1 | /* Create new context. |
2 | Copyright (C) 2008-2022 Free Software Foundation, Inc. |
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 |
17 | <https://www.gnu.org/licenses/>. */ |
18 | |
19 | #include <libintl.h> |
20 | #include <stdarg.h> |
21 | #include <stdio.h> |
22 | #include <stdlib.h> |
23 | #include <sysdep.h> |
24 | #include <ucontext.h> |
25 | |
26 | /* POSIX only supports integer arguments. */ |
27 | |
28 | /* Stack must be 64-byte aligned at all times. */ |
29 | #define STACK_ALIGN 64 |
30 | /* Size of frame marker in unsigned long words. */ |
31 | #define FRAME_SIZE_UL 8 |
32 | /* Size of frame marker in bytes. */ |
33 | #define FRAME_SIZE_BYTES (8 * sizeof (unsigned long)) |
34 | /* Size of X arguments in bytes. */ |
35 | #define ARGS(x) (x * sizeof (unsigned long)) |
36 | |
37 | void |
38 | __makecontext (ucontext_t *ucp, void (*func) (void), int argc, ...) |
39 | { |
40 | unsigned long *sp, *osp; |
41 | va_list ap; |
42 | int i; |
43 | |
44 | /* Create a 64-byte aligned frame to store args. Use ss_sp if |
45 | it is available, otherwise be robust and use the currently |
46 | saved stack pointer. */ |
47 | if (ucp->uc_stack.ss_sp && ucp->uc_stack.ss_size) |
48 | osp = (unsigned long *)ucp->uc_stack.ss_sp; |
49 | else |
50 | osp = (unsigned long *)ucp->uc_mcontext.sc_gr[30]; |
51 | |
52 | sp = (unsigned long *)((((unsigned long) osp) |
53 | + FRAME_SIZE_BYTES + ARGS(argc) + STACK_ALIGN) |
54 | & ~(STACK_ALIGN - 1)); |
55 | |
56 | /* Use new frame. */ |
57 | ucp->uc_mcontext.sc_gr[30] = ((unsigned long) sp); |
58 | |
59 | /* Finish frame setup. */ |
60 | if (ucp->uc_link) |
61 | { |
62 | /* Returning to the next context and next frame. */ |
63 | sp[-4 / sizeof (unsigned long)] = ucp->uc_link->uc_mcontext.sc_gr[30]; |
64 | sp[-20 / sizeof (unsigned long)] = ucp->uc_link->uc_mcontext.sc_gr[2]; |
65 | } |
66 | else |
67 | { |
68 | /* This is the main context. No frame marker, and no return address. */ |
69 | sp[-4 / sizeof (unsigned long)] = 0x0; |
70 | sp[-20 / sizeof (unsigned long)] = 0x0; |
71 | } |
72 | |
73 | /* Store address to jump to. */ |
74 | ucp->uc_mcontext.sc_gr[2] = (unsigned long) func; |
75 | |
76 | /* Process arguments. */ |
77 | va_start (ap, argc); |
78 | for (i = 0; i < argc; ++i) |
79 | { |
80 | if (i < 4) |
81 | { |
82 | ucp->uc_mcontext.sc_gr[26-i] = va_arg (ap, int); |
83 | continue; |
84 | } |
85 | |
86 | if ((i < 8) && (sizeof (unsigned long) == 8)) |
87 | { |
88 | /* 64bit: r19-r22 are arg7-arg4. */ |
89 | ucp->uc_mcontext.sc_gr[22+4-i] = va_arg (ap, int); |
90 | continue; |
91 | } |
92 | |
93 | /* All other arguments go on the stack. */ |
94 | sp[-1 * (FRAME_SIZE_UL + 1 + i)] = va_arg (ap, int); |
95 | } |
96 | va_end (ap); |
97 | } |
98 | weak_alias(__makecontext, makecontext) |
99 | |