magic               7 kernel/elf.h     uint magic; // must equal ELF_MAGIC
magic              53 kernel/exec.c    if (elf.magic != ELF_MAGIC)
magic              45 kernel/fs.c      if (sb.magic != FSMAGIC)
magic              14 kernel/fs.h      uint magic;      // Must be FSMAGIC
magic              99 mkfs/mkfs.c      sb.magic = FSMAGIC;