134 lines
3.8 KiB
Go
134 lines
3.8 KiB
Go
// Copyright 2018 The gVisor Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// +build amd64 i386
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package arch
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import (
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"fmt"
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"syscall"
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"gvisor.dev/gvisor/pkg/cpuid"
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"gvisor.dev/gvisor/pkg/sentry/usermem"
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)
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// ErrFloatingPoint indicates a failed restore due to unusable floating point
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// state.
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type ErrFloatingPoint struct {
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// supported is the supported floating point state.
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supported uint64
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// saved is the saved floating point state.
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saved uint64
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}
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// Error returns a sensible description of the restore error.
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func (e ErrFloatingPoint) Error() string {
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return fmt.Sprintf("floating point state contains unsupported features; supported: %#x saved: %#x", e.supported, e.saved)
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}
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// XSTATE_BV does not exist if FXSAVE is used, but FXSAVE implicitly saves x87
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// and SSE state, so this is the equivalent XSTATE_BV value.
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const fxsaveBV uint64 = cpuid.XSAVEFeatureX87 | cpuid.XSAVEFeatureSSE
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// afterLoad is invoked by stateify.
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func (s *State) afterLoad() {
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old := s.x86FPState
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// Recreate the slice. This is done to ensure that it is aligned
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// appropriately in memory, and large enough to accommodate any new
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// state that may be saved by the new CPU. Even if extraneous new state
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// is saved, the state we care about is guaranteed to be a subset of
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// new state. Later optimizations can use less space when using a
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// smaller state component bitmap. Intel SDM Volume 1 Chapter 13 has
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// more info.
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s.x86FPState = newX86FPState()
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// x86FPState always contains all the FP state supported by the host.
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// We may have come from a newer machine that supports additional state
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// which we cannot restore.
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//
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// The x86 FP state areas are backwards compatible, so we can simply
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// truncate the additional floating point state.
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//
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// Applications should not depend on the truncated state because it
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// should relate only to features that were not exposed in the app
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// FeatureSet. However, because we do not *prevent* them from using
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// this state, we must verify here that there is no in-use state
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// (according to XSTATE_BV) which we do not support.
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if len(s.x86FPState) < len(old) {
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// What do we support?
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supportedBV := fxsaveBV
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if fs := cpuid.HostFeatureSet(); fs.UseXsave() {
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supportedBV = fs.ValidXCR0Mask()
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}
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// What was in use?
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savedBV := fxsaveBV
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if len(old) >= xstateBVOffset+8 {
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savedBV = usermem.ByteOrder.Uint64(old[xstateBVOffset:])
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}
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// Supported features must be a superset of saved features.
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if savedBV&^supportedBV != 0 {
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panic(ErrFloatingPoint{supported: supportedBV, saved: savedBV})
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}
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}
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// Copy to the new, aligned location.
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copy(s.x86FPState, old)
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}
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// +stateify savable
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type syscallPtraceRegs struct {
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R15 uint64
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R14 uint64
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R13 uint64
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R12 uint64
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Rbp uint64
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Rbx uint64
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R11 uint64
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R10 uint64
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R9 uint64
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R8 uint64
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Rax uint64
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Rcx uint64
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Rdx uint64
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Rsi uint64
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Rdi uint64
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Orig_rax uint64
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Rip uint64
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Cs uint64
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Eflags uint64
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Rsp uint64
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Ss uint64
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Fs_base uint64
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Gs_base uint64
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Ds uint64
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Es uint64
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Fs uint64
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Gs uint64
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}
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// saveRegs is invoked by stateify.
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func (s *State) saveRegs() syscallPtraceRegs {
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return syscallPtraceRegs(s.Regs)
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}
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// loadRegs is invoked by stateify.
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func (s *State) loadRegs(r syscallPtraceRegs) {
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s.Regs = syscall.PtraceRegs(r)
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}
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