1/* Create new context.
2 Copyright (C) 2022-2024 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 <sys/asm.h>
22#include <sys/ucontext.h>
23#include <stdarg.h>
24#include <assert.h>
25
26void
27__makecontext (ucontext_t *ucp, void (*func) (void), int argc, long int a0,
28 long int a1, long int a2, long int a3, long int a4, ...)
29{
30 extern void __start_context (void) attribute_hidden;
31 unsigned long int *sp;
32
33 _Static_assert(LARCH_REG_NARGS == 8,
34 "__makecontext assumes 8 argument registers");
35
36 /* Set up the stack. */
37 sp = (unsigned long int *)
38 (((uintptr_t) ucp->uc_stack.ss_sp + ucp->uc_stack.ss_size) & ALMASK);
39
40 /* Set up the register context.
41 ra = s0 = 0, terminating the stack for backtracing purposes.
42 s1 = the function we must call.
43 s2 = the subsequent context to run. */
44 ucp->uc_mcontext.__gregs[LARCH_REG_RA] = (uintptr_t) 0;
45 ucp->uc_mcontext.__gregs[LARCH_REG_S0] = (uintptr_t) 0;
46 ucp->uc_mcontext.__gregs[LARCH_REG_S1] = (uintptr_t) func;
47 ucp->uc_mcontext.__gregs[LARCH_REG_S2] = (uintptr_t) ucp->uc_link;
48 ucp->uc_mcontext.__gregs[LARCH_REG_SP] = (uintptr_t) sp;
49 ucp->uc_mcontext.__pc = (uintptr_t) &__start_context;
50
51 /* Put args in a0-a7, then put any remaining args on the stack. */
52 ucp->uc_mcontext.__gregs[LARCH_REG_A0 + 0] = (uintptr_t) a0;
53 ucp->uc_mcontext.__gregs[LARCH_REG_A0 + 1] = (uintptr_t) a1;
54 ucp->uc_mcontext.__gregs[LARCH_REG_A0 + 2] = (uintptr_t) a2;
55 ucp->uc_mcontext.__gregs[LARCH_REG_A0 + 3] = (uintptr_t) a3;
56 ucp->uc_mcontext.__gregs[LARCH_REG_A0 + 4] = (uintptr_t) a4;
57
58 if (__glibc_unlikely (argc > 5))
59 {
60 va_list vl;
61 va_start (vl, a4);
62
63 long int reg_args = argc < LARCH_REG_NARGS ? argc : LARCH_REG_NARGS;
64 for (long int i = 5; i < reg_args; i++)
65 ucp->uc_mcontext.__gregs[LARCH_REG_A0 + i] = va_arg (vl, unsigned long int);
66
67 long int stack_args = argc - reg_args;
68 if (stack_args > 0)
69 {
70 sp = (unsigned long int *)
71 (((uintptr_t) sp - stack_args * sizeof (long int)) & ALMASK);
72 ucp->uc_mcontext.__gregs[LARCH_REG_SP] = (uintptr_t) sp;
73 for (long int i = 0; i < stack_args; i++)
74 sp[i] = va_arg (vl, unsigned long int);
75 }
76
77 va_end (vl);
78 }
79}
80
81weak_alias (__makecontext, makecontext)
82

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