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522e6ee3 | 1 | /* Create new context. |
dff8da6b | 2 | Copyright (C) 2015-2024 Free Software Foundation, Inc. |
522e6ee3 CLT |
3 | This file is part of the GNU C Library. |
4 | ||
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. | |
9 | ||
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. | |
14 | ||
15 | You should have received a copy of the GNU Lesser General Public | |
16 | License along with the GNU C Library; if not, see | |
5a82c748 | 17 | <https://www.gnu.org/licenses/>. */ |
522e6ee3 CLT |
18 | |
19 | #include <sysdep.h> | |
20 | #include <stdarg.h> | |
21 | #include <stdint.h> | |
22 | #include <ucontext.h> | |
23 | ||
24 | /* makecontext sets up a stack and the registers for the | |
25 | user context. The stack looks like this: | |
26 | ||
27 | +-----------------------+ | |
28 | | padding as required | | |
29 | +-----------------------+ | |
30 | sp -> | parameters 5 to n | | |
31 | +-----------------------+ | |
32 | ||
33 | The registers are set up like this: | |
34 | r4--r7 : parameter 1 to 4 | |
35 | r16 : uc_link | |
36 | sp : stack pointer. | |
37 | */ | |
38 | ||
39 | void | |
40 | __makecontext (ucontext_t *ucp, void (*func) (void), int argc, ...) | |
41 | { | |
42 | extern void __startcontext (void); | |
43 | unsigned long *sp; | |
44 | va_list ap; | |
45 | int i; | |
46 | ||
47 | sp = (unsigned long *) | |
48 | ((uintptr_t) ucp->uc_stack.ss_sp + ucp->uc_stack.ss_size); | |
49 | ||
50 | /* Allocate stack arguments. */ | |
51 | sp -= argc < 4 ? 0 : argc - 4; | |
52 | ||
53 | /* Keep the stack aligned. */ | |
54 | sp = (unsigned long*) (((uintptr_t) sp) & -4L); | |
55 | ||
56 | /* Init version field. */ | |
57 | ucp->uc_mcontext.version = 2; | |
58 | /* Keep uc_link in r16. */ | |
59 | ucp->uc_mcontext.regs[15] = (uintptr_t) ucp->uc_link; | |
60 | /* Return address points to __startcontext(). */ | |
61 | ucp->uc_mcontext.regs[23] = (uintptr_t) &__startcontext; | |
62 | /* Frame pointer is null. */ | |
63 | ucp->uc_mcontext.regs[24] = (uintptr_t) 0; | |
64 | /* Restart in user-space starting at 'func'. */ | |
65 | ucp->uc_mcontext.regs[27] = (uintptr_t) func; | |
66 | /* Set stack pointer. */ | |
67 | ucp->uc_mcontext.regs[28] = (uintptr_t) sp; | |
68 | ||
69 | va_start (ap, argc); | |
70 | for (i = 0; i < argc; ++i) | |
71 | if (i < 4) | |
72 | ucp->uc_mcontext.regs[i + 3] = va_arg (ap, unsigned long); | |
73 | else | |
74 | sp[i - 4] = va_arg (ap, unsigned long); | |
75 | ||
76 | va_end (ap); | |
77 | } | |
78 | ||
79 | weak_alias (__makecontext, makecontext) |