/* * CDDL HEADER START * * The contents of this file are subject to the terms of the * Common Development and Distribution License (the "License"). * You may not use this file except in compliance with the License. * * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE * or http://www.opensolaris.org/os/licensing. * See the License for the specific language governing permissions * and limitations under the License. * * When distributing Covered Code, include this CDDL HEADER in each * file and include the License file at usr/src/OPENSOLARIS.LICENSE. * If applicable, add the following below this CDDL HEADER, with the * fields enclosed by brackets "[]" replaced with your own identifying * information: Portions Copyright [yyyy] [name of copyright owner] * * CDDL HEADER END */ /* * Copyright 2008 Sun Microsystems, Inc. All rights reserved. * Use is subject to license terms. */ /* Copyright (c) 1988 AT&T */ /* All Rights Reserved */ #pragma weak _makecontext = makecontext #include "lint.h" #include #include #include /* * The ucontext_t that the user passes in must have been primed with a * call to getcontext(2), have the uc_stack member set to reflect the * stack which this context will use, and have the uc_link member set * to the context which should be resumed when this context returns. * When makecontext() returns, the ucontext_t will be set to run the * given function with the given parameters on the stack specified by * uc_stack, and which will return to the ucontext_t specified by uc_link. */ /* * The original i386 ABI said that the stack pointer need be only 4-byte * aligned before a function call (STACK_ALIGN == 4). The ABI supplement * version 1.0 changed the required alignment to 16-byte for the benefit of * floating point code compiled using sse2. The compiler assumes this * alignment and maintains it for calls it generates. If the stack is * initially properly aligned, it will continue to be so aligned. If it is * not initially so aligned, it will never become so aligned. * * One slightly confusing detail to keep in mind is that the 16-byte * alignment (%esp & 0xf == 0) is true just *before* the call instruction. * The call instruction will then push a return value, decrementing %esp by * 4. Therefore, if one dumps %esp at the at the very first instruction in * a function, it will end with a 0xc. The compiler expects this and * compensates for it properly. * * Note: If you change this value, you need to change it in the following * files as well: * * - lib/libc/i386/threads/machdep.c * - lib/common/i386/crti.s * - lib/common/i386/crt1.s */ #undef STACK_ALIGN #define STACK_ALIGN 16 static void resumecontext(void); void makecontext(ucontext_t *ucp, void (*func)(), int argc, ...) { long *sp; long *tsp; va_list ap; size_t size; ucp->uc_mcontext.gregs[EIP] = (greg_t)func; size = sizeof (long) * (argc + 1); tsp = (long *)(((uintptr_t)ucp->uc_stack.ss_sp + ucp->uc_stack.ss_size - size) & ~(STACK_ALIGN - 1)); /* * Since we're emulating the call instruction, we must push the * return address (which involves adjusting the stack pointer to * have the proper 4-byte bias). */ sp = tsp - 1; *sp = (long)resumecontext; /* return address */ ucp->uc_mcontext.gregs[UESP] = (greg_t)sp; /* * "push" all the arguments */ va_start(ap, argc); while (argc-- > 0) *tsp++ = va_arg(ap, long); va_end(ap); } static void resumecontext(void) { ucontext_t uc; (void) getcontext(&uc); (void) setcontext(uc.uc_link); }