1 /* $NetBSD: makecontext.c,v 1.3 2008/04/28 20:22:57 martin Exp $ */ 2 3 /*- 4 * Copyright (c) 2003 The NetBSD Foundation, Inc. 5 * All rights reserved. 6 * 7 * This code is derived from software contributed to The NetBSD Foundation 8 * by Matt Thomas. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 20 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 21 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 22 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 23 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 24 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 25 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 26 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 27 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 28 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 29 * POSSIBILITY OF SUCH DAMAGE. 30 */ 31 32 #include <sys/cdefs.h> 33 #if defined(LIBC_SCCS) && !defined(lint) 34 __RCSID("$NetBSD: makecontext.c,v 1.3 2008/04/28 20:22:57 martin Exp $"); 35 #endif 36 37 #include <stddef.h> 38 #include <inttypes.h> 39 #include <ucontext.h> 40 #include "extern.h" 41 42 #include <stdarg.h> 43 44 void 45 makecontext(ucontext_t *ucp, void (*func)(void), int argc, ...) 46 { 47 __greg_t *gr = ucp->uc_mcontext.__gregs; 48 va_list ap; 49 int *sp; 50 int i; 51 52 /* Compute and align stack pointer. */ 53 sp = (int *) 54 (((uintptr_t)ucp->uc_stack.ss_sp + ucp->uc_stack.ss_size) & ~0x3); 55 56 /* 57 * Allocate necessary stack space for arguments including arg count 58 * and call frame 59 */ 60 sp -= argc + 1 + 5; 61 62 va_start(ap, argc); 63 sp[5] = argc; 64 for (i = 1; argc > 0; argc--, i++) 65 sp[5 + i] = va_arg(ap, int); 66 va_end(ap); 67 68 sp[0] = 0; /* condition handler is null */ 69 sp[1] = 0x20000000; /* make this a CALLS frame */ 70 sp[2] = 0; /* saved argument pointer */ 71 sp[3] = 0; /* saved frame pointer */ 72 sp[4] = (int)_resumecontext+2; /* return via trampoline code */ 73 74 gr[_REG_AP] = (__greg_t)(sp + 5); 75 gr[_REG_SP] = (__greg_t)sp; 76 gr[_REG_FP] = (__greg_t)sp; 77 gr[_REG_PC] = (__greg_t)func+2; 78 79 } 80