@gmail.com
+ * Distributed under the terms of the MIT License.
+ */
+
+
+#include "Symlink.h"
+
+#include "VerifyHeader.h"
+
+
+Symlink::Symlink(Inode* inode)
+	:
+	fInode(inode),
+	fSymlinkBuffer(NULL)
+{
+}
+
+
+Symlink::~Symlink()
+{
+	delete fSymlinkBuffer;
+}
+
+
+status_t
+Symlink::_FillMapEntry()
+{
+	void* pointerToMap = DIR_DFORK_PTR(fInode->Buffer(), fInode->CoreInodeSize());
+
+	uint64 firstHalf = *((uint64*)pointerToMap);
+	uint64 secondHalf = *((uint64*)pointerToMap + 1);
+		//dividing the 128 bits into 2 parts.
+	firstHalf = B_BENDIAN_TO_HOST_INT64(firstHalf);
+	secondHalf = B_BENDIAN_TO_HOST_INT64(secondHalf);
+	fMap.br_state = firstHalf >> 63;
+	fMap.br_startoff = (firstHalf & MASK(63)) >> 9;
+	fMap.br_startblock = ((firstHalf & MASK(9)) << 43) | (secondHalf >> 21);
+	fMap.br_blockcount = secondHalf & MASK(21);
+	TRACE("Extent::Init: startoff:(%" B_PRIu64 "), startblock:(%" B_PRIu64 "),"
+		"blockcount:(%" B_PRIu64 "),state:(%" B_PRIu8 ")\n", fMap.br_startoff, fMap.br_startblock,
+		fMap.br_blockcount, fMap.br_state);
+
+	return B_OK;
+}
+
+
+status_t
+Symlink::_FillBuffer()
+{
+	if (fMap.br_state != 0)
+		return B_BAD_VALUE;
+
+	int len = fInode->DirBlockSize();
+	fSymlinkBuffer = new(std::nothrow) char[len];
+	if (fSymlinkBuffer == NULL)
+		return B_NO_MEMORY;
+
+	xfs_daddr_t readPos =
+		fInode->FileSystemBlockToAddr(fMap.br_startblock);
+
+	if (read_pos(fInode->GetVolume()->Device(), readPos, fSymlinkBuffer, len)
+		!= len) {
+		ERROR("Extent::FillBlockBuffer(): IO Error");
+		return B_IO_ERROR;
+	}
+
+	return B_OK;
+}
+
+
+status_t
+Symlink::_ReadLocalLink(off_t pos, char* buffer, size_t* _length)
+{
+	// All symlinks contents are inside inode itself
+
+	size_t lengthToRead = fInode->Size();
+
+	if (*_length < lengthToRead)
+		lengthToRead = *_length;
+
+	char* offset = (char*)(DIR_DFORK_PTR(fInode->Buffer(), fInode->CoreInodeSize()));
+
+	memcpy(buffer, offset, lengthToRead);
+
+	*_length = lengthToRead;
+
+	return B_OK;
+
+}
+
+
+status_t
+Symlink::_ReadExtentLink(off_t pos, char* buffer, size_t* _length)
+{
+	status_t status;
+	// First fill up extent, then Symlink block buffer
+	status = _FillMapEntry();
+	if (status != B_OK)
+		return status;
+
+	status = _FillBuffer();
+	if (status != B_OK)
+		return status;
+
+	uint32 offset = 0;
+	// If it is Version 5 xfs then we have Symlink header
+	if (fInode->Version() == 3) {
+		SymlinkHeader* header = (SymlinkHeader*)fSymlinkBuffer;
+		if (!VerifyHeader<SymlinkHeader>(header, fSymlinkBuffer, fInode, 0, &fMap, 0)) {
+			ERROR("Invalid data header");
+			return B_BAD_VALUE;
+		}
+		offset += sizeof(SymlinkHeader);
+	}
+
+	size_t lengthToRead = fInode->Size();
+
+	if (*_length < lengthToRead)
+		lengthToRead = *_length;
+
+	memcpy(buffer, fSymlinkBuffer + offset, lengthToRead);
+
+	*_length = lengthToRead;
+
+	return B_OK;
+}
+
+
+status_t
+Symlink::ReadLink(off_t pos, char* buffer, size_t* _length)
+{
+	switch (fInode->Format()) {
+		case XFS_DINODE_FMT_LOCAL:
+			return _ReadLocalLink(pos, buffer, _length);
+		case XFS_DINODE_FMT_EXTENTS:
+			return _ReadExtentLink(pos, buffer, _length);
+		default:
+			return B_BAD_VALUE;
+	}
+}

