arm64 kvm: add a test case for kernel-tls checking

Signed-off-by: Bin Lu <bin.lu@arm.com>

pkg/sentry/platform/kvm/BUILD

@@ -63,6 +63,7 @@ go_test(
     name = "kvm_test",
     srcs = [
         "kvm_amd64_test.go",
+        "kvm_arm64_test.go",
         "kvm_test.go",
         "virtual_map_test.go",
     ],

pkg/sentry/platform/kvm/kvm_arm64_test.go

@@ -0,0 +1,32 @@
+// Copyright 2020 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 arm64
+
+package kvm
+
+import (
+	"testing"
+
+	"gvisor.dev/gvisor/pkg/sentry/platform/kvm/testutil"
+)
+
+func TestKernelTLS(t *testing.T) {
+        bluepillTest(t, func(c *vCPU) {
+                if !testutil.TLSWorks() {
+                        t.Errorf("tls does not work, and it should!")
+                }
+        })
+}
+

pkg/sentry/platform/kvm/testutil/testutil_arm64.go

@@ -23,6 +23,11 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 )
 
+// TLSWorks is a tls test.
+//
+// It returns true or false.
+func TLSWorks() bool
+
 // SetTestTarget sets the rip appropriately.
 func SetTestTarget(regs *arch.Registers, fn func()) {
 	regs.Pc = uint64(reflect.ValueOf(fn).Pointer())

pkg/sentry/platform/kvm/testutil/testutil_arm64.s

@@ -50,6 +50,22 @@ TEXT ·SpinLoop(SB),NOSPLIT,$0
 start:
 	B start
 
+TEXT ·TLSWorks(SB),NOSPLIT,$0-8
+        NO_LOCAL_POINTERS
+        MOVD $0x6789, R5
+        MSR R5, TPIDR_EL0
+        MOVD $SYS_GETPID, R8 // getpid
+        SVC
+        MRS TPIDR_EL0, R6
+        CMP R5, R6
+        BNE isNaN
+        MOVD $1, R0
+        MOVD R0, ret+0(FP)
+        RET
+isNaN:
+        MOVD $0, ret+0(FP)
+        RET
+
 TEXT ·FloatingPointWorks(SB),NOSPLIT,$0-8
 	NO_LOCAL_POINTERS
 	// gc will touch fpsimd, so we should test it.