114 lines
3.2 KiB
Go
114 lines
3.2 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 kvm
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import (
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"bufio"
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"fmt"
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"io"
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"os"
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"regexp"
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"strconv"
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"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
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)
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type virtualRegion struct {
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region
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accessType usermem.AccessType
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shared bool
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offset uintptr
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filename string
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}
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// mapsLine matches a single line from /proc/PID/maps.
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var mapsLine = regexp.MustCompile("([0-9a-f]+)-([0-9a-f]+) ([r-][w-][x-][sp]) ([0-9a-f]+) [0-9a-f]{2}:[0-9a-f]{2,} [0-9]+\\s+(.*)")
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// excludeRegion returns true if these regions should be excluded from the
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// physical map. Virtual regions need to be excluded if get_user_pages will
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// fail on those addresses, preventing KVM from satisfying EPT faults.
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//
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// This includes the VVAR page because the VVAR page may be mapped as I/O
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// memory. And the VDSO page is knocked out because the VVAR page is not even
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// recorded in /proc/self/maps on older kernels; knocking out the VDSO page
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// prevents code in the VDSO from accessing the VVAR address.
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//
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// This is called by the physical map functions, not applyVirtualRegions.
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func excludeVirtualRegion(r virtualRegion) bool {
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return r.filename == "[vvar]" || r.filename == "[vdso]"
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}
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// applyVirtualRegions parses the process maps file.
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//
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// Unlike mappedRegions, these are not consistent over time.
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func applyVirtualRegions(fn func(vr virtualRegion)) error {
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// Open /proc/self/maps.
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f, err := os.Open("/proc/self/maps")
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if err != nil {
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return err
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}
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defer f.Close()
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// Parse all entries.
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r := bufio.NewReader(f)
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for {
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b, err := r.ReadBytes('\n')
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if b != nil && len(b) > 0 {
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m := mapsLine.FindSubmatch(b)
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if m == nil {
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// This should not happen: kernel bug?
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return fmt.Errorf("badly formed line: %v", string(b))
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}
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start, err := strconv.ParseUint(string(m[1]), 16, 64)
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if err != nil {
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return fmt.Errorf("bad start address: %v", string(b))
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}
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end, err := strconv.ParseUint(string(m[2]), 16, 64)
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if err != nil {
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return fmt.Errorf("bad end address: %v", string(b))
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}
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read := m[3][0] == 'r'
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write := m[3][1] == 'w'
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execute := m[3][2] == 'x'
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shared := m[3][3] == 's'
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offset, err := strconv.ParseUint(string(m[4]), 16, 64)
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if err != nil {
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return fmt.Errorf("bad offset: %v", string(b))
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}
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fn(virtualRegion{
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region: region{
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virtual: uintptr(start),
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length: uintptr(end - start),
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},
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accessType: usermem.AccessType{
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Read: read,
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Write: write,
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Execute: execute,
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},
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shared: shared,
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offset: uintptr(offset),
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filename: string(m[5]),
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})
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}
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if err != nil && err == io.EOF {
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break
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} else if err != nil {
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return err
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}
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}
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return nil
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}
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