personality(2) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | VERSIONS | CONFORMING TO | SEE ALSO | COLOPHON

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 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 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         top

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

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

       setarch(8)

COLOPHON         top

       This page is part of release 5.13 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/.

Linux                          2021-03-22                 PERSONALITY(2)

Pages that refer to this page: mprotect(2)syscalls(2)proc(5)systemd.exec(5)systemd.unit(5)setarch(8)