add mount utility

Cargo.toml

@@ -40,6 +40,7 @@ feat_common_core = [
   "lsmem",
   "mcookie",
   "mesg",
+  "mount",
   "mountpoint",
   "nologin",
   "renice",
@@ -108,6 +109,7 @@ lslocks = { optional = true, version = "0.0.1", package = "uu_lslocks", path = "
 lsmem = { optional = true, version = "0.0.1", package = "uu_lsmem", path = "src/uu/lsmem" }
 mcookie = { optional = true, version = "0.0.1", package = "uu_mcookie", path = "src/uu/mcookie" }
 mesg = { optional = true, version = "0.0.1", package = "uu_mesg", path = "src/uu/mesg" }
+mount = { optional = true, version = "0.0.1", package = "uu_mount", path = "src/uu/mount" }
 mountpoint = { optional = true, version = "0.0.1", package = "uu_mountpoint", path = "src/uu/mountpoint" }
 nologin = { optional = true, version = "0.0.1", package = "uu_nologin", path = "src/uu/nologin" }
 renice = { optional = true, version = "0.0.1", package = "uu_renice", path = "src/uu/renice" }
@@ -121,6 +123,7 @@ ctor = "0.6.0"
 # dmesg test require fixed-boot-time feature turned on.
 dmesg = { version = "0.0.1", package = "uu_dmesg", path = "src/uu/dmesg", features = ["fixed-boot-time"] }
 libc = { workspace = true }
+mount = { version = "0.0.1", package = "uu_mount", path = "src/uu/mount" }
 pretty_assertions = "1"
 rand = { workspace = true }
 regex = { workspace = true }

src/uu/mount/Cargo.toml

@@ -0,0 +1,17 @@
+[package]
+name = "uu_mount"
+version = "0.0.1"
+edition = "2021"
+
+[lib]
+path = "src/mount.rs"
+
+[[bin]]
+name = "mount"
+path = "src/main.rs"
+
+[dependencies]
+clap = { workspace = true }
+libc = { workspace = true }
+thiserror = { workspace = true }
+uucore = { workspace = true }

src/uu/mount/mount.md

@@ -0,0 +1,109 @@
+# mount
+
+```
+mount [options]
+mount [options] <source> <directory>
+mount [options] <source> | <directory>
+mount [options] --source <source> [--target <directory>]
+mount [options] [--source <source>] --target <directory>
+mount [options] --make-{shared,slave,private,unbindable} <mountpoint>
+mount [options] --make-{rshared,rslave,rprivate,runbindable} <mountpoint>
+```
+
+Mount a filesystem, or show all currently mounted filesystems.
+
+When called without arguments, or with `-t` but no source and target, mount
+prints all currently mounted filesystems (read from `/proc/mounts` on Linux).
+The `-t` option filters the listing to entries of the given type. `-l` requests
+labels in listing output when they can be discovered from `/dev/disk/by-label`.
+
+When called with a source device and a target directory, mount attaches the
+filesystem found on the source to the target directory.
+
+When called with a single positional argument, mount resolves that argument via
+`/etc/fstab`. The argument may be either a source specifier or a mount point.
+`--source` and `--target` can be used to disambiguate that lookup.
+
+When called with `--make-*`, mount applies mount-propagation changes to the
+specified mountpoint. If a normal mount is also requested in the same command,
+the propagation changes are applied after the mount succeeds.
+
+## Supported contract
+
+This implementation currently targets **Linux** and is intended to provide a
+strong baseline `mount` with the core operational semantics in place:
+
+- no-argument listing from `/proc/mounts`
+- direct mounts plus `--bind`, `--rbind`, and `--move`
+- `--all` with already-mounted skipping, `-t` filtering, `-O` filtering, and
+  optional `--fork`
+- `/etc/fstab`-driven single-argument resolution, including alternate files via
+  `-T`
+- label/UUID/PARTLABEL/PARTUUID resolution
+- merged `fstab` + CLI `-o` options for fstab-derived mounts
+- optional mountpoint creation via `-m`
+- propagation changes via `--make-*`
+
+This command is **not yet a full upstream-compatible replacement** for every
+advanced `mount(8)` feature. The supported behavior is intentionally explicit so
+reviewers can evaluate the current contract clearly.
+
+## Options
+
+- `-a`, `--all` — mount all filesystems listed in `/etc/fstab` (respects `noauto`
+  and `-t` / `-O` filters)
+- `-B`, `--bind` — bind-mount a subtree at another location (`MS_BIND`)
+- `-R`, `--rbind` — recursively bind-mount a subtree (`MS_BIND | MS_REC`)
+- `-M`, `--move` — atomically move a mounted subtree to a new location
+  (`MS_MOVE`)
+- `--make-shared` — mark a subtree as shared
+- `--make-slave` — mark a subtree as slave
+- `--make-private` — mark a subtree as private
+- `--make-unbindable` — mark a subtree as unbindable
+- `--make-rshared` — recursively mark a whole subtree as shared
+- `--make-rslave` — recursively mark a whole subtree as slave
+- `--make-rprivate` — recursively mark a whole subtree as private
+- `--make-runbindable` — recursively mark a whole subtree as unbindable
+- `-f`, `--fake` — dry run; parse arguments and resolve devices but skip the
+  actual `mount(2)` syscall
+- `-F`, `--fork` — with `--all`, mount matching filesystems in separate worker
+  processes
+- `-T`, `--fstab PATH` — use an alternate fstab file instead of `/etc/fstab`
+- `-l`, `--show-labels` — show filesystem labels in listing output when
+  available
+- `-m`, `--mkdir` — create the target mountpoint if it does not already exist
+- `-n`, `--no-mtab` — do not write an entry to `/etc/mtab`
+- `-o`, `--options LIST` — comma-separated list of mount options (e.g.
+  `ro,noatime,uid=1000`); for `/etc/fstab`-resolved mounts, CLI options are
+  appended after `fstab` options so later values win
+- `-O`, `--test-opts LIST` — with `--all`, limit mounts to fstab entries whose
+  option field matches `LIST`
+- `-r`, `--read-only` — mount read-only (same as `-o ro`)
+- `-w`, `--read-write` — mount read-write, overriding a `ro` option from fstab
+- `-t`, `--types LIST` — filesystem type filter; prefix a type with `no` to
+  exclude it (e.g. `-t noext4`)
+- `-v`, `--verbose` — print a diagnostic line for each mount operation
+- `-L`, `--label LABEL` — mount the device with the given filesystem label
+- `-U`, `--uuid UUID` — mount the device with the given filesystem UUID
+- `--partlabel LABEL` — mount the partition with the given partition label
+  (`PARTLABEL=`)
+- `--partuuid UUID` — mount the partition with the given partition UUID
+  (`PARTUUID=`)
+- `--source SOURCE` — explicitly specify the source side of the mount or the
+  single-argument fstab lookup key
+- `--target DIRECTORY` — explicitly specify the target side of the mount or the
+  single-argument fstab lookup key
+
+## Notes
+
+- `--make-*` propagation operations are not combined with `--all`.
+- Propagation changes do not read `/etc/fstab`; provide the target mountpoint
+  explicitly when using them directly.
+
+## Deferred features
+
+Notable items that remain outside the current supported contract include:
+
+- alternate `--options-mode` handling beyond the current append-style merge
+- helper-specific behaviors outside this in-process Linux implementation
+- additional advanced `mount(8)` compatibility options not yet implemented

