commit 04bba1e5d84b6fd8d3a3b006bc240cd5d241ee30
Author: H.J. Lu <hjl.tools@gmail.com>
Date:   Wed Aug 5 13:51:56 2020 -0700

    x86: Set CPU usable feature bits conservatively [BZ #26552]
    
    Set CPU usable feature bits only for CPU features which are usable in
    user space and whose usability can be detected from user space, excluding
    features like FSGSBASE whose enable bit can only be checked in the kernel.

diff --git a/sysdeps/x86/cpu-features.c b/sysdeps/x86/cpu-features.c
index f13a1df4555c7000..6954728c47d0126b 100644
--- a/sysdeps/x86/cpu-features.c
+++ b/sysdeps/x86/cpu-features.c
@@ -44,107 +44,55 @@ extern void TUNABLE_CALLBACK (set_x86_shstk) (tunable_val_t *)
 static void
 update_usable (struct cpu_features *cpu_features)
 {
-  /* Before COMMON_CPUID_INDEX_80000001, copy the cpuid array elements to
-     the usable array.  */
-  unsigned int i;
-  for (i = 0; i < COMMON_CPUID_INDEX_80000001; i++)
-    cpu_features->features[i].usable = cpu_features->features[i].cpuid;
-
-  /* Before COMMON_CPUID_INDEX_80000001, clear the unknown usable bits
-     and the always zero bits.  */
-  CPU_FEATURE_UNSET (cpu_features, INDEX_1_ECX_16);
-  CPU_FEATURE_UNSET (cpu_features, INDEX_1_ECX_31);
-  CPU_FEATURE_UNSET (cpu_features, INDEX_1_EDX_10);
-  CPU_FEATURE_UNSET (cpu_features, INDEX_1_EDX_20);
-  CPU_FEATURE_UNSET (cpu_features, INDEX_1_EDX_30);
-  CPU_FEATURE_UNSET (cpu_features, INDEX_7_EBX_6);
-  CPU_FEATURE_UNSET (cpu_features, INDEX_7_EBX_22);
-  CPU_FEATURE_UNSET (cpu_features, INDEX_7_ECX_13);
-  CPU_FEATURE_UNSET (cpu_features, INDEX_7_ECX_15);
-  CPU_FEATURE_UNSET (cpu_features, INDEX_7_ECX_16);
-  CPU_FEATURE_UNSET (cpu_features, INDEX_7_ECX_23);
-  CPU_FEATURE_UNSET (cpu_features, INDEX_7_ECX_24);
-  CPU_FEATURE_UNSET (cpu_features, INDEX_7_ECX_26);
-  CPU_FEATURE_UNSET (cpu_features, INDEX_7_EDX_0);
-  CPU_FEATURE_UNSET (cpu_features, INDEX_7_EDX_1);
-  CPU_FEATURE_UNSET (cpu_features, INDEX_7_EDX_5);
-  CPU_FEATURE_UNSET (cpu_features, INDEX_7_EDX_6);
-  CPU_FEATURE_UNSET (cpu_features, INDEX_7_EDX_7);
-  CPU_FEATURE_UNSET (cpu_features, INDEX_7_EDX_9);
-  CPU_FEATURE_UNSET (cpu_features, INDEX_7_EDX_11);
-  CPU_FEATURE_UNSET (cpu_features, INDEX_7_EDX_12);
-  CPU_FEATURE_UNSET (cpu_features, INDEX_7_EDX_13);
-  CPU_FEATURE_UNSET (cpu_features, INDEX_7_EDX_17);
-  CPU_FEATURE_UNSET (cpu_features, INDEX_7_EDX_19);
-  CPU_FEATURE_UNSET (cpu_features, INDEX_7_EDX_21);
-  CPU_FEATURE_UNSET (cpu_features, INDEX_7_EDX_23);
-
-  /* EAX/EBX from COMMON_CPUID_INDEX_1 and EAX from COMMON_CPUID_INDEX_7
-     aren't used for CPU feature detection.  */
-  cpu_features->features[COMMON_CPUID_INDEX_1].usable.eax = 0;
-  cpu_features->features[COMMON_CPUID_INDEX_1].usable.ebx = 0;
-  cpu_features->features[COMMON_CPUID_INDEX_7].usable.eax = 0;
-
