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x86: Check the lower byte of EAX of CPUID leaf 2 (RHEL-76211)

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Resolves: RHEL-76211
This commit is contained in:
Patsy Griffin 2025-04-17 10:23:33 -04:00
parent ac595d4a50
commit d72b902998
2 changed files with 74 additions and 1 deletions
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69
glibc-RHEL-76211.patch Normal file
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@ -0,0 +1,69 @@
commit 1493622f4f9048ffede3fbedb64695efa49d662a
Author: H.J. Lu <hjl.tools@gmail.com>
Date: Mon Aug 28 12:08:14 2023 -0700
x86: Check the lower byte of EAX of CPUID leaf 2 [BZ #30643]
The old Intel software developer manual specified that the low byte of
EAX of CPUID leaf 2 returned 1 which indicated the number of rounds of
CPUDID leaf 2 was needed to retrieve the complete cache information. The
newer Intel manual has been changed to that it should always return 1
and be ignored. If the lower byte isn't 1, CPUID leaf 2 can't be used.
In this case, we ignore CPUID leaf 2 and use CPUID leaf 4 instead. If
CPUID leaf 4 doesn't contain the cache information, cache information
isn't available at all. This addresses BZ #30643.
diff --git a/sysdeps/x86/dl-cacheinfo.h b/sysdeps/x86/dl-cacheinfo.h
index 5ddb35c9d9..87486054f9 100644
--- a/sysdeps/x86/dl-cacheinfo.h
+++ b/sysdeps/x86/dl-cacheinfo.h
@@ -187,7 +187,7 @@ intel_check_word (int name, unsigned int value, bool *has_level_2,
++round;
}
/* There is no other cache information anywhere else. */
- break;
+ return -1;
}
else
{
@@ -257,28 +257,23 @@ handle_intel (int name, const struct cpu_features *cpu_features)
/* OK, we can use the CPUID instruction to get all info about the
caches. */
- unsigned int cnt = 0;
- unsigned int max = 1;
long int result = 0;
bool no_level_2_or_3 = false;
bool has_level_2 = false;
+ unsigned int eax;
+ unsigned int ebx;
+ unsigned int ecx;
+ unsigned int edx;
+ __cpuid (2, eax, ebx, ecx, edx);
- while (cnt++ < max)
+ /* The low byte of EAX of CPUID leaf 2 should always return 1 and it
+ should be ignored. If it isn't 1, use CPUID leaf 4 instead. */
+ if ((eax & 0xff) != 1)
+ return intel_check_word (name, 0xff, &has_level_2, &no_level_2_or_3,
+ cpu_features);
+ else
{
- unsigned int eax;
- unsigned int ebx;
- unsigned int ecx;
- unsigned int edx;
- __cpuid (2, eax, ebx, ecx, edx);
-
- /* The low byte of EAX in the first round contain the number of
- rounds we have to make. At least one, the one we are already
- doing. */
- if (cnt == 1)
- {
- max = eax & 0xff;
- eax &= 0xffffff00;
- }
+ eax &= 0xffffff00;
/* Process the individual registers' value. */
result = intel_check_word (name, eax, &has_level_2,

6
glibc.spec
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@ -115,7 +115,7 @@ end \
Summary: The GNU libc libraries
Name: glibc
Version: %{glibcversion}
Release: %{glibcrelease}.16
Release: %{glibcrelease}.17
# In general, GPLv2+ is used by programs, LGPLv2+ is used for
# libraries.
@ -1262,6 +1262,7 @@ Patch1027: glibc-RHEL-78390.patch
Patch1028: glibc-RHEL-83306-1.patch
Patch1029: glibc-RHEL-83306-2.patch
Patch1030: glibc-RHEL-35280.patch
Patch1031: glibc-RHEL-76211.patch
##############################################################################
# Continued list of core "glibc" package information:
@ -2923,6 +2924,9 @@ fi
%{_libdir}/libpthread_nonshared.a
%changelog
* Wed Apr 16 2025 Patsy Griffin <patsy@redhat.com> - 2.28-251.17
- x86: Check the lower byte of EAX of CPUID leaf 2 (RHEL-76211)
* Thu Mar 27 2025 Arjun Shankar <arjun@redhat.com> - 2.28-251.16
- nscd: Fix an unlikely TTL issue in the netgroup cache (RHEL-35280)