Move ring0 package.

This allows the package to serve as a general purpose ring0 support package, as
opposed to being bound to specific sentry platforms.

Updates #5039

PiperOrigin-RevId: 355220044

1 files changed, 119 insertions, 0 deletions

diff --git a/pkg/ring0/lib_amd64.go b/pkg/ring0/lib_amd64.go
new file mode 100644
index 000000000..0ec5c3bc5
--- /dev/null
+++ b/pkg/ring0/lib_amd64.go
@@ -0,0 +1,119 @@
+// Copyright 2018 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// +build amd64
+
+package ring0
+
+import (
+	"gvisor.dev/gvisor/pkg/cpuid"
+)
+
+// LoadFloatingPoint loads floating point state by the most efficient mechanism
+// available (set by Init).
+var LoadFloatingPoint func(*byte)
+
+// SaveFloatingPoint saves floating point state by the most efficient mechanism
+// available (set by Init).
+var SaveFloatingPoint func(*byte)
+
+// fxrstor uses fxrstor64 to load floating point state.
+func fxrstor(*byte)
+
+// xrstor uses xrstor to load floating point state.
+func xrstor(*byte)
+
+// fxsave uses fxsave64 to save floating point state.
+func fxsave(*byte)
+
+// xsave uses xsave to save floating point state.
+func xsave(*byte)
+
+// xsaveopt uses xsaveopt to save floating point state.
+func xsaveopt(*byte)
+
+// WriteFS sets the GS address (set by init).
+var WriteFS func(addr uintptr)
+
+// wrfsbase writes to the GS base address.
+func wrfsbase(addr uintptr)
+
+// wrfsmsr writes to the GS_BASE MSR.
+func wrfsmsr(addr uintptr)
+
+// WriteGS sets the GS address (set by init).
+var WriteGS func(addr uintptr)
+
+// wrgsbase writes to the GS base address.
+func wrgsbase(addr uintptr)
+
+// wrgsmsr writes to the GS_BASE MSR.
+func wrgsmsr(addr uintptr)
+
+// readCR2 reads the current CR2 value.
+func readCR2() uintptr
+
+// fninit initializes the floating point unit.
+func fninit()
+
+// xsetbv writes to an extended control register.
+func xsetbv(reg, value uintptr)
+
+// xgetbv reads an extended control register.
+func xgetbv(reg uintptr) uintptr
+
+// wrmsr reads to the given MSR.
+func wrmsr(reg, value uintptr)
+
+// rdmsr reads the given MSR.
+func rdmsr(reg uintptr) uintptr
+
+// Mostly-constants set by Init.
+var (
+	hasSMEP       bool
+	hasPCID       bool
+	hasXSAVEOPT   bool
+	hasXSAVE      bool
+	hasFSGSBASE   bool
+	validXCR0Mask uintptr
+)
+
+// Init sets function pointers based on architectural features.
+//
+// This must be called prior to using ring0.
+func Init(featureSet *cpuid.FeatureSet) {
+	hasSMEP = featureSet.HasFeature(cpuid.X86FeatureSMEP)
+	hasPCID = featureSet.HasFeature(cpuid.X86FeaturePCID)
+	hasXSAVEOPT = featureSet.UseXsaveopt()
+	hasXSAVE = featureSet.UseXsave()
+	hasFSGSBASE = featureSet.HasFeature(cpuid.X86FeatureFSGSBase)
+	validXCR0Mask = uintptr(featureSet.ValidXCR0Mask())
+	if hasXSAVEOPT {
+		SaveFloatingPoint = xsaveopt
+		LoadFloatingPoint = xrstor
+	} else if hasXSAVE {
+		SaveFloatingPoint = xsave
+		LoadFloatingPoint = xrstor
+	} else {
+		SaveFloatingPoint = fxsave
+		LoadFloatingPoint = fxrstor
+	}
+	if hasFSGSBASE {
+		WriteFS = wrfsbase
+		WriteGS = wrgsbase
+	} else {
+		WriteFS = wrfsmsr
+		WriteGS = wrgsmsr
+	}
+}