1/* Create new context. RISC-V version.
2 Copyright (C) 2001-2022 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 <sysdep.h>
20#include <sys/asm.h>
21#include <sys/ucontext.h>
22#include <stdarg.h>
23#include <assert.h>
24
25void
26__makecontext (ucontext_t *ucp, void (*func) (void), int argc,
27 long int a0, long int a1, long int a2, long int a3, long int a4,
28 ...)
29{
30 extern void __start_context (void) attribute_hidden;
31 long int i, sp;
32
33 _Static_assert (REG_NARGS == 8, "__makecontext assumes 8 argument registers");
34
35 /* Set up the stack. */
36 sp = ((long int) ucp->uc_stack.ss_sp + ucp->uc_stack.ss_size) & ALMASK;
37
38 /* Set up the register context.
39 ra = s0 = 0, terminating the stack for backtracing purposes.
40 s1 = the function we must call.
41 s2 = the subsequent context to run. */
42 ucp->uc_mcontext.__gregs[REG_RA] = 0;
43 ucp->uc_mcontext.__gregs[REG_S0] = 0;
44 ucp->uc_mcontext.__gregs[REG_S1] = (long int) func;
45 ucp->uc_mcontext.__gregs[REG_S2] = (long int) ucp->uc_link;
46 ucp->uc_mcontext.__gregs[REG_SP] = sp;
47 ucp->uc_mcontext.__gregs[REG_PC] = (long int) &__start_context;
48
49 /* Put args in a0-a7, then put any remaining args on the stack. */
50 ucp->uc_mcontext.__gregs[REG_A0 + 0] = a0;
51 ucp->uc_mcontext.__gregs[REG_A0 + 1] = a1;
52 ucp->uc_mcontext.__gregs[REG_A0 + 2] = a2;
53 ucp->uc_mcontext.__gregs[REG_A0 + 3] = a3;
54 ucp->uc_mcontext.__gregs[REG_A0 + 4] = a4;
55
56 if (__glibc_unlikely (argc > 5))
57 {
58 va_list vl;
59 va_start (vl, a4);
60
61 long reg_args = argc < REG_NARGS ? argc : REG_NARGS;
62 for (i = 5; i < reg_args; i++)
63 ucp->uc_mcontext.__gregs[REG_A0 + i] = va_arg (vl, long);
64
65 long int stack_args = argc - reg_args;
66 if (stack_args > 0)
67 {
68 sp = (sp - stack_args * sizeof (long int)) & ALMASK;
69 ucp->uc_mcontext.__gregs[REG_SP] = sp;
70 for (i = 0; i < stack_args; i++)
71 ((long int *) sp)[i] = va_arg (vl, long int);
72 }
73
74 va_end (vl);
75 }
76}
77
78weak_alias (__makecontext, makecontext)
79

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