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Avoid ELF lookup race.

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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.
This commit is contained in:
Ulrich Drepper
2009-12-15 12:32:27 -08:00
parent 2510d01ddb
commit 2af6396817
4 changed files with 23 additions and 8 deletions
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8
elf/dl-object.c
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@ -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;