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// Copyright 2019 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 strace
import (
"fmt"
"gvisor.dev/gvisor/pkg/sentry/kernel"
"gvisor.dev/gvisor/pkg/sentry/syscalls/linux"
"gvisor.dev/gvisor/pkg/usermem"
)
func fdsFromSet(t *kernel.Task, set []byte) []int {
var fds []int
// Append n if the n-th bit is 1.
for i, v := range set {
for j := 0; j < 8; j++ {
if (v>>j)&1 == 1 {
fds = append(fds, i*8+j)
}
}
}
return fds
}
func fdSet(t *kernel.Task, nfds int, addr usermem.Addr) string {
if nfds < 0 {
return fmt.Sprintf("%#x (negative nfds)", addr)
}
if addr == 0 {
return "null"
}
// Calculate the size of the fd set (one bit per fd).
nBytes := (nfds + 7) / 8
nBitsInLastPartialByte := nfds % 8
set, err := linux.CopyInFDSet(t, addr, nBytes, nBitsInLastPartialByte)
if err != nil {
return fmt.Sprintf("%#x (error decoding fdset: %s)", addr, err)
}
return fmt.Sprintf("%#x %v", addr, fdsFromSet(t, set))
}
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