Enable thread local storage support on arm64.

Linux use the task.thread.uw.tp_value field to store the
TLS pointer on arm64 platform, and we use a similar way
in gvisor to store it in the arch/State struct.

Signed-off-by: Haibo Xu <haibo.xu@arm.com>
Change-Id: Ie76b5c6d109bc27ccfd594008a96753806db7764

4 files changed, 89 insertions, 0 deletions

diff --git a/pkg/sentry/platform/ptrace/BUILD b/pkg/sentry/platform/ptrace/BUILD
index 95abd321e..30402c2df 100644
--- a/pkg/sentry/platform/ptrace/BUILD
+++ b/pkg/sentry/platform/ptrace/BUILD
@@ -9,6 +9,7 @@ go_library(
         "ptrace.go",
         "ptrace_amd64.go",
         "ptrace_arm64.go",
+        "ptrace_arm64_unsafe.go",
         "ptrace_unsafe.go",
         "stub_amd64.s",
         "stub_arm64.s",
diff --git a/pkg/sentry/platform/ptrace/ptrace_amd64.go b/pkg/sentry/platform/ptrace/ptrace_amd64.go
index db0212538..24fc5dc62 100644
--- a/pkg/sentry/platform/ptrace/ptrace_amd64.go
+++ b/pkg/sentry/platform/ptrace/ptrace_amd64.go
@@ -31,3 +31,17 @@ func fpRegSet(useXsave bool) uintptr {
 func stackPointer(r *syscall.PtraceRegs) uintptr {
 	return uintptr(r.Rsp)
 }
+
+// x86 use the fs_base register to store the TLS pointer which can be
+// get/set in "func (t *thread) get/setRegs(regs *syscall.PtraceRegs)".
+// So both of the get/setTLS() operations are noop here.
+
+// getTLS gets the thread local storage register.
+func (t *thread) getTLS(tls *uint64) error {
+	return nil
+}
+
+// setTLS sets the thread local storage register.
+func (t *thread) setTLS(tls *uint64) error {
+	return nil
+}
diff --git a/pkg/sentry/platform/ptrace/ptrace_arm64_unsafe.go b/pkg/sentry/platform/ptrace/ptrace_arm64_unsafe.go
new file mode 100644
index 000000000..32b8a6be9
--- /dev/null
+++ b/pkg/sentry/platform/ptrace/ptrace_arm64_unsafe.go
@@ -0,0 +1,62 @@
+// 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 ptrace
+
+import (
+	"syscall"
+	"unsafe"
+
+	"gvisor.dev/gvisor/pkg/abi/linux"
+)
+
+// getTLS gets the thread local storage register.
+func (t *thread) getTLS(tls *uint64) error {
+	iovec := syscall.Iovec{
+		Base: (*byte)(unsafe.Pointer(tls)),
+		Len:  uint64(unsafe.Sizeof(*tls)),
+	}
+	_, _, errno := syscall.RawSyscall6(
+		syscall.SYS_PTRACE,
+		syscall.PTRACE_GETREGSET,
+		uintptr(t.tid),
+		linux.NT_ARM_TLS,
+		uintptr(unsafe.Pointer(&iovec)),
+		0, 0)
+	if errno != 0 {
+		return errno
+	}
+	return nil
+}
+
+// setTLS sets the thread local storage register.
+func (t *thread) setTLS(tls *uint64) error {
+	iovec := syscall.Iovec{
+		Base: (*byte)(unsafe.Pointer(tls)),
+		Len:  uint64(unsafe.Sizeof(*tls)),
+	}
+	_, _, errno := syscall.RawSyscall6(
+		syscall.SYS_PTRACE,
+		syscall.PTRACE_SETREGSET,
+		uintptr(t.tid),
+		linux.NT_ARM_TLS,
+		uintptr(unsafe.Pointer(&iovec)),
+		0, 0)
+	if errno != 0 {
+		return errno
+	}
+	return nil
+}
diff --git a/pkg/sentry/platform/ptrace/subprocess.go b/pkg/sentry/platform/ptrace/subprocess.go
index 31b7cec53..a644609ef 100644
--- a/pkg/sentry/platform/ptrace/subprocess.go
+++ b/pkg/sentry/platform/ptrace/subprocess.go
@@ -506,6 +506,9 @@ func (s *subprocess) switchToApp(c *context, ac arch.Context) bool {
 	regs := &ac.StateData().Regs
 	t.resetSysemuRegs(regs)
 
+	// Extract TLS register
+	tls := uint64(ac.TLS())
+
 	// Check for interrupts, and ensure that future interrupts will signal t.
 	if !c.interrupt.Enable(t) {
 		// Pending interrupt; simulate.
@@ -526,6 +529,9 @@ func (s *subprocess) switchToApp(c *context, ac arch.Context) bool {
 	if err := t.setFPRegs(fpState, uint64(fpLen), useXsave); err != nil {
 		panic(fmt.Sprintf("ptrace set fpregs (%+v) failed: %v", fpState, err))
 	}
+	if err := t.setTLS(&tls); err != nil {
+		panic(fmt.Sprintf("ptrace set tls (%+v) failed: %v", tls, err))
+	}
 
 	for {
 		// Start running until the next system call.
@@ -555,6 +561,12 @@ func (s *subprocess) switchToApp(c *context, ac arch.Context) bool {
 		if err := t.getFPRegs(fpState, uint64(fpLen), useXsave); err != nil {
 			panic(fmt.Sprintf("ptrace get fpregs failed: %v", err))
 		}
+		if err := t.getTLS(&tls); err != nil {
+			panic(fmt.Sprintf("ptrace get tls failed: %v", err))
+		}
+		if !ac.SetTLS(uintptr(tls)) {
+			panic(fmt.Sprintf("tls value %v is invalid", tls))
+		}
 
 		// Is it a system call?
 		if sig == (syscallEvent | syscall.SIGTRAP) {