1 /*
2 * Copyright (C) 2024 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 use anyhow::anyhow;
18 use memmap2::MmapMut;
19 use std::fs::{self, OpenOptions};
20
21 use aconfig_storage_file::AconfigStorageError::{self, FileReadFail, MapFileFail};
22
23 /// Get the mutable memory mapping of a storage file
24 ///
25 /// # Safety
26 ///
27 /// The memory mapped file may have undefined behavior if there are writes to this
28 /// file not thru this memory mapped file or there are concurrent writes to this
29 /// memory mapped file. Ensure all writes to the underlying file are thru this memory
30 /// mapped file and there are no concurrent writes.
map_file(file_path: &str) -> Result<MmapMut, AconfigStorageError>31 pub(crate) unsafe fn map_file(file_path: &str) -> Result<MmapMut, AconfigStorageError> {
32 // make sure file has read write permission
33 let perms = fs::metadata(file_path).unwrap().permissions();
34 if perms.readonly() {
35 return Err(MapFileFail(anyhow!("fail to map non read write storage file {}", file_path)));
36 }
37
38 let file =
39 OpenOptions::new().read(true).write(true).open(file_path).map_err(|errmsg| {
40 FileReadFail(anyhow!("Failed to open file {}: {}", file_path, errmsg))
41 })?;
42
43 unsafe {
44 let mapped_file = MmapMut::map_mut(&file).map_err(|errmsg| {
45 MapFileFail(anyhow!("fail to map storage file {}: {}", file_path, errmsg))
46 })?;
47 Ok(mapped_file)
48 }
49 }
50
51 #[cfg(test)]
52 mod tests {
53 use super::*;
54 use crate::test_utils::copy_to_temp_file;
55 use std::io::Read;
56
57 #[test]
test_mapped_file_contents()58 fn test_mapped_file_contents() {
59 let mut rw_val_file = copy_to_temp_file("./tests/flag.val", false).unwrap();
60 let mut rw_info_file = copy_to_temp_file("./tests/flag.info", false).unwrap();
61 let flag_val = rw_val_file.path().display().to_string();
62 let flag_info = rw_info_file.path().display().to_string();
63
64 let mut content = Vec::new();
65 rw_val_file.read_to_end(&mut content).unwrap();
66
67 // SAFETY:
68 // The safety here is guaranteed here as no writes happens to this temp file
69 unsafe {
70 let mmaped_file = map_file(&flag_val).unwrap();
71 assert_eq!(mmaped_file[..], content[..]);
72 }
73
74 let mut content = Vec::new();
75 rw_info_file.read_to_end(&mut content).unwrap();
76
77 // SAFETY:
78 // The safety here is guaranteed here as no writes happens to this temp file
79 unsafe {
80 let mmaped_file = map_file(&flag_info).unwrap();
81 assert_eq!(mmaped_file[..], content[..]);
82 }
83 }
84
85 #[test]
test_mapped_read_only_file()86 fn test_mapped_read_only_file() {
87 let ro_val_file = copy_to_temp_file("./tests/flag.val", true).unwrap();
88 let flag_val = ro_val_file.path().display().to_string();
89
90 // SAFETY:
91 // The safety here is guaranteed here as no writes happens to this temp file
92 unsafe {
93 let error = map_file(&flag_val).unwrap_err();
94 assert_eq!(
95 format!("{:?}", error),
96 format!("MapFileFail(fail to map non read write storage file {})", flag_val)
97 );
98 }
99 }
100 }
101