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
37void
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}
98weak_alias(__makecontext, makecontext)
99

source code of glibc/sysdeps/unix/sysv/linux/hppa/makecontext.c