189 lines
5.1 KiB
Groff
189 lines
5.1 KiB
Groff
.\" $NetBSD: malloc.9,v 1.3 1996/11/11 00:05:11 lukem Exp $
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.\"
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.\" Copyright (c) 1996 The NetBSD Foundation, Inc.
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.\" All rights reserved.
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.\"
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.\" This code is derived from software contributed to The NetBSD Foundation
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.\" by Paul Kranenburg.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the NetBSD
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.\" Foundation, Inc. and its contributors.
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.\" 4. Neither the name of The NetBSD Foundation nor the names of its
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.\" contributors may be used to endorse or promote products derived
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.\" from this software without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE
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.\" LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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.\" POSSIBILITY OF SUCH DAMAGE.
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.\"
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.Dd June 16, 1996
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.Dt MALLOC 9
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.Os FreeBSD
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.Sh NAME
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.Nm malloc ,
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.Nm MALLOC ,
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.Nm free ,
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.Nm FREE
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.Nd kernel memory management routines
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.Sh SYNOPSIS
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.Fd #include <sys/types.h>
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.Fd #include <sys/malloc.h>
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.Ft void *
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.Fn malloc "unsigned long size" "struct malloc_type *type" "int flags"
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.Fn MALLOC "space" "cast" "unsigned long size" "struct malloc_type *type" "int flags"
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.Ft void
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.Fn free "void *addr" "struct malloc_type *type"
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.Fn FREE "void *addr" "struct malloc_type *type"
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.Sh DESCRIPTION
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The
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.Fn malloc
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function allocates uninitialized memory in kernel address space for an
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object whose size is specified by
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.Fa size .
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.Fn free
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releases memory at address
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.Fa addr
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that was previously allocated by
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.Fn malloc
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for re-use.
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The
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.Fn MALLOC
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macro variant is functionally equivalent to
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.Bd -literal -offset indent
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(space) = (cast)malloc((u_long)(size), type, flags)
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.Ed
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.Pp
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and the
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.Fn FREE
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macro variant is equivalent to
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.Bd -literal -offset indent
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free((addr), type)
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.Ed
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.Pp
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Unlike its standard C library counterpart
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.Pq Xr malloc 3 ,
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the kernel version takes two more arguments. The
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.Fa flags
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argument further qualifies
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.Fn malloc No Ns 's
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operational characteristics as follows:
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.Bl -tag -offset indent
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.It Dv M_NOWAIT
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Causes
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.Fn malloc
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to return
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.Dv NULL
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if the request cannot be immediately fulfilled due to resource shortage.
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Otherwise,
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.Fn malloc
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may call sleep to wait for resources to be released by other processes.
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If this flag is not set,
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.Fn malloc
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will never return
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.Dv NULL .
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Note that
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.Dv M_WAITOK
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is conveniently defined to be 0, and hence maybe or'ed into the
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.Fa flags
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argument to indicate that it's Ok to wait for resources.
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.El
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.Pp
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Currently, only one flag is defined.
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.Pp
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The
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.Fa type
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argument is used to perform statistics on memory usage, and for
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basic sanity checks.
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The statistics can be examined by
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.Sq vmstat -m .
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.Pp
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A
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.Fa type
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is defined using the
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.Va malloc_type_t
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typedef like this:
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.Bd -literal -offset indent
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/* sys/something/foo_extern.h */
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extern malloc_type_t M_FOOBUF;
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/* sys/something/foo_main.c */
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malloc_type_t M_FOOBUF = {
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"Foo Buffers",
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"Buffers for foo data in transit to the InfImpDrive"
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};
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/* sys/something/foo_subr.c */
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...
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MALLOC(buf, sizeof *buf, struct foo_buf *, M_FOOBUF, M_NOWAIT);
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.Be
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.Sh RETURN VALUES
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.Fn malloc
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returns a kernel virtual address that is suitably aligned for storage of
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any type of object.
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.Sh SEE ALSO
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.Xr vmstat 8
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.Sh DIAGNOSTICS
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A kernel compiled with the
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.Dv DIAGNOSTIC
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configuration option attempts to detect detect memory corruption caused by
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such things as writing outside the allocated area and imbalanced calls to the
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.Fn malloc
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and
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.Fn free
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functions. Failing consistency checks will cause a panic or a system console
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message:
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.Bl -bullet -offset indent -compact
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.Pp
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.It
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panic:
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.Dq malloc: bogus type
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.It
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panic:
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.Dq malloc: allocation too large
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.It
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panic:
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.Dq malloc: wrong bucket
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.It
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panic:
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.Dq malloc: lost data
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.It
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panic:
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.Dq free: address 0x%x out of range
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.It
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panic:
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.Dq free: type %d out of range
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.It
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panic:
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.Dq free: unaligned addr Aq description of object
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.It
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panic:
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.Dq free: item modified
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.It
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panic:
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.Dq free: multiple free[s]
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.It
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.Dq Data modified on freelist: Aq description of object
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.El
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