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gdb: Patching

 
 17.6 Patching Programs
 ======================
 
 By default, GDB opens the file containing your program's executable code
 (or the corefile) read-only.  This prevents accidental alterations to
 machine code; but it also prevents you from intentionally patching your
 program's binary.
 
    If you'd like to be able to patch the binary, you can specify that
 explicitly with the 'set write' command.  For example, you might want to
 turn on internal debugging flags, or even to make emergency repairs.
 
 'set write on'
 'set write off'
      If you specify 'set write on', GDB opens executable and core files
      for both reading and writing; if you specify 'set write off' (the
      default), GDB opens them read-only.
 
      If you have already loaded a file, you must load it again (using
      the 'exec-file' or 'core-file' command) after changing 'set write',
      for your new setting to take effect.
 
 'show write'
      Display whether executable files and core files are opened for
      writing as well as reading.
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