1 /* $NetBSD: makecontext.c,v 1.2 2004/02/28 15:57:21 drochner Exp $ */ 2 3 /*- 4 * Copyright (c) 1999 The NetBSD Foundation, Inc. 5 * All rights reserved. 6 * 7 * This code is derived from software contributed to The NetBSD Foundation 8 * by Klaus Klein. 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 * 3. All advertising materials mentioning features or use of this software 19 * must display the following acknowledgement: 20 * This product includes software developed by the NetBSD 21 * Foundation, Inc. and its contributors. 22 * 4. Neither the name of The NetBSD Foundation nor the names of its 23 * contributors may be used to endorse or promote products derived 24 * from this software without specific prior written permission. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 27 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 28 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 29 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 30 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 31 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 32 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 33 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 34 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 35 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 36 * POSSIBILITY OF SUCH DAMAGE. 37 * 38 * Modified from the i386 version for x86_64 by fvdl@wasabisystems.com. 39 * 40 */ 41 42 #include <sys/cdefs.h> 43 #if defined(LIBC_SCCS) && !defined(lint) 44 __RCSID("$NetBSD: makecontext.c,v 1.2 2004/02/28 15:57:21 drochner Exp $"); 45 #endif 46 47 #include <inttypes.h> 48 #include <stddef.h> 49 #include <ucontext.h> 50 #include "extern.h" 51 52 #include <stdarg.h> 53 54 void 55 makecontext(ucontext_t *ucp, void (*func)(void), int argc, ...) 56 { 57 __greg_t *gr = ucp->uc_mcontext.__gregs; 58 uintptr_t *sp; 59 va_list ap; 60 int stackargs, i; 61 62 stackargs = argc - 6; 63 64 /* LINTED __greg_t is safe */ 65 gr[_REG_RIP] = (__greg_t)func; 66 67 /* LINTED uintptr_t is safe */ 68 sp = (uintptr_t *) 69 ((uintptr_t)ucp->uc_stack.ss_sp + ucp->uc_stack.ss_size); 70 71 /* LINTED uintptr_t is safe */ 72 sp = (uintptr_t *)(((uintptr_t)sp & ~15)); 73 sp--; 74 if (stackargs > 0) 75 sp -= stackargs; 76 /* LINTED __greg_t is safe */ 77 gr[_REG_URSP] = (__greg_t)sp; 78 gr[_REG_RBP] = (__greg_t)0; /* Wipe out frame pointer. */ 79 80 /* Put return address on top of stack. */ 81 /* LINTED uintptr_t is safe */ 82 *sp++ = (uintptr_t)_resumecontext; 83 84 /* 85 * Construct argument list. 86 * The registers used to pass the first 6 arguments 87 * (rdi, rsi, rdx, rcx, r8, r9) are the first 6 in gregs, 88 * in that order, so those arguments can just be copied to 89 * the gregs array. 90 */ 91 va_start(ap, argc); 92 for (i = 0; i < 6 && argc > 0; i++) { 93 argc--; 94 /* LINTED __greg_t is safe */ 95 gr[i] = va_arg(ap, __greg_t); 96 } 97 98 while (stackargs-- > 0) { 99 /* LINTED uintptr_t is safe */ 100 *sp++ = va_arg(ap, uintptr_t); 101 } 102 103 va_end(ap); 104 } 105