Kernel: Add fchown() syscall.

Kernel/FileSystem/FileDescriptor.cpp

@@ -324,3 +324,10 @@ void FileDescriptor::set_file_flags(dword flags)
     m_should_append = flags & O_APPEND;
     m_file_flags = flags;
 }
+
+KResult FileDescriptor::chown(uid_t uid, gid_t gid)
+{
+    if (!m_inode)
+        return KResult(-EINVAL);
+    return m_inode->chown(uid, gid);
+}

Kernel/FileSystem/FileDescriptor.h

@@ -101,6 +101,8 @@ public:
 
     off_t offset() const { return m_current_offset; }
 
+    KResult chown(uid_t, gid_t);
+
 private:
     friend class VFS;
     FileDescriptor(RetainPtr<File>&&, SocketRole = SocketRole::None);

Kernel/Process.cpp

@@ -1991,6 +1991,14 @@ int Process::sys$fchmod(int fd, mode_t mode)
     return descriptor->fchmod(mode);
 }
 
+int Process::sys$fchown(int fd, uid_t uid, gid_t gid)
+{
+    auto* descriptor = file_descriptor(fd);
+    if (!descriptor)
+        return -EBADF;
+    return descriptor->chown(uid, gid);
+}
+
 int Process::sys$chown(const char* pathname, uid_t uid, gid_t gid)
 {
     if (!validate_read_str(pathname))

Kernel/Process.h

@@ -177,6 +177,7 @@ public:
     int sys$chmod(const char* pathname, mode_t);
     int sys$fchmod(int fd, mode_t);
     int sys$chown(const char* pathname, uid_t, gid_t);
+    int sys$fchown(int fd, uid_t, gid_t);
     int sys$socket(int domain, int type, int protocol);
     int sys$bind(int sockfd, const sockaddr* addr, socklen_t);
     int sys$listen(int sockfd, int backlog);

Kernel/Syscall.cpp

@@ -242,6 +242,8 @@ static dword handle(RegisterDump& regs, dword function, dword arg1, dword arg2,
         return current->process().sys$release_shared_buffer((int)arg1);
     case Syscall::SC_chown:
         return current->process().sys$chown((const char*)arg1, (uid_t)arg2, (gid_t)arg3);
+    case Syscall::SC_fchown:
+        return current->process().sys$fchown((int)arg1, (uid_t)arg2, (gid_t)arg3);
     case Syscall::SC_restore_signal_mask:
         return current->process().sys$restore_signal_mask((dword)arg1);
     case Syscall::SC_seal_shared_buffer:

Kernel/Syscall.h

@@ -106,8 +106,9 @@
     __ENUMERATE_SYSCALL(beep)                   \
     __ENUMERATE_SYSCALL(getsockname)            \
     __ENUMERATE_SYSCALL(getpeername)            \
-    __ENUMERATE_SYSCALL(sched_setparam)          \
+    __ENUMERATE_SYSCALL(sched_setparam)         \
-    __ENUMERATE_SYSCALL(sched_getparam)
+    __ENUMERATE_SYSCALL(sched_getparam)         \
+    __ENUMERATE_SYSCALL(fchown)                 \
 
 namespace Syscall {
 

LibC/unistd.cpp

@@ -28,6 +28,12 @@ int chown(const char* pathname, uid_t uid, gid_t gid)
     __RETURN_WITH_ERRNO(rc, rc, -1);
 }
 
+int fchown(int fd, uid_t uid, gid_t gid)
+{
+    int rc = syscall(SC_fchown, fd, uid, gid);
+    __RETURN_WITH_ERRNO(rc, rc, -1);
+}
+
 pid_t fork()
 {
     int rc = syscall(SC_fork);

LibC/unistd.h

@@ -88,6 +88,7 @@ long fpathconf(int fd, int name);
 long pathconf(const char* path, int name);
 char* getlogin();
 int chown(const char* pathname, uid_t, gid_t);
+int fchown(int fd, uid_t, gid_t);
 int ftruncate(int fd, off_t length);
 
 enum