src/uu/mount/src/errors.rs

@@ -0,0 +1,66 @@
+// This file is part of the uutils util-linux package.
+//
+// For the full copyright and license information, please view the LICENSE
+// file that was distributed with this source code.
+
+use thiserror::Error;
+use uucore::error::UError;
+
+pub const EXIT_MOUNT_FAILED: i32 = 32;
+
+#[derive(Error, Debug)]
+pub enum MountError {
+    #[error("cannot open /proc/mounts: {0}")]
+    ProcMounts(std::io::Error),
+
+    #[error("cannot read {0}: {1}")]
+    FstabRead(String, std::io::Error),
+
+    #[error("I/O error: {0}")]
+    Fstab(#[from] std::io::Error),
+
+    #[error("cannot find device with label {0:?}")]
+    LabelNotFound(String),
+
+    #[error("cannot find device with UUID {0:?}")]
+    UuidNotFound(String),
+
+    #[error("cannot find mount entry for {0:?} in fstab")]
+    FstabEntryNotFound(String),
+
+    #[error("no mount point specified and none found in fstab for {0}")]
+    NoMountPoint(String),
+
+    #[error("cannot create mount point {0}: {1}")]
+    CreateMountPoint(String, std::io::Error),
+
+    #[error("cannot fork mount worker: {0}")]
+    Fork(std::io::Error),
+
+    #[error("cannot wait for mount worker: {0}")]
+    Wait(std::io::Error),
+
+    #[error("invalid source path: {0}")]
+    InvalidSource(std::ffi::NulError),
+
+    #[error("invalid target path: {0}")]
+    InvalidTarget(std::ffi::NulError),
+
+    #[error("invalid filesystem type: {0}")]
+    InvalidFSType(std::ffi::NulError),
+
+    #[error("invalid mount options: {0}")]
+    InvalidOptions(std::ffi::NulError),
+
+    #[error("mount: {1} on {2}: {0}")]
+    MountFailed(std::io::Error, String, String),
+}
+
+impl UError for MountError {
+    fn code(&self) -> i32 {
+        match self {
+            MountError::MountFailed(_, _, _) => EXIT_MOUNT_FAILED,
+            _ => 1,
+        }
+    }
+}

src/uu/mount/src/escape.rs

@@ -0,0 +1,32 @@
+// This file is part of the uutils util-linux package.
+//
+// For the full copyright and license information, please view the LICENSE
+// file that was distributed with this source code.
+
+/// Expand octal escape sequences of the form `\NNN` used in mount-table style
+/// files to encode whitespace and other special characters.
+pub(crate) fn unescape_octal(s: &str) -> String {
+    let mut result: Vec<u8> = Vec::with_capacity(s.len());
+    let bytes = s.as_bytes();
+    let mut i = 0;
+    while i < bytes.len() {
+        if bytes[i] == b'\\' && i + 3 < bytes.len() {
+            let (a, b, c) = (bytes[i + 1], bytes[i + 2], bytes[i + 3]);
+            if a.is_ascii_digit()
+                && a < b'8'
+                && b.is_ascii_digit()
+                && b < b'8'
+                && c.is_ascii_digit()
+                && c < b'8'
+            {
+                let value = (a - b'0') * 64 + (b - b'0') * 8 + (c - b'0');
+                result.push(value);
+                i += 4;
+                continue;
+            }
+        }
+        result.push(bytes[i]);
+        i += 1;
+    }
+    String::from_utf8_lossy(&result).into_owned()
+}