108 lines
3.5 KiB
C
108 lines
3.5 KiB
C
/*
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* Copyright (c) 2003 Marcel Moolenaar
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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#include <sys/types.h>
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#include <sys/ucontext.h>
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#include <stdarg.h>
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#include <stdlib.h>
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typedef void (*func_t)(uint64_t, uint64_t, uint64_t, uint64_t, uint64_t,
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uint64_t);
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/* Prototypes */
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static void makectx_wrapper(ucontext_t *ucp, func_t func, uint64_t *args);
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__weak_reference(__makecontext, makecontext);
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void
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__makecontext(ucontext_t *ucp, void (*start)(void), int argc, ...)
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{
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uint64_t *args;
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uint64_t *sp;
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va_list ap;
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int i;
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/* A valid context is required. */
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if ((ucp == NULL) || (ucp->uc_mcontext.mc_len != sizeof(mcontext_t)))
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return;
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else if ((argc < 0) || (argc > 6) || (ucp->uc_stack.ss_sp == NULL) ||
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(ucp->uc_stack.ss_size < MINSIGSTKSZ)) {
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/*
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* This should really return -1 with errno set to ENOMEM
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* or something, but the spec says that makecontext is
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* a void function. At least make sure that the context
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* isn't valid so it can't be used without an error.
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*/
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ucp->uc_mcontext.mc_len = 0;
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return;
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}
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/* Align the stack to 16 bytes. */
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sp = (uint64_t *)(ucp->uc_stack.ss_sp + ucp->uc_stack.ss_size);
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sp = (uint64_t *)((uint64_t)sp & ~15UL);
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/* Allocate space for a maximum of 6 arguments on the stack. */
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args = sp - 6;
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/*
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* Account for arguments on stack and do the funky C entry alignment.
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* This means that we need an 8-byte-odd alignment since the ABI expects
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* the return address to be pushed, thus breaking the 16 byte alignment.
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*/
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sp -= 7;
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/* Add the arguments: */
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va_start(ap, argc);
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for (i = 0; i < argc; i++)
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args[i] = va_arg(ap, uint64_t);
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va_end(ap);
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for (i = argc; i < 6; i++)
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args[i] = 0;
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ucp->uc_mcontext.mc_rdi = (register_t)ucp;
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ucp->uc_mcontext.mc_rsi = (register_t)start;
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ucp->uc_mcontext.mc_rdx = (register_t)args;
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ucp->uc_mcontext.mc_rbp = 0;
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ucp->uc_mcontext.mc_rbx = (register_t)sp;
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ucp->uc_mcontext.mc_rsp = (register_t)sp;
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ucp->uc_mcontext.mc_rip = (register_t)makectx_wrapper;
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}
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static void
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makectx_wrapper(ucontext_t *ucp, func_t func, uint64_t *args)
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{
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(*func)(args[0], args[1], args[2], args[3], args[4], args[5]);
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if (ucp->uc_link == NULL)
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exit(0);
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setcontext((const ucontext_t *)ucp->uc_link);
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/* should never get here */
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abort();
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/* NOTREACHED */
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}
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