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PiperOrigin-RevId: 194583126
Change-Id: Ica1d8821a90f74e7e745962d71801c598c652463

1 files changed, 97 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..cb38d098a
--- /dev/null
+++ b/pkg/sentry/arch/arch_state_x86.go
@@ -0,0 +1,97 @@
+// Copyright 2018 Google Inc.
+//
+// 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 (
+	"sync"
+	"syscall"
+
+	"gvisor.googlesource.com/gvisor/pkg/log"
+)
+
+// warnOnce is used to warn about truncated state only once.
+var warnOnce sync.Once
+
+// 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 section 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.
+	if len(s.x86FPState) < len(old) {
+		warnOnce.Do(func() {
+			// This will occur on every instance of state, don't
+			// bother warning more than once.
+			log.Infof("dropping %d bytes of floating point state; the application should not depend on this state", len(old)-len(s.x86FPState))
+		})
+	}
+
+	// Copy to the new, aligned location.
+	copy(s.x86FPState, old)
+}
+
+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)
+}