-  /* Starting from COMMON_CPUID_INDEX_80000001, copy the cpuid bits to
-     usable bits.  */
+  /* Copy the cpuid bits to usable bits for CPU featuress whose usability
+     in user space can be detected without additonal OS support.  */
+  CPU_FEATURE_SET_USABLE (cpu_features, SSE3);
+  CPU_FEATURE_SET_USABLE (cpu_features, PCLMULQDQ);
+  CPU_FEATURE_SET_USABLE (cpu_features, SSSE3);
+  CPU_FEATURE_SET_USABLE (cpu_features, CMPXCHG16B);
+  CPU_FEATURE_SET_USABLE (cpu_features, SSE4_1);
+  CPU_FEATURE_SET_USABLE (cpu_features, SSE4_2);
+  CPU_FEATURE_SET_USABLE (cpu_features, MOVBE);
+  CPU_FEATURE_SET_USABLE (cpu_features, POPCNT);
+  CPU_FEATURE_SET_USABLE (cpu_features, AES);
+  CPU_FEATURE_SET_USABLE (cpu_features, OSXSAVE);
+  CPU_FEATURE_SET_USABLE (cpu_features, TSC);
+  CPU_FEATURE_SET_USABLE (cpu_features, CX8);
+  CPU_FEATURE_SET_USABLE (cpu_features, CMOV);
+  CPU_FEATURE_SET_USABLE (cpu_features, CLFSH);
+  CPU_FEATURE_SET_USABLE (cpu_features, MMX);
+  CPU_FEATURE_SET_USABLE (cpu_features, FXSR);
+  CPU_FEATURE_SET_USABLE (cpu_features, SSE);
+  CPU_FEATURE_SET_USABLE (cpu_features, SSE2);
+  CPU_FEATURE_SET_USABLE (cpu_features, HTT);
+  CPU_FEATURE_SET_USABLE (cpu_features, BMI1);
+  CPU_FEATURE_SET_USABLE (cpu_features, HLE);
+  CPU_FEATURE_SET_USABLE (cpu_features, BMI2);
+  CPU_FEATURE_SET_USABLE (cpu_features, ERMS);
+  CPU_FEATURE_SET_USABLE (cpu_features, RTM);
+  CPU_FEATURE_SET_USABLE (cpu_features, RDSEED);
+  CPU_FEATURE_SET_USABLE (cpu_features, ADX);
+  CPU_FEATURE_SET_USABLE (cpu_features, CLFLUSHOPT);
+  CPU_FEATURE_SET_USABLE (cpu_features, CLWB);
+  CPU_FEATURE_SET_USABLE (cpu_features, SHA);
+  CPU_FEATURE_SET_USABLE (cpu_features, PREFETCHWT1);
+  CPU_FEATURE_SET_USABLE (cpu_features, OSPKE);
+  CPU_FEATURE_SET_USABLE (cpu_features, WAITPKG);
+  CPU_FEATURE_SET_USABLE (cpu_features, GFNI);
+  CPU_FEATURE_SET_USABLE (cpu_features, RDPID);
+  CPU_FEATURE_SET_USABLE (cpu_features, CLDEMOTE);
+  CPU_FEATURE_SET_USABLE (cpu_features, MOVDIRI);
+  CPU_FEATURE_SET_USABLE (cpu_features, MOVDIR64B);
+  CPU_FEATURE_SET_USABLE (cpu_features, FSRM);
+  CPU_FEATURE_SET_USABLE (cpu_features, SERIALIZE);
+  CPU_FEATURE_SET_USABLE (cpu_features, TSXLDTRK);
   CPU_FEATURE_SET_USABLE (cpu_features, LAHF64_SAHF64);
-  CPU_FEATURE_SET_USABLE (cpu_features, SVM);
   CPU_FEATURE_SET_USABLE (cpu_features, LZCNT);
   CPU_FEATURE_SET_USABLE (cpu_features, SSE4A);
   CPU_FEATURE_SET_USABLE (cpu_features, PREFETCHW);
-  CPU_FEATURE_SET_USABLE (cpu_features, XOP);
-  CPU_FEATURE_SET_USABLE (cpu_features, LWP);
-  CPU_FEATURE_SET_USABLE (cpu_features, FMA4);
   CPU_FEATURE_SET_USABLE (cpu_features, TBM);
-  CPU_FEATURE_SET_USABLE (cpu_features, SYSCALL_SYSRET);
-  CPU_FEATURE_SET_USABLE (cpu_features, NX);
-  CPU_FEATURE_SET_USABLE (cpu_features, PAGE1GB);
