diff options
Diffstat (limited to 'elf/dl-lookup.c')
| -rw-r--r-- | elf/dl-lookup.c | 243 |
1 files changed, 228 insertions, 15 deletions
diff --git a/elf/dl-lookup.c b/elf/dl-lookup.c index 702fd3b824..7ac87702a4 100644 --- a/elf/dl-lookup.c +++ b/elf/dl-lookup.c @@ -18,11 +18,13 @@ Boston, MA 02111-1307, USA. */ #include <alloca.h> +#include <stdlib.h> #include <string.h> #include <unistd.h> #include <ldsodefs.h> #include "dl-hash.h" #include <dl-machine.h> +#include <bits/libc-lock.h> #include <assert.h> @@ -59,6 +61,15 @@ struct sym_val /* Statistics function. */ unsigned long int _dl_num_relocations; +/* During the program run we must not modify the global data of + loaded shared object simultanously in two threads. Therefore we + protect `_dl_open' and `_dl_close' in dl-close.c. + + This must be a recursive lock since the initializer function of + the loaded object might as well require a call to this function. + At this time it is not anymore a problem to modify the tables. */ +__libc_lock_define (extern, _dl_load_lock) + /* We have two different situations when looking up a simple: with or without versioning. gcc is not able to optimize a single function @@ -70,6 +81,105 @@ unsigned long int _dl_num_relocations; #include "do-lookup.h" +/* Add extra dependency on MAP to UNDEF_MAP. */ +static int +add_dependency (struct link_map *undef_map, struct link_map *map) +{ + struct link_map **list; + unsigned act; + unsigned int i; + int result = 0; + + /* Make sure nobody can unload the object while we are at it. */ + __libc_lock_lock (_dl_load_lock); + + /* Determine whether UNDEF_MAP already has a reference to MAP. First + look in the normal dependencies. */ + list = undef_map->l_searchlist.r_list; + act = undef_map->l_searchlist.r_nlist; + + for (i = 0; i < act; ++i) + if (list[i] == map) + break; + + if (__builtin_expect (i, act) == act) + { + /* No normal dependency. See whether we already had to add it + to the special list of dynamic dependencies. */ + list = undef_map->l_reldeps; + act = undef_map->l_reldepsact; + + for (i = 0; i < act; ++i) + if (list[i] == map) + break; + + if (i == act) + { + /* The object is not yet in the dependency list. Before we add + it make sure just one more time the object we are about to + reference is still available. There is a brief period in + which the object could have been removed since we found the + definition. */ + struct link_map *runp = _dl_loaded; + + while (runp != NULL && runp != map) + runp = runp->l_next; + + if (runp != NULL) + { + /* The object is still available. Add the reference now. */ + if (act >= undef_map->l_reldepsmax) + { + /* Allocate more memory for the dependency list. Since + this can never happen during the startup phase we can + use `realloc'. */ + void *newp; + + undef_map->l_reldepsmax += 5; + newp = realloc (undef_map->l_reldeps, + undef_map->l_reldepsmax); + + if (__builtin_expect (newp != NULL, 1)) + undef_map->l_reldeps = (struct link_map **) newp; + else + /* Correct the addition. */ + undef_map->l_reldepsmax -= 5; + } + + /* If we didn't manage to allocate memory for the list this + is no fatal mistake. We simply increment the use counter + of the referenced object and don't record the dependencies. + This means this increment can never be reverted and the + object will never be unloaded. This is semantically the + correct behaviour. */ + if (act < undef_map->l_reldepsmax) + undef_map->l_reldeps[undef_map->l_reldepsact++] = map; + + /* And increment the counter in the referenced object. */ + ++map->l_opencount; + + /* Display information if we are debugging. */ + if (__builtin_expect (_dl_debug_files, 0)) + _dl_debug_message (1, "\nfile=", + map->l_name[0] ? map->l_name : _dl_argv[0], + "; needed by ", + undef_map->l_name[0] + ? undef_map->l_name : _dl_argv[0], + " (relocation dependency)\n\n", NULL); + } + else + /* Whoa, that was bad luck. We have to search again. */ + result = -1; + } + } + + /* Release the lock. */ + __libc_lock_unlock (_dl_load_lock); + + return result; +} + + /* Search loaded objects' symbol tables for a definition of the symbol UNDEF_NAME. */ @@ -90,7 +200,24 @@ _dl_lookup_symbol (const char *undef_name, struct link_map *undef_map, for (scope = symbol_scope; *scope; ++scope) if (do_lookup (undef_name, undef_map, hash, *ref, ¤t_value, *scope, 0, NULL, reloc_type)) - break; + { + /* We have to check whether this would bind UNDEF_MAP to an object + in the global scope which was dynamically loaded. In this case + we have to prevent the latter from being unloaded unless the + UNDEF_MAP object is also unloaded. */ + if (current_value.m->l_global + && (__builtin_expect (current_value.m->l_type, lt_library) + == lt_loaded) + && undef_map != current_value.m + /* Add UNDEF_MAP to the dependencies. */ + && add_dependency (undef_map, current_value.m) < 0) + /* Something went wrong. Perhaps the object we tried to reference + was just removed. Try finding another definition. */ + return _dl_lookup_symbol (undef_name, undef_map, ref, symbol_scope, + reloc_type); + + break; + } if (current_value.s == NULL) { @@ -104,7 +231,7 @@ _dl_lookup_symbol (const char *undef_name, struct link_map *undef_map, return 0; } - if (_dl_debug_bindings) + if (__builtin_expect (_dl_debug_bindings, 0)) _dl_debug_message (1, "binding file ", (reference_name && reference_name[0] ? reference_name @@ -143,13 +270,47 @@ _dl_lookup_symbol_skip (const char *undef_name, for (i = 0; (*scope)->r_duplist[i] != skip_map; ++i) assert (i < (*scope)->r_nduplist); - if (i >= (*scope)->r_nlist - || ! do_lookup (undef_name, undef_map, hash, *ref, ¤t_value, - *scope, i, skip_map, 0)) + if (i < (*scope)->r_nlist + && do_lookup (undef_name, undef_map, hash, *ref, ¤t_value, + *scope, i, skip_map, 0)) + { + /* We have to check whether this would bind UNDEF_MAP to an object + in the global scope which was dynamically loaded. In this case + we have to prevent the latter from being unloaded unless the + UNDEF_MAP object is also unloaded. */ + if (current_value.m->l_global + && (__builtin_expect (current_value.m->l_type, lt_library) + == lt_loaded) + && undef_map != current_value.m + /* Add UNDEF_MAP to the dependencies. */ + && add_dependency (undef_map, current_value.m) < 0) + /* Something went wrong. Perhaps the object we tried to reference + was just removed. Try finding another definition. */ + return _dl_lookup_symbol_skip (undef_name, undef_map, ref, + symbol_scope, skip_map); + } + else while (*++scope) if (do_lookup (undef_name, undef_map, hash, *ref, ¤t_value, *scope, 0, skip_map, 0)) - break; + { + /* We have to check whether this would bind UNDEF_MAP to an object + in the global scope which was dynamically loaded. In this case + we have to prevent the latter from being unloaded unless the + UNDEF_MAP object is also unloaded. */ + if (current_value.m->l_global + && (__builtin_expect (current_value.m->l_type, lt_library) + == lt_loaded) + && undef_map != current_value.m + /* Add UNDEF_MAP to the dependencies. */ + && add_dependency (undef_map, current_value.m) < 0) + /* Something went wrong. Perhaps the object we tried to reference + was just removed. Try finding another definition. */ + return _dl_lookup_symbol_skip (undef_name, undef_map, ref, + symbol_scope, skip_map); + + break; + } if (current_value.s == NULL) { @@ -157,7 +318,7 @@ _dl_lookup_symbol_skip (const char *undef_name, return 0; } - if (_dl_debug_bindings) + if (__builtin_expect (_dl_debug_bindings, 0)) _dl_debug_message (1, "binding file ", (reference_name && reference_name[0] ? reference_name @@ -198,7 +359,25 @@ _dl_lookup_versioned_symbol (const char *undef_name, ¤t_value, *scope, 0, version, NULL, reloc_type); if (res > 0) - break; + { + /* We have to check whether this would bind UNDEF_MAP to an object + in the global scope which was dynamically loaded. In this case + we have to prevent the latter from being unloaded unless the + UNDEF_MAP object is also unloaded. */ + if (current_value.m->l_global + && (__builtin_expect (current_value.m->l_type, lt_library) + == lt_loaded) + && undef_map != current_value.m + /* Add UNDEF_MAP to the dependencies. */ + && add_dependency (undef_map, current_value.m) < 0) + /* Something went wrong. Perhaps the object we tried to reference + was just removed. Try finding another definition. */ + return _dl_lookup_versioned_symbol (undef_name, undef_map, ref, + symbol_scope, version, + reloc_type); + + break; + } if (res < 0) { @@ -232,7 +411,7 @@ _dl_lookup_versioned_symbol (const char *undef_name, return 0; } - if (_dl_debug_bindings) + if (__builtin_expect (_dl_debug_bindings, 0)) _dl_debug_message (1, "binding file ", (reference_name && reference_name[0] ? reference_name @@ -271,15 +450,49 @@ _dl_lookup_versioned_symbol_skip (const char *undef_name, for (i = 0; (*scope)->r_duplist[i] != skip_map; ++i) assert (i < (*scope)->r_nduplist); - if (i >= (*scope)->r_nlist - || ! do_lookup_versioned (undef_name, undef_map, hash, *ref, - ¤t_value, *scope, i, version, skip_map, - 0)) + if (i < (*scope)->r_nlist + && do_lookup_versioned (undef_name, undef_map, hash, *ref, + ¤t_value, *scope, i, version, skip_map, 0)) + { + /* We have to check whether this would bind UNDEF_MAP to an object + in the global scope which was dynamically loaded. In this case + we have to prevent the latter from being unloaded unless the + UNDEF_MAP object is also unloaded. */ + if (current_value.m->l_global + && (__builtin_expect (current_value.m->l_type, lt_library) + == lt_loaded) + && undef_map != current_value.m + /* Add UNDEF_MAP to the dependencies. */ + && add_dependency (undef_map, current_value.m) < 0) + /* Something went wrong. Perhaps the object we tried to reference + was just removed. Try finding another definition. */ + return _dl_lookup_versioned_symbol_skip (undef_name, undef_map, ref, + symbol_scope, version, + skip_map); + } + else while (*++scope) if (do_lookup_versioned (undef_name, undef_map, hash, *ref, ¤t_value, *scope, 0, version, skip_map, 0)) - break; + { + /* We have to check whether this would bind UNDEF_MAP to an object + in the global scope which was dynamically loaded. In this case + we have to prevent the latter from being unloaded unless the + UNDEF_MAP object is also unloaded. */ + if (current_value.m->l_global + && (__builtin_expect (current_value.m->l_type, lt_library) + == lt_loaded) + && undef_map != current_value.m + /* Add UNDEF_MAP to the dependencies. */ + && add_dependency (undef_map, current_value.m) < 0) + /* Something went wrong. Perhaps the object we tried to reference + was just removed. Try finding another definition. */ + return _dl_lookup_versioned_symbol_skip (undef_name, undef_map, + ref, symbol_scope, + version, skip_map); + break; + } if (current_value.s == NULL) { @@ -298,7 +511,7 @@ _dl_lookup_versioned_symbol_skip (const char *undef_name, return 0; } - if (_dl_debug_bindings) + if (__builtin_expect (_dl_debug_bindings, 0)) _dl_debug_message (1, "binding file ", (reference_name && reference_name[0] ? reference_name |