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 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 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
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 4.09 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/.
Opportunity
Personal Opportunity - Free software gives you access to billions of dollars of software at no cost. Use this software for your business, personal use or to develop a profitable skill. Access to source code provides access to a level of capabilities/information that companies protect though copyrights. Open source is a core component of the Internet and it is available to you. Leverage the billions of dollars in resources and capabilities to build a career, establish a business or change the world. The potential is endless for those who understand the opportunity.
Business Opportunity - Goldman Sachs, IBM and countless large corporations are leveraging open source to reduce costs, develop products and increase their bottom lines. Learn what these companies know about open source and how open source can give you the advantage.
Free Software
Free Software provides computer programs and capabilities at no cost but more importantly, it provides the freedom to run, edit, contribute to, and share the software. The importance of free software is a matter of access, not price. Software at no cost is a benefit but ownership rights to the software and source code is far more significant.
Free Office Software - The Libre Office suite provides top desktop productivity tools for free. This includes, a word processor, spreadsheet, presentation engine, drawing and flowcharting, database and math applications. Libre Office is available for Linux or Windows.
Free Books
The Free Books Library is a collection of thousands of the most popular public domain books in an online readable format. The collection includes great classical literature and more recent works where the U.S. copyright has expired. These books are yours to read and use without restrictions.
Source Code - Want to change a program or know how it works? Open Source provides the source code for its programs so that anyone can use, modify or learn how to write those programs themselves. Visit the GNU source code repositories to download the source.
Education
Study at Harvard, Stanford or MIT - Open edX provides free online courses from Harvard, MIT, Columbia, UC Berkeley and other top Universities. Hundreds of courses for almost all major subjects and course levels. Open edx also offers some paid courses and selected certifications.
Linux Manual Pages - A man or manual page is a form of software documentation found on Linux/Unix operating systems. Topics covered include computer programs (including library and system calls), formal standards and conventions, and even abstract concepts.
