Add basic symlink support.

- sys$readlink + readlink()
- Add a /proc/PID/exe symlink to the process's executable.
- Print symlink contents in ls output.
- Some work on plumbing options into VFS::open().

VirtualFileSystem/FileSystem.cpp

@@ -74,7 +74,8 @@ ByteBuffer FileSystem::readEntireInode(InodeIdentifier inode, FileHandle* handle
         return nullptr;
     }
 
-    auto contents = ByteBuffer::createUninitialized(metadata.size);
+    size_t initialSize = metadata.size ? metadata.size : 4096;
+    auto contents = ByteBuffer::createUninitialized(initialSize);
 
     Unix::ssize_t nread;
     byte buffer[512];
@@ -87,6 +88,7 @@ ByteBuffer FileSystem::readEntireInode(InodeIdentifier inode, FileHandle* handle
         memcpy(out, buffer, nread);
         out += nread;
         offset += nread;
+        ASSERT(offset <= initialSize); // FIXME: Support dynamically growing the buffer.
     }
     if (nread < 0) {
         kprintf("[fs] readInode: ERROR: %d\n", nread);

VirtualFileSystem/SyntheticFileSystem.cpp

@@ -60,12 +60,12 @@ auto SyntheticFileSystem::createTextFile(String&& name, String&& text) -> OwnPtr
     file->metadata.size = file->data.size();
     file->metadata.uid = 100;
     file->metadata.gid = 200;
-    file->metadata.mode = 04;
+    file->metadata.mode = 0040644;
     file->metadata.mtime = mepoch;
     return file;
 }
 
-auto SyntheticFileSystem::createGeneratedFile(String&& name, Function<ByteBuffer()>&& generator) -> OwnPtr<File>
+auto SyntheticFileSystem::createGeneratedFile(String&& name, Function<ByteBuffer()>&& generator, Unix::mode_t mode) -> OwnPtr<File>
 {
     auto file = make<File>();
     file->generator = move(generator);
@@ -73,7 +73,7 @@ auto SyntheticFileSystem::createGeneratedFile(String&& name, Function<ByteBuffer
     file->metadata.size = 0;
     file->metadata.uid = 0;
     file->metadata.gid = 0;
-    file->metadata.mode = 0100644;
+    file->metadata.mode = mode;
     file->metadata.mtime = mepoch;
     return file;
 }
@@ -146,9 +146,8 @@ bool SyntheticFileSystem::enumerateDirectoryInode(InodeIdentifier inode, Functio
     callback({ ".", synInode.metadata.inode });
     callback({ "..", synInode.parent });
 
-    for (auto& child : synInode.children) {
+    for (auto& child : synInode.children)
         callback({ child->name, child->metadata.inode });
-    }
     return true;
 }
 
@@ -214,8 +213,8 @@ Unix::ssize_t SyntheticFileSystem::readInodeBytes(InodeIdentifier inode, Unix::o
             generatedData = handle->generatorCache();
         }
     }
-    auto* data = generatedData ? &generatedData : &file.data;
 
+    auto* data = generatedData ? &generatedData : &file.data;
     Unix::ssize_t nread = min(static_cast<Unix::off_t>(data->size() - offset), static_cast<Unix::off_t>(count));
     memcpy(buffer, data->pointer() + offset, nread);
     if (nread == 0 && handle && handle->generatorCache())

VirtualFileSystem/SyntheticFileSystem.h

@@ -40,7 +40,7 @@ protected:
 
     OwnPtr<File> createDirectory(String&& name);
     OwnPtr<File> createTextFile(String&& name, String&& text);
-    OwnPtr<File> createGeneratedFile(String&& name, Function<ByteBuffer()>&&);
+    OwnPtr<File> createGeneratedFile(String&& name, Function<ByteBuffer()>&&, Unix::mode_t = 0100644);
 
     InodeIdentifier addFile(OwnPtr<File>&&, InodeIndex parent = RootInodeIndex);
     bool removeFile(InodeIndex);

