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93 lines
3.1 KiB
C
93 lines
3.1 KiB
C
/* Create new context.
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Copyright (C) 2008-2015 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Contributed by David S. Miller <davem@davemloft.net>, 2008.
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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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/* Sets up the outgoing arguments and the program counter for a user
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context for the requested function call.
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Returning to the correct parent context is pretty simple on
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Sparc. We only need to link up the register windows correctly.
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Since global registers are clobbered by calls, we need not be
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concerned about those, and thus is all could be worked out without
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using a trampoline.
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Except that we must deal with the signal mask, thus a trampoline
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is unavoidable. 32-bit stackframe layout:
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+-----------------------------------------+
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| 7th and further parameters |
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+-----------------------------------------+
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| backup storage for initial 6 parameters |
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+-----------------------------------------+
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| struct return pointer |
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+-----------------------------------------+
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| 8 incoming registers |
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+-----------------------------------------+
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| 8 local registers |
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%sp --> +-----------------------------------------+
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*/
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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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unsigned long int *sp;
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va_list ap;
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int i;
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sp = (unsigned long int *) (ucp->uc_stack.ss_sp + ucp->uc_stack.ss_size);
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sp -= 16 + 7 + argc;
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sp = (unsigned long int *) (((uintptr_t) sp) & ~(8 - 1));
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for (i = 0; i < 8; i++)
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sp[i + 8] = ucp->uc_mcontext.gregs[REG_O0 + i];
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/* The struct return pointer is essentially unused, so we can
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place the link there. */
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sp[16] = (unsigned long int) ucp->uc_link;
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va_start (ap, argc);
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/* Fill in outgoing arguments, including those which will
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end up being passed on the stack. */
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for (i = 0; i < argc; i++)
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{
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unsigned long int arg = va_arg (ap, unsigned long int);
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if (i < 6)
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ucp->uc_mcontext.gregs[REG_O0 + i] = arg;
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else
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sp[i + 23 - 6] = arg;
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}
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va_end (ap);
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ucp->uc_mcontext.gregs[REG_O6] = (unsigned long int) sp;
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ucp->uc_mcontext.gregs[REG_O7] = ((unsigned long int) __start_context) - 8;
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ucp->uc_mcontext.gregs[REG_PC] = (unsigned long int) func;
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ucp->uc_mcontext.gregs[REG_nPC] = ucp->uc_mcontext.gregs[REG_PC] + 4;
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}
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weak_alias (__makecontext, makecontext)
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