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// 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 kvm
import (
"fmt"
"sync"
"syscall"
"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
)
type hostMap struct {
// mu protects below.
mu sync.RWMutex
// set contains host mappings.
set hostMapSet
}
type hostMapEntry struct {
addr uintptr
length uintptr
}
func (hm *hostMap) forEachEntry(r usermem.AddrRange, fn func(offset uint64, m hostMapEntry)) {
for seg := hm.set.FindSegment(r.Start); seg.Ok() && seg.Start() < r.End; seg = seg.NextSegment() {
length := uintptr(seg.Range().Length())
segOffset := uint64(0) // Adjusted below.
if seg.End() > r.End {
length -= uintptr(seg.End() - r.End)
}
if seg.Start() < r.Start {
length -= uintptr(r.Start - seg.Start())
} else {
segOffset = uint64(seg.Start() - r.Start)
}
fn(segOffset, hostMapEntry{
addr: seg.Value(),
length: length,
})
}
}
func (hm *hostMap) createMappings(r usermem.AddrRange, at usermem.AccessType, fd int, offset uint64) (ms []hostMapEntry, err error) {
// Replace any existing mappings.
hm.forEachEntry(r, func(segOffset uint64, m hostMapEntry) {
_, _, errno := syscall.RawSyscall6(
syscall.SYS_MMAP,
m.addr,
m.length,
uintptr(at.Prot()),
syscall.MAP_FIXED|syscall.MAP_SHARED,
uintptr(fd),
uintptr(offset+segOffset))
if errno != 0 && err == nil {
err = errno
}
})
if err != nil {
return nil, err
}
// Add in necessary new mappings.
for gap := hm.set.FindGap(r.Start); gap.Ok() && gap.Start() < r.End; {
length := uintptr(gap.Range().Length())
gapOffset := uint64(0) // Adjusted below.
if gap.End() > r.End {
length -= uintptr(gap.End() - r.End)
}
if gap.Start() < r.Start {
length -= uintptr(r.Start - gap.Start())
} else {
gapOffset = uint64(gap.Start() - r.Start)
}
// Map the host file memory.
hostAddr, _, errno := syscall.RawSyscall6(
syscall.SYS_MMAP,
0,
length,
uintptr(at.Prot()),
syscall.MAP_SHARED,
uintptr(fd),
uintptr(offset+gapOffset))
if errno != 0 {
return nil, errno
}
// Insert into the host set and move to the next gap.
gap = hm.set.Insert(gap, gap.Range().Intersect(r), hostAddr).NextGap()
}
// Collect all slices.
hm.forEachEntry(r, func(_ uint64, m hostMapEntry) {
ms = append(ms, m)
})
return ms, nil
}
// CreateMappings creates a new set of host mapping entries.
func (hm *hostMap) CreateMappings(r usermem.AddrRange, at usermem.AccessType, fd int, offset uint64) (ms []hostMapEntry, err error) {
hm.mu.Lock()
ms, err = hm.createMappings(r, at, fd, offset)
hm.mu.Unlock()
return
}
func (hm *hostMap) deleteMapping(r usermem.AddrRange) {
// Remove all the existing mappings.
hm.forEachEntry(r, func(_ uint64, m hostMapEntry) {
_, _, errno := syscall.RawSyscall(
syscall.SYS_MUNMAP,
m.addr,
m.length,
0)
if errno != 0 {
// Should never happen.
panic(fmt.Sprintf("unmap error: %v", errno))
}
})
// Knock the range out.
hm.set.RemoveRange(r)
}
// DeleteMapping deletes the given range.
func (hm *hostMap) DeleteMapping(r usermem.AddrRange) {
hm.mu.Lock()
hm.deleteMapping(r)
hm.mu.Unlock()
}
// hostMapSetFunctions is used in the implementation of mapSet.
type hostMapSetFunctions struct{}
func (hostMapSetFunctions) MinKey() usermem.Addr { return 0 }
func (hostMapSetFunctions) MaxKey() usermem.Addr { return ^usermem.Addr(0) }
func (hostMapSetFunctions) ClearValue(val *uintptr) { *val = 0 }
func (hostMapSetFunctions) Merge(r1 usermem.AddrRange, addr1 uintptr, r2 usermem.AddrRange, addr2 uintptr) (uintptr, bool) {
if addr1+uintptr(r1.Length()) != addr2 {
return 0, false
}
// Since the two regions are contiguous in both the key space and the
// value space, we can just store a single segment with the first host
// virtual address; the logic above operates based on the size of the
// segments.
return addr1, true
}
func (hostMapSetFunctions) Split(r usermem.AddrRange, hostAddr uintptr, split usermem.Addr) (uintptr, uintptr) {
return hostAddr, hostAddr + uintptr(split-r.Start)
}
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