magic               7 kernel/elf.h     uint magic;  // must equal ELF_MAGIC
magic              46 kernel/exec.c    if(elf.magic != ELF_MAGIC)
magic              44 kernel/fs.c      if(sb.magic != FSMAGIC)
magic              15 kernel/fs.h      uint magic;        // Must be FSMAGIC
magic              96 mkfs/mkfs.c      sb.magic = FSMAGIC;