starnix_modules_erofs/
lib.rs

1// Copyright 2026 The Fuchsia Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5use fidl_fuchsia_erofs::{ErofsMarker, ErofsServeRequest};
6use fidl_fuchsia_io as fio;
7use fuchsia_component::client::connect_to_protocol_sync;
8use starnix_core::fs::fuchsia::RemoteFs;
9use starnix_core::mm::ProtectionFlags;
10use starnix_core::task::CurrentTask;
11use starnix_core::vfs::{CacheMode, FileSystem, FileSystemHandle, FileSystemOptions};
12use starnix_logging::{impossible_error, log_error, log_info};
13use starnix_uapi::errors::Errno;
14use starnix_uapi::mount_flags::FileSystemFlags;
15use starnix_uapi::open_flags::OpenFlags;
16use starnix_uapi::{errno, from_status_like_fdio};
17use std::sync::atomic::Ordering;
18use zx::{MonotonicInstant, VmoChildOptions};
19
20pub fn new_fs(
21    current_task: &CurrentTask,
22    options: FileSystemOptions,
23) -> Result<FileSystemHandle, Errno> {
24    let kernel = current_task.kernel();
25
26    // EROFS is strictly read-only.
27    if !options.flags.load(Ordering::Relaxed).contains(FileSystemFlags::RDONLY) {
28        return Err(errno!(EROFS));
29    }
30
31    let fsoffset = options.params.get_as::<u64>(b"fsoffset")?;
32
33    let source_device = current_task.open_file(options.source.as_ref(), OpenFlags::RDONLY)?;
34    let memory = source_device.get_memory(current_task, None, ProtectionFlags::READ)?;
35    let backing_vmo = memory
36        .as_vmo()
37        .ok_or_else(|| errno!(EINVAL))?
38        .duplicate_handle(zx::Rights::SAME_RIGHTS)
39        .map_err(impossible_error)?;
40
41    let backing_vmo = match fsoffset {
42        None => {
43            log_info!("mounting erofs image source={:?}", options.source);
44            backing_vmo
45        }
46        Some(fsoffset) if fsoffset > 0 => {
47            let page_size = zx::system_get_page_size() as u64;
48            if fsoffset % page_size != 0 {
49                log_error!("fsoffset {} is not page-aligned (page size {})", fsoffset, page_size);
50                return Err(errno!(EINVAL));
51            }
52            let vmo_size = backing_vmo.get_size().map_err(impossible_error)?;
53            let clone_len = vmo_size.checked_sub(fsoffset).ok_or_else(|| {
54                log_error!("fsoffset {} exceeds vmo size {}", fsoffset, vmo_size);
55                errno!(EINVAL)
56            })?;
57            log_info!("mounting erofs image with fsoffset={}, len={}", fsoffset, clone_len);
58            backing_vmo.create_child(VmoChildOptions::SLICE, fsoffset, clone_len).map_err(|e| {
59                log_error!("Failed to create child VMO slice for fsoffset {}: {:?}", fsoffset, e);
60                errno!(EINVAL)
61            })?
62        }
63        Some(_) => {
64            log_info!("mounting erofs image with fsoffset of zero");
65            backing_vmo
66        }
67    };
68
69    let erofs_provider = connect_to_protocol_sync::<ErofsMarker>().map_err(|_| errno!(ENOENT))?;
70
71    let (root_client, root_server) = fidl::endpoints::create_endpoints();
72    erofs_provider
73        .serve(
74            ErofsServeRequest {
75                backing_vmo: Some(backing_vmo),
76                root: Some(root_server),
77                ..Default::default()
78            },
79            MonotonicInstant::INFINITE,
80        )
81        .map_err(|e| {
82            log_error!("FIDL error on Erofs.Serve: {e:?}");
83            errno!(EIO)
84        })?
85        .map_err(|e| {
86            log_error!("Erofs.Serve failed: {e:?}");
87            from_status_like_fdio!(zx::Status::err_from_raw(e))
88        })?;
89
90    let (remotefs, root_node, info, node_id) =
91        RemoteFs::new(root_client.into_channel(), fio::PERM_READABLE, "erofs")?;
92
93    let fs =
94        FileSystem::new(kernel, CacheMode::Cached(kernel.fs_cache_config()), remotefs, options)?;
95
96    fs.create_root_with_info(node_id, root_node, info);
97
98    Ok(fs)
99}
starnix_modules_erofs/lib.rs

starnix_modules_erofs/
lib.rs
