2 Copyright (C) 2001-2023 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <https://www.gnu.org/licenses/>. */
21 #include "ucontext_i.h"
27 /* Load the address of the function we are supposed to run. */
30 /* Compute the address of the stack. The information comes from
31 to us_stack element. */
32 movl oSS_SP(%eax), %edx
34 addl oSS_SIZE(%eax), %edx
36 /* Remember the number of parameters for the exit handler since
37 it has to remove them. We store the number in the EBX register
38 which the function we will call must preserve. */
42 /* Make room on the new stack for the parameters.
43 Room for the arguments, return address (== L(exitcode)) and
44 oLINK pointer is needed. One of the pointer sizes is subtracted
45 after aligning the stack. */
47 leal -4(%edx,%ecx,4), %edx
50 /* Align the stack. */
51 andl $0xfffffff0, %edx
54 /* Store the future stack pointer. */
57 /* Put the next context on the new stack (from the uc_link
59 movl oLINK(%eax), %eax
60 movl %eax, 4(%edx,%ecx,4)
62 /* Copy all the parameters. */
64 1: movl 12(%esp,%ecx,4), %eax
65 movl %eax, (%edx,%ecx,4)
70 /* If the function we call returns we must continue with the
71 context which is given in the uc_link element. To do this
72 set the return address for the function the user provides
73 to a little bit of helper code which does the magic (see
77 cfi_adjust_cfa_offset (4)
79 cfi_adjust_cfa_offset (-4)
80 addl $L(exitcode)-1b, %ecx
83 movl $L(exitcode), (%edx)
85 /* We need to terminate the FDE here instead of after ret because
86 the unwinder looks at ra-1 for unwind information. */
89 /* 'makecontext' returns no value. */
92 /* This is the helper code which gets called if a function which
93 is registered with 'makecontext' returns. In this case we
94 have to install the context listed in the uc_link element of
95 the context 'makecontext' manipulated at the time of the
96 'makecontext' call. If the pointer is NULL the process must
99 /* This removes the parameters passed to the function given to
100 'makecontext' from the stack. EBX contains the number of
101 parameters (see above). */
102 leal (%esp,%ebx,4), %esp
104 cmpl $0, (%esp) /* Check the next context. */
105 je 2f /* If it is zero exit. */
107 call HIDDEN_JUMPTARGET(__setcontext)
108 /* If this returns (which can happen if the syscall fails) we'll
109 exit the program with the return error value (-1). */
113 /* Exit with status 0. */
117 /* Align the stack and pass the exit code (from %eax). */
118 andl $0xfffffff0, %esp
122 call HIDDEN_JUMPTARGET(exit)
123 /* The 'exit' call should never return. In case it does cause
124 the process to terminate. */
129 weak_alias (__makecontext, makecontext)