personality - set the process execution domain
Standard C library (libc, -lc)
#include <sys/personality.h>
int personality(unsigned long persona);
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.
On success, the previous persona is returned. On error, -1
is returned, and errno is set to indicate the error.
- EINVAL
- The kernel was unable to change the personality.