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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.