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