servers/procfs/type.h

   1 #ifndef _PROCFS_TYPE_H
   2 #define _PROCFS_TYPE_H
   3
   4 typedef void *data_t;           /* abstract data type; can hold pointer */
   5
   6 struct load {
   7         clock_t ticks;          /* in this umber of ticks: */
   8         long proc_load;         /* .. the CPU had this load */
   9 };
  10
  11 /* ProcFS supports two groups of files: dynamic files, which are created within
  12  * process-specific (PID) directories, and static files, which are global. For
  13  * both, the following structure is used to construct the files.
  14  *
  15  * For dynamic files, the rules are simple: only regular files are supported
  16  * (although partial support for symbolic links is already present), and the
  17  * 'data' field must be filled with a pointer to a function of the type:
  18  *
  19  *   void (*)(int slot)
  20  *
  21  * The function will be called whenever a read request for the file is made;
  22  * 'slot' contains the kernel slot number of the process being queried (so for
  23  * the PM and VFS process tables, NR_TASKS has to be subtracted from the slot
  24  * number to find the right slot). The function is expected to produce
  25  * appropriate output using the buf_printf() function.
  26  *
  27  * For static files, regular files and directories are supported. For
  28  * directories, the 'data' field must be a pointer to another 'struct file'
  29  * array that specifies the contents of the directory - this directory will
  30  * the be created recursively. For regular files, the 'data' field must point
  31  * to a function of the type:
  32  *
  33  *   void (*)(void)
  34  *
  35  * Here too, the function will be called upon a read request, and it is
  36  * supposed to "fill" the file using buf_printf(). Obviously, for static files,
  37  * there is no slot number.
  38  *
  39  * For both static and dynamic files, 'mode' must specify the file type as well
  40  * as the access mode, and in both cases, each array is terminated with an
  41  * entry that has its name set to NULL.
  42  */
  43 /* The internal link between static/dynamic files/directories and VTreeFS'
  44  * indexes and cbdata values is as follows:
  45  * - Dynamic directories are always PID directories in the root directory.
  46  *   They are generated automatically, and are not specified using a "struct
  47  *   file" structure. Their index is their slot number, so that getdents()
  48  *   calls always return any PID at most once. Their cbdata value is the PID of
  49  *   the process associated with that dynamic directory, for the purpose of
  50  *   comparing old and new PIDs after updating process tables (without having
  51  *   to atoi() the directory's name).
  52  * - Dynamic files are always in such a dynamic directory. Their index is the
  53  *   array index into the "struct file" array of pid files (pid_files[]). They
  54  *   are indexed at all, because they may be deleted at any time due to inode
  55  *   shortages, independently of other dynamic files in the same directory, and
  56  *   recreating them without index would again risk possibly inconsistent
  57  *   getdents() results, where for example the same file shows up twice.
  58  *   VTreeFS currently does not distinguish between indexed and delatable files
  59  *   and hence, all dynamic files must be indexed so as to be deletable anyway.
  60  * - Static directories have no index (they are not and must not be deletable),
  61  *   and although their cbdata is their associated 'data' field from their
  62  *   "struct file" entries, their cbdata value is currently not relied on
  63  *   anywhere. Then again, as of writing, there are no static directories at
  64  *   all.
  65  * - Static files have no index either (for the same reason). Their cbdata is
  66  *   also their 'data' field from the "struct file" entry creating the file,
  67  *   and this is used to actually call the callback function directly.
  68  */
  69 struct file {
  70         char *name;             /* file name, maximum length PNAME_MAX */
  71         pmode_t mode;           /* file mode, including file type */
  72         data_t data;            /* custom data associated with this file */
  73 };
  74
  75 #endif /* _PROCFS_TYPE_H */