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122 lines
3.8 KiB
C
122 lines
3.8 KiB
C
/* Create new context.
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Copyright (C) 2002-2017 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Contributed by Andreas Jaeger <aj@suse.de>, 2002.
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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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<http://www.gnu.org/licenses/>. */
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#include <sysdep.h>
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#include <stdarg.h>
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#include <stdint.h>
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#include <ucontext.h>
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#include "ucontext_i.h"
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/* This implementation can handle any ARGC value but only
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normal integer parameters.
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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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+-----------------------+
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| next context |
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+-----------------------+
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| parameter 7-n |
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+-----------------------+
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| trampoline address |
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%rsp -> +-----------------------+
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The registers are set up like this:
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%rdi,%rsi,%rdx,%rcx,%r8,%r9: parameter 1 to 6
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%rbx : address of next context
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%rsp : stack pointer.
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*/
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/* XXX: This implementation currently only handles integer arguments.
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To handle long int and pointer arguments the va_arg arguments needs
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to be changed to long and also the stdlib/tst-setcontext.c file needs
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to be changed to pass long arguments to makecontext. */
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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 __start_context (void);
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greg_t *sp;
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unsigned int idx_uc_link;
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va_list ap;
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int i;
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/* Generate room on stack for parameter if needed and uc_link. */
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sp = (greg_t *) ((uintptr_t) ucp->uc_stack.ss_sp
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+ ucp->uc_stack.ss_size);
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sp -= (argc > 6 ? argc - 6 : 0) + 1;
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/* Align stack and make space for trampoline address. */
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sp = (greg_t *) ((((uintptr_t) sp) & -16L) - 8);
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idx_uc_link = (argc > 6 ? argc - 6 : 0) + 1;
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/* Setup context ucp. */
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/* Address to jump to. */
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ucp->uc_mcontext.gregs[REG_RIP] = (uintptr_t) func;
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/* Setup rbx.*/
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ucp->uc_mcontext.gregs[REG_RBX] = (uintptr_t) &sp[idx_uc_link];
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ucp->uc_mcontext.gregs[REG_RSP] = (uintptr_t) sp;
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/* Setup stack. */
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sp[0] = (uintptr_t) &__start_context;
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sp[idx_uc_link] = (uintptr_t) ucp->uc_link;
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va_start (ap, argc);
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/* Handle arguments.
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The standard says the parameters must all be int values. This is
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an historic accident and would be done differently today. For
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x86-64 all integer values are passed as 64-bit values and
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therefore extending the API to copy 64-bit values instead of
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32-bit ints makes sense. It does not break existing
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functionality and it does not violate the standard which says
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that passing non-int values means undefined behavior. */
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for (i = 0; i < argc; ++i)
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switch (i)
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{
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case 0:
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ucp->uc_mcontext.gregs[REG_RDI] = va_arg (ap, greg_t);
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break;
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case 1:
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ucp->uc_mcontext.gregs[REG_RSI] = va_arg (ap, greg_t);
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break;
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case 2:
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ucp->uc_mcontext.gregs[REG_RDX] = va_arg (ap, greg_t);
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break;
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case 3:
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ucp->uc_mcontext.gregs[REG_RCX] = va_arg (ap, greg_t);
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break;
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case 4:
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ucp->uc_mcontext.gregs[REG_R8] = va_arg (ap, greg_t);
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break;
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case 5:
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ucp->uc_mcontext.gregs[REG_R9] = va_arg (ap, greg_t);
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break;
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default:
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/* Put value on stack. */
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sp[i - 5] = va_arg (ap, greg_t);
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break;
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}
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va_end (ap);
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}
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weak_alias (__makecontext, makecontext)
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