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// Copyright 2018 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 mm
import (
"gvisor.dev/gvisor/pkg/context"
"gvisor.dev/gvisor/pkg/errors/linuxerr"
"gvisor.dev/gvisor/pkg/hostarch"
"gvisor.dev/gvisor/pkg/sentry/kernel/shm"
"gvisor.dev/gvisor/pkg/sentry/memmap"
)
// DetachShm unmaps a sysv shared memory segment.
func (mm *MemoryManager) DetachShm(ctx context.Context, addr hostarch.Addr) error {
if addr != addr.RoundDown() {
// "... shmaddr is not aligned on a page boundary." - man shmdt(2)
return linuxerr.EINVAL
}
var detached *shm.Shm
var vgap vmaGapIterator
var droppedIDs []memmap.MappingIdentity
// This must run after mm.mappingMu.Unlock().
defer func() {
for _, id := range droppedIDs {
id.DecRef(ctx)
}
}()
mm.mappingMu.Lock()
defer mm.mappingMu.Unlock()
// Find and remove the first vma containing an address >= addr that maps a
// segment originally attached at addr.
vseg := mm.vmas.LowerBoundSegment(addr)
for vseg.Ok() {
vma := vseg.ValuePtr()
if shm, ok := vma.mappable.(*shm.Shm); ok && vseg.Start() >= addr && uint64(vseg.Start()-addr) == vma.off {
detached = shm
vgap, droppedIDs = mm.unmapLocked(ctx, vseg.Range(), droppedIDs)
vseg = vgap.NextSegment()
break
} else {
vseg = vseg.NextSegment()
}
}
if detached == nil {
// There is no shared memory segment attached at addr.
return linuxerr.EINVAL
}
// Remove all vmas that could have been created by the same attach.
end := addr + hostarch.Addr(detached.EffectiveSize())
for vseg.Ok() && vseg.End() <= end {
vma := vseg.ValuePtr()
if vma.mappable == detached && uint64(vseg.Start()-addr) == vma.off {
vgap, droppedIDs = mm.unmapLocked(ctx, vseg.Range(), droppedIDs)
vseg = vgap.NextSegment()
} else {
vseg = vseg.NextSegment()
}
}
return nil
}
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