1 /* $NetBSD: makecontext.c,v 1.3 2008/04/28 20:22:57 martin Exp $ */ 2 3 /*- 4 * Copyright (c) 2001 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 * 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 <inttypes.h> 38 #include <stddef.h> 39 #include <ucontext.h> 40 #include "extern.h" 41 42 #if __STDC__ 43 #include <stdarg.h> 44 #else 45 #include <varargs.h> 46 #endif 47 48 void 49 makecontext(ucontext_t *ucp, void (*func)(void), int argc, ...) 50 { 51 __greg_t *gr = ucp->uc_mcontext.__gregs; 52 __greg_t sp, *spp; 53 int i; 54 va_list ap; 55 56 sp = (__greg_t) ((uintptr_t)ucp->uc_stack.ss_sp 57 + ucp->uc_stack.ss_size); 58 sp -= 2 + (argc > 8 ? argc - 8: 0); /* Make room for call frame. */ 59 sp = (__greg_t) ((uintptr_t)sp & ~0xf); 60 61 /* 62 * Start executing at <func> -- when <func> completes, return to 63 * <_resumecontext>. 64 */ 65 gr[_REG_R1] = sp; 66 gr[_REG_LR] = (__greg_t)_resumecontext; 67 gr[_REG_PC] = (__greg_t)func; // XXX -- this is the descriptor address! 68 69 /* Wipe out stack frame backchain pointer. */ 70 spp = (__greg_t *)sp; 71 *spp = 0; 72 73 /* Construct argument list. */ 74 va_start(ap, argc); 75 /* Up to the first eight arguments are passed in r3-10. */ 76 for (i = 0; i < argc && i < 8; i++) 77 gr[_REG_R3 + i] = va_arg(ap, long); 78 /* Pass remaining arguments on the stack above the backchain/lr gap. */ 79 for (spp += 2; i < argc; i++) 80 *spp++ = va_arg(ap, long); 81 va_end(ap); 82 } 83