[PATCH] Obey LD_HWCAP_MASK in ld.so.cache lookups.

[Roland McGrath <roland at redhat dot com>]

The LD_HWCAP_MASK environment variable affects direct library searching and
ldconfig runs, but does not affect the most-common situation: cache-based
lookups after ldconfig ran without an LD_HWCAP_MASK setting.  That seems
obviously wrong to me.

This is on branch roland/hwcap_mask.  I can't see any reason it should not
always have been this way, but just in case I didn't merge it to master.
Unless there is a good reason not to, merge it.


Thanks,
Roland


2010-04-05  Roland McGrath  <roland@redhat.com>

	* elf/dl-cache.c (_dl_load_cache_lookup): Obey dl_hwcap_mask.

	* elf/dl-support.c (_dl_hwcap_mask): New variable.

diff --git a/elf/dl-cache.c b/elf/dl-cache.c
index bbeba77..5a01c2e 100644
--- a/elf/dl-cache.c
+++ b/elf/dl-cache.c
@@ -1,5 +1,6 @@
 /* Support for reading /etc/ld.so.cache files written by Linux ldconfig.
-   Copyright (C) 1996-2002, 2003, 2004, 2006 Free Software Foundation, Inc.
+   Copyright (C) 1996-2002,2003,2004,2006,2010
+	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
@@ -255,17 +256,19 @@ _dl_load_cache_lookup (const char *name)
       if (platform != (uint64_t) -1)
 	platform = 1ULL << platform;
 
-      /* Only accept hwcap if it's for the right platform.  */
 #define _DL_HWCAP_TLS_MASK (1LL << 63)
+      uint64_t hwcap_exclude = ~((GLRO(dl_hwcap) & GLRO(dl_hwcap_mask))
+				 | _DL_HWCAP_PLATFORM | _DL_HWCAP_TLS_MASK);
+
+      /* Only accept hwcap if it's for the right platform.  */
 #define HWCAP_CHECK \
+      if (lib->hwcap & hwcap_exclude)					      \
+	continue;							      \
       if (GLRO(dl_osversion) && lib->osversion > GLRO(dl_osversion))	      \
 	continue;							      \
       if (_DL_PLATFORMS_COUNT						      \
 	  && (lib->hwcap & _DL_HWCAP_PLATFORM) != 0			      \
 	  && (lib->hwcap & _DL_HWCAP_PLATFORM) != platform)		      \
-	continue;							      \
-      if (lib->hwcap							      \
-	  & ~(GLRO(dl_hwcap) | _DL_HWCAP_PLATFORM | _DL_HWCAP_TLS_MASK))      \
 	continue
       SEARCH_CACHE (cache_new);
     }
diff --git a/elf/dl-support.c b/elf/dl-support.c
index bcf0e2a..65b2575 100644
--- a/elf/dl-support.c
+++ b/elf/dl-support.c
@@ -1,5 +1,5 @@
 /* Support for dynamic linking code in static libc.
-   Copyright (C) 1996-2008, 2009 Free Software Foundation, Inc.
+   Copyright (C) 1996-2008,2009,2010 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
@@ -126,6 +126,14 @@ ElfW(Phdr) *_dl_phdr;
 size_t _dl_phnum;
 uint64_t _dl_hwcap __attribute__ ((nocommon));
 
+/* This is not initialized to HWCAP_IMPORTANT, matching the definition
+   of _dl_important_hwcaps, below, where no hwcap strings are ever
+   used.  This mask is still used to mediate the lookups in the cache
+   file.  Since there is no way to set this nonzero (we don't grok the
+   LD_HWCAP_MASK environment variable here), there is no real point in
+   setting _dl_hwcap nonzero below, but we do anyway.  */
+uint64_t _dl_hwcap_mask __attribute__ ((nocommon));
+
 /* Prevailing state of the stack, PF_X indicating it's executable.  */
 ElfW(Word) _dl_stack_flags = PF_R|PF_W|PF_X;