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97 lines
3.1 KiB
C
97 lines
3.1 KiB
C
/* Copyright (C) 2001-2020 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Contributed by Martin Schwidefsky (schwidefsky@de.ibm.com).
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#include <libintl.h>
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#include <stdarg.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <ucontext.h>
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/* This implementation can handle any ARGC value but only
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normal integer type parameters. Parameters of type float,
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double, complex and structure with sizes 0, 2, 4 or 8
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won't work.
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makecontext sets up a stack and the registers for the
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user context. The stack looks like this:
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size offset
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%r15 -> +-----------------------+
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4 | back chain (zero) | 0
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4 | reserved | 4
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88 | save area for (*func) | 8
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+-----------------------+
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n | overflow parameters | 96
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+-----------------------+
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The registers are set up like this:
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%r2-%r6: parameters 1 to 5
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%r7 : (*func) pointer
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%r8 : uc_link from ucontext structure
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%r9 : address of setcontext
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%r14 : return address to uc_link trampoline
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%r15 : stack pointer.
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The trampoline looks like this:
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basr %r14,%r7
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lr %r2,%r8
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br %r9. */
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void
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__makecontext (ucontext_t *ucp, void (*func) (void), int argc, ...)
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{
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extern void __makecontext_ret (void);
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unsigned long int *sp;
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va_list ap;
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sp = (unsigned long int *) (((unsigned long int) ucp->uc_stack.ss_sp
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+ ucp->uc_stack.ss_size) & -8L);
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/* Set the return address to trampoline. */
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ucp->uc_mcontext.gregs[14] = (long int) __makecontext_ret;
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/* Set register parameters. */
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va_start (ap, argc);
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for (int i = 0; i < argc && i < 5; ++i)
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ucp->uc_mcontext.gregs[2 + i] = va_arg (ap, long int);
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/* The remaining arguments go to the overflow area. */
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if (argc > 5)
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{
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sp -= argc - 5;
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for (int i = 5; i < argc; ++i)
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sp[i - 5] = va_arg (ap, long int);
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}
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va_end (ap);
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/* Make room for the save area and set the backchain. */
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sp -= 24;
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*sp = 0;
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/* Pass (*func) to __makecontext_ret in %r7. */
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ucp->uc_mcontext.gregs[7] = (long int) func;
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/* Pass ucp->uc_link to __makecontext_ret in %r8. */
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ucp->uc_mcontext.gregs[8] = (long int) ucp->uc_link;
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/* Pass address of setcontext in %r9. */
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ucp->uc_mcontext.gregs[9] = (long int) &setcontext;
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/* Set stack pointer. */
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ucp->uc_mcontext.gregs[15] = (long int) sp;
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}
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weak_alias (__makecontext, makecontext)
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