   CPU_FEATURE_SET_USABLE (cpu_features, RDTSCP);
-  CPU_FEATURE_SET_USABLE (cpu_features, LM);
-  CPU_FEATURE_SET_USABLE (cpu_features, XSAVEOPT);
-  CPU_FEATURE_SET_USABLE (cpu_features, XSAVEC);
-  CPU_FEATURE_SET_USABLE (cpu_features, XGETBV_ECX_1);
-  CPU_FEATURE_SET_USABLE (cpu_features, XSAVES);
-  CPU_FEATURE_SET_USABLE (cpu_features, XFD);
-  CPU_FEATURE_SET_USABLE (cpu_features, INVARIANT_TSC);
   CPU_FEATURE_SET_USABLE (cpu_features, WBNOINVD);
-  CPU_FEATURE_SET_USABLE (cpu_features, AVX512_BF16);
-
-  /* MPX has been deprecated.  */
-  CPU_FEATURE_UNSET (cpu_features, MPX);
-
-  /* Clear the usable bits which require OS support.  */
-  CPU_FEATURE_UNSET (cpu_features, FMA);
-  CPU_FEATURE_UNSET (cpu_features, AVX);
-  CPU_FEATURE_UNSET (cpu_features, F16C);
-  CPU_FEATURE_UNSET (cpu_features, AVX2);
-  CPU_FEATURE_UNSET (cpu_features, AVX512F);
-  CPU_FEATURE_UNSET (cpu_features, AVX512DQ);
-  CPU_FEATURE_UNSET (cpu_features, AVX512_IFMA);
-  CPU_FEATURE_UNSET (cpu_features, AVX512PF);
-  CPU_FEATURE_UNSET (cpu_features, AVX512ER);
-  CPU_FEATURE_UNSET (cpu_features, AVX512CD);
-  CPU_FEATURE_UNSET (cpu_features, AVX512BW);
-  CPU_FEATURE_UNSET (cpu_features, AVX512VL);
-  CPU_FEATURE_UNSET (cpu_features, AVX512_VBMI);
-  CPU_FEATURE_UNSET (cpu_features, PKU);
-  CPU_FEATURE_UNSET (cpu_features, AVX512_VBMI2);
-  CPU_FEATURE_UNSET (cpu_features, VAES);
-  CPU_FEATURE_UNSET (cpu_features, VPCLMULQDQ);
-  CPU_FEATURE_UNSET (cpu_features, AVX512_VNNI);
-  CPU_FEATURE_UNSET (cpu_features, AVX512_BITALG);
-  CPU_FEATURE_UNSET (cpu_features, AVX512_VPOPCNTDQ);
-  CPU_FEATURE_UNSET (cpu_features, AVX512_4VNNIW);
-  CPU_FEATURE_UNSET (cpu_features, AVX512_4FMAPS);
-  CPU_FEATURE_UNSET (cpu_features, AVX512_VP2INTERSECT);
-  CPU_FEATURE_UNSET (cpu_features, AMX_BF16);
-  CPU_FEATURE_UNSET (cpu_features, AMX_TILE);
-  CPU_FEATURE_UNSET (cpu_features, AMX_INT8);
-  CPU_FEATURE_UNSET (cpu_features, XOP);
-  CPU_FEATURE_UNSET (cpu_features, FMA4);
-  CPU_FEATURE_UNSET (cpu_features, XSAVEC);
-  CPU_FEATURE_UNSET (cpu_features, XFD);
-  CPU_FEATURE_UNSET (cpu_features, AVX512_BF16);
 
   /* Can we call xgetbv?  */
   if (CPU_FEATURES_CPU_P (cpu_features, OSXSAVE))
@@ -243,8 +191,11 @@ update_usable (struct cpu_features *cpu_features)
 	  CPU_FEATURE_SET_USABLE (cpu_features, AMX_INT8);
 	}
 
-
-      /* XFD is usable only when OSXSAVE is enabled.  */
+      /* These features are usable only when OSXSAVE is enabled.  */
+      CPU_FEATURE_SET (cpu_features, XSAVE);
+      CPU_FEATURE_SET_USABLE (cpu_features, XSAVEOPT);
+      CPU_FEATURE_SET_USABLE (cpu_features, XSAVEC);
+      CPU_FEATURE_SET_USABLE (cpu_features, XGETBV_ECX_1);
       CPU_FEATURE_SET_USABLE (cpu_features, XFD);
 
       /* For _dl_runtime_resolve, set xsave_state_size to xsave area
