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