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Ext4Pkg: Add a directory entry tree.
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This helps us track directories and directory entries,
which helps us getting a general idea of how the filesystem
looks. In the future, it might serve as a directory cache.
Right now, it only lets us know which name "." and ".." may refer
to, which fixes a EFI_FILE_PROTOCOL::GetInfo() bug that got triggered
by ShellPkg, in some MdePkg code.

Cc: Leif Lindholm <[email protected]>
Cc: Michael D Kinney <[email protected]>
Cc: Bret Barkelew <[email protected]>
Signed-off-by: Pedro Falcato <[email protected]>
Reviewed-by: Michael D Kinney <[email protected]>
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@heatd @mdkinney
heatd authored and mdkinney committed Aug 24, 2021
1 parent 45e37d8 commit 21b1853
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Showing 7 changed files with 301 additions and 64 deletions.
238 changes: 195 additions & 43 deletions Features/Ext4Pkg/Ext4Dxe/Directory.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -194,13 +194,8 @@ Ext4OpenDirent (
)
{
EFI_STATUS Status;
CHAR16 FileNameBuf[EXT4_NAME_MAX + 1];
CHAR16 FileName[EXT4_NAME_MAX + 1];
EXT4_FILE *File;
CHAR16 *FileName;
UINTN DestMax;

FileName = FileNameBuf;
DestMax = ARRAY_SIZE (FileNameBuf);

File = AllocateZeroPool (sizeof (EXT4_FILE));

Expand All @@ -209,23 +204,32 @@ Ext4OpenDirent (
goto Error;
}

Status = Ext4GetUcs2DirentName (Entry, FileNameBuf);
Status = Ext4GetUcs2DirentName (Entry, FileName);

if (EFI_ERROR (Status)) {
goto Error;
}

if (StrCmp (FileNameBuf, L".") == 0) {
// We're using the parent directory's name
FileName = Directory->FileName;
DestMax = StrLen (FileName) + 1;
}
if (StrCmp (FileName, L".") == 0) {
// We're using the parent directory's dentry
File->Dentry = Directory->Dentry;

File->FileName = AllocateZeroPool (StrSize (FileName));
ASSERT (File->Dentry != NULL);

if (!File->FileName) {
Status = EFI_OUT_OF_RESOURCES;
goto Error;
Ext4RefDentry (File->Dentry);
} else if (StrCmp (FileName, L"..") == 0) {
// Using the parent's parent's dentry
File->Dentry = Directory->Dentry->Parent;

ASSERT (File->Dentry != NULL);

Ext4RefDentry (File->Dentry);
} else {
File->Dentry = Ext4CreateDentry (FileName, Directory->Dentry);

if (!File->Dentry) {
goto Error;
}
}

Status = Ext4InitExtentsMap (File);
Expand All @@ -234,9 +238,6 @@ Ext4OpenDirent (
goto Error;
}

// This should not fail.
StrCpyS (File->FileName, DestMax, FileName);

File->InodeNum = Entry->inode;

Ext4SetupFile (File, Partition);
Expand All @@ -255,8 +256,8 @@ Ext4OpenDirent (

Error:
if (File != NULL) {
if (File->FileName != NULL) {
FreePool (File->FileName);
if (File->Dentry != NULL) {
Ext4UnrefDentry (File->Dentry);
}

if (File->ExtentsMap != NULL) {
Expand Down Expand Up @@ -333,52 +334,47 @@ Ext4OpenVolume (
OUT EFI_FILE_PROTOCOL **Root
)
{
EXT4_INODE *RootInode;
EFI_STATUS Status;
EXT4_FILE *RootDir;
EXT4_INODE *RootInode;
EFI_STATUS Status;
EXT4_FILE *RootDir;
EXT4_PARTITION *Partition;

Partition = (EXT4_PARTITION *)This;

// 2 is always the root inode number in ext4
Status = Ext4ReadInode ((EXT4_PARTITION *)This, 2, &RootInode);
Status = Ext4ReadInode (Partition, EXT4_ROOT_INODE_NR, &RootInode);

if (EFI_ERROR (Status)) {
DEBUG ((DEBUG_ERROR, "[ext4] Could not open root inode - status %x\n", Status));
DEBUG ((DEBUG_ERROR, "[ext4] Could not open root inode - error %r\n", Status));
return Status;
}

RootDir = AllocateZeroPool (sizeof (EXT4_FILE));

if (!RootDir) {
if (RootDir == NULL) {
FreePool (RootInode);
return EFI_OUT_OF_RESOURCES;
}

// The filename will be "\"(null terminated of course)
RootDir->FileName = AllocateZeroPool (2 * sizeof (CHAR16));

if (!RootDir->FileName) {
FreePool (RootDir);
FreePool (RootInode);
return EFI_OUT_OF_RESOURCES;
}

RootDir->FileName[0] = L'\\';

RootDir->Inode = RootInode;
RootDir->InodeNum = 2;
RootDir->InodeNum = EXT4_ROOT_INODE_NR;

Status = Ext4InitExtentsMap (RootDir);

if (EFI_ERROR (Status)) {
FreePool (RootDir->FileName);
FreePool (RootInode);
FreePool (RootDir);
return EFI_OUT_OF_RESOURCES;
}

