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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
}
// forEach iterates over all mappings in the given range.
//
// Precondition: segFn and gapFn must be non-nil.
func (hm *hostMap) forEach(
r usermem.AddrRange,
segFn func(offset uint64, m hostMapEntry),
gapFn func(offset uint64, length uintptr) (uintptr, bool)) {
seg, gap := hm.set.Find(r.Start)
for {
if seg.Ok() && seg.Start() < r.End {
// A valid segment: pass information.
overlap := seg.Range().Intersect(r)
segOffset := uintptr(overlap.Start - seg.Start())
mapOffset := uint64(overlap.Start - r.Start)
segFn(mapOffset, hostMapEntry{
addr: seg.Value() + segOffset,
length: uintptr(overlap.Length()),
})
seg, gap = seg.NextNonEmpty()
} else if gap.Ok() && gap.Start() < r.End {
// A gap: pass gap information.
overlap := gap.Range().Intersect(r)
mapOffset := uint64(overlap.Start - r.Start)
addr, ok := gapFn(mapOffset, uintptr(overlap.Length()))
if ok {
seg = hm.set.Insert(gap, overlap, addr)
seg, gap = seg.NextNonEmpty()
} else {
seg = gap.NextSegment()
gap = hostMapGapIterator{} // Invalid.
}
} else {
// Terminal.
break
}
}
}
func (hm *hostMap) createMappings(r usermem.AddrRange, at usermem.AccessType, fd int, offset uint64) (ms []hostMapEntry, err error) {
hm.forEach(r, func(mapOffset uint64, m hostMapEntry) {
// Replace any existing mappings.
_, _, errno := syscall.RawSyscall6(
syscall.SYS_MMAP,
m.addr,
m.length,
uintptr(at.Prot()),
syscall.MAP_FIXED|syscall.MAP_SHARED,
uintptr(fd),
uintptr(offset+mapOffset))
if errno != 0 && err == nil {
err = errno
}
}, func(mapOffset uint64, length uintptr) (uintptr, bool) {
// Create a new mapping.
addr, _, errno := syscall.RawSyscall6(
syscall.SYS_MMAP,
0,
length,
uintptr(at.Prot()),
syscall.MAP_SHARED,
uintptr(fd),
uintptr(offset+mapOffset))
if errno != 0 {
err = errno
return 0, false
}
return addr, true
})
if err != nil {
return nil, err
}
// Collect all entries.
//
// We do this after the first iteration because some segments may have
// been merged in the above, and we'll return the simplest form. This
// also provides a basic sanity check in the form of no gaps.
hm.forEach(r, func(_ uint64, m hostMapEntry) {
ms = append(ms, m)
}, func(uint64, uintptr) (uintptr, bool) {
// Should not happen: we just mapped this above.
panic("unexpected gap")
})
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.forEach(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))
}
}, func(uint64, uintptr) (uintptr, bool) {
// Sometimes deleteMapping will be called on a larger range
// than physical mappings are defined. That's okay.
return 0, false
})
// Knock the entire 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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