67 lines
2.2 KiB
Go
67 lines
2.2 KiB
Go
// Copyright 2019 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 gofer
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import (
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"syscall"
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"unsafe"
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"gvisor.dev/gvisor/pkg/safemem"
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)
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// Preconditions: !dsts.IsEmpty().
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func hostPreadv(fd int32, dsts safemem.BlockSeq, off int64) (uint64, error) {
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// No buffering is necessary regardless of safecopy; host syscalls will
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// return EFAULT if appropriate, instead of raising SIGBUS.
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if dsts.NumBlocks() == 1 {
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// Use pread() instead of preadv() to avoid iovec allocation and
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// copying.
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dst := dsts.Head()
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n, _, e := syscall.Syscall6(syscall.SYS_PREAD64, uintptr(fd), dst.Addr(), uintptr(dst.Len()), uintptr(off), 0, 0)
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if e != 0 {
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return 0, e
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}
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return uint64(n), nil
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}
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iovs := safemem.IovecsFromBlockSeq(dsts)
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n, _, e := syscall.Syscall6(syscall.SYS_PREADV, uintptr(fd), uintptr((unsafe.Pointer)(&iovs[0])), uintptr(len(iovs)), uintptr(off), 0, 0)
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if e != 0 {
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return 0, e
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}
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return uint64(n), nil
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}
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// Preconditions: !srcs.IsEmpty().
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func hostPwritev(fd int32, srcs safemem.BlockSeq, off int64) (uint64, error) {
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// No buffering is necessary regardless of safecopy; host syscalls will
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// return EFAULT if appropriate, instead of raising SIGBUS.
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if srcs.NumBlocks() == 1 {
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// Use pwrite() instead of pwritev() to avoid iovec allocation and
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// copying.
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src := srcs.Head()
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n, _, e := syscall.Syscall6(syscall.SYS_PWRITE64, uintptr(fd), src.Addr(), uintptr(src.Len()), uintptr(off), 0, 0)
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if e != 0 {
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return 0, e
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}
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return uint64(n), nil
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}
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iovs := safemem.IovecsFromBlockSeq(srcs)
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n, _, e := syscall.Syscall6(syscall.SYS_PWRITEV, uintptr(fd), uintptr((unsafe.Pointer)(&iovs[0])), uintptr(len(iovs)), uintptr(off), 0, 0)
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if e != 0 {
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return 0, e
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}
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return uint64(n), nil
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}
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