Annotation of sys/arch/i386/stand/libsa/alloca.S, Revision 1.1.1.1
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 1.4 2003/06/02 23:27:47 millert 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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