In directory boot/multiboot/multiboot_main.c,multiboot_main() at last calls "exit(main(argc, argv, environ))", is this main() kernel's main function?such as the main() function in hello kernel hello.c,then the main () in kernel's hello.c will return 0, so exit(0)(in multiboot_main()) reboots pc ?
during the initialization,when does it enter into protected mode ? whether beginning of multiboot.S,pc has been already in protected mode ?