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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 vfs2
import (
"gvisor.dev/gvisor/pkg/abi/linux"
"gvisor.dev/gvisor/pkg/sentry/arch"
"gvisor.dev/gvisor/pkg/sentry/fsimpl/tmpfs"
"gvisor.dev/gvisor/pkg/sentry/kernel"
"gvisor.dev/gvisor/pkg/syserror"
)
const (
memfdPrefix = "memfd:"
memfdMaxNameLen = linux.NAME_MAX - len(memfdPrefix)
memfdAllFlags = uint32(linux.MFD_CLOEXEC | linux.MFD_ALLOW_SEALING)
)
// MemfdCreate implements the linux syscall memfd_create(2).
func MemfdCreate(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
addr := args[0].Pointer()
flags := args[1].Uint()
if flags&^memfdAllFlags != 0 {
// Unknown bits in flags.
return 0, nil, syserror.EINVAL
}
allowSeals := flags&linux.MFD_ALLOW_SEALING != 0
cloExec := flags&linux.MFD_CLOEXEC != 0
name, err := t.CopyInString(addr, memfdMaxNameLen)
if err != nil {
return 0, nil, err
}
shmMount := t.Kernel().ShmMount()
file, err := tmpfs.NewMemfd(shmMount, t.Credentials(), allowSeals, memfdPrefix+name)
if err != nil {
return 0, nil, err
}
fd, err := t.NewFDFromVFS2(0, file, kernel.FDFlags{
CloseOnExec: cloExec,
})
if err != nil {
return 0, nil, err
}
return uintptr(fd), nil, nil
}
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