apps,nanos-lite,loader: use fs_filesz() to get file size

apps/nanos-lite/src/fs.c

@@ -27,6 +27,10 @@ enum {FD_STDIN, FD_STDOUT, FD_STDERR, FD_FB, FD_EVENTS, FD_DISPINFO, FD_NORMAL};
 
 Fstate files[FD_NORMAL + NR_FILES];
 
+size_t fs_filesz(int fd) {
+  return file_table[ files[fd].index ].size;
+}
+
 void ramdisk_read(void *, uint32_t, uint32_t);
 void ramdisk_write(const void *, uint32_t, uint32_t);
 size_t read_events(void *buf);

apps/nanos-lite/src/loader.c

@@ -5,6 +5,7 @@
 #define INIT_FILE "/bin/hello"
 
 void ramdisk_read(void *, off_t, size_t);
+size_t fs_filesz(int fd);
 
 #define STACK_SIZE (128 * PGSIZE)
 
@@ -12,7 +13,7 @@ uintptr_t loader() {
   Log("Loading user program %s...", INIT_FILE);
 
   int fd = fs_open(INIT_FILE, 0, 0);
-  ssize_t len = fs_read(fd, (void *)0x4000000, 0x10000000);  // read many enough
+  ssize_t len = fs_read(fd, (void *)0x4000000, fs_filesz(fd));
   fs_close(fd);
   Log("Read %d bytes", len);