The Design and Implementation of the FreeBSD Operating System, Second Edition
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FreeBSD/Linux Kernel Cross Reference
sys/sys/param.h

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    1 /*-
    2  * Copyright (c) 1982, 1986, 1989, 1993
    3  *      The Regents of the University of California.  All rights reserved.
    4  * (c) UNIX System Laboratories, Inc.
    5  * All or some portions of this file are derived from material licensed
    6  * to the University of California by American Telephone and Telegraph
    7  * Co. or Unix System Laboratories, Inc. and are reproduced herein with
    8  * the permission of UNIX System Laboratories, Inc.
    9  *
   10  * Redistribution and use in source and binary forms, with or without
   11  * modification, are permitted provided that the following conditions
   12  * are met:
   13  * 1. Redistributions of source code must retain the above copyright
   14  *    notice, this list of conditions and the following disclaimer.
   15  * 2. Redistributions in binary form must reproduce the above copyright
   16  *    notice, this list of conditions and the following disclaimer in the
   17  *    documentation and/or other materials provided with the distribution.
   18  * 4. Neither the name of the University nor the names of its contributors
   19  *    may be used to endorse or promote products derived from this software
   20  *    without specific prior written permission.
   21  *
   22  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   23  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   24  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   25  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   26  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   27  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   28  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   29  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   30  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   31  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   32  * SUCH DAMAGE.
   33  *
   34  *      @(#)param.h     8.3 (Berkeley) 4/4/95
   35  * $FreeBSD: src/sys/sys/param.h,v 1.209.2.16.2.1 2006/05/12 15:47:05 kensmith Exp $
   36  */
   37 
   38 #ifndef _SYS_PARAM_H_
   39 #define _SYS_PARAM_H_
   40 
   41 #include <sys/_null.h>
   42 
   43 #define BSD     199506          /* System version (year & month). */
   44 #define BSD4_3  1
   45 #define BSD4_4  1
   46 
   47 /* 
   48  * __FreeBSD_version numbers are documented in the Porter's Handbook.
   49  * If you bump the version for any reason, you should update the documentation
   50  * there.
   51  * Currently this lives here:
   52  *
   53  *      doc/en_US.ISO8859-1/books/porters-handbook/book.sgml
   54  *
   55  * scheme is:  <major><two digit minor><0 if release branch, otherwise 1>xx
   56  */
   57 #undef __FreeBSD_version
   58 #define __FreeBSD_version 505000        /* Master, propagated to newvers */
   59 
   60 #ifndef LOCORE
   61 #include <sys/types.h>
   62 #endif
   63 
   64 /*
   65  * Machine-independent constants (some used in following include files).
   66  * Redefined constants are from POSIX 1003.1 limits file.
