[review] Remove all loaded objects if dlopen fails, ignoring NODELETE [BZ #20839]

["Christian Häggström (Code Review)" <gerrit@gnutoolchain-gerrit.osci.io>]

Christian Häggström has posted comments on this change.

Change URL: https://gnutoolchain-gerrit.osci.io/r/c/glibc/+/471
......................................................................


Patch Set 1:

(3 comments)

I haven't tested the patch, just some small remarks on the code.

https://gnutoolchain-gerrit.osci.io/r/c/glibc/+/471/1/elf/dl-lookup.c 
File elf/dl-lookup.c:

https://gnutoolchain-gerrit.osci.io/r/c/glibc/+/471/1/elf/dl-lookup.c@322 
PS1, Line 322: 
317 | 	     setting the appropriate flag.  */
318 | 	  if (__glibc_unlikely (GLRO (dl_debug_mask) & DL_DEBUG_BINDINGS)
319 | 	      && map->l_nodelete == link_map_nodelete_inactive)
320 | 	    _dl_debug_printf ("\
321 | marking %s [%lu] as NODELETE due to unique symbol\n",
322 > 			      map->l_name, map->l_ns);
323 | 	  if (flags & DL_LOOKUP_FOR_RELOCATE)
324 | 	    map->l_nodelete = link_map_nodelete_pending;
325 | 	  else
326 | 	    map->l_nodelete = link_map_nodelete_active;
327 | 	}

Please make a macro for the debug printouts to reduce the clutter.


https://gnutoolchain-gerrit.osci.io/r/c/glibc/+/471/1/include/link.h 
File include/link.h:

https://gnutoolchain-gerrit.osci.io/r/c/glibc/+/471/1/include/link.h@94 
PS1, Line 94: 
83 | enum link_map_nodelete
   | ...
89 |  link_map_nodelete_active,
90 | 
91 |  /* This link map cannot be deallocated after dlopen has succeded.
92 |     dlopen turns this into link_map_nodelete_active.  dlclose treats
93 |     this intermediate state as link_map_nodelete_active.  */
94 >  link_map_nodelete_pending,
95 | };
96 | 
97 | 
98 | /* Structure describing a loaded shared object.  The `l_next' and `l_prev'
99 |    members form a chain of all the shared objects loaded at startup.

I would prefer if the constants were in caps, like LINK_MAP_NODELETE_INACTIVE, right now they look like global variables when reading the code.


https://gnutoolchain-gerrit.osci.io/r/c/glibc/+/471/1/include/link.h@223 
PS1, Line 223: 
107 | struct link_map
    | ...
218 | 				       freed, ie. not allocated with
219 | 				       the dummy malloc in ld.so.  */
220 | 
221 |     /* Actually of type enum link_map_nodelete.  Separate byte due to
222 |        concurrent access.  Only valid for l_type == lt_loaded.  */
223 >     unsigned char l_nodelete;
224 | 
225 | #include <link_map.h>
226 | 
227 |     /* Collected information about own RPATH directories.  */
228 |     struct r_search_path_struct l_rpath_dirs;

Is this variable accessed from different threads? In that case, please mention which lock that needs to be held in order to access this variable.

Please initialize it explicitly to link_map_nodelete_inactive in _dl_new_object(). Or write link_map_nodelete_inactive = 0 in the enum definition to clarify that we depend on calloc's zero initialization.



-- 
Gerrit-Project: glibc
Gerrit-Branch: master
Gerrit-Change-Id: Ib2a3d86af6f92d75baca65431d74783ee0dbc292
Gerrit-Change-Number: 471
Gerrit-PatchSet: 1
Gerrit-Owner: Florian Weimer <fweimer@redhat.com>
Gerrit-CC: Christian Häggström <gnugerrit@kalvdans.no-ip.org>
Gerrit-Comment-Date: Thu, 31 Oct 2019 20:18:00 +0000
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