45 lines
1.5 KiB
Go
45 lines
1.5 KiB
Go
// Copyright 2020 The gVisor Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package vfs2
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import (
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"reflect"
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"runtime"
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"unsafe"
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"gvisor.dev/gvisor/pkg/abi/linux"
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"gvisor.dev/gvisor/pkg/gohacks"
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"gvisor.dev/gvisor/pkg/sentry/kernel"
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"gvisor.dev/gvisor/pkg/usermem"
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)
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const sizeofEpollEvent = int(unsafe.Sizeof(linux.EpollEvent{}))
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func copyOutEvents(t *kernel.Task, addr usermem.Addr, events []linux.EpollEvent) (int, error) {
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if len(events) == 0 {
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return 0, nil
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}
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// Cast events to a byte slice for copying.
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var eventBytes []byte
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eventBytesHdr := (*reflect.SliceHeader)(unsafe.Pointer(&eventBytes))
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eventBytesHdr.Data = uintptr(gohacks.Noescape(unsafe.Pointer(&events[0])))
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eventBytesHdr.Len = len(events) * sizeofEpollEvent
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eventBytesHdr.Cap = len(events) * sizeofEpollEvent
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copiedBytes, err := t.CopyOutBytes(addr, eventBytes)
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runtime.KeepAlive(events)
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copiedEvents := copiedBytes / sizeofEpollEvent // rounded down
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return copiedEvents, err
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}
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