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

NAME         top

       personality - set the process execution domain

SYNOPSIS         top

       #include <sys/personality.h>

       int personality(unsigned long persona);

DESCRIPTION         top

       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

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

       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

       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

       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

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

       PER_LINUX (since Linux 1.2.0)

       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

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

       PER_SCOSVR3 (since Linux 1.2.0)
              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

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

       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         top

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

ERRORS         top

       EINVAL The kernel was unable to change the personality.

VERSIONS         top

       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         top

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

SEE ALSO         top


COLOPHON         top

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Linux                            2016-03-15                   PERSONALITY(2)