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>
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  26 .\" Created   Sat Aug 21 1995     Thomas K. Dyas <tdyas@eden.rutgers.edu>
  27 .\"
  28 .\" typo corrected, aeb, 950825
  29 .\" added layout change from joey, 960722
  30 .\" changed prototype, documented 0xffffffff, aeb, 030101
  31 .\" Modified 2004-11-03 patch from Martin Schulze <joey@infodrom.org>
  32 .\"
  33 .TH PERSONALITY 2 2017-09-15 "Linux" "Linux Programmer's Manual"
  34 .SH NAME
  35 personality \- set the process execution domain
  36 .SH SYNOPSIS
  37 .B #include <sys/personality.h>
  38 .PP
  39 .BI "int personality(unsigned long " persona );
  40 .SH DESCRIPTION
  41 Linux supports different execution domains, or personalities, for each
  42 process.
  43 Among other things, execution domains tell Linux how to map
  44 signal numbers into signal actions.
  45 The execution domain system allows
  46 Linux to provide limited support for binaries compiled under other
  47 UNIX-like operating systems.
  48 .PP
  49 If
  50 .I persona
  51 is not
  52 0xffffffff, then
  53 .BR personality ()
  54 sets the caller's execution domain to the value specified by
  55 .IR persona .
  56 Specifying
  57 .IR persona
  58 as 0xffffffff provides a way of retrieving
  59 the current persona without changing it.
  60 .PP
  61 A list of the available execution domains can be found in
  62 .IR <sys/personality.h> .
  63 The execution domain is a 32-bit value in which the top three
  64 bytes are set aside for flags that cause the kernel to modify the
  65 behavior of certain system calls so as to emulate historical or
  66 architectural quirks.
  67 The least significant byte is a value defining the personality
  68 the kernel should assume.
  69 The flag values are as follows:
  70 .TP
  71 .BR ADDR_COMPAT_LAYOUT " (since Linux 2.6.9)"
  72 With this flag set, provide legacy virtual address space layout.
  73 .TP
  74 .BR ADDR_NO_RANDOMIZE " (since Linux 2.6.12)"
  75 With this flag set, disable address-space-layout randomization.
  76 .TP
  77 .BR ADDR_LIMIT_32BIT " (since Linux 2.2)"
  78 Limit the address space to 32 bits.
  79 .TP
  80 .BR ADDR_LIMIT_3GB " (since Linux 2.4.0)"
  81 With this flag set, use 0xc0000000 as the offset at which to search
  82 a virtual memory chunk on
  83 .BR mmap (2);
  84 otherwise use 0xffffe000.
  85 .TP
  86 .BR FDPIC_FUNCPTRS " (since Linux 2.6.11)"
  87 User-space function pointers to signal handlers point
  88 (on certain architectures) to descriptors.
  89 .TP
  90 .BR MMAP_PAGE_ZERO " (since Linux 2.4.0)"
  91 Map page 0 as read-only
  92 (to support binaries that depend on this SVr4 behavior).
  93 .TP
  94 .BR READ_IMPLIES_EXEC " (since Linux 2.6.8)"
  95 With this flag set,
  96 .BR PROT_READ
  97 implies
  98 .BR PROT_EXEC
  99 for
 100 .BR mmap (2).
 101 .TP
 102 .BR SHORT_INODE " (since Linux 2.4.0)"
 103 No effects(?).
 104 .TP
 105 .BR STICKY_TIMEOUTS " (since Linux 1.2.0)"
 106 With this flag set,
 107 .BR select (2),
 108 .BR pselect (2),
 109 and
 110 .BR ppoll (2)
 111 do not modify the returned timeout argument when
 112 interrupted by a signal handler.
 113 .TP
 114 .BR UNAME26 " (since Linux 3.1)"
 115 Have
 116 .BR uname (2)
 117 report a 2.6.40+ version number rather than a 3.x version number.
 118 Added as a stopgap measure to support broken applications that
 119 could not handle the kernel version-numbering switch from 2.6.x to 3.x.
 120 .TP
 121 .BR WHOLE_SECONDS " (since Linux 1.2.0)"
 122 No effects(?).
 123 .PP
 124 The available execution domains are:
 125 .TP
 126 .BR PER_BSD " (since Linux 1.2.0)"
 127 BSD. (No effects.)
 128 .TP
 129 .BR PER_HPUX " (since Linux 2.4)"
 130 Support for 32-bit HP/UX.
 131 This support was never complete, and was dropped so that since Linux 4.0,
 132 this value has no effect.
 133 .TP
 134 .BR PER_IRIX32 " (since Linux 2.2)"
 135 IRIX 5 32-bit.
 136 Never fully functional; support dropped in Linux 2.6.27.
 137 Implies
 138 .BR STICKY_TIMEOUTS .
 139 .TP
 140 .BR PER_IRIX64 " (since Linux 2.2)"
 141 IRIX 6 64-bit.
 142 Implies
 143 .BR STICKY_TIMEOUTS ;
 144 otherwise no effects.
