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// Copyright 2020 The gVisor Authors.
//
// 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 host
import (
"gvisor.dev/gvisor/pkg/context"
"gvisor.dev/gvisor/pkg/safemem"
"gvisor.dev/gvisor/pkg/sentry/fs/fsutil"
"gvisor.dev/gvisor/pkg/sentry/memmap"
"gvisor.dev/gvisor/pkg/sync"
"gvisor.dev/gvisor/pkg/usermem"
)
// inodePlatformFile implements memmap.File. It exists solely because inode
// cannot implement both kernfs.Inode.IncRef and memmap.File.IncRef.
//
// inodePlatformFile should only be used if inode.canMap is true.
type inodePlatformFile struct {
*inode
// fdRefsMu protects fdRefs.
fdRefsMu sync.Mutex
// fdRefs counts references on memmap.File offsets. It is used solely for
// memory accounting.
fdRefs fsutil.FrameRefSet
// fileMapper caches mappings of the host file represented by this inode.
fileMapper fsutil.HostFileMapper
// fileMapperInitOnce is used to lazily initialize fileMapper.
fileMapperInitOnce sync.Once
}
// IncRef implements memmap.File.IncRef.
//
// Precondition: i.inode.canMap must be true.
func (i *inodePlatformFile) IncRef(fr memmap.FileRange) {
i.fdRefsMu.Lock()
i.fdRefs.IncRefAndAccount(fr)
i.fdRefsMu.Unlock()
}
// DecRef implements memmap.File.DecRef.
//
// Precondition: i.inode.canMap must be true.
func (i *inodePlatformFile) DecRef(fr memmap.FileRange) {
i.fdRefsMu.Lock()
i.fdRefs.DecRefAndAccount(fr)
i.fdRefsMu.Unlock()
}
// MapInternal implements memmap.File.MapInternal.
//
// Precondition: i.inode.canMap must be true.
func (i *inodePlatformFile) MapInternal(fr memmap.FileRange, at usermem.AccessType) (safemem.BlockSeq, error) {
return i.fileMapper.MapInternal(fr, i.hostFD, at.Write)
}
// FD implements memmap.File.FD.
func (i *inodePlatformFile) FD() int {
return i.hostFD
}
// AddMapping implements memmap.Mappable.AddMapping.
//
// Precondition: i.inode.canMap must be true.
func (i *inode) AddMapping(ctx context.Context, ms memmap.MappingSpace, ar usermem.AddrRange, offset uint64, writable bool) error {
i.mapsMu.Lock()
mapped := i.mappings.AddMapping(ms, ar, offset, writable)
for _, r := range mapped {
i.pf.fileMapper.IncRefOn(r)
}
i.mapsMu.Unlock()
return nil
}
// RemoveMapping implements memmap.Mappable.RemoveMapping.
//
// Precondition: i.inode.canMap must be true.
func (i *inode) RemoveMapping(ctx context.Context, ms memmap.MappingSpace, ar usermem.AddrRange, offset uint64, writable bool) {
i.mapsMu.Lock()
unmapped := i.mappings.RemoveMapping(ms, ar, offset, writable)
for _, r := range unmapped {
i.pf.fileMapper.DecRefOn(r)
}
i.mapsMu.Unlock()
}
// CopyMapping implements memmap.Mappable.CopyMapping.
//
// Precondition: i.inode.canMap must be true.
func (i *inode) CopyMapping(ctx context.Context, ms memmap.MappingSpace, srcAR, dstAR usermem.AddrRange, offset uint64, writable bool) error {
return i.AddMapping(ctx, ms, dstAR, offset, writable)
}
// Translate implements memmap.Mappable.Translate.
//
// Precondition: i.inode.canMap must be true.
func (i *inode) Translate(ctx context.Context, required, optional memmap.MappableRange, at usermem.AccessType) ([]memmap.Translation, error) {
mr := optional
return []memmap.Translation{
{
Source: mr,
File: &i.pf,
Offset: mr.Start,
Perms: usermem.AnyAccess,
},
}, nil
}
// InvalidateUnsavable implements memmap.Mappable.InvalidateUnsavable.
//
// Precondition: i.inode.canMap must be true.
func (i *inode) InvalidateUnsavable(ctx context.Context) error {
// We expect the same host fd across save/restore, so all translations
// should be valid.
return nil
}
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