   67  *
   68  * MAXCOMLEN should be >= sizeof(ac_comm) (see <acct.h>)
   69  * MAXLOGNAME should be == UT_NAMESIZE+1 (see <utmp.h>)
   70  */
   71 #include <sys/syslimits.h>
   72 
   73 #define MAXCOMLEN       19              /* max command name remembered */
   74 #define MAXINTERP       32              /* max interpreter file name length */
   75 #define MAXLOGNAME      17              /* max login name length (incl. NUL) */
   76 #define MAXUPRC         CHILD_MAX       /* max simultaneous processes */
   77 #define NCARGS          ARG_MAX         /* max bytes for an exec function */
   78 #define NGROUPS         NGROUPS_MAX     /* max number groups */
   79 #define NOFILE          OPEN_MAX        /* max open files per process */
   80 #define NOGROUP         65535           /* marker for empty group set member */
   81 #define MAXHOSTNAMELEN  256             /* max hostname size */
   82 #define SPECNAMELEN     63              /* max length of devicename */
   83 
   84 /* More types and definitions used throughout the kernel. */
   85 #ifdef _KERNEL
   86 #if (defined(BURN_BRIDGES) || __FreeBSD_version >= 600000) \
   87         && defined(OBSOLETE_IN_6)
   88 #error "This file contains obsolete code to be removed in 6.0-current"
   89 #endif
   90 #include <sys/cdefs.h>
   91 #include <sys/errno.h>
   92 #include <sys/time.h>
   93 #include <sys/priority.h>
   94 
   95 #define FALSE   0
   96 #define TRUE    1
   97 #endif
   98 
   99 #ifndef _KERNEL
  100 /* Signals. */
  101 #include <sys/signal.h>
  102 #endif
  103 
  104 /* Machine type dependent parameters. */
  105 #include <machine/param.h>
  106 #ifndef _KERNEL
  107 #include <sys/limits.h>
  108 #endif
  109 
  110 #ifndef _NO_NAMESPACE_POLLUTION
  111 
  112 #ifndef DEV_BSHIFT
  113 #define DEV_BSHIFT      9               /* log2(DEV_BSIZE) */
  114 #endif
  115 #define DEV_BSIZE       (1<<DEV_BSHIFT)
  116 
  117 #ifndef BLKDEV_IOSIZE
  118 #define BLKDEV_IOSIZE  PAGE_SIZE        /* default block device I/O size */
  119 #endif
  120 #ifndef DFLTPHYS
  121 #define DFLTPHYS        (64 * 1024)     /* default max raw I/O transfer size */
  122 #endif
  123 #ifndef MAXPHYS
  124 #define MAXPHYS         (128 * 1024)    /* max raw I/O transfer size */
  125 #endif
  126 #ifndef MAXDUMPPGS
  127 #define MAXDUMPPGS      (DFLTPHYS/PAGE_SIZE)
  128 #endif
  129 
  130 /*
  131  * Constants related to network buffer management.
  132  * MCLBYTES must be no larger than PAGE_SIZE.
  133  */
  134 #ifndef MSIZE
  135 #define MSIZE           256             /* size of an mbuf */
  136 #endif  /* MSIZE */
  137 
  138 #ifndef MCLSHIFT
  139 #define MCLSHIFT        11              /* convert bytes to mbuf clusters */
  140 #endif  /* MCLSHIFT */
  141 
  142 #define MCLBYTES        (1 << MCLSHIFT) /* size of an mbuf cluster */
  143 
  144 /*
  145  * Some macros for units conversion
  146  */
  147 
  148 /* clicks to bytes */
  149 #ifndef ctob
  150 #define ctob(x) ((x)<<PAGE_SHIFT)
  151 #endif
  152 
  153 /* bytes to clicks */
  154 #ifndef btoc
  155 #define btoc(x) (((vm_offset_t)(x)+PAGE_MASK)>>PAGE_SHIFT)
  156 #endif
  157 
  158 /*
  159  * btodb() is messy and perhaps slow because `bytes' may be an off_t.  We
  160  * want to shift an unsigned type to avoid sign extension and we don't
  161  * want to widen `bytes' unnecessarily.  Assume that the result fits in
  162  * a daddr_t.
