diff options
| -rw-r--r-- | elf/dl-sort-maps.c | 32 | ||||
| -rw-r--r-- | elf/dso-sort-tests-1.def | 7 |
2 files changed, 30 insertions, 9 deletions
diff --git a/elf/dl-sort-maps.c b/elf/dl-sort-maps.c index 5b550b1e94..3e2a6a584e 100644 --- a/elf/dl-sort-maps.c +++ b/elf/dl-sort-maps.c @@ -182,8 +182,9 @@ dfs_traversal (struct link_map ***rpo, struct link_map *map, static void _dl_sort_maps_dfs (struct link_map **maps, unsigned int nmaps, - bool force_first __attribute__ ((unused)), bool for_fini) + bool force_first, bool for_fini) { + struct link_map *first_map = maps[0]; for (int i = nmaps - 1; i >= 0; i--) maps[i]->l_visited = 0; @@ -208,14 +209,6 @@ _dl_sort_maps_dfs (struct link_map **maps, unsigned int nmaps, Adjusting the order so that maps[0] is last traversed naturally avoids this problem. - Further, the old "optimization" of skipping the main object at maps[0] - from the call-site (i.e. _dl_sort_maps(maps+1,nmaps-1)) is in general - no longer valid, since traversing along object dependency-links - may "find" the main object even when it is not included in the initial - order (e.g. a dlopen()'ed shared object can have circular dependencies - linked back to itself). In such a case, traversing N-1 objects will - create a N-object result, and raise problems. - To summarize, just passing in the full list, and iterating from back to front makes things much more straightforward. */ @@ -274,6 +267,27 @@ _dl_sort_maps_dfs (struct link_map **maps, unsigned int nmaps, } memcpy (maps, rpo, sizeof (struct link_map *) * nmaps); + + /* Skipping the first object at maps[0] is not valid in general, + since traversing along object dependency-links may "find" that + first object even when it is not included in the initial order + (e.g., a dlopen'ed shared object can have circular dependencies + linked back to itself). In such a case, traversing N-1 objects + will create a N-object result, and raise problems. Instead, + force the object back into first place after sorting. This naive + approach may introduce further dependency ordering violations + compared to rotating the cycle until the first map is again in + the first position, but as there is a cycle, at least one + violation is already present. */ + if (force_first && maps[0] != first_map) + { + int i; + for (i = 0; maps[i] != first_map; ++i) + ; + assert (i < nmaps); + memmove (&maps[1], maps, i * sizeof (maps[0])); + maps[0] = first_map; + } } void diff --git a/elf/dso-sort-tests-1.def b/elf/dso-sort-tests-1.def index 5f7f18ef27..4bf9052db1 100644 --- a/elf/dso-sort-tests-1.def +++ b/elf/dso-sort-tests-1.def @@ -64,3 +64,10 @@ output: b>a>{}<a<b 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 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];} 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];} + +# Test that even in the presence of dependency loops involving dlopen'ed +# object, that object is initialized last (and not unloaded prematurely). +# Final destructor order is indeterminate due to the cycle. +tst-bz28937: {+a;+b;-b;+c;%c};a->a1;a->a2;a2->a;b->b1;c->a1;c=>a1 +output(glibc.rtld.dynamic_sort=1): {+a[a2>a1>a>];+b[b1>b>];-b[<b<b1];+c[c>];%c(a1());}<a<a2<c<a1 +output(glibc.rtld.dynamic_sort=2): {+a[a2>a1>a>];+b[b1>b>];-b[<b<b1];+c[c>];%c(a1());}<a2<a<c<a1 |