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elf: Fix force_first handling in dlclose (bug 30981)
The force_first parameter was ineffective because the dlclose'd object was not necessarily the first in the maps array. Also enable force_first handling unconditionally, regardless of namespace. The initial object in a namespace should be destructed first, too. The _dl_sort_maps_dfs function had early returns for relocation dependency processing which broke force_first handling, too, and this is fixed in this change as well. Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
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@ -153,6 +153,16 @@ _dl_close_worker (struct link_map *map, bool force)
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}
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assert (idx == nloaded);
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/* Put the dlclose'd map first, so that its destructor runs first.
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The map variable is NULL after a retry. */
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if (map != NULL)
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{
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maps[map->l_idx] = maps[0];
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maps[map->l_idx]->l_idx = map->l_idx;
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maps[0] = map;
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maps[0]->l_idx = 0;
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}
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/* Keep track of the lowest index link map we have covered already. */
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int done_index = -1;
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while (++done_index < nloaded)
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@ -226,9 +236,10 @@ _dl_close_worker (struct link_map *map, bool force)
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}
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}
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/* Sort the entries. We can skip looking for the binary itself which is
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at the front of the search list for the main namespace. */
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_dl_sort_maps (maps, nloaded, (nsid == LM_ID_BASE), true);
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/* Sort the entries. Unless retrying, the maps[0] object (the
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original argument to dlclose) needs to remain first, so that its
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destructor runs first. */
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_dl_sort_maps (maps, nloaded, /* force_first */ map != NULL, true);
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/* Call all termination functions at once. */
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bool unload_any = false;
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@ -732,7 +743,11 @@ _dl_close_worker (struct link_map *map, bool force)
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/* Recheck if we need to retry, release the lock. */
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out:
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if (dl_close_state == rerun)
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goto retry;
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{
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/* The map may have been deallocated. */
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map = NULL;
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goto retry;
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}
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dl_close_state = not_pending;
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}
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@ -255,13 +255,12 @@ _dl_sort_maps_dfs (struct link_map **maps, unsigned int nmaps,
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The below memcpy is not needed in the do_reldeps case here,
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since we wrote back to maps[] during DFS traversal. */
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if (maps_head == maps)
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return;
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break;
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}
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assert (maps_head == maps);
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return;
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}
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memcpy (maps, rpo, sizeof (struct link_map *) * nmaps);
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else
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memcpy (maps, rpo, sizeof (struct link_map *) * nmaps);
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/* Skipping the first object at maps[0] is not valid in general,
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since traversing along object dependency-links may "find" that
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@ -56,14 +56,16 @@ output: b>a>{}<a<b
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# relocation(dynamic) dependencies. While this is technically unspecified, the
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# presumed reasonable practical behavior is for the destructor order to respect
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# the static DT_NEEDED links (here this means the a->b->c->d order).
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# The older dynamic_sort=1 algorithm does not achieve this, while the DFS-based
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# dynamic_sort=2 algorithm does, although it is still arguable whether going
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# beyond spec to do this is the right thing to do.
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# The older dynamic_sort=1 algorithm originally did not achieve this,
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# but this was a bug in the way _dl_sort_maps was called from _dl_close_worker,
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# effectively disabling proper force_first handling.
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# The new dynamic_sort=2 algorithm shows the effect of the simpler force_first
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# handling: the a object is simply moved to the front.
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# The below expected outputs are what the two algorithms currently produce
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# respectively, for regression testing purposes.
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tst-bz15311: {+a;+e;+f;+g;+d;%d;-d;-g;-f;-e;-a};a->b->c->d;d=>[ba];c=>a;b=>e=>a;c=>f=>b;d=>g=>c
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output(glibc.rtld.dynamic_sort=1): {+a[d>c>b>a>];+e[e>];+f[f>];+g[g>];+d[];%d(b(e(a()))a()g(c(a()f(b(e(a()))))));-d[];-g[];-f[];-e[];-a[<a<c<d<g<f<b<e];}
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output(glibc.rtld.dynamic_sort=2): {+a[d>c>b>a>];+e[e>];+f[f>];+g[g>];+d[];%d(b(e(a()))a()g(c(a()f(b(e(a()))))));-d[];-g[];-f[];-e[];-a[<g<f<a<b<c<d<e];}
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output(glibc.rtld.dynamic_sort=1): {+a[d>c>b>a>];+e[e>];+f[f>];+g[g>];+d[];%d(b(e(a()))a()g(c(a()f(b(e(a()))))));-d[];-g[];-f[];-e[];-a[<a<b<c<d<g<f<e];}
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output(glibc.rtld.dynamic_sort=2): {+a[d>c>b>a>];+e[e>];+f[f>];+g[g>];+d[];%d(b(e(a()))a()g(c(a()f(b(e(a()))))));-d[];-g[];-f[];-e[];-a[<a<g<f<b<c<d<e];}
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# Test that even in the presence of dependency loops involving dlopen'ed
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# object, that object is initialized last (and not unloaded prematurely).
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