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.
