PERSONALITY(2)		   Linux Programmer's Manual		PERSONALITY(2)



NAME
       personality - set the process execution domain

SYNOPSIS
       #include <sys/personality.h>

       int personality(unsigned long persona);

DESCRIPTION
       Linux  supports different execution domains, or personalities, for each
       process.	 Among other things, execution domains tell Linux how  to  map
       signal numbers into signal actions.  The execution domain system allows
       Linux to provide limited support	 for  binaries	compiled  under	 other
       UNIX-like operating systems.

       If persona is not 0xffffffff, then personality() sets the caller's exe-
       cution domain to the value specified by persona.	 Specifying persona as
       0xffffffff  provides  a	way  of retrieving the current persona without
       changing it.

       A list of the available execution domains can be found in  <sys/person-
       ality.h>.   The	execution  domain  is  a 32-bit value in which the top
       three bytes are set aside for flags that cause the kernel to modify the
       behavior	 of certain system calls so as to emulate historical or archi-
       tectural quirks.	 The least significant byte is value defining the per-
       sonality the kernel should assume.  The flag values are as follows:

       ADDR_COMPAT_LAYOUT (since Linux 2.6.9)
	      With this flag set, provide legacy virtual address space layout.

       ADDR_NO_RANDOMIZE (since Linux 2.6.12)
	      With this flag set, disable address-space-layout randomization.

       ADDR_LIMIT_32BIT (since Linux 2.2)
	      Limit the address space to 32 bits.

       ADDR_LIMIT_3GB (since Linux 2.4.0)
	      With  this  flag	set,  use 0xc0000000 as the offset at which to
	      search  a	 virtual  memory  chunk	 on  mmap(2);  otherwise   use
	      0xffffe000.

       FDPIC_FUNCPTRS (since Linux 2.6.11)
	      User-space  function  pointers to signal handlers point (on cer-
	      tain architectures) to descriptors.

       MMAP_PAGE_ZERO (since Linux 2.4.0)
	      Map page 0 as read-only (to support binaries that depend on this
	      SVr4 behavior).

       READ_IMPLIES_EXEC (since Linux 2.6.8)
	      With this flag set, PROT_READ implies PROT_EXEC for mmap(2).

       SHORT_INODE (since Linux 2.4.0)
	      No effects(?).

       STICKY_TIMEOUTS (since Linux 1.2.0)
	      With  this  flag set, select(2), pselect(2), and ppoll(2) do not
	      modify the returned timeout argument when interrupted by a  sig-
	      nal handler.

       UNAME26 (since Linux 3.1)
	      Have  uname(2) report a 2.6.40+ version number rather than a 3.x
	      version number.  Added as a stopgap measure  to  support	broken
	      applications  that could not handle the kernel version-numbering
	      switch from 2.6.x to 3.x.

       WHOLE_SECONDS (since Linux 1.2.0)
	      No effects(?).

       The available execution domains are:

       PER_BSD (since Linux 1.2.0)
	      BSD. (No effects.)

       PER_HPUX (since Linux 2.4)
	      Support for 32-bit HP/UX.	 This support was never complete,  and
	      was dropped so that since Linux 4.0, this value has no effect.

       PER_IRIX32 (since Linux 2.2)
	      IRIX 5 32-bit.  Never fully functional; support dropped in Linux
	      2.6.27.  Implies STICKY_TIMEOUTS.

       PER_IRIX64 (since Linux 2.2)
	      IRIX 6 64-bit.  Implies STICKY_TIMEOUTS; otherwise no effects.

       PER_IRIXN32 (since Linux 2.2)
	      IRIX  6  new  32-bit.   Implies  STICKY_TIMEOUTS;	 otherwise  no
	      effects.

       PER_ISCR4 (since Linux 1.2.0)
	      Implies STICKY_TIMEOUTS; otherwise no effects.

       PER_LINUX (since Linux 1.2.0)
	      Linux.

       PER_LINUX32 (since Linux 2.2)
	      [To be documented.]

       PER_LINUX32_3GB (since Linux 2.4)
	      Implies ADDR_LIMIT_3GB.

       PER_LINUX_32BIT (since Linux 2.0)
	      Implies ADDR_LIMIT_32BIT.

       PER_LINUX_FDPIC (since Linux 2.6.11)
	      Implies FDPIC_FUNCPTRS.

       PER_OSF4 (since Linux 2.4)
	      OSF/1  v4.  On alpha, clear top 32 bits of iov_len in the user's
	      buffer for  compatibility	 with  old  versions  of  OSF/1	 where
	      iov_len was defined as.  int.

       PER_OSR5 (since Linux 2.4)
	      Implies STICKY_TIMEOUTS and WHOLE_SECONDS; otherwise no effects.

       PER_RISCOS (since Linux 2.2)
	      [To be documented.]

       PER_SCOSVR3 (since Linux 1.2.0)
	      Implies  STICKY_TIMEOUTS, WHOLE_SECONDS, and SHORT_INODE; other-
	      wise no effects.

       PER_SOLARIS (since Linux 2.4)
	      Implies STICKY_TIMEOUTS; otherwise no effects.

       PER_SUNOS (since Linux 2.4.0)
	      Implies STICKY_TIMEOUTS.	 Divert	 library  and  dynamic	linker
	      searches	to  /usr/gnemul.   Buggy,  largely  unmaintained,  and
	      almost entirely unused; support was removed in Linux 2.6.26.

       PER_SVR3 (since Linux 1.2.0)
	      Implies STICKY_TIMEOUTS and SHORT_INODE; otherwise no effects.

       PER_SVR4 (since Linux 1.2.0)
	      Implies  STICKY_TIMEOUTS	and   MMAP_PAGE_ZERO;	otherwise   no
	      effects.

       PER_UW7 (since Linux 2.4)
	      Implies	STICKY_TIMEOUTS	  and	MMAP_PAGE_ZERO;	 otherwise  no
	      effects.

       PER_WYSEV386 (since Linux 1.2.0)
	      Implies STICKY_TIMEOUTS and SHORT_INODE; otherwise no effects.

       PER_XENIX (since Linux 1.2.0)
	      Implies STICKY_TIMEOUTS and SHORT_INODE; otherwise no effects.

RETURN VALUE
       On success,  the	 previous  persona  is	returned.   On	error,	-1  is
       returned, and errno is set appropriately.

ERRORS
       EINVAL The kernel was unable to change the personality.

VERSIONS
       This  system  call  first appeared in Linux 1.1.20 (and thus first in a
       stable kernel release with Linux 1.2.0); library support was  added  in
       glibc 2.3.

CONFORMING TO
       personality()  is  Linux-specific  and  should  not be used in programs
       intended to be portable.

SEE ALSO
       setarch(8)

COLOPHON
       This page is part of release 4.10 of the Linux  man-pages  project.   A
       description  of	the project, information about reporting bugs, and the
       latest	 version    of	  this	  page,	   can	   be	  found	    at
       https://www.kernel.org/doc/man-pages/.



Linux				  2016-03-15			PERSONALITY(2)