/* * Copyright (c) 2007 Apple Inc. All rights reserved. * * @APPLE_LICENSE_HEADER_START@ * * This file contains Original Code and/or Modifications of Original Code * as defined in and that are subject to the Apple Public Source License * Version 2.0 (the 'License'). You may not use this file except in * compliance with the License. Please obtain a copy of the License at * http://www.opensource.apple.com/apsl/ and read it before using this * file. * * The Original Code and all software distributed under the License are * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES, * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT. * Please see the License for the specific language governing rights and * limitations under the License. * * @APPLE_LICENSE_HEADER_END@ */ /* * Copyright (c) 2001 Daniel M. Eischen <deischen@freebsd.org> * 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. Neither the name of the author nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``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 OR CONTRIBUTORS 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. */ #if defined(__i386__) #include <sys/cdefs.h> #include <sys/param.h> #include <sys/signal.h> #include <sys/ucontext.h> #include <errno.h> #include <stdarg.h> #include <stdlib.h> #include <ucontext.h> #include <unistd.h> /* Prototypes */ extern void _ctx_start(ucontext_t *, int argc, ...); void _ctx_done (ucontext_t *ucp) { if (ucp->uc_link == NULL) exit(0); else { /* * Since this context has finished, don't allow it * to be restarted without being reinitialized (via * setcontext or swapcontext). */ ucp->uc_mcsize = 0; /* Set context to next one in link */ /* XXX - what to do for error, abort? */ setcontext((const ucontext_t *)ucp->uc_link); abort(); /* should never get here */ } } void makecontext(ucontext_t *ucp, void (*start)(void), int argc, ...) { va_list ap; char *stack_top; intptr_t *argp; int i; if (ucp == NULL) return; else if ((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_mcsize = 0; } /* XXX - Do we want to sanity check argc? */ else if ((argc < 0) || (argc > NCARGS)) { ucp->uc_mcsize = 0; } /* Make sure the context is valid. */ else { /* * Arrange the stack as follows: * * _ctx_start() - context start wrapper * start() - user start routine * arg1 - first argument, aligned(16) * ... * argn * ucp - this context, %ebp points here * * When the context is started, control will return to * the context start wrapper which will pop the user * start routine from the top of the stack. After that, * the top of the stack will be setup with all arguments * necessary for calling the start routine. When the * start routine returns, the context wrapper then sets * the stack pointer to %ebp which was setup to point to * the base of the stack (and where ucp is stored). It * will then call _ctx_done() to swap in the next context * (uc_link != 0) or exit the program (uc_link == 0). */ mcontext_t mc; stack_top = (char *)(ucp->uc_stack.ss_sp + ucp->uc_stack.ss_size - sizeof(intptr_t)); /* * Adjust top of stack to allow for 3 pointers (return * address, _ctx_start, and ucp) and argc arguments. * We allow the arguments to be pointers also. The first * argument to the user function must be properly aligned. */ stack_top = stack_top - (sizeof(intptr_t) * (1 + argc)); stack_top = (char *)((unsigned)stack_top & ~15); stack_top = stack_top - (2 * sizeof(intptr_t)); argp = (intptr_t *)stack_top; /* * Setup the top of the stack with the user start routine * followed by all of its aguments and the pointer to the * ucontext. We need to leave a spare spot at the top of * the stack because setcontext will move eip to the top * of the stack before returning. */ *argp = (intptr_t)_ctx_start; /* overwritten with same value */ argp++; *argp = (intptr_t)start; argp++; /* Add all the arguments: */ va_start(ap, argc); for (i = 0; i < argc; i++) { *argp = va_arg(ap, intptr_t); argp++; } va_end(ap); /* The ucontext is placed at the bottom of the stack. */ *argp = (intptr_t)ucp; /* * Set the machine context to point to the top of the * stack and the program counter to the context start * wrapper. Note that setcontext() pushes the return * address onto the top of the stack, so allow for this * by adjusting the stack downward 1 slot. Also set * %esi to point to the base of the stack where ucp * is stored. */ mc = ucp->uc_mcontext; mc->__ss.__esi = (int)argp; mc->__ss.__ebp = 0; mc->__ss.__esp = (int)stack_top + sizeof(caddr_t); mc->__ss.__eip = (int)_ctx_start; } } #endif /* __i386__ */