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[Fwd: Bug#161788: libc6 always loads i686 libraries from cache when available, ignoring the host arch]

Can you verify this, and fix this if it is really the problem?

Thanks
	Christoph
--- Begin Message --- 
Package: libc6
Severity: grave

Here's a cute one. On any i386 platform, when there is an
i686-specific library in ld.so.cache, libc6 will prefer it over all
other libraries in the cache, even if the local system is really
i[345]86.

The problem is specific to cached libraries, and should not occur on
other architectures.

This causes the latest version of libssl to crash with SIGILL on
i[345]86 systems. It can be directly diagnosed by setting
LD_DEBUG=libs and looking at the first few lines generated when the
offending binary is run, and observing that /usr/lib/i686/libcrypto*
is being loaded from the cache.

When _dl_load_cache_lookup searches the cache, it checks the platform
using this expression (sysdeps/generic/dl-cache.c around line 233):
      if (_DL_PLATFORMS_COUNT && platform != -1				      \
	  && (lib->hwcap & _DL_HWCAP_PLATFORM) != 0			      \
	  && (lib->hwcap & _DL_HWCAP_PLATFORM) != platform)		      \
	continue;							      \

_DL_HWCAP_PLATFORM is a mask that is supposed to match all the bits in
an hwcap field that can represent the current platform. Unfortunately,
it's got the wrong value. Here's the fix (haven't tested this yet,
glibc takes too long to build, but some bit-twiddling in gdb indicates
it should work):

--- sysdeps/unix/sysv/linux/i386/dl-procinfo.h~	2001-07-22 21:24:56.000000000 +0100
+++ sysdeps/unix/sysv/linux/i386/dl-procinfo.h	2002-09-21 16:38:34.000000000 +0100
@@ -34,7 +34,7 @@
 /* Start at 48 to reserve some space.  */
 #define _DL_FIRST_PLATFORM	48
 /* Mask to filter out platforms.  */
-#define _DL_HWCAP_PLATFORM	(7ULL << _DL_FIRST_PLATFORM)
+#define _DL_HWCAP_PLATFORM	(((1ULL << _DL_PLATFORMS_COUNT) - 1) << _DL_FIRST_PLATFORM)
 
 
 static inline int

The value '7' clearly dates from when there were only three platforms,
and never got updated when i686 was added. The practical upshot is
that the bit for 'i686' is never considered by anything to be a
platform, so the entry in ld.so.cache is assumed to be for any
platform.

-- 
  .''`.  ** Debian GNU/Linux ** | Andrew Suffield
 : :' :  http://www.debian.org/ | Dept. of Computing,
 `. `'                          | Imperial College,
   `-             -><-          | London, UK

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