[COMMITTED 2.33] x86: use default cache size if it cannot be determined [BZ #28784]

[COMMITTED 2.33] x86: use default cache size if it cannot be determined [BZ #28784]

[Aurelien Jarno]

In some cases (e.g QEMU, non-Intel/AMD CPU) the cache information can
not be retrieved and the corresponding values are set to 0.

Commit 2d651eb9265d ("x86: Move x86 processor cache info to
cpu_features") changed the behaviour in such case by defining the
__x86_shared_cache_size and __x86_data_cache_size variables to 0 instead
of using the default values. This cause an issue with the i686 SSE2
optimized bzero/routine which assumes that the cache size is at least
128 bytes, and otherwise tries to zero/set the whole address space minus
128 bytes.

Fix that by restoring the original code to only update
__x86_shared_cache_size and __x86_data_cache_size variables if the
corresponding cache sizes are not zero.

Fixes bug 28784
Fixes commit 2d651eb9265d

Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
(cherry picked from commit c242fcce06e3102ca663b2f992611d0bda4f2668)
---
 NEWS                    |  1 +
 sysdeps/x86/cacheinfo.h | 14 ++++++++++----
 2 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/NEWS b/NEWS
index 6091d5bd82..6e4221ca86 100644
--- a/NEWS
+++ b/NEWS
@@ -271,6 +271,7 @@ The following bugs are resolved with this release:
   [27237] malloc: deadlock in malloc/tst-malloc-stats-cancellation
   [27256] locale: Assertion failure in ISO-2022-JP-3 gconv module
     related to combining characters (CVE-2021-3326)
+  [28784] x86: crash in 32bit memset-sse2.s when the cache size can not be determined
 
 \f
 Version 2.32
diff --git a/sysdeps/x86/cacheinfo.h b/sysdeps/x86/cacheinfo.h
index 68c253542f..0f850bdf12 100644
--- a/sysdeps/x86/cacheinfo.h
+++ b/sysdeps/x86/cacheinfo.h
@@ -63,16 +63,22 @@ init_cacheinfo (void)
   __x86_raw_data_cache_size = data;
   /* Round data cache size to multiple of 256 bytes.  */
   data = data & ~255L;
-  __x86_data_cache_size_half = data / 2;
-  __x86_data_cache_size = data;
+  if (data > 0)
+    {
+      __x86_data_cache_size_half = data / 2;
+      __x86_data_cache_size = data;
+    }
 
   long int shared = cpu_features->shared_cache_size;
   __x86_raw_shared_cache_size_half = shared / 2;
   __x86_raw_shared_cache_size = shared;
   /* Round shared cache size to multiple of 256 bytes.  */
   shared = shared & ~255L;
-  __x86_shared_cache_size_half = shared / 2;
-  __x86_shared_cache_size = shared;
+  if (shared > 0)
+    {
+      __x86_shared_cache_size_half = shared / 2;
+      __x86_shared_cache_size = shared;
+    }
 
   __x86_shared_non_temporal_threshold
     = cpu_features->non_temporal_threshold;
-- 
2.34.1