prctl - Process operations


SYNOPSIS

       prctl         [-v]         [-h|--help]         [--version]
       <-q|--unaligned=[silent|signal|default]> [command]


DESCRIPTION

       prctl allows you  to  query  or  control  certain  process
       behavior.   At  present, the only supported option is han­
       dling of unaligned memory accesses by a process.   When  a
       process  performs  an  unaligned memory access, by default
       the kernel would emulate the  unaligned  access  correctly
       and  log the unaligned access in syslog. This behavior can
       be  changed  so  the  kernel  could  either  emulate   the
       unaligned  access  correctly  without  logging an error or
       send SIGBUS to the process.

       prctl can optionally be followed by a command. If  a  com­
       mand  is  specified,  prctl will exec the command with the
       processor behavior set to as specified by the options.  If
       a  command  is  not specified, prctl will fork a new shell
       unless the command only queried the current settings.  The
       shell  started by prctl will be as defined by the environ­
       ment variable SHELL. If environment variable SHELL is  not
       defined,  shell in the password entry for the user will be
       started. If a shell is not found in  the  password  entry,
       bash will be started.

   OPTIONS
       -v     Verbose mode. In verbose mode, any new settings are
              confirmed with a message on stdout.

       --help Print usage information and exit.

       --version
              Print software version and exit.

       -q     Query the current settings for the process  options
              controllable by prctl.

       --unaligned=[silent|signal|default]]
              Set unaligned memory access behavior to not log the
              access (silent), send SIGBUS to the  process  (sig­
              nal),  or  do  the default (default). If a value is
              not  specified  after  "=",  current   setting   is
              returned.

              one takes effect.


EXAMPLES

       prctl --unaligned=signal
              starts  up  a  shell (as defined by the environment
              variable SHELL) and sets  up  any  process  running
              under   this  shell  to  be  sent  SIGBUS  upon  an
              unaligned memory access.

       prctl --unaligned=signal gdb tst
              starts up a gdb session for the program "tst"  with
              the  process  set  to  receive SIGBUS upon unligned
              memory access.

       prctl --unaligned=
              displays the current setting for  unaligned  memory
              access handling.

       prctl --unaligned= gdb tst
              displays  the  current setting for unaligned memory
              access handling and starts up a gdb session for the
              program "tst".


NOTES

       prctl works on 2.4.0 and above kernels only.


SEE ALSO

       prctl(2)


AUTHOR

       Khalid Aziz <khalid_aziz@hp.com>


LICENSE

       This software is made available under the GNU General Pub­
       lic License (GPL) Version 2.  This software comes with  NO
       WARRANTY.


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