27 .\" The contents of this file are subject to the terms of the
  28 .\" Common Development and Distribution License (the "License").
  29 .\" You may not use this file except in compliance with the License.
  30 .\"
  31 .\" You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
  32 .\" or http://www.opensolaris.org/os/licensing.
  33 .\" See the License for the specific language governing permissions
  34 .\" and limitations under the License.
  35 .\"
  36 .\" When distributing Covered Code, include this CDDL HEADER in each
  37 .\" file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  38 .\" If applicable, add the following below this CDDL HEADER, with the
  39 .\" fields enclosed by brackets "[]" replaced with your own identifying
  40 .\" information: Portions Copyright [yyyy] [name of copyright owner]
  41 .\"
  42 .\"
  43 .\" Copyright 1989 AT&T
  44 .\" Portions Copyright (c) 1992, X/Open Company Limited.  All Rights Reserved.
  45 .\" Copyright (c) 2001, Sun Microsystems, Inc.  All Rights Reserved.
  46 .\" Copyright 2022 OmniOS Community Edition (OmniOSce) Association.

  47 .\"
  48 .Dd November 24, 2022
  49 .Dt GETCONTEXT 2
  50 .Os
  51 .Sh NAME
  52 .Nm getcontext ,

  53 .Nm setcontext
  54 .Nd get and set current user context
  55 .Sh SYNOPSIS
  56 .In ucontext.h
  57 .Ft int
  58 .Fo getcontext
  59 .Fa "ucontext_t *ucp"
  60 .Fc
  61 .Ft int





  62 .Fo setcontext
  63 .Fa "const ucontext_t *ucp"
  64 .Fc
  65 .Sh DESCRIPTION
  66 The
  67 .Fn getcontext
  68 function initializes the structure pointed to by
  69 .Fa ucp
  70 to the current user context of the calling process.
  71 The
  72 .Vt ucontext_t
  73 type that
  74 .Fa ucp
  75 points to defines the user context and includes the contents of the calling
  76 process' machine registers, the signal mask, and the current execution stack.
  77 .Pp
  78 The






















































  79 .Fn setcontext
  80 function restores the user context pointed to by
  81 .Fa ucp .
  82 A successful call to
  83 .Fn setcontext
  84 does not return; program execution resumes at the point specified by the
  85 .Fa ucp
  86 argument passed to
  87 .Fn setcontext .
  88 The
  89 .Fa ucp
  90 argument should be created either by a prior call to
  91 .Fn getcontext ,
  92 or by being passed as an argument to a signal handler.
  93 If the
  94 .Fa ucp
  95 argument was created with
  96 .Fn getcontext ,
  97 program execution continues as if the corresponding call of
  98 .Fn getcontext

 114 argument was passed to a signal handler, program execution continues with the
 115 program instruction following the instruction interrupted by the signal.
 116 If the
 117 .Fa uc_link
 118 member of the
 119 .Vt ucontext_t
 120 structure pointed to by the
 121 .Fa ucp
 122 argument is
 123 .Dv NULL ,
 124 then this context is the main context, and the process
 125 will exit when this context returns.
 126 The effects of passing a
 127 .Fa ucp
 128 argument obtained from any other source are unspecified.
 129 .Sh RETURN VALUES
 130 On successful completion,
 131 .Fn setcontext
 132 does not return and
 133 .Fn getcontext


 134 returns 0.
 135 Otherwise, -1 is returned.
 136 .Sh ERRORS
 137 No errors are defined.















 138 .Sh USAGE
 139 When a signal handler is executed, the current user context is saved and a new
 140 context is created.
 141 If the thread leaves the signal handler via
 142 .Xr longjmp 3C ,
 143 then it is unspecified whether the context at the time of the corresponding
 144 .Xr setjmp 3C
 145 call is restored and thus whether future calls to
 146 .Fn getcontext
 147 will provide an accurate representation of the current context, since the
 148 context restored by
 149 .Xr longjmp 3C
 150 may not contain all the information that
 151 .Fn setcontext
 152 requires.
 153 Signal handlers should use
 154 .Xr siglongjmp 3C
 155 instead.
 156 .Pp
 157 Portable applications should not modify or access the
 158 .Fa uc_mcontext
 159 member of
 160 .Vt ucontext_t .
 161 A portable application cannot assume that context includes any process-wide
 162 static data, possibly including
 163 .Va errno .
 164 Users manipulating contexts should take care to handle these explicitly when
 165 required.
 166 .Sh INTERFACE STABILITY
 167 .Sy Committed
 168 .Sh SEE ALSO
 169 .Xr sigaction 2 ,
 170 .Xr sigaltstack 2 ,
 171 .Xr sigprocmask 2 ,
 172 .Xr bsd_signal 3C ,
 173 .Xr makecontext 3C ,
 174 .Xr setjmp 3C ,
 175 .Xr sigsetjmp 3C ,

