personality(2)

1personality(2)                System Calls Manual               personality(2)
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NAME

6       personality - set the process execution domain
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LIBRARY

9       Standard C library (libc, -lc)
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SYNOPSIS

12       #include <sys/personality.h>
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14       int personality(unsigned long persona);
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DESCRIPTION

17       Linux  supports different execution domains, or personalities, for each
18       process.  Among other things, execution domains tell Linux how  to  map
19       signal numbers into signal actions.  The execution domain system allows
20       Linux to provide limited support  for  binaries  compiled  under  other
21       UNIX-like operating systems.
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23       If persona is not 0xffffffff, then personality() sets the caller's exe‐
24       cution domain to the value specified by persona.  Specifying persona as
25       0xffffffff  provides  a  way  of retrieving the current persona without
26       changing it.
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28       A list of the available execution domains can be found in  <sys/person‐
29       ality.h>.   The  execution  domain  is  a 32-bit value in which the top
30       three bytes are set aside for flags that cause the kernel to modify the
31       behavior  of certain system calls so as to emulate historical or archi‐
32       tectural quirks.  The least significant byte is a  value  defining  the
33       personality the kernel should assume.  The flag values are as follows:
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35       ADDR_COMPAT_LAYOUT (since Linux 2.6.9)
36              With this flag set, provide legacy virtual address space layout.
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38       ADDR_NO_RANDOMIZE (since Linux 2.6.12)
39              With this flag set, disable address-space-layout randomization.
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41       ADDR_LIMIT_32BIT (since Linux 2.2)
42              Limit the address space to 32 bits.
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44       ADDR_LIMIT_3GB (since Linux 2.4.0)
45              With  this  flag  set,  use 0xc0000000 as the offset at which to
46              search  a  virtual  memory  chunk  on  mmap(2);  otherwise   use
47              0xffffe000.  Applies to 32-bit x86 processes only.
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49       FDPIC_FUNCPTRS (since Linux 2.6.11)
50              User-space  function  pointers  to  signal handlers point to de‐
51              scriptors.  Applies only to ARM if BINFMT_ELF_FDPIC and SuperH.
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53       MMAP_PAGE_ZERO (since Linux 2.4.0)
54              Map page 0 as read-only (to support binaries that depend on this
55              SVr4 behavior).
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57       READ_IMPLIES_EXEC (since Linux 2.6.8)
58              With this flag set, PROT_READ implies PROT_EXEC for mmap(2).
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60       SHORT_INODE (since Linux 2.4.0)
61              No effect.
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63       STICKY_TIMEOUTS (since Linux 1.2.0)
64              With  this  flag set, select(2), pselect(2), and ppoll(2) do not
65              modify the returned timeout argument when interrupted by a  sig‐
66              nal handler.
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68       UNAME26 (since Linux 3.1)
69              Have  uname(2)  report a 2.6.(40+x) version number rather than a
70              MAJOR.x version number.  Added as a stopgap measure  to  support
71              broken  applications  that  could not handle the kernel version-
72              numbering switch from Linux 2.6.x to Linux 3.x.
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74       WHOLE_SECONDS (since Linux 1.2.0)
75              No effect.
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77       The available execution domains are:
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79       PER_BSD (since Linux 1.2.0)
80              BSD. (No effects.)
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82       PER_HPUX (since Linux 2.4)
83              Support for 32-bit HP/UX.  This support was never complete,  and
84              was dropped so that since Linux 4.0, this value has no effect.
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86       PER_IRIX32 (since Linux 2.2)
87              IRIX 5 32-bit.  Never fully functional; support dropped in Linux
88              2.6.27.  Implies STICKY_TIMEOUTS.
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90       PER_IRIX64 (since Linux 2.2)
91              IRIX 6 64-bit.  Implies STICKY_TIMEOUTS; otherwise no effect.
