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NAME

       personality - set the process execution domain

LIBRARY

       Standard C library (libc, -lc)

SYNOPSIS

       #include <sys/personality.h>

       int personality(unsigned long persona);

DESCRIPTION

       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.  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 SuperH.

       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 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 3.x.

       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 effect.

       PER_IRIXN32 (since Linux 2.2)
              IRIX 6 new 32-bit.  Implies STICKY_TIMEOUTS; otherwise no effect.

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

       PER_LINUX (since Linux 1.2.0)
              Linux.

       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 Documentation/arm64/asymmetric-32bit.rst).

       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

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

ERRORS

       EINVAL The kernel was unable to change the personality.

STANDARDS

       Linux.

HISTORY

       Linux 1.1.20, glibc 2.3.

SEE ALSO

       setarch(8)