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 execution 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/personality.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 architectural quirks.  The least
       significant byte is value defining the personality 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 certain 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 signal 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; otherwise 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

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