  163  */
  164 #ifndef btodb
  165 #define btodb(bytes)                    /* calculates (bytes / DEV_BSIZE) */ \
  166         (sizeof (bytes) > sizeof(long) \
  167          ? (daddr_t)((unsigned long long)(bytes) >> DEV_BSHIFT) \
  168          : (daddr_t)((unsigned long)(bytes) >> DEV_BSHIFT))
  169 #endif
  170 
  171 #ifndef dbtob
  172 #define dbtob(db)                       /* calculates (db * DEV_BSIZE) */ \
  173         ((off_t)(db) << DEV_BSHIFT)
  174 #endif
  175 
  176 #endif /* _NO_NAMESPACE_POLLUTION */
  177 
  178 #define PRIMASK 0x0ff
  179 #define PCATCH  0x100           /* OR'd with pri for tsleep to check signals */
  180 #define PDROP   0x200   /* OR'd with pri to stop re-entry of interlock mutex */
  181 
  182 #define NZERO   0               /* default "nice" */
  183 
  184 #define NBBY    8               /* number of bits in a byte */
  185 #define NBPW    sizeof(int)     /* number of bytes per word (integer) */
  186 
  187 #define CMASK   022             /* default file mask: S_IWGRP|S_IWOTH */
  188 
  189 #define NODEV   (dev_t)(-1)     /* non-existent device */
  190 
  191 #define CBLOCK  128             /* Clist block size, must be a power of 2. */
  192 #define CBQSIZE (CBLOCK/NBBY)   /* Quote bytes/cblock - can do better. */
  193                                 /* Data chars/clist. */
  194 #define CBSIZE  (CBLOCK - sizeof(struct cblock *) - CBQSIZE)
  195 #define CROUND  (CBLOCK - 1)    /* Clist rounding. */
  196 
  197 /*
  198  * File system parameters and macros.
  199  *
  200  * MAXBSIZE -   Filesystems are made out of blocks of at most MAXBSIZE bytes
  201  *              per block.  MAXBSIZE may be made larger without effecting
  202  *              any existing filesystems as long as it does not exceed MAXPHYS,
  203  *              and may be made smaller at the risk of not being able to use
  204  *              filesystems which require a block size exceeding MAXBSIZE.
  205  *
  206  * BKVASIZE -   Nominal buffer space per buffer, in bytes.  BKVASIZE is the
  207  *              minimum KVM memory reservation the kernel is willing to make.
  208  *              Filesystems can of course request smaller chunks.  Actual 
  209  *              backing memory uses a chunk size of a page (PAGE_SIZE).
  210  *
  211  *              If you make BKVASIZE too small you risk seriously fragmenting
  212  *              the buffer KVM map which may slow things down a bit.  If you
  213  *              make it too big the kernel will not be able to optimally use 
  214  *              the KVM memory reserved for the buffer cache and will wind 
  215  *              up with too-few buffers.
  216  *
  217  *              The default is 16384, roughly 2x the block size used by a
  218  *              normal UFS filesystem.
  219  */
  220 #define MAXBSIZE        65536   /* must be power of 2 */
  221 #define BKVASIZE        16384   /* must be power of 2 */
  222 #define BKVAMASK        (BKVASIZE-1)
  223 
  224 /*
  225  * MAXPATHLEN defines the longest permissible path length after expanding
  226  * symbolic links. It is used to allocate a temporary buffer from the buffer
  227  * pool in which to do the name expansion, hence should be a power of two,
  228  * and must be less than or equal to MAXBSIZE.  MAXSYMLINKS defines the
  229  * maximum number of symbolic links that may be expanded in a path name.
  230  * It should be set high enough to allow all legitimate uses, but halt
  231  * infinite loops reasonably quickly.
  232  */
  233 #define MAXPATHLEN      PATH_MAX
  234 #define MAXSYMLINKS     32
  235 
  236 /* Bit map related macros. */
  237 #define setbit(a,i)     ((a)[(i)/NBBY] |= 1<<((i)%NBBY))
  238 #define clrbit(a,i)     ((a)[(i)/NBBY] &= ~(1<<((i)%NBBY)))
  239 #define isset(a,i)      ((a)[(i)/NBBY] & (1<<((i)%NBBY)))
  240 #define isclr(a,i)      (((a)[(i)/NBBY] & (1<<((i)%NBBY))) == 0)
  241 
  242 /* Macros for counting and rounding. */
  243 #ifndef howmany
  244 #define howmany(x, y)   (((x)+((y)-1))/(y))
  245 #endif
  246 #define rounddown(x, y) (((x)/(y))*(y))
  247 #define roundup(x, y)   ((((x)+((y)-1))/(y))*(y))  /* to any y */
  248 #define roundup2(x, y)  (((x)+((y)-1))&(~((y)-1))) /* if y is powers of two */
  249 #define powerof2(x)     ((((x)-1)&(x))==0)
  250 
  251 /* Macros for min/max. */
  252 #define MIN(a,b) (((a)<(b))?(a):(b))
  253 #define MAX(a,b) (((a)>(b))?(a):(b))
  254 
  255 #ifdef _KERNEL
  256 /*
  257  * Basic byte order function prototypes for non-inline functions.