VirtualFileSystem/VirtualFileSystem.cpp

@@ -5,6 +5,7 @@
 #include <AK/kmalloc.h>
 #include <AK/kstdio.h>
 #include <AK/ktime.h>
+#include "sys-errno.h"
 
 //#define VFS_DEBUG
 
@@ -104,7 +105,8 @@ bool VirtualFileSystem::mount(RetainPtr<FileSystem>&& fileSystem, const String&
 {
     ASSERT(fileSystem);
 
-    auto inode = resolvePath(path);
+    int error;
+    auto inode = resolvePath(path, error);
     if (!inode.isValid()) {
         kprintf("[VFS] mount can't resolve mount point '%s'\n", path.characters());
         return false;
@@ -172,7 +174,8 @@ void VirtualFileSystem::freeNode(Node* node)
 
 bool VirtualFileSystem::isDirectory(const String& path, InodeIdentifier base)
 {
-    auto inode = resolvePath(path, base);
+    int error;
+    auto inode = resolvePath(path, error, base);
     if (!inode.isValid())
         return false;
 
@@ -226,7 +229,8 @@ void VirtualFileSystem::enumerateDirectoryInode(InodeIdentifier directoryInode,
 
 void VirtualFileSystem::listDirectory(const String& path)
 {
-    auto directoryInode = resolvePath(path);
+    int error;
+    auto directoryInode = resolvePath(path, error);
     if (!directoryInode.isValid())
         return;
 
@@ -326,7 +330,8 @@ void VirtualFileSystem::listDirectory(const String& path)
 
 void VirtualFileSystem::listDirectoryRecursively(const String& path)
 {
-    auto directory = resolvePath(path);
+    int error;
+    auto directory = resolvePath(path, error);
     if (!directory.isValid())
         return;
 
@@ -351,17 +356,19 @@ bool VirtualFileSystem::touch(const String& path)
 {
     Locker locker(VirtualFileSystem::lock());
 
-    auto inode = resolvePath(path);
+    int error;
+    auto inode = resolvePath(path, error);
     if (!inode.isValid())
         return false;
     return inode.fileSystem()->setModificationTime(inode, ktime(nullptr));
 }
 
-OwnPtr<FileHandle> VirtualFileSystem::open(const String& path, InodeIdentifier base)
+OwnPtr<FileHandle> VirtualFileSystem::open(const String& path, int options, InodeIdentifier base)
 {
     Locker locker(VirtualFileSystem::lock());
 
-    auto inode = resolvePath(path, base);
+    int error;
+    auto inode = resolvePath(path, error, base, options);
     if (!inode.isValid())
         return nullptr;
     auto vnode = getOrCreateNode(inode);
@@ -397,7 +404,8 @@ InodeIdentifier VirtualFileSystem::resolveSymbolicLink(const String& basePath, I
         return { };
     char buf[4096];
     ksprintf(buf, "/%s/%s", basePath.characters(), String((const char*)symlinkContents.pointer(), symlinkContents.size()).characters());
-    return resolvePath(buf);
+    int error;
+    return resolvePath(buf, error);
 }
 
 String VirtualFileSystem::absolutePath(InodeIdentifier inode)
@@ -407,6 +415,7 @@ String VirtualFileSystem::absolutePath(InodeIdentifier inode)
     if (!inode.isValid())
         return String();
 
+    int error;
     Vector<InodeIdentifier> lineage;
     while (inode != m_rootNode->inode) {
         if (auto* mount = findMountForGuest(inode))
@@ -414,7 +423,7 @@ String VirtualFileSystem::absolutePath(InodeIdentifier inode)
         else
             lineage.append(inode);
         if (inode.metadata().isDirectory()) {
-            inode = resolvePath("..", inode);
+            inode = resolvePath("..", error, inode);
         } else
             inode = inode.fileSystem()->findParentOfInode(inode);
         ASSERT(inode.isValid());
@@ -434,7 +443,7 @@ String VirtualFileSystem::absolutePath(InodeIdentifier inode)
     return builder.build();
 }
 
