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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/errors/linuxerr"
"gvisor.dev/gvisor/pkg/hostarch"
"gvisor.dev/gvisor/pkg/sentry/arch"
"gvisor.dev/gvisor/pkg/sentry/fsimpl/tmpfs"
"gvisor.dev/gvisor/pkg/sentry/kernel"
"gvisor.dev/gvisor/pkg/sentry/memmap"
"gvisor.dev/gvisor/pkg/syserror"
)
// Mmap implements Linux syscall mmap(2).
func Mmap(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
prot := args[2].Int()
flags := args[3].Int()
fd := args[4].Int()
fixed := flags&linux.MAP_FIXED != 0
private := flags&linux.MAP_PRIVATE != 0
shared := flags&linux.MAP_SHARED != 0
anon := flags&linux.MAP_ANONYMOUS != 0
map32bit := flags&linux.MAP_32BIT != 0
// Require exactly one of MAP_PRIVATE and MAP_SHARED.
if private == shared {
return 0, nil, linuxerr.EINVAL
}
opts := memmap.MMapOpts{
Length: args[1].Uint64(),
Offset: args[5].Uint64(),
Addr: args[0].Pointer(),
Fixed: fixed,
Unmap: fixed,
Map32Bit: map32bit,
Private: private,
Perms: hostarch.AccessType{
Read: linux.PROT_READ&prot != 0,
Write: linux.PROT_WRITE&prot != 0,
Execute: linux.PROT_EXEC&prot != 0,
},
MaxPerms: hostarch.AnyAccess,
GrowsDown: linux.MAP_GROWSDOWN&flags != 0,
Precommit: linux.MAP_POPULATE&flags != 0,
}
if linux.MAP_LOCKED&flags != 0 {
opts.MLockMode = memmap.MLockEager
}
defer func() {
if opts.MappingIdentity != nil {
opts.MappingIdentity.DecRef(t)
}
}()
if !anon {
// Convert the passed FD to a file reference.
file := t.GetFileVFS2(fd)
if file == nil {
return 0, nil, syserror.EBADF
}
defer file.DecRef(t)
// mmap unconditionally requires that the FD is readable.
if !file.IsReadable() {
return 0, nil, syserror.EACCES
}
// MAP_SHARED requires that the FD be writable for PROT_WRITE.
if shared && !file.IsWritable() {
opts.MaxPerms.Write = false
}
if err := file.ConfigureMMap(t, &opts); err != nil {
return 0, nil, err
}
} else if shared {
// Back shared anonymous mappings with an anonymous tmpfs file.
opts.Offset = 0
file, err := tmpfs.NewZeroFile(t, t.Credentials(), t.Kernel().ShmMount(), opts.Length)
if err != nil {
return 0, nil, err
}
defer file.DecRef(t)
if err := file.ConfigureMMap(t, &opts); err != nil {
return 0, nil, err
}
}
rv, err := t.MemoryManager().MMap(t, opts)
return uintptr(rv), nil, err
}
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