fs/proc/sysvipc.c

   1 /*
   2  *  linux/fs/proc/sysvipc.c
   3  *
   4  *  Copyright (c) 1999 Dragos Acostachioaie
   5  *
   6  *  This code is derived from linux/fs/proc/generic.c,
   7  *  which is Copyright (C) 1991, 1992 Linus Torvalds.
   8  *
   9  *  /proc/sysvipc directory handling functions
  10  */
  11 #include <linux/errno.h>
  12 #include <linux/sched.h>
  13 #include <linux/proc_fs.h>
  14 #include <linux/stat.h>
  15 #include <linux/mm.h>
  16
  17 #include <asm/uaccess.h>
  18
  19 #ifndef MIN
  20 #define MIN(a,b) (((a) < (b)) ? (a) : (b))
  21 #endif
  22
  23 /* 4K page size but our output routines use some slack for overruns */
  24 #define PROC_BLOCK_SIZE (3*1024)
  25
  26 static ssize_t
  27 proc_sysvipc_read(struct file * file, char * buf, size_t nbytes, loff_t *ppos)
  28 {
  29         struct inode * inode = file->f_dentry->d_inode;
  30         char    *page;
  31         ssize_t retval=0;
  32         int     eof=0;
  33         ssize_t n, count;
  34         char    *start;
  35         struct proc_dir_entry * dp;
  36
  37         dp = (struct proc_dir_entry *) inode->u.generic_ip;
  38         if (!(page = (char*) __get_free_page(GFP_KERNEL)))
  39                 return -ENOMEM;
  40
  41         while ((nbytes > 0) && !eof)
  42         {
  43                 count = MIN(PROC_BLOCK_SIZE, nbytes);
  44
  45                 start = NULL;
  46                 if (dp->get_info) {
  47                         /*
  48                          * Handle backwards compatibility with the old net
  49                          * routines.
  50                          *
  51                          * XXX What gives with the file->f_flags & O_ACCMODE
  52                          * test?  Seems stupid to me....
  53                          */
  54                         n = dp->get_info(page, &start, *ppos, count,
  55                                  (file->f_flags & O_ACCMODE) == O_RDWR);
  56                         if (n < count)
  57                                 eof = 1;
  58                 } else if (dp->read_proc) {
  59                         n = dp->read_proc(page, &start, *ppos,
  60                                           count, &eof, dp->data);
  61                 } else
  62                         break;
  63
  64                 if (!start) {
  65                         /*
  66                          * For proc files that are less than 4k
  67                          */
  68                         start = page + *ppos;
  69                         n -= *ppos;
  70                         if (n <= 0)
  71                                 break;
  72                         if (n > count)
  73                                 n = count;
  74                 }
  75                 if (n == 0)
  76                         break;  /* End of file */
  77                 if (n < 0) {
  78                         if (retval == 0)
  79                                 retval = n;
  80                         break;
  81                 }
  82
  83                 /* This is a hack to allow mangling of file pos independent
  84                  * of actual bytes read.  Simply place the data at page,
  85                  * return the bytes, and set `start' to the desired offset
  86                  * as an unsigned int. - Paul.Russell@rustcorp.com.au
  87                  */
  88                 n -= copy_to_user(buf, start < page ? page : start, n);
  89                 if (n == 0) {
  90                         if (retval == 0)
  91                                 retval = -EFAULT;
  92                         break;
  93                 }
  94
  95                 *ppos += start < page ? (long)start : n; /* Move down the file */
  96                 nbytes -= n;
  97                 buf += n;
  98                 retval += n;
  99         }
 100         free_page((unsigned long) page);
 101         return retval;
 102 }
 103
 104 static struct file_operations proc_sysvipc_operations = {
 105     NULL,               /* lseek   */
 106     proc_sysvipc_read,  /* read    */
 107     NULL,               /* write   */
 108     NULL,               /* readdir */
 109     NULL,               /* poll    */
 110     NULL,               /* ioctl   */
 111     NULL,               /* mmap    */
 112     NULL,               /* no special open code    */
 113     NULL,               /* no special release code */
 114     NULL                /* can't fsync */
 115 };
 116
 117 /*
 118  * proc directories can do almost nothing..
 119  */
 120 struct inode_operations proc_sysvipc_inode_operations = {
 121         &proc_sysvipc_operations, /* default net file-ops */
 122         NULL,                   /* create */
 123         NULL,                   /* lookup */
 124         NULL,                   /* link */
 125         NULL,                   /* unlink */
 126         NULL,                   /* symlink */
 127         NULL,                   /* mkdir */
 128         NULL,                   /* rmdir */
 129         NULL,                   /* mknod */
 130         NULL,                   /* rename */
 131         NULL,                   /* readlink */
 132         NULL,                   /* follow_link */
 133         NULL,                   /* get_block */
 134         NULL,                   /* readpage */
 135         NULL,                   /* writepage */
 136         NULL,                   /* flushpage */
 137         NULL,                   /* truncate */
 138         NULL,                   /* permission */
 139         NULL,                   /* smap */
 140         NULL                    /* revalidate */
 141 };