-InodeIdentifier VirtualFileSystem::resolvePath(const String& path, InodeIdentifier base)
+InodeIdentifier VirtualFileSystem::resolvePath(const String& path, int& error, InodeIdentifier base, int options)
 {
     if (path.isEmpty())
         return { };
@@ -455,12 +464,14 @@ InodeIdentifier VirtualFileSystem::resolvePath(const String& path, InodeIdentifi
 #ifdef VFS_DEBUG
             kprintf("invalid metadata\n");
 #endif
+            error = -EIO;
             return { };
         }
         if (!metadata.isDirectory()) {
 #ifdef VFS_DEBUG
             kprintf("not directory\n");
 #endif
+            error = -EIO;
             return { };
         }
         inode = inode.fileSystem()->childOfDirectoryInodeWithName(inode, part);
@@ -468,6 +479,7 @@ InodeIdentifier VirtualFileSystem::resolvePath(const String& path, InodeIdentifi
 #ifdef VFS_DEBUG
             kprintf("bad child\n");
 #endif
+            error = -EIO;
             return { };
         }
 #ifdef VFS_DEBUG
@@ -489,6 +501,14 @@ InodeIdentifier VirtualFileSystem::resolvePath(const String& path, InodeIdentifi
         }
         metadata = inode.metadata();
         if (metadata.isSymbolicLink()) {
+            if (i == parts.size() - 1) {
+                if (options & O_NOFOLLOW) {
+                    error = -ELOOP;
+                    return { };
+                }
+                if (options & O_NOFOLLOW_NOERROR)
+                    return inode;
+            }
             char buf[4096] = "";
             char* p = buf;
             for (unsigned j = 0; j < i; ++j) {
@@ -497,6 +517,7 @@ InodeIdentifier VirtualFileSystem::resolvePath(const String& path, InodeIdentifi
             inode = resolveSymbolicLink(buf, inode);
             if (!inode.isValid()) {
                 kprintf("Symbolic link resolution failed :(\n");
+                error = -ENOENT;
                 return { };
             }
         }

VirtualFileSystem/VirtualFileSystem.h

@@ -12,6 +12,13 @@
 #include "Limits.h"
 #include "FileSystem.h"
 
+#define O_RDONLY 0
+#define O_WRONLY 1
+#define O_RDWR 2
+#define O_DIRECTORY 00200000
+#define O_NOFOLLOW 00400000
+#define O_NOFOLLOW_NOERROR 0x4000000
+
 class CharacterDevice;
 class FileHandle;
 
@@ -79,7 +86,7 @@ public:
     bool mountRoot(RetainPtr<FileSystem>&&);
     bool mount(RetainPtr<FileSystem>&&, const String& path);
 
-    OwnPtr<FileHandle> open(const String& path, InodeIdentifier base = InodeIdentifier());
+    OwnPtr<FileHandle> open(const String& path, int options = 0, InodeIdentifier base = InodeIdentifier());
     OwnPtr<FileHandle> create(const String& path, InodeIdentifier base = InodeIdentifier());
     OwnPtr<FileHandle> mkdir(const String& path, InodeIdentifier base = InodeIdentifier());
 
@@ -98,7 +105,7 @@ private:
     friend class FileHandle;
 
     void enumerateDirectoryInode(InodeIdentifier, Function<bool(const FileSystem::DirectoryEntry&)>);
-    InodeIdentifier resolvePath(const String& path, InodeIdentifier base = InodeIdentifier());
+    InodeIdentifier resolvePath(const String& path, int& error, InodeIdentifier base = InodeIdentifier(), int options = 0);
     InodeIdentifier resolveSymbolicLink(const String& basePath, InodeIdentifier symlinkInode);
 
     RetainPtr<Node> allocateNode();

VirtualFileSystem/sys-errno.h

@@ -34,5 +34,5 @@
 #define EPIPE     32    // Broken pipe
 #define EDOM      33    // Math argument out of domain of func
 #define ERANGE    34    // Math result not representable
-
+#define ELOOP     40    // Too many symbolic links
 #define EOVERFLOW 75    // Value too large for defined data type