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Add M_CANFAIL malloc(9) flag. This flag changes behaviour in M_WAITOK

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case when the requested memory size can't ever be granted - instead
of panic, malloc(9) would return failure (NULL).
Note kernel code should do proper bound checking, rather than
depend on M_CANFAIL. This flag is only supposed to be used in very
special cases, where common bound checking is not appropriate.

Discussed on tech-kern@, name ``M_CANFAIL'' suggested by Chuck Cranor.
This commit is contained in:
jdolecek 2001-12-04 20:13:19 +00:00
parent ceb358f80c
commit c152d680d8
2 changed files with 8 additions and 7 deletions
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6
sys/kern/kern_malloc.c
View File

@ -1,4 +1,4 @@
/* $NetBSD: kern_malloc.c,v 1.67 2001/11/30 01:54:21 enami Exp $ */
/* $NetBSD: kern_malloc.c,v 1.68 2001/12/04 20:13:19 jdolecek Exp $ */
/*
* Copyright (c) 1996 Christopher G. Demetriou. All rights reserved.
@ -37,7 +37,7 @@
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: kern_malloc.c,v 1.67 2001/11/30 01:54:21 enami Exp $");
__KERNEL_RCSID(0, "$NetBSD: kern_malloc.c,v 1.68 2001/12/04 20:13:19 jdolecek Exp $");
#include "opt_lockdebug.h"
@ -279,7 +279,7 @@ malloc(size, type, flags)
* are completely free and which are in buckets
* with too many free elements.)
*/
if ((flags & M_NOWAIT) == 0)
if ((flags & (M_NOWAIT|M_CANFAIL)) == 0)
panic("malloc: out of space in kmem_map");
splx(s);
return ((void *) NULL);

9
sys/sys/malloc.h
View File

@ -1,4 +1,4 @@
/* $NetBSD: malloc.h,v 1.68 2001/11/17 03:50:27 lukem Exp $ */
/* $NetBSD: malloc.h,v 1.69 2001/12/04 20:13:20 jdolecek Exp $ */
/*
* Copyright (c) 1987, 1993
@ -48,10 +48,11 @@
/*
* flags to malloc
*/
#define M_WAITOK 0x0000
#define M_NOWAIT 0x0001
#define M_WAITOK 0x0000 /* can wait for resources */
#define M_NOWAIT 0x0001 /* do not wait for resources */
#define M_ZERO 0x0002 /* zero the allocation */
#define M_CANFAIL 0x0004 /* can fail if requested memory can't ever
* be allocated */
/*
* Types of memory to be allocated
*/