 176 .Xr ucontext.h 3HEAD ,
 177 .Xr attributes 7 ,
 178 .Xr standards 7

  27 .\" The contents of this file are subject to the terms of the
  28 .\" Common Development and Distribution License (the "License").
  29 .\" You may not use this file except in compliance with the License.
  30 .\"
  31 .\" You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
  32 .\" or http://www.opensolaris.org/os/licensing.
  33 .\" See the License for the specific language governing permissions
  34 .\" and limitations under the License.
  35 .\"
  36 .\" When distributing Covered Code, include this CDDL HEADER in each
  37 .\" file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  38 .\" If applicable, add the following below this CDDL HEADER, with the
  39 .\" fields enclosed by brackets "[]" replaced with your own identifying
  40 .\" information: Portions Copyright [yyyy] [name of copyright owner]
  41 .\"
  42 .\"
  43 .\" Copyright 1989 AT&T
  44 .\" Portions Copyright (c) 1992, X/Open Company Limited.  All Rights Reserved.
  45 .\" Copyright (c) 2001, Sun Microsystems, Inc.  All Rights Reserved.
  46 .\" Copyright 2022 OmniOS Community Edition (OmniOSce) Association.
  47 .\" Copyright 2023 Oxide Computer Company
  48 .\"
  49 .Dd January 24, 2022
  50 .Dt GETCONTEXT 2
  51 .Os
  52 .Sh NAME
  53 .Nm getcontext ,
  54 .Nm getcontext_extd ,
  55 .Nm setcontext
  56 .Nd get and set current user context
  57 .Sh SYNOPSIS
  58 .In ucontext.h
  59 .Ft int
  60 .Fo getcontext
  61 .Fa "ucontext_t *ucp"
  62 .Fc
  63 .Ft int
  64 .Fo getcontext_extd
  65 .Fa "ucontext_t *ucp"
  66 .Fa "uint32_t flags"
  67 .Fc
  68 .Ft int
  69 .Fo setcontext
  70 .Fa "const ucontext_t *ucp"
  71 .Fc
  72 .Sh DESCRIPTION
  73 The
  74 .Fn getcontext
  75 function initializes the structure pointed to by
  76 .Fa ucp
  77 to the current user context of the calling process.
  78 The
  79 .Vt ucontext_t
  80 type that
  81 .Fa ucp
  82 points to defines the user context and includes the contents of the calling
  83 process' machine registers, the signal mask, and the current execution stack.
  84 .Pp
  85 The
  86 .Vt ucontext_t
  87 structure is a part of the system ABI.
  88 However, most architectures have added additional register states such as the
  89 extended vector and floating point registers that are not part of that.
  90 To facilitate getting that state
  91 .Pq such as the x86 xsave area
  92 the
  93 .Fn getcontext_extd
  94 function exists.
  95 Once called, the context will be initialized and is suitable for use in other
  96 context operations just as though one had called
  97 .Fn getcontext .
  98 .Pp
  99 Unlike the
 100 .Fn getcontext
 101 function,
 102 .Fn getcontext_extd
 103 assumes that callers have previously initialized
 104 .Fa ucp
 105 and thus it treats additional members
 106 .Po
 107 such as the
 108 .Fa uc_xsave
 109 member on x86
 110 .Pc
 111 as potentially valid.
 112 To allow for all extended states to be copied out,
 113 .Fa ucp
 114 must be allocated with
 115 .Xr ucontext_alloc 3C .
 116 Otherwise whether it is declared on the stack, as global data, allocated
 117 dynamically, or part of a structure,
 118 .Fa ucp
 119 must be zeroed through a call to
 120 .Xr bzero 3C
 121 or
 122 .Xr memset 3C
 123 prior to calling
 124 .Fn getcontext_extd .
 125 Improper initialization can lead to memory safety bugs, making it critical that
 126 this is done.
 127 .Pp
 128 The
 129 .Fa flags
 130 member must be zero and is present to allow for what is copied out to change in
 131 the future.
 132 This indicates that the system should attempt to copy out all extended states,
 133 though if the
 134 .Vt ucontext_t
 135 was not allocated with
 136 .Xr ucontext_alloc 3C ,
 137 some extended states may not be.
 138 .Pp
 139 The
 140 .Fn setcontext
 141 function restores the user context pointed to by
 142 .Fa ucp .
 143 A successful call to
 144 .Fn setcontext
 145 does not return; program execution resumes at the point specified by the
 146 .Fa ucp
 147 argument passed to
 148 .Fn setcontext .
 149 The
 150 .Fa ucp
 151 argument should be created either by a prior call to
 152 .Fn getcontext ,
 153 or by being passed as an argument to a signal handler.
 154 If the
 155 .Fa ucp
 156 argument was created with
 157 .Fn getcontext ,
 158 program execution continues as if the corresponding call of
 159 .Fn getcontext

