99 lines
2.8 KiB
Go
99 lines
2.8 KiB
Go
// Copyright 2018 Google LLC
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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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package arch
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import (
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"sync"
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"syscall"
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"gvisor.googlesource.com/gvisor/pkg/log"
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)
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// warnOnce is used to warn about truncated state only once.
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var warnOnce sync.Once
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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 section 13 has 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. Applications should
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// not depend on the truncated state because it should relate only to
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// features that were not exposed in the app FeatureSet.
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if len(s.x86FPState) < len(old) {
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warnOnce.Do(func() {
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// This will occur on every instance of state, don't
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// bother warning more than once.
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log.Infof("dropping %d bytes of floating point state; the application should not depend on this state", len(old)-len(s.x86FPState))
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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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