ipc/shm_block.c

   1 /***************************************************************************
   2  * Copyright 1995, Technion, Israel Institute of Technology
   3  * Electrical Eng, Software Lab.
   4  * Author:    Michael Veksler.
   5  ***************************************************************************
   6  * File:      shm_block.c
   7  * Purpose:   Treat a shared memory block.
   8  ***************************************************************************
   9  */
  10 #ifdef CONFIG_IPC
  11
  12 #define inline __inline__
  13 #include <sys/types.h>
  14 #include <sys/sem.h>
  15 #include <assert.h>
  16 #include <unistd.h>
  17 #include <stdlib.h>
  18 #include "debug.h"
  19 #include "global.h"
  20 #include "selectors.h"
  21 #include "shm_fragment.h"
  22 #include "shm_block.h"
  23 #include "shm_semaph.h"
  24 #include "dde_proc.h"
  25 #include "xmalloc.h"
  26
  27 /* How each shmid is maped to local pointer */
  28 /* Only attached shm blocks are in this construct */
  29 struct local_shm_map *shm_map=NULL;
  30
  31 /* setup a new shm block (construct a shm block object).
  32  *    block: The pointer to the memory block (local mapping)
  33  *    first: The first data byte (excluding header stuff),
  34  *           if 0  (zero) Use the default.
  35  *    size:  The size of the memory block.
  36  */
  37 void shm_setup_block(struct shm_block *block, int first, int size)
  38 {
  39   TRACE(shm,"Setting up shm block at 0x%08x\n",(int )block);
  40   /* setup block internal data structure */
  41   if (first <= 0) {
  42      first=sizeof(*block);
  43      /* round up - so everything starts on cache line boundary
  44       * (assume cache line=32 bytes, may be bigger/smaller for
  45       *  different processors and different L2 caches .)
  46       */
  47      first=(first+0x1f) & ~0x1f;
  48   }
  49   block->free=size-first;
  50   block->next_shm_id=-1; /* IPC shm ID (for initial linking) */
  51   block->proc_idx= curr_proc_idx;
  52   /* block->size is initialized in shm_FragmentInit */
  53   shm_FragmentInit(block, first, size);  /* first item in the free list */
  54
  55   TRACE(shm, "block was set up at 0x%08x, size=0x%04xKB, 1st usable=%02x\n",
  56               (int )block,size/1024,first);
  57 }
  58
  59 /* shm_attach_block: attach existing shm block, setup selectors
  60  * shm_id - id of the block to attach.
  61  * proc_idx - if not -1, puts this data into local mapping
  62  * map - localy mapped info about this block.
  63  */
  64 /* NOTE: there is no check if this block is already attached.
  65  *       Attaching the same block more than once - is possible
  66  *       In case of doubt use shm_locate_block.
  67  */
  68 struct shm_block *shm_attach_block(int shm_id, int proc_idx,
  69                                    struct local_shm_map *map)
  70 {
  71   struct shm_block *block;
  72   struct shmid_ds ds;
  73   struct local_shm_map *this;
  74
  75   shmctl(shm_id, IPC_STAT, &ds );
  76
  77   block=(struct shm_block*)shmat(shm_id, NULL, 0);
  78   if (block==NULL || block == (struct shm_block*) -1) return NULL;
  79
  80   this=(struct local_shm_map *)xmalloc(sizeof(*this));
  81   this->next= shm_map;
  82   shm_map   = this;
  83   this->shm_id= shm_id;
  84   this->ptr = block;
  85
  86   if (proc_idx < 0)
  87       this->proc_idx=block->proc_idx;
  88   else
  89       this->proc_idx=proc_idx;
  90
  91   if (map != NULL) {
  92      memcpy(map, this, sizeof(map));
  93      map->next= NULL;           /* don't pass private info */
  94   }
  95
  96   return block;
  97 }
  98
  99 struct shm_block *shm_create_block(int first, int size, int *shm_id)
 100 {
 101   struct shm_block *block;
 102
 103   if (size==0)
 104      size=SHM_MINBLOCK;
 105   else
 106      /* round up size to a multiple of SHM_MINBLOCK */
 107      size= (size+SHM_MINBLOCK-1) & ~(SHM_MINBLOCK-1);
 108   *shm_id= shmget ( IPC_PRIVATE, size ,0700);
 109   if (*shm_id==-1)
 110      return NULL;
 111   block=shm_attach_block(*shm_id, curr_proc_idx, NULL);
 112   if (block!=NULL)
 113      shm_setup_block(block, first, size);
 114
 115   return block;
 116 }
 117
 118 /*
 119 ** Locate attached block. (return it, or NULL on failure)
 120 ** shm_id is the block we look for.
 121 ** *map - will get all the info related to this local map + proc_idx
 122 **        (may be NULL)
 123 ** *seg - will get the segment this block is attached to.
 124 */
 125 struct shm_block *shm_locate_attached_block(int shm_id,
 126                                             struct local_shm_map *map)
 127 {
 128   struct local_shm_map *curr;
 129
 130   for (curr=  shm_map ; curr != NULL ; curr= curr->next) {
 131      if (curr->shm_id == shm_id) {
 132         if (map) {
 133             memcpy(map, curr, sizeof(*curr) );
 134             map->next = NULL;   /* this is private info ! */
 135         }
 136         return curr->ptr;
 137     }
 138   }
 139
 140   /* block not found !  */
 141   return 0;
 142 }
 143
 144 /* shm_locate_block: see shm_attach_block.
 145    In addition to shm_attach_block, make sure this
 146    block is not already attached.
 147    */
 148 struct shm_block *shm_locate_block(int shm_id, struct local_shm_map *map)
 149 {
 150
 151   struct shm_block *ret;
 152   ret= shm_locate_attached_block(shm_id, map);
 153   if (ret!=NULL)
 154      return ret;
 155   /* block not found ! , try to attach */
 156   return shm_attach_block(shm_id, -1, map);
 157 }
 158
 159 static void forget_attached(int shmid)
 160 {
 161   struct local_shm_map *curr, **point_to_curr;
 162
 163   for (curr= shm_map,    point_to_curr= &shm_map ;
 164        curr != NULL ;
 165        curr= curr->next, point_to_curr= &curr->next ) {
 166      if (curr->shm_id == shmid) {
 167         *point_to_curr= curr->next;
 168         return;
 169      }
 170   }
 171 }
 172
 173 /* delete chain of shm blocks (pointing to each other)
 174  * Do it in reverse order. (This is what the recursion is for)
 175  */
 176 void shm_delete_chain(int *shmid)
 177 {
 178   struct shm_block *block;
 179
 180   if (*shmid == -1)
 181       return;
 182
 183   block= shm_locate_block(*shmid, NULL);
 184   forget_attached( *shmid );
 185   if (block == NULL)
 186       return;
 187   shm_delete_chain(&block->next_shm_id);
 188   shmctl(*shmid, IPC_RMID, NULL);
 189   *shmid=-1;
 190   shmdt((char *)block);
 191 }
 192
 193 #endif  /* CONFIG_IPC */