src/add-ons/kernel/file_systems/xfs/Symlink.h

@@ -0,0 +1,68 @@
+/*
+ * Copyright 2022, Raghav Sharma, raghavself28@gmail.com
+ * Distributed under the terms of the MIT License.
+ */
+#ifndef XFS_SYMLINK_H
+#define XFS_SYMLINK_H
+
+
+#include "Inode.h"
+
+
+#define SYMLINK_MAGIC 0x58534c4d
+
+
+// Used only on Version 5
+struct SymlinkHeader {
+public:
+
+			uint32				Magic()
+								{ return B_BENDIAN_TO_HOST_INT32(sl_magic); }
+
+			uint64				Blockno()
+								{ return B_BENDIAN_TO_HOST_INT64(sl_blkno); }
+
+			uuid_t*				Uuid()
+								{ return &sl_uuid; }
+
+			uint64				Owner()
+								{ return B_BENDIAN_TO_HOST_INT64(sl_owner); }
+
+	static	uint32				ExpectedMagic(int8 whichDirectory, Inode* inode)
+								{ return SYMLINK_MAGIC; }
+
+	static	uint32				CRCOffset()
+								{ return offsetof(SymlinkHeader, sl_crc); }
+
+private:
+			uint32				sl_magic;
+			uint32				sl_offset;
+			uint32				sl_bytes;
+public:
+			uint32				sl_crc;
+private:
+			uuid_t				sl_uuid;
+			uint64				sl_owner;
+			uint64				sl_blkno;
+			uint64				sl_lsn;
+};
+
+
+// This class will handle all formats of Symlinks in xfs
+class Symlink {
+public:
+								Symlink(Inode* inode);
+								~Symlink();
+			status_t			ReadLink(off_t pos, char* buffer, size_t* _length);
+private:
+			status_t			_FillMapEntry();
+			status_t			_FillBuffer();
+			status_t			_ReadLocalLink(off_t pos, char* buffer, size_t* _length);
+			status_t			_ReadExtentLink(off_t pos, char* buffer, size_t* _length);
+
+			Inode*				fInode;
+			ExtentMapEntry		fMap;
+			char*				fSymlinkBuffer;
+};
+
+#endif

src/add-ons/kernel/file_systems/xfs/kernel_interface.cpp

@@ -9,6 +9,7 @@
 #include "Directory.h"
 #include "Inode.h"
 #include "ShortAttribute.h"
+#include "Symlink.h"
 #include "Utility.h"
 #include "Volume.h"
 
@@ -353,7 +354,18 @@ static status_t
 xfs_read_link(fs_volume *_volume, fs_vnode *_node, char *buffer,
 	size_t *_bufferSize)
 {
-	return B_NOT_SUPPORTED;
+	TRACE("XFS_READ_SYMLINK\n");
+
+	Inode* inode = (Inode*)_node->private_node;
+
+	if (!inode->IsSymLink())
+		return B_BAD_VALUE;
+
+	Symlink symlink(inode);
+
+	status_t result = symlink.ReadLink(0, buffer, _bufferSize);
+
+	return result;
 }
 
 

src/tests/add-ons/kernel/file_systems/xfs/xfs_shell/Jamfile

@@ -51,6 +51,7 @@ local xfsSource =
 	Node.cpp
 	ShortAttribute.cpp
 	ShortDirectory.cpp
+	Symlink.cpp
 	Volume.cpp
 	xfs.cpp
 ;