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/* Copyright (C) 2001-2022 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
<https://www.gnu.org/licenses/>. */
#include <libintl.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <ucontext.h>
/* This implementation can handle any ARGC value but only
normal integer type parameters. Parameters of type float,
double, complex and structure with sizes 0, 2, 4 or 8
won't work.
makecontext sets up a stack and the registers for the
user context. The stack looks like this:
size offset
%r15 -> +-----------------------+
8 | back chain (zero) | 0
8 | reserved | 8
144 | save area for (*func) | 16
+-----------------------+
n | overflow parameters | 160
+-----------------------+
The registers are set up like this:
%r2-%r6: parameters 1 to 5
%r7 : (*func) pointer
%r8 : uc_link from ucontext structure
%r9 : address of setcontext
%r14 : return address to uc_link trampoline
%r15 : stack pointer.
The trampoline looks like this:
basr %r14,%r7
lgr %r2,%r8
br %r9. */
void
__makecontext (ucontext_t *ucp, void (*func) (void), int argc, ...)
{
extern void __makecontext_ret (void);
unsigned long int *sp;
va_list ap;
sp = (unsigned long int *) (((unsigned long int) ucp->uc_stack.ss_sp
+ ucp->uc_stack.ss_size) & -8L);
/* Set the return address to trampoline. */
ucp->uc_mcontext.gregs[14] = (long int) __makecontext_ret;
/* Set register parameters. */
va_start (ap, argc);
for (int i = 0; i < argc && i < 5; ++i)
ucp->uc_mcontext.gregs[2 + i] = va_arg (ap, long int);
/* The remaining arguments go to the overflow area. */
if (argc > 5)
{
sp -= argc - 5;
for (int i = 5; i < argc; ++i)
sp[i - 5] = va_arg (ap, long int);
}
va_end (ap);
/* Make room for the save area and set the backchain. */
sp -= 20;
*sp = 0;
/* Pass (*func) to __makecontext_ret in %r7. */
ucp->uc_mcontext.gregs[7] = (long int) func;
/* Pass ucp->uc_link to __makecontext_ret in %r8. */
ucp->uc_mcontext.gregs[8] = (long int) ucp->uc_link;
/* Pass address of setcontext in %r9. */
ucp->uc_mcontext.gregs[9] = (long int) &setcontext;
/* Set stack pointer. */
ucp->uc_mcontext.gregs[15] = (long int) sp;
}
weak_alias (__makecontext, makecontext)
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