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// Copyright 2018 Google LLC
//
// 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 kvm
import (
"bufio"
"fmt"
"io"
"os"
"regexp"
"strconv"
"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
)
type virtualRegion struct {
region
accessType usermem.AccessType
shared bool
offset uintptr
filename string
}
// mapsLine matches a single line from /proc/PID/maps.
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+(.*)")
// excludeRegion returns true if these regions should be excluded from the
// physical map. Virtual regions need to be excluded if get_user_pages will
// fail on those addresses, preventing KVM from satisfying EPT faults.
//
// This includes the VVAR page because the VVAR page may be mapped as I/O
// memory. And the VDSO page is knocked out because the VVAR page is not even
// recorded in /proc/self/maps on older kernels; knocking out the VDSO page
// prevents code in the VDSO from accessing the VVAR address.
//
// This is called by the physical map functions, not applyVirtualRegions.
func excludeVirtualRegion(r virtualRegion) bool {
return r.filename == "[vvar]" || r.filename == "[vdso]"
}
// applyVirtualRegions parses the process maps file.
//
// Unlike mappedRegions, these are not consistent over time.
func applyVirtualRegions(fn func(vr virtualRegion)) error {
// Open /proc/self/maps.
f, err := os.Open("/proc/self/maps")
if err != nil {
return err
}
defer f.Close()
// Parse all entries.
r := bufio.NewReader(f)
for {
b, err := r.ReadBytes('\n')
if b != nil && len(b) > 0 {
m := mapsLine.FindSubmatch(b)
if m == nil {
// This should not happen: kernel bug?
return fmt.Errorf("badly formed line: %v", string(b))
}
start, err := strconv.ParseUint(string(m[1]), 16, 64)
if err != nil {
return fmt.Errorf("bad start address: %v", string(b))
}
end, err := strconv.ParseUint(string(m[2]), 16, 64)
if err != nil {
return fmt.Errorf("bad end address: %v", string(b))
}
read := m[3][0] == 'r'
write := m[3][1] == 'w'
execute := m[3][2] == 'x'
shared := m[3][3] == 's'
offset, err := strconv.ParseUint(string(m[4]), 16, 64)
if err != nil {
return fmt.Errorf("bad offset: %v", string(b))
}
fn(virtualRegion{
region: region{
virtual: uintptr(start),
length: uintptr(end - start),
},
accessType: usermem.AccessType{
Read: read,
Write: write,
Execute: execute,
},
shared: shared,
offset: uintptr(offset),
filename: string(m[5]),
})
}
if err != nil && err == io.EOF {
break
} else if err != nil {
return err
}
}
return nil
}
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