Ext4SetupFile (RootDir, (EXT4_PARTITION *)This);
Ext4SetupFile (RootDir, Partition);
*Root = &RootDir->Protocol;

InsertTailList (&((EXT4_PARTITION *)This)->OpenFiles, &RootDir->OpenFilesListNode);
InsertTailList (&Partition->OpenFiles, &RootDir->OpenFilesListNode);

ASSERT (Partition->RootDentry != NULL);
RootDir->Dentry = Partition->RootDentry;

Ext4RefDentry (RootDir->Dentry);

return EFI_SUCCESS;
}
Expand Down Expand Up @@ -525,3 +521,159 @@ Ext4ReadDir (
Out:
return Status;
}

/**
Removes a dentry from the other's list.
@param[in out] Parent Pointer to the parent EXT4_DENTRY.
@param[in out] ToBeRemoved Pointer to the child EXT4_DENTRY.
**/
STATIC
VOID
Ext4RemoveDentry (
IN OUT EXT4_DENTRY *Parent,
IN OUT EXT4_DENTRY *ToBeRemoved
)
{
EXT4_DENTRY *D;
LIST_ENTRY *Entry;
LIST_ENTRY *NextEntry;

BASE_LIST_FOR_EACH_SAFE (Entry, NextEntry, &Parent->Children) {
D = EXT4_DENTRY_FROM_DENTRY_LIST (Entry);

if (D == ToBeRemoved) {
RemoveEntryList (Entry);
return;
}
}

DEBUG ((DEBUG_ERROR, "[ext4] Ext4RemoveDentry did not find the asked-for dentry\n"));
}

/**
Adds a dentry to the other's list.
The dentry that is added to the other one's list gets ->Parent set to Parent,
and the parent gets its reference count incremented.
@param[in out] Parent Pointer to the parent EXT4_DENTRY.
@param[in out] ToBeAdded Pointer to the child EXT4_DENTRY.
**/
STATIC
VOID
Ext4AddDentry (
IN OUT EXT4_DENTRY *Parent,
IN OUT EXT4_DENTRY *ToBeAdded
)
{
ToBeAdded->Parent = Parent;
InsertTailList (&Parent->Children, &ToBeAdded->ListNode);
Ext4RefDentry (Parent);
}

/**
Creates a new dentry object.
@param[in] Name Name of the dentry.
@param[in out opt] Parent Parent dentry, if it's not NULL.
@return The new allocated and initialised dentry.
The ref count will be set to 1.
**/
EXT4_DENTRY *
Ext4CreateDentry (
IN CONST CHAR16 *Name,
IN OUT EXT4_DENTRY *Parent OPTIONAL
)
{
EXT4_DENTRY *Dentry;
EFI_STATUS Status;

Dentry = AllocateZeroPool (sizeof (EXT4_DENTRY));

if (Dentry == NULL) {
return NULL;
}

Dentry->RefCount = 1;

// This StrCpyS should not fail.
Status = StrCpyS (Dentry->Name, ARRAY_SIZE (Dentry->Name), Name);

ASSERT_EFI_ERROR (Status);

InitializeListHead (&Dentry->Children);

if (Parent != NULL) {
Ext4AddDentry (Parent, Dentry);
}

DEBUG ((DEBUG_FS, "[ext4] Created dentry %s\n", Name));

return Dentry;
}

/**
Increments the ref count of the dentry.
@param[in out] Dentry Pointer to a valid EXT4_DENTRY.
**/
VOID
Ext4RefDentry (
IN OUT EXT4_DENTRY *Dentry
)
{
UINTN OldRef;

OldRef = Dentry->RefCount;

Dentry->RefCount++;

// I'm not sure if this (Refcount overflow) is a valid concern,
// but it's better to be safe than sorry.
ASSERT (OldRef < Dentry->RefCount);
}

/**
Deletes the dentry.
@param[in out] Dentry Pointer to a valid EXT4_DENTRY.
**/
STATIC
VOID
Ext4DeleteDentry (
IN OUT EXT4_DENTRY *Dentry
)
{
if (Dentry->Parent) {
Ext4RemoveDentry (Dentry->Parent, Dentry);
Ext4UnrefDentry (Dentry->Parent);
}

DEBUG ((DEBUG_FS, "[ext4] Deleted dentry %s\n", Dentry->Name));
FreePool (Dentry);
}

/**
Decrements the ref count of the dentry.
If the ref count is 0, it's destroyed.
@param[in out] Dentry Pointer to a valid EXT4_DENTRY.
@retval True if it was destroyed, false if it's alive.
**/
BOOLEAN
Ext4UnrefDentry (
IN OUT EXT4_DENTRY *Dentry
)
{
Dentry->RefCount--;

if (Dentry->RefCount == 0) {
Ext4DeleteDentry (Dentry);
return TRUE;
}

return FALSE;
}
3 changes: 3 additions & 0 deletions Features/Ext4Pkg/Ext4Dxe/Ext4Disk.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -451,4 +451,7 @@ typedef struct {
typedef UINT64 EXT4_BLOCK_NR;
typedef UINT32 EXT4_INO_NR;

// 2 is always the root inode number in ext4
#define EXT4_ROOT_INODE_NR 2

#endif
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