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93       PER_IRIXN32 (since Linux 2.2)
94              IRIX 6 new 32-bit.  Implies STICKY_TIMEOUTS;  otherwise  no  ef‐
95              fect.
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97       PER_ISCR4 (since Linux 1.2.0)
98              Implies STICKY_TIMEOUTS; otherwise no effect.
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100       PER_LINUX (since Linux 1.2.0)
101              Linux.
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103       PER_LINUX32 (since Linux 2.2)
104              uname(2)  returns the name of the 32-bit architecture in the ma‐
105              chine field ("i686" instead of "x86_64", &c.).
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107              Under ia64 (Itanium), processes with this personality don't have
108              the O_LARGEFILE open(2) flag forced.
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110              Under  64-bit  ARM, setting this personality is forbidden if ex‐
111              ecve(2)ing a 32-bit process would also be forbidden (cf. the al‐
112              low_mismatched_32bit_el0   kernel   parameter   and   Documenta‐
113              tion/arm64/asymmetric-32bit.rst).
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115       PER_LINUX32_3GB (since Linux 2.4)
116              Same as PER_LINUX32, but implies ADDR_LIMIT_3GB.
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118       PER_LINUX_32BIT (since Linux 2.0)
119              Same as PER_LINUX, but implies ADDR_LIMIT_32BIT.
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121       PER_LINUX_FDPIC (since Linux 2.6.11)
122              Same as PER_LINUX, but implies FDPIC_FUNCPTRS.
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124       PER_OSF4 (since Linux 2.4)
125              OSF/1 v4.  No effect since Linux 6.1, which removed a.out binary
126              support.   Before,  on alpha, would clear top 32 bits of iov_len
127              in the user's buffer for  compatibility  with  old  versions  of
128              OSF/1 where iov_len was defined as.  int.
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130       PER_OSR5 (since Linux 2.4)
131              SCO  OpenServer  5.   Implies STICKY_TIMEOUTS and WHOLE_SECONDS;
132              otherwise no effect.
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134       PER_RISCOS (since Linux 2.3.7; macro since Linux 2.3.13)
135              Acorn RISC OS/Arthur (MIPS).  No  effect.   Up  to  Linux  v4.0,
136              would  set  the  emulation  altroot  to  /usr/gnemul/riscos (cf.
137              PER_SUNOS, below).  Before then, up to Linux 2.6.3, just  Arthur
138              emulation.
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140       PER_SCOSVR3 (since Linux 1.2.0)
141              SCO UNIX System V Release 3.  Same as PER_OSR5, but also implies
142              SHORT_INODE.
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144       PER_SOLARIS (since Linux 2.4)
145              Solaris.  Implies STICKY_TIMEOUTS; otherwise no effect.
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147       PER_SUNOS (since Linux 2.4.0)
148              Sun OS.  Same as PER_BSD, but implies STICKY_TIMEOUTS.  Prior to
149              Linux  2.6.26,  diverted  library and dynamic linker searches to
150              /usr/gnemul.  Buggy, largely unmaintained, and  almost  entirely
151              unused.
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153       PER_SVR3 (since Linux 1.2.0)
154              AT&T  UNIX  System  V  Release  3.   Implies STICKY_TIMEOUTS and
155              SHORT_INODE; otherwise no effect.
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157       PER_SVR4 (since Linux 1.2.0)
158              AT&T UNIX System  V  Release  4.   Implies  STICKY_TIMEOUTS  and
159              MMAP_PAGE_ZERO; otherwise no effect.
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161       PER_UW7 (since Linux 2.4)
162              UnixWare  7.  Implies STICKY_TIMEOUTS and MMAP_PAGE_ZERO; other‐
163              wise no effect.
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165       PER_WYSEV386 (since Linux 1.2.0)
166              WYSE UNIX System V/386.  Implies STICKY_TIMEOUTS  and  SHORT_IN‐
167              ODE; otherwise no effect.
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169       PER_XENIX (since Linux 1.2.0)
170              XENIX.   Implies  STICKY_TIMEOUTS  and SHORT_INODE; otherwise no
171              effect.
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RETURN VALUE

174       On success, the previous persona is returned.   On  error,  -1  is  re‐
175       turned, and errno is set to indicate the error.
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ERRORS

178       EINVAL The kernel was unable to change the personality.
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STANDARDS

181       Linux.
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HISTORY

184       Linux 1.1.20, glibc 2.3.
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