  258  */
  259 #ifndef _BYTEORDER_PROTOTYPED
  260 #define _BYTEORDER_PROTOTYPED
  261 __BEGIN_DECLS
  262 __uint32_t       htonl(__uint32_t);
  263 __uint16_t       htons(__uint16_t);
  264 __uint32_t       ntohl(__uint32_t);
  265 __uint16_t       ntohs(__uint16_t);
  266 __END_DECLS
  267 #endif
  268 
  269 #ifndef lint
  270 #ifndef _BYTEORDER_FUNC_DEFINED
  271 #define _BYTEORDER_FUNC_DEFINED
  272 #define htonl(x)        __htonl(x)
  273 #define htons(x)        __htons(x)
  274 #define ntohl(x)        __ntohl(x)
  275 #define ntohs(x)        __ntohs(x)
  276 #endif /* !_BYTEORDER_FUNC_DEFINED */
  277 #endif /* lint */
  278 #endif /* _KERNEL */
  279 
  280 /*
  281  * Constants for setting the parameters of the kernel memory allocator.
  282  *
  283  * 2 ** MINBUCKET is the smallest unit of memory that will be
  284  * allocated. It must be at least large enough to hold a pointer.
  285  *
  286  * Units of memory less or equal to MAXALLOCSAVE will permanently
  287  * allocate physical memory; requests for these size pieces of
  288  * memory are quite fast. Allocations greater than MAXALLOCSAVE must
  289  * always allocate and free physical memory; requests for these
  290  * size allocations should be done infrequently as they will be slow.
  291  *
  292  * Constraints: PAGE_SIZE <= MAXALLOCSAVE <= 2 ** (MINBUCKET + 14), and
  293  * MAXALLOCSIZE must be a power of two.
  294  */
  295 #if defined(__alpha__) || defined(__ia64__) || defined(__sparc64__)
  296 #define MINBUCKET       5               /* 5 => min allocation of 32 bytes */
  297 #else
  298 #define MINBUCKET       4               /* 4 => min allocation of 16 bytes */
  299 #endif
  300 #define MAXALLOCSAVE    (2 * PAGE_SIZE)
  301 
  302 /*
  303  * Scale factor for scaled integers used to count %cpu time and load avgs.
  304  *
  305  * The number of CPU `tick's that map to a unique `%age' can be expressed
  306  * by the formula (1 / (2 ^ (FSHIFT - 11))).  The maximum load average that
  307  * can be calculated (assuming 32 bits) can be closely approximated using
  308  * the formula (2 ^ (2 * (16 - FSHIFT))) for (FSHIFT < 15).
  309  *
  310  * For the scheduler to maintain a 1:1 mapping of CPU `tick' to `%age',
  311  * FSHIFT must be at least 11; this gives us a maximum load avg of ~1024.
  312  */
  313 #define FSHIFT  11              /* bits to right of fixed binary point */
  314 #define FSCALE  (1<<FSHIFT)
  315 
  316 #define dbtoc(db)                       /* calculates devblks to pages */ \
  317         ((db + (ctodb(1) - 1)) >> (PAGE_SHIFT - DEV_BSHIFT))
  318  
  319 #define ctodb(db)                       /* calculates pages to devblks */ \
  320         ((db) << (PAGE_SHIFT - DEV_BSHIFT))
  321 
  322 #endif  /* _SYS_PARAM_H_ */

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