PERSONALITY(2)            (2017-09-15)             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 personali-
          ties, 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 pro-
          vide 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 retriev-
          ing 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 personal-
          ity the kernel should assume.  The flag values are as fol-
          lows:

          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 ran-
               domization.

          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); oth-
               erwise use 0xffffe000.

          FDPIC_FUNCPTRS (since Linux 2.6.11)
               User-space function pointers to signal handlers point
               (on certain architectures) to descriptors.

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          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 inter-
               rupted 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 com-
               plete, 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.

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          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 unmain-
               tained, 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.

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          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
          This page is part of release 5.10 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 https://www.kernel.org/doc/man-pages/.

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