PRCTL(1)						      General Commands Manual							  PRCTL(1)

NAME

       prctl - Process operations

SYNOPSIS

       prctl [-v] [-h|--help] [--version] <-q|<options....>> [command]

       where <options> are:

       --unaligned=[silent|signal|default]

       --fpemu=[silent|signal|default]

DESCRIPTION

       prctl  allows  you  to query or control certain process behavior.  Supported options are handling of unaligned memory accesses and floating
       point assistance faults 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. Similarly when a process  encounters	a  floating  point
       assist fault, kernel would invoke floating point emulator and log the floating point assist fault. This behavior can be changed so the ker-
       nel could either emulate floating point operation without logging an error or send SIGFPE to the offending process.

       prctl can optionally be followed by a command. If a command 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 environment 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 (signal), or do the default
	      (default). If a value is not specified after "=", current setting is returned.

       --fpemu=[silent|signal|default]]
	      Set floating point assist fault behavior to not log the faulti (silent), send SIGFPE to the process  (signal),  or  do  the  default
	      (default). If a value is not specified after "=", current setting is returned.

       If an option is specified multiple times, the last 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.

       --fpemu= option is specific to IPF (Itanium Processor Family, previously known as IA-64) and is supported  on  kernels  2.4.11  and  above.
       Other architectures and kernels may return "Invalid argument" error.

       prctl(2)

AUTHOR

       Khalid Aziz <khalid_aziz@hp.com>

LICENSE

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

								Process operations							  PRCTL(1)