From: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date: Fri, 18 Apr 2025 12:52:04 +0000 (-0300)
Subject: x86: Fix UB in x86_cpu_present/x86_cpu_active
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=7417fcf25a1a2398bac3126577ae6a8d7cd6db4a;p=thirdparty%2Fglibc.git

x86: Fix UB in x86_cpu_present/x86_cpu_active

The elf/tst-cpu-features-supports (and other tests that check for
CPU features) triggers the following issue with ubsan:

UBSAN: Undefined behaviour in ../sysdeps/x86/sys/platform/x86.h:59:42 left shift of 1 by 31 cannot be represented in type 'int'

The active_array is unsigned, so use an unsigned constant as well.
---

diff --git a/sysdeps/x86/sys/platform/x86.h b/sysdeps/x86/sys/platform/x86.h
index 7f4aeac0c6..340146c225 100644
--- a/sysdeps/x86/sys/platform/x86.h
+++ b/sysdeps/x86/sys/platform/x86.h
@@ -40,7 +40,7 @@ x86_cpu_present (unsigned int __index)
   unsigned int __bit = __reg & (8 * sizeof (unsigned int) - 1);
   __reg /= 8 * sizeof (unsigned int);
 
-  return __ptr->cpuid_array[__reg] & (1 << __bit);
+  return __ptr->cpuid_array[__reg] & (1U << __bit);
 }
 
 static __inline__ bool
@@ -56,7 +56,7 @@ x86_cpu_active (unsigned int __index)
   unsigned int __bit = __reg & (8 * sizeof (unsigned int) - 1);
   __reg /= 8 * sizeof (unsigned int);
 
-  return __ptr->active_array[__reg] & (1 << __bit);
+  return __ptr->active_array[__reg] & (1U << __bit);
 }
 
 /* CPU_FEATURE_PRESENT evaluates to true if CPU supports the feature.  */