2009/054: dlinfo(3c) - segment mapping retrieval

[Rod Evans]

------------------------------------------------------------------------

I'm sponsoring the following case for myself.	This case qualifies for
Architectural self-review, but I wish to record the following information.

------------------------------------------------------------------------

A request has been made for ld.so.1 to return an objects segment mapping
information.  This method of obtaining the data would be more light weight
than having to go through things like /proc.

     6237063 request extension to dl* family to provide segment bounds
             information

With the approach of mmapobj(2), this request was put on hold, so that we
could return a public/consistent data structure.  mmapobj(2) has integrated,
and ld.so.1 now uses it(6686372).

dlinfo() will return mmapobj_result_t data by using two new flags:

  > #define	RTLD_DI_MMAPS    12		/* obtain objects mappings or */
  > #define	RTLD_DI_MMAPCNT	 13		/*	mapping count */

An auxiliary structure is used to maintain the data:

  > typedef struct {
  > 	uint_t		dlm_cnt;	/* number of mapings */
  > 	mmapobj_result_t *dlm_maps;	/* mapping information */
  > } Dl_mapinfo_t;

The user will first determine the number of mappings using a RTLD_DI_MMAPCNT
request, and then provide the appropriate buffer to a RTLD_DI_MMAPS request.
This model follows the RTLD_DI_SERINFOSIZE/RTLD_DI_SERINFO model, approved
with PSARC/2000/164 (bug id 4239213).

------------------------------------------------------------------------

  Standard C Library Functions                           dlinfo(3C)

      .....
      RTLD_DI_MMAPCNT

          Initialize a Dl_mapinfo_t structure for the handle  that
          is  specified, for use in a RTLD_DI_MMAPS request. The p
          argument is a Dl_mapinfo_t pointer (Dl_mapinfo_t *p). On
          return  from  a  RTLD_DI_MMAPCNT  request,  the  dlm_cnt
          member indicates the number of segment mappings that the
          associated object uses.

          To  obtain  the  complete  mapping  information  for  an
          object,  a  mmapobj_result_t  array  for dlm_cnt entries
          must be allocated and assigned to the  dlm_maps  member.
          This   initialized   structure   is  then  passed  to  a
          RTLD_DI_MMAPS request. See EXAMPLES.

      RTLD_DI_MMAPS

          Obtain segment mapping information for the  handle  that
          is  specified.  The p argument is a Dl_mapinfo_t pointer
          (Dl_mapinfo_t *p). This structure  must  be  initialized
          from a previous RTLD_DI_MMAPCNT request.

          Segment mapping information is provided in an  array  of
          mmapobj_result_t structures that originate from the mma-
          pobj(2) of the associated  object.  The  dlm_cnt  member
          from  a previous RTLD_DI_MMAPCNT request must be used to
          allocate a mmapobj_result_t array. This array should  be
          assigned to the dlm_maps member. This initialized struc-
          ture is then passed to a  RTLD_DI_MMAPS  request,  where
          the  segment  mapping information is copied to the allo-
          cated mmapobj_result_t array. See EXAMPLES.

      .....

      Example 2: Use dlinfo() to obtain segment information.

      The following example demonstrates how a dynamic object  can
      inspect  its  segment  mapping  information. For simplicity,
      error checking has been omitted

          Dl_mapinfo_t   mi;
          uint_t         cnt;

          /* determine the number of segment mappings */
          dlinfo(RTLD_SELF, RTLD_DI_MMAPCNT, &mi);

          /* allocate the appropriate mapping array */
          mi.dlm_maps = malloc(mi.dlm_cnt * sizeof (mmapobj_result_t));

          /* obtain the mapping information */
          dlinfo(RTLD_SELF, RTLD_DI_MMAPS, &mi);

          for (cnt = 0; cnt < mi.dlm_cnt; cnt++) {
              (void) printf("addr=%x - memory size=%x\n",
                  mi.dlm_maps[cnt].mr_addr, mi.dlm_maps[cnt].mr_msize);
          }

------------------------------------------------------------------------
Release binding:		Patch/Micro

    dlfcn.h:
         Dl_mapinfo_t		Committed.
	RTLD_DI_SERINFO		Committed.
	RTLD_DI_SERINFOSIZE	Committed.

-- 
Rod.