personality(2) — Linux manual page


personality(2)             System Calls Manual            personality(2)

NAME         top

       personality - set the process execution domain

LIBRARY         top

       Standard C library (libc, -lc)

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

       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
              0xffffe000.  Applies to 32-bit x86 processes only.

       FDPIC_FUNCPTRS (since Linux 2.6.11)
              User-space function pointers to signal handlers point to
              descriptors.  Applies only to ARM if BINFMT_ELF_FDPIC and

       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

       SHORT_INODE (since Linux 2.4.0)
              No effect.

       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+x) version number rather
              than a MAJOR.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

       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

       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 effect.

       PER_LINUX (since Linux 1.2.0)

       PER_LINUX32 (since Linux 2.2)
              uname(2) returns the name of the 32-bit architecture in
              the machine field ("i686" instead of "x86_64", &c.).

              Under ia64 (Itanium), processes with this personality
              don't have the O_LARGEFILE open(2) flag forced.

              Under 64-bit ARM, setting this personality is forbidden if
              execve(2)ing a 32-bit process would also be forbidden (cf.
              the allow_mismatched_32bit_el0 kernel parameter and

       PER_LINUX32_3GB (since Linux 2.4)
              Same as PER_LINUX32, but implies ADDR_LIMIT_3GB.

       PER_LINUX_32BIT (since Linux 2.0)
              Same as PER_LINUX, but implies ADDR_LIMIT_32BIT.

       PER_LINUX_FDPIC (since Linux 2.6.11)
              Same as PER_LINUX, but implies FDPIC_FUNCPTRS.

       PER_OSF4 (since Linux 2.4)
              OSF/1 v4.  No effect since Linux 6.1, which removed a.out
              binary support.  Before, on alpha, would 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)
              SCO OpenServer 5.  Implies STICKY_TIMEOUTS and
              WHOLE_SECONDS; otherwise no effect.

       PER_RISCOS (since Linux 2.3.7; macro since Linux 2.3.13)
              Acorn RISC OS/Arthur (MIPS).  No effect.  Up to Linux
              v4.0, would set the emulation altroot to
              /usr/gnemul/riscos (cf. PER_SUNOS, below).  Before then,
              up to Linux 2.6.3, just Arthur emulation.

       PER_SCOSVR3 (since Linux 1.2.0)
              SCO UNIX System V Release 3.  Same as PER_OSR5, but also
              implies SHORT_INODE.

       PER_SOLARIS (since Linux 2.4)
              Solaris.  Implies STICKY_TIMEOUTS; otherwise no effect.

       PER_SUNOS (since Linux 2.4.0)
              Sun OS.  Same as PER_BSD, but implies STICKY_TIMEOUTS.
              Prior to Linux 2.6.26, diverted library and dynamic linker
              searches to /usr/gnemul.  Buggy, largely unmaintained, and
              almost entirely unused.

       PER_SVR3 (since Linux 1.2.0)
              AT&T UNIX System V Release 3.  Implies STICKY_TIMEOUTS and
              SHORT_INODE; otherwise no effect.

       PER_SVR4 (since Linux 1.2.0)
              AT&T UNIX System V Release 4.  Implies STICKY_TIMEOUTS and
              MMAP_PAGE_ZERO; otherwise no effect.

       PER_UW7 (since Linux 2.4)
              UnixWare 7.  Implies STICKY_TIMEOUTS and MMAP_PAGE_ZERO;
              otherwise no effect.

       PER_WYSEV386 (since Linux 1.2.0)
              WYSE UNIX System V/386.  Implies STICKY_TIMEOUTS and
              SHORT_INODE; otherwise no effect.

       PER_XENIX (since Linux 1.2.0)
              XENIX.  Implies STICKY_TIMEOUTS and SHORT_INODE; otherwise
              no effect.

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.

STANDARDS         top


HISTORY         top

       Linux 1.1.20, glibc 2.3.

SEE ALSO         top


Linux man-pages (unreleased)     (date)                   personality(2)

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