man2/personality.2

   1 .\" Copyright (C) 1995, Thomas K. Dyas <tdyas@eden.rutgers.edu>
   2 .\" and Copyright (C) 2016, Michael Kerrisk <mtk.manpages@gmail.com>
   3 .\"
   4 .\" SPDX-License-Identifier: Linux-man-pages-copyleft
   5 .\"
   6 .\" Created   Sat Aug 21 1995     Thomas K. Dyas <tdyas@eden.rutgers.edu>
   7 .\"
   8 .\" typo corrected, aeb, 950825
   9 .\" added layout change from joey, 960722
  10 .\" changed prototype, documented 0xffffffff, aeb, 030101
  11 .\" Modified 2004-11-03 patch from Martin Schulze <joey@infodrom.org>
  12 .\"
  13 .TH PERSONALITY 2 2021-03-22 "Linux" "Linux Programmer's Manual"
  14 .SH NAME
  15 personality \- set the process execution domain
  16 .SH LIBRARY
  17 Standard C library
  18 .RI ( libc ", " \-lc )
  19 .SH SYNOPSIS
  20 .nf
  21 .B #include <sys/personality.h>
  22 .PP
  23 .BI "int personality(unsigned long " persona );
  24 .fi
  25 .SH DESCRIPTION
  26 Linux supports different execution domains, or personalities, for each
  27 process.
  28 Among other things, execution domains tell Linux how to map
  29 signal numbers into signal actions.
  30 The execution domain system allows
  31 Linux to provide limited support for binaries compiled under other
  32 UNIX-like operating systems.
  33 .PP
  34 If
  35 .I persona
  36 is not
  37 0xffffffff, then
  38 .BR personality ()
  39 sets the caller's execution domain to the value specified by
  40 .IR persona .
  41 Specifying
  42 .IR persona
  43 as 0xffffffff provides a way of retrieving
  44 the current persona without changing it.
  45 .PP
  46 A list of the available execution domains can be found in
  47 .IR <sys/personality.h> .
  48 The execution domain is a 32-bit value in which the top three
  49 bytes are set aside for flags that cause the kernel to modify the
  50 behavior of certain system calls so as to emulate historical or
  51 architectural quirks.
  52 The least significant byte is a value defining the personality
  53 the kernel should assume.
  54 The flag values are as follows:
  55 .TP
  56 .BR ADDR_COMPAT_LAYOUT " (since Linux 2.6.9)"
  57 With this flag set, provide legacy virtual address space layout.
  58 .TP
  59 .BR ADDR_NO_RANDOMIZE " (since Linux 2.6.12)"
  60 With this flag set, disable address-space-layout randomization.
  61 .TP
  62 .BR ADDR_LIMIT_32BIT " (since Linux 2.2)"
  63 Limit the address space to 32 bits.
  64 .TP
  65 .BR ADDR_LIMIT_3GB " (since Linux 2.4.0)"
  66 With this flag set, use 0xc0000000 as the offset at which to search
  67 a virtual memory chunk on
  68 .BR mmap (2);
  69 otherwise use 0xffffe000.
  70 .TP
  71 .BR FDPIC_FUNCPTRS " (since Linux 2.6.11)"
  72 User-space function pointers to signal handlers point
  73 (on certain architectures) to descriptors.
  74 .TP
  75 .BR MMAP_PAGE_ZERO " (since Linux 2.4.0)"
  76 Map page 0 as read-only
  77 (to support binaries that depend on this SVr4 behavior).
  78 .TP
  79 .BR READ_IMPLIES_EXEC " (since Linux 2.6.8)"
  80 With this flag set,
  81 .BR PROT_READ
  82 implies
  83 .BR PROT_EXEC
  84 for
  85 .BR mmap (2).
  86 .TP
  87 .BR SHORT_INODE " (since Linux 2.4.0)"
  88 No effects(?).
  89 .TP
  90 .BR STICKY_TIMEOUTS " (since Linux 1.2.0)"
  91 With this flag set,
  92 .BR select (2),
  93 .BR pselect (2),
  94 and
  95 .BR ppoll (2)
  96 do not modify the returned timeout argument when
  97 interrupted by a signal handler.
  98 .TP
  99 .BR UNAME26 " (since Linux 3.1)"
 100 Have
 101 .BR uname (2)
 102 report a 2.6.40+ version number rather than a 3.x version number.
 103 Added as a stopgap measure to support broken applications that
 104 could not handle the kernel version-numbering switch from 2.6.x to 3.x.
 105 .TP
 106 .BR WHOLE_SECONDS " (since Linux 1.2.0)"
 107 No effect.
 108 .PP
 109 The available execution domains are:
 110 .TP
 111 .BR PER_BSD " (since Linux 1.2.0)"
 112 BSD. (No effects.)
 113 .TP
 114 .BR PER_HPUX " (since Linux 2.4)"
 115 Support for 32-bit HP/UX.
 116 This support was never complete, and was dropped so that since Linux 4.0,
 117 this value has no effect.
 118 .TP
 119 .BR PER_IRIX32 " (since Linux 2.2)"
 120 IRIX 5 32-bit.
 121 Never fully functional; support dropped in Linux 2.6.27.
 122 Implies
 123 .BR STICKY_TIMEOUTS .
