From f17cfa4d53742923b5c91b149b82a05bcda3ea20 Mon Sep 17 00:00:00 2001
From: Michael Pratt <mpratt@google.com>
Date: Thu, 25 Apr 2019 17:45:56 -0700
Subject: Perform explicit CPUID and FP state compatibility checks on restore

PiperOrigin-RevId: 245341004
Change-Id: Ic4d581039d034a8ae944b43e45e84eb2c3973657
---
 pkg/cpuid/cpuid.go | 34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)

(limited to 'pkg/cpuid')

diff --git a/pkg/cpuid/cpuid.go b/pkg/cpuid/cpuid.go
index 64e2e68f1..61441150e 100644
--- a/pkg/cpuid/cpuid.go
+++ b/pkg/cpuid/cpuid.go
@@ -446,6 +446,20 @@ const (
 	extendedFeatures                                       // Returns some extended feature bits in edx and ecx.
 )
 
+// These are the extended floating point state features. They are used to
+// enumerate floating point features in XCR0, XSTATE_BV, etc.
+const (
+	XSAVEFeatureX87         = 1 << 0
+	XSAVEFeatureSSE         = 1 << 1
+	XSAVEFeatureAVX         = 1 << 2
+	XSAVEFeatureBNDREGS     = 1 << 3
+	XSAVEFeatureBNDCSR      = 1 << 4
+	XSAVEFeatureAVX512op    = 1 << 5
+	XSAVEFeatureAVX512zmm0  = 1 << 6
+	XSAVEFeatureAVX512zmm16 = 1 << 7
+	XSAVEFeaturePKRU        = 1 << 9
+)
+
 var cpuFreqMHz float64
 
 // x86FeaturesFromString includes features from x86FeatureStrings and
@@ -561,6 +575,26 @@ func (fs *FeatureSet) Intel() bool {
 	return fs.VendorID == "GenuineIntel"
 }
 
+// ErrIncompatible is returned by FeatureSet.HostCompatible if fs is not a
+// subset of the host feature set.
+type ErrIncompatible struct {
+	message string
+}
+
+// Error implements error.
+func (e ErrIncompatible) Error() string {
+	return e.message
+}
+
+// CheckHostCompatible returns nil if fs is a subset of the host feature set.
+func (fs *FeatureSet) CheckHostCompatible() error {
+	hfs := HostFeatureSet()
+	if diff := fs.Subtract(hfs); diff != nil {
+		return ErrIncompatible{fmt.Sprintf("CPU feature set %v incompatible with host feature set %v (missing: %v)", fs.FlagsString(false), hfs.FlagsString(false), diff)}
+	}
+	return nil
+}
+
 // Helper to convert 3 regs into 12-byte vendor ID.
 func vendorIDFromRegs(bx, cx, dx uint32) string {
 	bytes := make([]byte, 0, 12)
-- 
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