| /* Create new context. |
| Copyright (C) 2015-2018 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) |