 124 .TP
 125 .BR PER_IRIX64 " (since Linux 2.2)"
 126 IRIX 6 64-bit.
 127 Implies
 128 .BR STICKY_TIMEOUTS ;
 129 otherwise no effects.
 130 .TP
 131 .BR PER_IRIXN32 " (since Linux 2.2)"
 132 IRIX 6 new 32-bit.
 133 Implies
 134 .BR STICKY_TIMEOUTS ;
 135 otherwise no effects.
 136 .TP
 137 .BR PER_ISCR4 " (since Linux 1.2.0)"
 138 Implies
 139 .BR STICKY_TIMEOUTS ;
 140 otherwise no effects.
 141 .TP
 142 .BR PER_LINUX " (since Linux 1.2.0)"
 143 Linux.
 144 .TP
 145 .BR PER_LINUX32 " (since Linux 2.2)"
 146 [To be documented.]
 147 .TP
 148 .BR PER_LINUX32_3GB " (since Linux 2.4)"
 149 Implies
 150 .BR ADDR_LIMIT_3GB .
 151 .TP
 152 .BR PER_LINUX_32BIT " (since Linux 2.0)"
 153 Implies
 154 .BR ADDR_LIMIT_32BIT .
 155 .TP
 156 .BR PER_LINUX_FDPIC " (since Linux 2.6.11)"
 157 Implies
 158 .BR FDPIC_FUNCPTRS .
 159 .TP
 160 .BR PER_OSF4 " (since Linux 2.4)"
 161 OSF/1 v4.
 162 On alpha,
 163 .\" Following is from a comment in arch/alpha/kernel/osf_sys.c
 164 clear top 32 bits of iov_len in the user's buffer for
 165 compatibility with old versions of OSF/1 where iov_len
 166 was defined as.
 167 .IR int .
 168 .TP
 169 .BR PER_OSR5 " (since Linux 2.4)"
 170 Implies
 171 .BR STICKY_TIMEOUTS
 172 and
 173 .BR WHOLE_SECONDS ;
 174 otherwise no effects.
 175 .TP
 176 .BR PER_RISCOS " (since Linux 2.2)"
 177 [To be documented.]
 178 .TP
 179 .BR PER_SCOSVR3 " (since Linux 1.2.0)"
 180 Implies
 181 .BR STICKY_TIMEOUTS ,
 182 .BR WHOLE_SECONDS ,
 183 and
 184 .BR SHORT_INODE ;
 185 otherwise no effects.
 186 .TP
 187 .BR PER_SOLARIS " (since Linux 2.4)"
 188 Implies
 189 .BR STICKY_TIMEOUTS ;
 190 otherwise no effects.
 191 .TP
 192 .BR PER_SUNOS " (since Linux 2.4.0)"
 193 Implies
 194 .BR STICKY_TIMEOUTS .
 195 Divert library and dynamic linker searches to
 196 .IR /usr/gnemul .
 197 Buggy, largely unmaintained, and almost entirely unused;
 198 support was removed in Linux 2.6.26.
 199 .TP
 200 .BR PER_SVR3 " (since Linux 1.2.0)"
 201 Implies
 202 .BR STICKY_TIMEOUTS
 203 and
 204 .BR SHORT_INODE ;
 205 otherwise no effects.
 206 .TP
 207 .BR PER_SVR4 " (since Linux 1.2.0)"
 208 Implies
 209 .BR STICKY_TIMEOUTS
 210 and
 211 .BR MMAP_PAGE_ZERO ;
 212 otherwise no effects.
 213 .TP
 214 .BR PER_UW7 " (since Linux 2.4)"
 215 Implies
 216 .BR STICKY_TIMEOUTS
 217 and
 218 .BR MMAP_PAGE_ZERO ;
 219 otherwise no effects.
 220 .TP
 221 .BR PER_WYSEV386 " (since Linux 1.2.0)"
 222 Implies
 223 .BR STICKY_TIMEOUTS
 224 and
 225 .BR SHORT_INODE ;
 226 otherwise no effects.
 227 .TP
 228 .BR PER_XENIX " (since Linux 1.2.0)"
 229 Implies
 230 .BR STICKY_TIMEOUTS
 231 and
 232 .BR SHORT_INODE ;
 233 otherwise no effects.
 234 .SH RETURN VALUE
 235 On success, the previous
 236 .I persona
 237 is returned.
 238 On error, \-1 is returned, and
 239 .I errno
 240 is set to indicate the error.
 241 .SH ERRORS
 242 .TP
 243 .B EINVAL
 244 The kernel was unable to change the personality.
 245 .SH VERSIONS
 246 This system call first appeared in Linux 1.1.20
 247 (and thus first in a stable kernel release with Linux 1.2.0);
 248 library support was added in glibc 2.3.
 249 .\" personality wrapper first appeared in glibc 1.90,
 250 .\" <sys/personality.h> was added later in 2.2.91.
 251 .SH CONFORMING TO
 252 .BR personality ()
 253 is Linux-specific and should not be used in programs intended to
 254 be portable.
 255 .SH SEE ALSO
 256 .BR setarch (8)