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

       personality - set the process execution domain

       #include <sys/personality.h>

       int personality(unsigned long persona);

       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

       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

       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)

       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.

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

       EINVAL The kernel was unable to change the personality.

       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.

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


       This page is part of release 5.12 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

Linux                              2021-03-22                     PERSONALITY(2)