NAME

       personality - set the process execution domain

LIBRARY

       Standard C library (libc, -lc)

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 a 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 Linux 2.6.x to Linux 3.x.

       WHOLE_SECONDS (since Linux 1.2.0)
              No effect.

       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
       to indicate the error.

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.

STANDARDS

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

SEE ALSO

       setarch(8)