UserspaceEmulator: Implement chown

Now we can run 'ue chown anon ReadMe.md' :^)

Userland/DevTools/UserspaceEmulator/Emulator.cpp

@@ -529,6 +529,8 @@ u32 Emulator::virt_syscall(u32 function, u32 arg1, u32 arg2, u32 arg3)
         return virt$ftruncate(arg1, arg2);
     case SC_umask:
         return virt$umask(arg1);
+    case SC_chown:
+        return virt$chown(arg1);
     default:
         reportln("\n=={}==  \033[31;1mUnimplemented syscall: {}\033[0m, {:p}", getpid(), Syscall::to_string((Syscall::Function)function), function);
         dump_backtrace();
@@ -611,6 +613,18 @@ int Emulator::virt$chmod(FlatPtr path_addr, size_t path_length, mode_t mode)
     return syscall(SC_chmod, path.data(), path.size(), mode);
 }
 
+int Emulator::virt$chown(FlatPtr params_addr)
+{
+    Syscall::SC_chown_params params;
+    mmu().copy_from_vm(&params, params_addr, sizeof(params));
+
+    auto path = mmu().copy_buffer_from_vm((FlatPtr)params.path.characters, params.path.length);
+    params.path.characters = (const char*)path.data();
+    params.path.length = path.size();
+
+    return syscall(SC_chown, &params);
+}
+
 int Emulator::virt$fchmod(int fd, mode_t mode)
 {
     return syscall(SC_fchmod, fd, mode);

Userland/DevTools/UserspaceEmulator/Emulator.h

@@ -127,6 +127,7 @@ private:
     int virt$dbgputch(char);
     int virt$chmod(FlatPtr, size_t, mode_t);
     int virt$fchmod(int, mode_t);
+    int virt$chown(FlatPtr);
     int virt$fchown(int, uid_t, gid_t);
     int virt$clock_settime(uint32_t clock_id, FlatPtr user_ts);
     int virt$listen(int, int);