1 | /* Create new context. |
2 | Copyright (C) 2002-2022 Free Software Foundation, Inc. |
3 | |
4 | This file is part of the GNU C Library. |
5 | |
6 | The GNU C Library is free software; you can redistribute it and/or |
7 | modify it under the terms of the GNU Lesser General Public |
8 | License as published by the Free Software Foundation; either |
9 | version 2.1 of the License, or (at your option) any later version. |
10 | |
11 | The GNU C Library is distributed in the hope that it will be useful, |
12 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
13 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
14 | Lesser General Public License for more details. |
15 | |
16 | You should have received a copy of the GNU Lesser General Public |
17 | License along with the GNU C Library; if not, see |
18 | <https://www.gnu.org/licenses/>. */ |
19 | |
20 | #include <sysdep.h> |
21 | #include <stdarg.h> |
22 | #include <stdint.h> |
23 | #include <ucontext.h> |
24 | |
25 | |
26 | /* makecontext sets up a stack and the registers for the |
27 | user context. The stack looks like this: |
28 | |
29 | +-----------------------+ |
30 | | padding as required | |
31 | +-----------------------+ |
32 | sp -> | parameter 7-n | |
33 | +-----------------------+ |
34 | |
35 | The registers are set up like this: |
36 | %x0 .. %x7: parameter 1 to 8 |
37 | %x19 : uc_link |
38 | %sp : stack pointer. |
39 | */ |
40 | |
41 | void |
42 | __makecontext (ucontext_t *ucp, void (*func) (void), int argc, ...) |
43 | { |
44 | extern void __startcontext (void); |
45 | uint64_t *sp; |
46 | va_list ap; |
47 | int i; |
48 | |
49 | sp = (uint64_t *) |
50 | ((uintptr_t) ucp->uc_stack.ss_sp + ucp->uc_stack.ss_size); |
51 | |
52 | /* Allocate stack arguments. */ |
53 | sp -= argc < 8 ? 0 : argc - 8; |
54 | |
55 | /* Keep the stack aligned. */ |
56 | sp = (uint64_t *) (((uintptr_t) sp) & -16L); |
57 | |
58 | ucp->uc_mcontext.regs[19] = (uintptr_t) ucp->uc_link; |
59 | ucp->uc_mcontext.sp = (uintptr_t) sp; |
60 | ucp->uc_mcontext.pc = (uintptr_t) func; |
61 | ucp->uc_mcontext.regs[29] = (uintptr_t) 0; |
62 | ucp->uc_mcontext.regs[30] = (uintptr_t) &__startcontext; |
63 | |
64 | va_start (ap, argc); |
65 | for (i = 0; i < argc; ++i) |
66 | if (i < 8) |
67 | ucp->uc_mcontext.regs[i] = va_arg (ap, uint64_t); |
68 | else |
69 | sp[i - 8] = va_arg (ap, uint64_t); |
70 | |
71 | va_end (ap); |
72 | } |
73 | |
74 | weak_alias (__makecontext, makecontext) |
75 | |