@@ -439,23 +439,7 @@ add_name_to_object (struct link_map *l, const char *name)
newname->name = memcpy (newname + 1, name, name_len);
newname->next = NULL;
newname->dont_free = 0;
- /* CONCURRENCY NOTES:
-
- Make sure the initialization of newname happens before its address is
- read from the lastp->next store below.
-
- GL(dl_load_lock) is held here (and by other writers, e.g. dlclose), so
- readers of libname_list->next (e.g. _dl_check_caller or the reads above)
- can use that for synchronization, however the read in _dl_name_match_p
- may be executed without holding the lock during _dl_runtime_resolve
- (i.e. lazy symbol resolution when a function of library l is called).
-
- The release MO store below synchronizes with the acquire MO load in
- _dl_name_match_p. Other writes need to synchronize with that load too,
- however those happen either early when the process is single threaded
- (dl_main) or when the library is unloaded (dlclose) and the user has to
- synchronize library calls with unloading. */
- atomic_store_release (&lastp->next, newname);
+ lastp->next = newname;
}
/* Standard search directories. */
@@ -94,22 +94,9 @@ check_match (const char *const undef_name,
const ElfW(Half) *verstab = map->l_versyms;
if (version != NULL)
{
- if (__glibc_unlikely (verstab == NULL))
- {
- /* We need a versioned symbol but haven't found any. If
- this is the object which is referenced in the verneed
- entry it is a bug in the library since a symbol must
- not simply disappear.
-
- It would also be a bug in the object since it means that
- the list of required versions is incomplete and so the
- tests in dl-version.c haven't found a problem.*/
- assert (version->filename == NULL
- || ! _dl_name_match_p (version->filename, map));
-
- /* Otherwise we accept the symbol. */
- }
- else
+ /* If there is no version information, accept the symbol. This
+ can happen during symbol interposition. */
+ if (__glibc_likely (verstab != NULL))
{
/* We can match the version information or use the
default one if it is not hidden. */
@@ -75,9 +75,7 @@ _dl_name_match_p (const char *name, const struct link_map *map)
if (strcmp (name, runp->name) == 0)
return 1;
else
- /* Synchronize with the release MO store in add_name_to_object.
- See CONCURRENCY NOTES in add_name_to_object in dl-load.c. */
- runp = atomic_load_acquire (&runp->next);
+ runp = runp->next;
return 0;
}
This case is detected early in the elf/dl-versionc.c consistency checks. (These checks could be disabled in the future to allow the removal of symbol versioning from objects.) Commit f0b2132b35 ("ld.so: Support moving versioned symbols between sonames [BZ #24741]) removed another call to _dl_name_match_p. The _dl_check_caller function no longer exists, and the remaining calls to _dl_name_match_p happen under the loader lock. This means that atomic accesses are no longer required for the l_libname list. This supersedes commit 395be7c218 ("elf: Fix data race in _dl_name_match_p [BZ #21349]"). --- elf/dl-load.c | 18 +----------------- elf/dl-lookup.c | 19 +++---------------- elf/dl-misc.c | 4 +--- 3 files changed, 5 insertions(+), 36 deletions(-)