.\" Copyright (C) 1995, Thomas K. Dyas <tdyas@eden.rutgers.edu>
+.\" and Copyright (C) 2016, Michael Kerrisk <mtk.manpages@gmail.com>
.\"
.\" %%%LICENSE_START(VERBATIM)
.\" Permission is granted to make and distribute verbatim copies of this
.\" changed prototype, documented 0xffffffff, aeb, 030101
.\" Modified 2004-11-03 patch from Martin Schulze <joey@infodrom.org>
.\"
-.TH PERSONALITY 2 2003-01-01 "Linux" "Linux Programmer's Manual"
+.TH PERSONALITY 2 2017-09-15 "Linux" "Linux Programmer's Manual"
.SH NAME
personality \- set the process execution domain
.SH SYNOPSIS
.B #include <sys/personality.h>
-.sp
+.PP
.BI "int personality(unsigned long " persona );
.SH DESCRIPTION
Linux supports different execution domains, or personalities, for each
The execution domain system allows
Linux to provide limited support for binaries compiled under other
UNIX-like operating systems.
-
-This function will return the current
-.BR personality ()
-when
-.I persona
-equals 0xffffffff.
-Otherwise, it will make the execution domain
-referenced by
+.PP
+If
.I persona
-the new execution domain of the calling process.
+is not
+0xffffffff, then
+.BR personality ()
+sets the caller's execution domain to the value specified by
+.IR persona .
+Specifying
+.IR persona
+as 0xffffffff provides a way of retrieving
+the current persona without changing it.
+.PP
+A list of the available execution domains can be found in
+.IR <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 value defining the personality
+the kernel should assume.
+The flag values are as follows:
+.TP
+.BR ADDR_COMPAT_LAYOUT " (since Linux 2.6.9)"
+With this flag set, provide legacy virtual address space layout.
+.TP
+.BR ADDR_NO_RANDOMIZE " (since Linux 2.6.12)"
+With this flag set, disable address-space-layout randomization.
+.TP
+.BR ADDR_LIMIT_32BIT " (since Linux 2.2)"
+Limit the address space to 32 bits.
+.TP
+.BR 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
+.BR mmap (2);
+otherwise use 0xffffe000.
+.TP
+.BR FDPIC_FUNCPTRS " (since Linux 2.6.11)"
+User-space function pointers to signal handlers point
+(on certain architectures) to descriptors.
+.TP
+.BR MMAP_PAGE_ZERO " (since Linux 2.4.0)"
+Map page 0 as read-only
+(to support binaries that depend on this SVr4 behavior).
+.TP
+.BR READ_IMPLIES_EXEC " (since Linux 2.6.8)"
+With this flag set,
+.BR PROT_READ
+implies
+.BR PROT_EXEC
+for
+.BR mmap (2).
+.TP
+.BR SHORT_INODE " (since Linux 2.4.0)"
+No effects(?).
+.TP
+.BR STICKY_TIMEOUTS " (since Linux 1.2.0)"
+With this flag set,
+.BR select (2),
+.BR pselect (2),
+and
+.BR ppoll (2)
+do not modify the returned timeout argument when
+interrupted by a signal handler.
+.TP
+.BR UNAME26 " (since Linux 3.1)"
+Have
+.BR 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.
+.TP
+.BR WHOLE_SECONDS " (since Linux 1.2.0)"
+No effects(?).
+.PP
+The available execution domains are:
+.TP
+.BR PER_BSD " (since Linux 1.2.0)"
+BSD. (No effects.)
+.TP
+.BR 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.
+.TP
+.BR PER_IRIX32 " (since Linux 2.2)"
+IRIX 5 32-bit.
+Never fully functional; support dropped in Linux 2.6.27.
+Implies
+.BR STICKY_TIMEOUTS .
+.TP
+.BR PER_IRIX64 " (since Linux 2.2)"
+IRIX 6 64-bit.
