kernel+libc: Add truncate and ftruncate

kernel/src/sys/file.cpp

@@ -229,3 +229,32 @@ Result<u64> sys_umask(Registers*, SyscallArgs args)
 
     return old_umask;
 }
+
+Result<u64> sys_truncate(Registers*, SyscallArgs args)
+{
+    auto path = TRY(MemoryManager::strdup_from_user(args[0]));
+    size_t length = (size_t)args[1];
+
+    auto* current = Scheduler::current();
+    auto inode = TRY(VFS::resolve_path(path.chars(), current->auth, current->current_directory));
+
+    if (!VFS::can_write(inode, current->auth)) return err(EACCES);
+
+    TRY(inode->truncate(length));
+
+    return 0;
+}
+
+Result<u64> sys_ftruncate(Registers*, SyscallArgs args)
+{
+    int fd = (int)args[0];
+    size_t length = (size_t)args[1];
+
+    auto* current = Scheduler::current();
+    auto description = TRY(current->resolve_fd(fd))->description;
+    if (!(description->flags & O_WRONLY)) return err(EBADF);
+
+    TRY(description->inode->truncate(length));
+
+    return 0;
+}

libc/include/unistd.h

@@ -184,6 +184,12 @@ extern "C"
     /* Set the process group associated with a terminal file descriptor. */
     int tcsetpgrp(int fd, pid_t pgrp);
 
+    /* Truncate a file to a specific length. */
+    int truncate(const char* path, size_t size);
+
+    /* Truncate a file to a specific length. */
+    int ftruncate(int fd, size_t size);
+
 #ifdef __cplusplus
 }
 #endif

libc/src/unistd.cpp

@@ -498,4 +498,16 @@ extern "C"
     {
         return ioctl(fd, TIOCSPGRP, &pgid);
     }
+
+    int truncate(const char* path, size_t size)
+    {
+        long rc = syscall(SYS_truncate, path, size);
+        __errno_return(rc, int);
+    }
+
+    int ftruncate(int fd, size_t size)
+    {
+        long rc = syscall(SYS_ftruncate, fd, size);
+        __errno_return(rc, int);
+    }
 }

libluna/include/luna/Syscall.h

@@ -7,7 +7,8 @@
                 _e(fstatat) _e(chdir) _e(getcwd) _e(unlinkat) _e(uname) _e(sethostname) _e(dup2) _e(pipe) _e(mount)    \
                     _e(umount) _e(pstat) _e(getrusage) _e(symlinkat) _e(readlinkat) _e(umask) _e(linkat) _e(faccessat) \
                         _e(pivot_root) _e(sigreturn) _e(sigaction) _e(kill) _e(sigprocmask) _e(setpgid) _e(isatty)     \
-                            _e(getpgid) _e(socket) _e(bind) _e(connect) _e(listen) _e(accept) _e(poll) _e(msync)
+                            _e(getpgid) _e(socket) _e(bind) _e(connect) _e(listen) _e(accept) _e(poll) _e(msync)       \
+                                _e(truncate) _e(ftruncate)
 
 enum Syscalls
 {