diff options
| author | Ulrich Drepper <drepper@redhat.com> | 2009-12-15 12:32:27 -0800 |
|---|---|---|
| committer | Ulrich Drepper <drepper@redhat.com> | 2009-12-15 12:32:27 -0800 |
| commit | 2af6396817fb9df98e63de75dd59fd999ee9f1d0 (patch) | |
| tree | d66827c66d770f1f3d697dbb027b59064e6ab0e0 /elf | |
| parent | 2510d01ddba195f8cfaa3c2349f75e0612719d82 (diff) | |
| download | glibc-2af6396817fb9df98e63de75dd59fd999ee9f1d0.tar.gz glibc-2af6396817fb9df98e63de75dd59fd999ee9f1d0.tar.xz glibc-2af6396817fb9df98e63de75dd59fd999ee9f1d0.zip | |
Avoid ELF lookup race.
On some architectures the update of the l_used field in the lookup functions races with setting the other bits in the bitfield. Simply avoid this and optimize use of l_used in general.
Diffstat (limited to 'elf')
| -rw-r--r-- | elf/dl-lookup.c | 7 | ||||
| -rw-r--r-- | elf/dl-object.c | 8 |
2 files changed, 10 insertions, 5 deletions
diff --git a/elf/dl-lookup.c b/elf/dl-lookup.c index c1a1366d6f..763ec16fa4 100644 --- a/elf/dl-lookup.c +++ b/elf/dl-lookup.c @@ -777,7 +777,7 @@ _dl_lookup_symbol_x (const char *undef_name, struct link_map *undef_map, if (__builtin_expect (protected != 0, 0)) { /* It is very tricky. We need to figure out what value to - return for the protected symbol. */ + return for the protected symbol. */ if (type_class == ELF_RTYPE_CLASS_PLT) { if (current_value.s != NULL && current_value.m != undef_map) @@ -822,7 +822,8 @@ _dl_lookup_symbol_x (const char *undef_name, struct link_map *undef_map, version, type_class, flags, skip_map); /* The object is used. */ - current_value.m->l_used = 1; + if (__builtin_expect (current_value.m->l_used == 0, 0)) + current_value.m->l_used = 1; if (__builtin_expect (GLRO(dl_debug_mask) & (DL_DEBUG_BINDINGS|DL_DEBUG_PRELINK), 0)) @@ -844,7 +845,7 @@ _dl_setup_hash (struct link_map *map) Elf_Symndx nchain; if (__builtin_expect (map->l_info[DT_ADDRTAGIDX (DT_GNU_HASH) + DT_NUM - + DT_THISPROCNUM + DT_VERSIONTAGNUM + + DT_THISPROCNUM + DT_VERSIONTAGNUM + DT_EXTRANUM + DT_VALNUM] != NULL, 1)) { Elf32_Word *hash32 diff --git a/elf/dl-object.c b/elf/dl-object.c index be4ea38f9f..788e2c07b9 100644 --- a/elf/dl-object.c +++ b/elf/dl-object.c @@ -1,5 +1,5 @@ /* Storage management for the chain of loaded shared objects. - Copyright (C) 1995-2002,2004,2006,2007,2008 Free Software Foundation, Inc. + Copyright (C) 1995-2002,2004,2006-2008,2009 Free Software Foundation, Inc. This file is part of the GNU C Library. The GNU C Library is free software; you can redistribute it and/or @@ -67,6 +67,10 @@ _dl_new_object (char *realname, const char *libname, int type, new->l_name = realname; new->l_type = type; + /* If we set the bit now since we know it is never used we avoid + dirtying the cache line later. */ + if ((GLRO(dl_debug_mask) & DL_DEBUG_UNUSED) == 0) + new->l_used = 1; new->l_loader = loader; #if NO_TLS_OFFSET != 0 new->l_tls_offset = NO_TLS_OFFSET; @@ -174,7 +178,7 @@ _dl_new_object (char *realname, const char *libname, int type, if (result == NULL) { /* We were not able to determine the current directory. - Note that free(origin) is OK if origin == NULL. */ + Note that free(origin) is OK if origin == NULL. */ free (origin); origin = (char *) -1; goto out; |