1/* Create new context. C-SKY version.
2 Copyright (C) 2018-2022 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 <stdarg.h>
20#include <ucontext.h>
21
22/* Number of arguments that go in registers. */
23#define NREG_ARGS 4
24
25/* Take a context previously prepared via getcontext() and set to
26 call func() with the given int only args. */
27void
28__makecontext (ucontext_t *ucp, void (*func) (void), int argc, ...)
29{
30 extern void __startcontext (void);
31 unsigned long *funcstack;
32 va_list vl;
33 unsigned long *regptr;
34 unsigned int reg;
35 int misaligned;
36
37 /* Start at the top of stack. */
38 funcstack = (unsigned long *) (ucp->uc_stack.ss_sp + ucp->uc_stack.ss_size);
39
40 /* Ensure the stack stays eight byte aligned. */
41 misaligned = ((unsigned long) funcstack & 4) != 0;
42
43 if ((argc > NREG_ARGS) && (argc & 1) != 0)
44 misaligned = !misaligned;
45
46 if (misaligned)
47 funcstack -= 1;
48
49 va_start (vl, argc);
50
51 /* Reserve space for the on-stack arguments. */
52 if (argc > NREG_ARGS)
53 funcstack -= (argc - NREG_ARGS);
54
55 ucp->uc_mcontext.__gregs.__usp = (unsigned long) funcstack;
56 ucp->uc_mcontext.__gregs.__pc = (unsigned long) func;
57
58 /* Exit to startcontext() with the next context in R9. */
59 ucp->uc_mcontext.__gregs.__regs[5] = (unsigned long) ucp->uc_link;
60 ucp->uc_mcontext.__gregs.__lr = (unsigned long) __startcontext;
61
62 /* The first four arguments go into registers. */
63 regptr = &(ucp->uc_mcontext.__gregs.__a0);
64
65 for (reg = 0; (reg < argc) && (reg < NREG_ARGS); reg++)
66 *regptr++ = va_arg (vl, unsigned long);
67
68 /* And the remainder on the stack. */
69 for (; reg < argc; reg++)
70 *funcstack++ = va_arg (vl, unsigned long);
71
72 va_end (vl);
73}
74weak_alias (__makecontext, makecontext)
75

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