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- /* Create new context.
- Copyright (C) 2015-2019 Free Software Foundation, Inc.
- This file is part of the GNU C Library.
- The GNU C Library is free software; you can redistribute it and/or
- modify it under the terms of the GNU Lesser General Public
- License as published by the Free Software Foundation; either
- version 2.1 of the License, or (at your option) any later version.
- The GNU C Library is distributed in the hope that it will be useful,
- but WITHOUT ANY WARRANTY; without even the implied warranty of
- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- Lesser General Public License for more details.
- You should have received a copy of the GNU Lesser General Public
- License along with the GNU C Library; if not, see
- <http://www.gnu.org/licenses/>. */
- #include <sysdep.h>
- #include <stdarg.h>
- #include <stdint.h>
- #include <ucontext.h>
- /* makecontext sets up a stack and the registers for the
- user context. The stack looks like this:
- +-----------------------+
- | padding as required |
- +-----------------------+
- sp -> | parameters 5 to n |
- +-----------------------+
- The registers are set up like this:
- r4--r7 : parameter 1 to 4
- r16 : uc_link
- sp : stack pointer.
- */
- void
- __makecontext (ucontext_t *ucp, void (*func) (void), int argc, ...)
- {
- extern void __startcontext (void);
- unsigned long *sp;
- va_list ap;
- int i;
- sp = (unsigned long *)
- ((uintptr_t) ucp->uc_stack.ss_sp + ucp->uc_stack.ss_size);
- /* Allocate stack arguments. */
- sp -= argc < 4 ? 0 : argc - 4;
- /* Keep the stack aligned. */
- sp = (unsigned long*) (((uintptr_t) sp) & -4L);
- /* Init version field. */
- ucp->uc_mcontext.version = 2;
- /* Keep uc_link in r16. */
- ucp->uc_mcontext.regs[15] = (uintptr_t) ucp->uc_link;
- /* Return address points to __startcontext(). */
- ucp->uc_mcontext.regs[23] = (uintptr_t) &__startcontext;
- /* Frame pointer is null. */
- ucp->uc_mcontext.regs[24] = (uintptr_t) 0;
- /* Restart in user-space starting at 'func'. */
- ucp->uc_mcontext.regs[27] = (uintptr_t) func;
- /* Set stack pointer. */
- ucp->uc_mcontext.regs[28] = (uintptr_t) sp;
- va_start (ap, argc);
- for (i = 0; i < argc; ++i)
- if (i < 4)
- ucp->uc_mcontext.regs[i + 3] = va_arg (ap, unsigned long);
- else
- sp[i - 4] = va_arg (ap, unsigned long);
- va_end (ap);
- }
- weak_alias (__makecontext, makecontext)
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