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