Kernel+Userland: Add the rename() syscall along with a basic /bin/mv.

Kernel/FileSystem/VirtualFileSystem.cpp

@@ -312,6 +312,50 @@ KResult VFS::chmod(const String& path, mode_t mode, Inode& base)
     return chmod(*inode, mode);
 }
 
+KResult VFS::rename(const String& old_path, const String& new_path, Inode& base)
+{
+    RetainPtr<Inode> old_parent_inode;
+    auto old_inode_or_error = resolve_path_to_inode(old_path, base, &old_parent_inode);
+    if (old_inode_or_error.is_error())
+        return old_inode_or_error.error();
+    auto old_inode = old_inode_or_error.value();
+
+    RetainPtr<Inode> new_parent_inode;
+    auto new_inode_or_error = resolve_path_to_inode(new_path, base, &new_parent_inode);
+    if (new_inode_or_error.is_error()) {
+        if (new_inode_or_error.error() != -ENOENT)
+            return new_inode_or_error.error();
+    }
+
+    if (!new_parent_inode->metadata().may_write(current->process()))
+        return KResult(-EACCES);
+
+    if (!old_parent_inode->metadata().may_write(current->process()))
+        return KResult(-EACCES);
+
+    if (!new_inode_or_error.is_error()) {
+        auto new_inode = new_inode_or_error.value();
+        // FIXME: Is this really correct? Check what other systems do.
+        if (new_inode.ptr() == old_inode.ptr())
+            return KSuccess;
+        if (new_inode->is_directory() && !old_inode->is_directory())
+            return KResult(-EISDIR);
+        auto result = new_parent_inode->remove_child(new_parent_inode->reverse_lookup(new_inode->identifier()));
+        if (result.is_error())
+            return result;
+    }
+
+    auto result = new_parent_inode->add_child(old_inode->identifier(), FileSystemPath(new_path).basename(), 0 /* FIXME: file type? */);
+    if (result.is_error())
+        return result;
+
+    result = old_parent_inode->remove_child(old_parent_inode->reverse_lookup(old_inode->identifier()));
+    if (result.is_error())
+        return result;
+
+    return KSuccess;
+}
+
 KResult VFS::chown(const String& path, uid_t a_uid, gid_t a_gid, Inode& base)
 {
     auto inode_or_error = resolve_path_to_inode(path, base);

Kernel/FileSystem/VirtualFileSystem.h

@@ -75,6 +75,7 @@ public:
     KResult access(const String& path, int mode, Inode& base);
     KResult stat(const String& path, int options, Inode& base, struct stat&);
     KResult utime(const String& path, Inode& base, time_t atime, time_t mtime);
+    KResult rename(const String& oldpath, const String& newpath, Inode& base);
     KResultOr<Retained<Inode>> open_directory(const String& path, Inode& base);
 
     void register_device(Device&);

Kernel/Process.cpp

@@ -2445,3 +2445,12 @@ int Process::sys$donate(int tid)
     Scheduler::donate_to(beneficiary, "sys$donate");
     return 0;
 }
+
+int Process::sys$rename(const char* oldpath, const char* newpath)
+{
+    if (!validate_read_str(oldpath))
+        return -EFAULT;
+    if (!validate_read_str(newpath))
+        return -EFAULT;
+    return VFS::the().rename(String(oldpath), String(newpath), cwd_inode());
+}

Kernel/Process.h

@@ -180,6 +180,7 @@ public:
     int sys$setsockopt(const Syscall::SC_setsockopt_params*);
     int sys$restore_signal_mask(dword mask);
     int sys$create_thread(int(*)(void*), void*);
+    int sys$rename(const char* oldpath, const char* newpath);
 
     int sys$create_shared_buffer(pid_t peer_pid, int, void** buffer);
     void* sys$get_shared_buffer(int shared_buffer_id);

Kernel/Syscall.cpp

@@ -241,6 +241,8 @@ static dword handle(RegisterDump& regs, dword function, dword arg1, dword arg2,
         return current->process().sys$setsockopt((const SC_setsockopt_params*)arg1);
     case Syscall::SC_create_thread:
         return current->process().sys$create_thread((int(*)(void*))arg1, (void*)arg2);
+    case Syscall::SC_rename:
+        return current->process().sys$rename((const char*)arg1, (const char*)arg2);
     default:
         kprintf("<%u> int0x82: Unknown function %u requested {%x, %x, %x}\n", current->process().pid(), function, arg1, arg2, arg3);
         break;

Kernel/Syscall.h

@@ -95,6 +95,7 @@
     __ENUMERATE_SYSCALL(create_thread) \
     __ENUMERATE_SYSCALL(gettid) \
     __ENUMERATE_SYSCALL(donate) \
+    __ENUMERATE_SYSCALL(rename) \
 
 
 namespace Syscall {

Kernel/sync.sh

@@ -79,6 +79,7 @@ cp -v ../Userland/uc mnt/bin/uc
 cp -v ../Userland/tc mnt/bin/tc
 cp -v ../Userland/host mnt/bin/host
 cp -v ../Userland/qs mnt/bin/qs
+cp -v ../Userland/mv mnt/bin/mv
 chmod 4755 mnt/bin/su
 cp -v ../Applications/Terminal/Terminal mnt/bin/Terminal
 cp -v ../Applications/FontEditor/FontEditor mnt/bin/FontEditor