+Implies
+.BR STICKY_TIMEOUTS ;
+otherwise no effects.
+.TP
+.BR PER_IRIXN32 " (since Linux 2.2)"
+IRIX 6 new 32-bit.
+Implies
+.BR STICKY_TIMEOUTS ;
+otherwise no effects.
+.TP
+.BR PER_ISCR4 " (since Linux 1.2.0)"
+Implies
+.BR STICKY_TIMEOUTS ;
+otherwise no effects.
+.TP
+.BR PER_LINUX " (since Linux 1.2.0)"
+Linux.
+.TP
+.BR PER_LINUX32 " (since Linux 2.2)"
+[To be documented.]
+.TP
+.BR PER_LINUX32_3GB " (since Linux 2.4)"
+Implies
+.BR ADDR_LIMIT_3GB .
+.TP
+.BR PER_LINUX_32BIT " (since Linux 2.0)"
+Implies
+.BR ADDR_LIMIT_32BIT .
+.TP
+.BR PER_LINUX_FDPIC " (since Linux 2.6.11)"
+Implies
+.BR FDPIC_FUNCPTRS .
+.TP
+.BR PER_OSF4 " (since Linux 2.4)"
+OSF/1 v4.
+On alpha,
+.\" Following is from a comment in arch/alpha/kernel/osf_sys.c
+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.
+.IR int .
+.TP
+.BR PER_OSR5 " (since Linux 2.4)"
+Implies
+.BR STICKY_TIMEOUTS
+and
+.BR WHOLE_SECONDS ;
+otherwise no effects.
+.TP
+.BR PER_RISCOS " (since Linux 2.2)"
+[To be documented.]
+.TP
+.BR PER_SCOSVR3 " (since Linux 1.2.0)"
+Implies
+.BR STICKY_TIMEOUTS ,
+.BR WHOLE_SECONDS ,
+and
+.BR SHORT_INODE ;
+otherwise no effects.
+.TP
+.BR PER_SOLARIS " (since Linux 2.4)"
+Implies
+.BR STICKY_TIMEOUTS ;
+otherwise no effects.
+.TP
+.BR PER_SUNOS " (since Linux 2.4.0)"
+Implies
+.BR STICKY_TIMEOUTS .
+Divert library and dynamic linker searches to
+.IR /usr/gnemul .
+Buggy, largely unmaintained, and almost entirely unused;
+support was removed in Linux 2.6.26.
+.TP
+.BR PER_SVR3 " (since Linux 1.2.0)"
+Implies
+.BR STICKY_TIMEOUTS
+and
+.BR SHORT_INODE ;
+otherwise no effects.
+.TP
+.BR PER_SVR4 " (since Linux 1.2.0)"
+Implies
+.BR STICKY_TIMEOUTS
+and
+.BR MMAP_PAGE_ZERO ;
+otherwise no effects.
+.TP
+.BR PER_UW7 " (since Linux 2.4)"
+Implies
+.BR STICKY_TIMEOUTS
+and
+.BR MMAP_PAGE_ZERO ;
+otherwise no effects.
+.TP
+.BR PER_WYSEV386 " (since Linux 1.2.0)"
+Implies
+.BR STICKY_TIMEOUTS
+and
+.BR SHORT_INODE ;
+otherwise no effects.
+.TP
+.BR PER_XENIX " (since Linux 1.2.0)"
+Implies
+.BR STICKY_TIMEOUTS
+and
+.BR SHORT_INODE ;
+otherwise no effects.
.SH RETURN VALUE
On success, the previous
.I persona
.TP
.B EINVAL
The kernel was unable to change the personality.
+.SH 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.
+.\" personality wrapper first appeared in glibc 1.90,
+.\" <sys/personality.h> was added later in 2.2.91.
.SH CONFORMING TO
.BR personality ()
is Linux-specific and should not be used in programs intended to
be portable.
+.SH SEE ALSO
+.BR setarch (8)
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