1 files changed, 131 insertions, 0 deletions
diff --git a/pkg/sentry/arch/arch_state_x86.go b/pkg/sentry/arch/arch_state_x86.go
new file mode 100644
index 000000000..bb52d8db0
--- /dev/null
+++ b/pkg/sentry/arch/arch_state_x86.go
@@ -0,0 +1,131 @@
+// 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.
+
+package arch
+
+import (
+	"fmt"
+	"syscall"
+
+	"gvisor.googlesource.com/gvisor/pkg/cpuid"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
+)
+
+// ErrFloatingPoint indicates a failed restore due to unusable floating point
+// state.
+type ErrFloatingPoint struct {
+	// supported is the supported floating point state.
+	supported uint64
+
+	// saved is the saved floating point state.
+	saved uint64
+}
+
+// Error returns a sensible description of the restore error.
+func (e ErrFloatingPoint) Error() string {
+	return fmt.Sprintf("floating point state contains unsupported features; supported: %#x saved: %#x", e.supported, e.saved)
+}
+
+// XSTATE_BV does not exist if FXSAVE is used, but FXSAVE implicitly saves x87
+// and SSE state, so this is the equivalent XSTATE_BV value.
+const fxsaveBV uint64 = cpuid.XSAVEFeatureX87 | cpuid.XSAVEFeatureSSE
+
+// afterLoad is invoked by stateify.
+func (s *State) afterLoad() {
+	old := s.x86FPState
+
+	// Recreate the slice. This is done to ensure that it is aligned
+	// appropriately in memory, and large enough to accommodate any new
+	// state that may be saved by the new CPU. Even if extraneous new state
+	// is saved, the state we care about is guaranteed to be a subset of
+	// new state. Later optimizations can use less space when using a
+	// smaller state component bitmap. Intel SDM Volume 1 Chapter 13 has
+	// more info.
+	s.x86FPState = newX86FPState()
+
+	// x86FPState always contains all the FP state supported by the host.
+	// We may have come from a newer machine that supports additional state
+	// which we cannot restore.
+	//
+	// The x86 FP state areas are backwards compatible, so we can simply
+	// truncate the additional floating point state.
+	//
+	// Applications should not depend on the truncated state because it
+	// should relate only to features that were not exposed in the app
+	// FeatureSet. However, because we do not *prevent* them from using
+	// this state, we must verify here that there is no in-use state
+	// (according to XSTATE_BV) which we do not support.
+	if len(s.x86FPState) < len(old) {
+		// What do we support?
+		supportedBV := fxsaveBV
+		if fs := cpuid.HostFeatureSet(); fs.UseXsave() {
+			supportedBV = fs.ValidXCR0Mask()
+		}
+
+		// What was in use?
+		savedBV := fxsaveBV
+		if len(old) >= xstateBVOffset+8 {
+			savedBV = usermem.ByteOrder.Uint64(old[xstateBVOffset:])
+		}
+
+		// Supported features must be a superset of saved features.
+		if savedBV&^supportedBV != 0 {
+			panic(ErrFloatingPoint{supported: supportedBV, saved: savedBV})
+		}
+	}
+
+	// Copy to the new, aligned location.
+	copy(s.x86FPState, old)
+}
+
+// +stateify savable
+type syscallPtraceRegs struct {
+	R15      uint64
+	R14      uint64
+	R13      uint64
+	R12      uint64
+	Rbp      uint64
+	Rbx      uint64
+	R11      uint64
+	R10      uint64
+	R9       uint64
+	R8       uint64
+	Rax      uint64
+	Rcx      uint64
+	Rdx      uint64
+	Rsi      uint64
+	Rdi      uint64
+	Orig_rax uint64
+	Rip      uint64
+	Cs       uint64
+	Eflags   uint64
+	Rsp      uint64
+	Ss       uint64
+	Fs_base  uint64
+	Gs_base  uint64
+	Ds       uint64
+	Es       uint64
+	Fs       uint64
+	Gs       uint64
+}
+
+// saveRegs is invoked by stateify.
+func (s *State) saveRegs() syscallPtraceRegs {
+	return syscallPtraceRegs(s.Regs)
+}
+
+// loadRegs is invoked by stateify.
+func (s *State) loadRegs(r syscallPtraceRegs) {
+	s.Regs = syscall.PtraceRegs(r)
+}