 145 .TP
 146 .BR PER_IRIXN32 " (since Linux 2.2)"
 147 IRIX 6 new 32-bit.
 148 Implies
 149 .BR STICKY_TIMEOUTS ;
 150 otherwise no effects.
 151 .TP
 152 .BR PER_ISCR4 " (since Linux 1.2.0)"
 153 Implies
 154 .BR STICKY_TIMEOUTS ;
 155 otherwise no effects.
 156 .TP
 157 .BR PER_LINUX " (since Linux 1.2.0)"
 158 Linux.
 159 .TP
 160 .BR PER_LINUX32 " (since Linux 2.2)"
 161 [To be documented.]
 162 .TP
 163 .BR PER_LINUX32_3GB " (since Linux 2.4)"
 164 Implies
 165 .BR ADDR_LIMIT_3GB .
 166 .TP
 167 .BR PER_LINUX_32BIT " (since Linux 2.0)"
 168 Implies
 169 .BR ADDR_LIMIT_32BIT .
 170 .TP
 171 .BR PER_LINUX_FDPIC " (since Linux 2.6.11)"
 172 Implies
 173 .BR FDPIC_FUNCPTRS .
 174 .TP
 175 .BR PER_OSF4 " (since Linux 2.4)"
 176 OSF/1 v4.
 177 On alpha,
 178 .\" Following is from a comment in arch/alpha/kernel/osf_sys.c
 179 clear top 32 bits of iov_len in the user's buffer for
 180 compatibility with old versions of OSF/1 where iov_len
 181 was defined as.
 182 .IR int .
 183 .TP
 184 .BR PER_OSR5 " (since Linux 2.4)"
 185 Implies
 186 .BR STICKY_TIMEOUTS
 187 and
 188 .BR WHOLE_SECONDS ;
 189 otherwise no effects.
 190 .TP
 191 .BR PER_RISCOS " (since Linux 2.2)"
 192 [To be documented.]
 193 .TP
 194 .BR PER_SCOSVR3 " (since Linux 1.2.0)"
 195 Implies
 196 .BR STICKY_TIMEOUTS ,
 197 .BR WHOLE_SECONDS ,
 198 and
 199 .BR SHORT_INODE ;
 200 otherwise no effects.
 201 .TP
 202 .BR PER_SOLARIS " (since Linux 2.4)"
 203 Implies
 204 .BR STICKY_TIMEOUTS ;
 205 otherwise no effects.
 206 .TP
 207 .BR PER_SUNOS " (since Linux 2.4.0)"
 208 Implies
 209 .BR STICKY_TIMEOUTS .
 210 Divert library and dynamic linker searches to
 211 .IR /usr/gnemul .
 212 Buggy, largely unmaintained, and almost entirely unused;
 213 support was removed in Linux 2.6.26.
 214 .TP
 215 .BR PER_SVR3 " (since Linux 1.2.0)"
 216 Implies
 217 .BR STICKY_TIMEOUTS
 218 and
 219 .BR SHORT_INODE ;
 220 otherwise no effects.
 221 .TP
 222 .BR PER_SVR4 " (since Linux 1.2.0)"
 223 Implies
 224 .BR STICKY_TIMEOUTS
 225 and
 226 .BR MMAP_PAGE_ZERO ;
 227 otherwise no effects.
 228 .TP
 229 .BR PER_UW7 " (since Linux 2.4)"
 230 Implies
 231 .BR STICKY_TIMEOUTS
 232 and
 233 .BR MMAP_PAGE_ZERO ;
 234 otherwise no effects.
 235 .TP
 236 .BR PER_WYSEV386 " (since Linux 1.2.0)"
 237 Implies
 238 .BR STICKY_TIMEOUTS
 239 and
 240 .BR SHORT_INODE ;
 241 otherwise no effects.
 242 .TP
 243 .BR PER_XENIX " (since Linux 1.2.0)"
 244 Implies
 245 .BR STICKY_TIMEOUTS
 246 and
 247 .BR SHORT_INODE ;
 248 otherwise no effects.
 249 .SH RETURN VALUE
 250 On success, the previous
 251 .I persona
 252 is returned.
 253 On error, \-1 is returned, and
 254 .I errno
 255 is set appropriately.
 256 .SH ERRORS
 257 .TP
 258 .B EINVAL
 259 The kernel was unable to change the personality.
 260 .SH VERSIONS
 261 This system call first appeared in Linux 1.1.20
 262 (and thus first in a stable kernel release with Linux 1.2.0);
 263 library support was added in glibc 2.3.
 264 .\" personality wrapper first appeared in glibc 1.90,
 265 .\" <sys/personality.h> was added later in 2.2.91.
 266 .SH CONFORMING TO
 267 .BR personality ()
 268 is Linux-specific and should not be used in programs intended to
 269 be portable.
 270 .SH SEE ALSO
 271 .BR setarch (8)