 175 argument was passed to a signal handler, program execution continues with the
 176 program instruction following the instruction interrupted by the signal.
 177 If the
 178 .Fa uc_link
 179 member of the
 180 .Vt ucontext_t
 181 structure pointed to by the
 182 .Fa ucp
 183 argument is
 184 .Dv NULL ,
 185 then this context is the main context, and the process
 186 will exit when this context returns.
 187 The effects of passing a
 188 .Fa ucp
 189 argument obtained from any other source are unspecified.
 190 .Sh RETURN VALUES
 191 On successful completion,
 192 .Fn setcontext
 193 does not return and
 194 .Fn getcontext
 195 and
 196 .Fn getcontext_extd
 197 returns 0.
 198 Otherwise, -1 is returned.
 199 .Sh ERRORS
 200 No errors are defined for
 201 .Fn getcontext
 202 or
 203 .Fn setcontext .
 204 .Pp
 205 The
 206 .Fn getcontext_extd
 207 function only sets
 208 .Va errno
 209 in some circumstances when it fails.
 210 The function may fail if:
 211 .Bl -tag -width Er
 212 .It Er EINVAL
 213 .Fa flags
 214 had invalid values.
 215 .El
 216 .Sh USAGE
 217 When a signal handler is executed, the current user context is saved and a new
 218 context is created.
 219 If the thread leaves the signal handler via
 220 .Xr longjmp 3C ,
 221 then it is unspecified whether the context at the time of the corresponding
 222 .Xr setjmp 3C
 223 call is restored and thus whether future calls to
 224 .Fn getcontext
 225 will provide an accurate representation of the current context, since the
 226 context restored by
 227 .Xr longjmp 3C
 228 may not contain all the information that
 229 .Fn setcontext
 230 requires.
 231 Signal handlers should use
 232 .Xr siglongjmp 3C
 233 instead.
 234 .Pp
 235 Portable applications should not modify or access the
 236 .Fa uc_mcontext
 237 member of
 238 .Vt ucontext_t .
 239 A portable application cannot assume that context includes any process-wide
 240 static data, possibly including
 241 .Va errno .
 242 Users manipulating contexts should take care to handle these explicitly when
 243 required.
 244 .Sh INTERFACE STABILITY
 245 .Sy Committed
 246 .Sh SEE ALSO
 247 .Xr sigaction 2 ,
 248 .Xr sigaltstack 2 ,
 249 .Xr sigprocmask 2 ,
 250 .Xr bsd_signal 3C ,
 251 .Xr makecontext 3C ,
 252 .Xr setjmp 3C ,
 253 .Xr sigsetjmp 3C ,
 254 .Xr ucontext_alloc 3C ,
 255 .Xr ucontext.h 3HEAD ,
 256 .Xr attributes 7 ,
 257 .Xr standards 7