- Process operations
allows you to query or control certain process behavior. Supported
Unaligned memory access:
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
("silent") or send SIGBUS to the process ("signal" and
"always-signal"). "always-signal" is available on ia64
Floating point assistance faults:
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 kernel could
either emulate floating point operation without logging an error
("silent") or send SIGFPE to the offending process
Machine check memory corruption kill policy:
If a hardware memeory
corruption is detected inside a thread's address space, mmemory corruption
kill policy determines whether the thread received SIGBUS as soon as
corruption is detected ("early"), when it accesses corrupted memory
("late"), or use system wide default.
can optionally be followed by a command. If a command is specified,
will exec the command with the processor behavior set to as
specified by the options. If a command is not specified, prctl
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.
- Verbose mode. In verbose mode, any new settings are confirmed with a
message on stdout.
- Print usage information and exit.
- Print software version and exit.
- Query the current settings for the process options controllable by prctl.
- Set unaligned memory access behavior to not log the access
(silent), send SIGBUS to the process ( signal), or do the
default ( default). On IA-64 architecture an additional value
always-signal is supported which causes a SIGBUS to be generated
every time an unaligned access occurs. Refer to the section titled
"Memory Datum Alignment and Atomicity" in "Intel IA-64
Architecture Software Developer's Manual: Volume 2" for details on
when an unaligned access would not generate signal normally. If a value is
not specified after "=", current setting is returned.
- 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.
- 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".
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.
Khalid Aziz <firstname.lastname@example.org>
This software is made available under the GNU General Public License (GPL)
Version 2. This software comes with NO WARRANTY.