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70 lines
2.4 KiB
70 lines
2.4 KiB
8 months ago
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commit 1493622f4f9048ffede3fbedb64695efa49d662a
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Author: H.J. Lu <hjl.tools@gmail.com>
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Date: Mon Aug 28 12:08:14 2023 -0700
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x86: Check the lower byte of EAX of CPUID leaf 2 [BZ #30643]
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The old Intel software developer manual specified that the low byte of
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EAX of CPUID leaf 2 returned 1 which indicated the number of rounds of
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CPUDID leaf 2 was needed to retrieve the complete cache information. The
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newer Intel manual has been changed to that it should always return 1
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and be ignored. If the lower byte isn't 1, CPUID leaf 2 can't be used.
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In this case, we ignore CPUID leaf 2 and use CPUID leaf 4 instead. If
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CPUID leaf 4 doesn't contain the cache information, cache information
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isn't available at all. This addresses BZ #30643.
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diff --git a/sysdeps/x86/dl-cacheinfo.h b/sysdeps/x86/dl-cacheinfo.h
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index f950e488cfbe42dd..bd2f2b65f78056ca 100644
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--- a/sysdeps/x86/dl-cacheinfo.h
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+++ b/sysdeps/x86/dl-cacheinfo.h
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@@ -187,7 +187,7 @@ intel_check_word (int name, unsigned int value, bool *has_level_2,
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++round;
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}
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/* There is no other cache information anywhere else. */
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- break;
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+ return -1;
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}
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else
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{
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@@ -257,28 +257,23 @@ handle_intel (int name, const struct cpu_features *cpu_features)
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/* OK, we can use the CPUID instruction to get all info about the
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caches. */
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- unsigned int cnt = 0;
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- unsigned int max = 1;
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long int result = 0;
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bool no_level_2_or_3 = false;
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bool has_level_2 = false;
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+ unsigned int eax;
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+ unsigned int ebx;
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+ unsigned int ecx;
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+ unsigned int edx;
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+ __cpuid (2, eax, ebx, ecx, edx);
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- while (cnt++ < max)
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+ /* The low byte of EAX of CPUID leaf 2 should always return 1 and it
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+ should be ignored. If it isn't 1, use CPUID leaf 4 instead. */
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+ if ((eax & 0xff) != 1)
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+ return intel_check_word (name, 0xff, &has_level_2, &no_level_2_or_3,
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+ cpu_features);
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+ else
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{
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- unsigned int eax;
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- unsigned int ebx;
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- unsigned int ecx;
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- unsigned int edx;
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- __cpuid (2, eax, ebx, ecx, edx);
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-
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- /* The low byte of EAX in the first round contain the number of
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- rounds we have to make. At least one, the one we are already
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- doing. */
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- if (cnt == 1)
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- {
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- max = eax & 0xff;
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- eax &= 0xffffff00;
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- }
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+ eax &= 0xffffff00;
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/* Process the individual registers' value. */
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result = intel_check_word (name, eax, &has_level_2,
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