Annotation of sys/arch/amd64/stand/libsa/alloca.S, Revision 1.1
1.1 ! nbrk 1: /*-
! 2: * Copyright (c) 1990 The Regents of the University of California.
! 3: * All rights reserved.
! 4: *
! 5: * This code is derived from software contributed to Berkeley by
! 6: * William Jolitz.
! 7: *
! 8: * Redistribution and use in source and binary forms, with or without
! 9: * modification, are permitted provided that the following conditions
! 10: * are met:
! 11: * 1. Redistributions of source code must retain the above copyright
! 12: * notice, this list of conditions and the following disclaimer.
! 13: * 2. Redistributions in binary form must reproduce the above copyright
! 14: * notice, this list of conditions and the following disclaimer in the
! 15: * documentation and/or other materials provided with the distribution.
! 16: * 3. Neither the name of the University nor the names of its contributors
! 17: * may be used to endorse or promote products derived from this software
! 18: * without specific prior written permission.
! 19: *
! 20: * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
! 21: * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
! 22: * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
! 23: * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
! 24: * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
! 25: * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
! 26: * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
! 27: * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
! 28: * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
! 29: * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
! 30: * SUCH DAMAGE.
! 31: */
! 32:
! 33: #include <machine/asm.h>
! 34:
! 35: #if defined(LIBC_SCCS)
! 36: .text
! 37: .asciz "$OpenBSD: alloca.S,v 1.1 2004/02/03 12:09:47 mickey Exp $"
! 38: #endif
! 39:
! 40: /* like alloc, but automatic free in return */
! 41:
! 42: ENTRY(alloca)
! 43: popl %edx /* pop return addr */
! 44: popl %eax /* pop amount to allocate */
! 45: movl %esp,%ecx
! 46: addl $3,%eax /* round up to next word */
! 47: andl $-4,%eax
! 48: subl %eax,%esp
! 49: movl %esp,%eax /* base of newly allocated space */
! 50: pushl 8(%ecx) /* copy possible saved registers */
! 51: pushl 4(%ecx)
! 52: pushl 0(%ecx)
! 53: pushl %eax /* dummy to pop at callsite */
! 54: jmp *%edx /* "return" */
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