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/* Create new context.
Copyright (C) 2002, 2004 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Andreas Jaeger <aj@suse.de>, 2002.
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, write to the Free
Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
02111-1307 USA. */
#include <sysdep.h>
#include <stdarg.h>
#include <ucontext.h>
#include "ucontext_i.h"
/* This implementation can handle any ARGC value but only
normal integer parameters.
makecontext sets up a stack and the registers for the
user context. The stack looks like this:
+-----------------------+
| next context |
+-----------------------+
| parameter 7-n |
+-----------------------+
| trampoline address |
%rsp -> +-----------------------+
The registers are set up like this:
%rdi,%rsi,%rdx,%rcx,%r8,%r9: parameter 1 to 6
%rbx : address of next context
%rsp : stack pointer.
*/
/* XXX: This implementation currently only handles integer arguments.
To handle long int and pointer arguments the va_arg arguments needs
to be changed to long and also the stdlib/tst-setcontext.c file needs
to be changed to pass long arguments to makecontext. */
void
__makecontext (ucontext_t *ucp, void (*func) (void), int argc, ...)
{
extern void __start_context (void);
unsigned long *sp, idx_uc_link;
va_list ap;
int i;
/* Generate room on stack for parameter if needed and uc_link. */
sp = (long *) ((long) ucp->uc_stack.ss_sp + ucp->uc_stack.ss_size);
sp -= (argc > 6 ? argc - 6 : 0) + 1;
/* Align stack and make space for trampoline address. */
sp = (long *) ((((long) sp) & -16L) - 8);
idx_uc_link = (argc > 6 ? argc - 6 : 0) + 1;
/* Setup context ucp. */
/* Address to jump to. */
ucp->uc_mcontext.gregs[REG_RIP] = (long) func;
/* Setup rbx.*/
ucp->uc_mcontext.gregs[REG_RBX] = (long) &sp[idx_uc_link];
ucp->uc_mcontext.gregs[REG_RSP] = (long) sp;
/* Setup stack. */
sp[0] = (long) &__start_context;
sp[idx_uc_link] = (long) ucp->uc_link;
va_start (ap, argc);
/* Handle arguments. */
for (i = 0; i < argc; ++i)
switch (i)
{
case 0:
ucp->uc_mcontext.gregs [REG_RDI] = va_arg (ap, int);
break;
case 1:
ucp->uc_mcontext.gregs [REG_RSI] = va_arg (ap, int);
break;
case 2:
ucp->uc_mcontext.gregs [REG_RDX] = va_arg (ap, int);
break;
case 3:
ucp->uc_mcontext.gregs [REG_RCX] = va_arg (ap, int);
break;
case 4:
ucp->uc_mcontext.gregs [REG_R8] = va_arg (ap, int);
break;
case 5:
ucp->uc_mcontext.gregs [REG_R9] = va_arg (ap, int);
break;
default:
/* Put value on stack. */
sp[(i - 5)] = va_arg (ap, int);
break;
}
va_end (ap);
}
weak_alias(__makecontext, makecontext)
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