Add mount2 syscall (#1024)

* Add mount2 syscall

* Fix: import CStr from core instead of std

* Remove unused generics from mount2 function

* Fix mount2 function to use Arg instead of CStr

* Change mount data to &CStr

src/mount/mount_unmount.rs

@@ -3,7 +3,12 @@
 use crate::backend::mount::types::{
     InternalMountFlags, MountFlags, MountFlagsArg, MountPropagationFlags, UnmountFlags,
 };
-use crate::{backend, io, path};
+use crate::{
+    backend,
+    ffi::CStr,
+    io,
+    path::{self, option_into_with_c_str},
+};
 
 /// `mount(source, target, filesystemtype, mountflags, data)`
 ///
@@ -36,6 +41,35 @@ pub fn mount<Source: path::Arg, Target: path::Arg, Fs: path::Arg, Data: path::Ar
     })
 }
 
+/// `mount2(source, target, filesystemtype, mountflags, data)`
+///
+/// # References
+///  - [Linux]
+///
+/// [Linux]: https://man7.org/linux/man-pages/man2/mount.2.html
+#[inline]
+pub fn mount2<Source: path::Arg, Target: path::Arg, Fs: path::Arg>(
+    source: Option<Source>,
+    target: Target,
+    file_system_type: Option<Fs>,
+    flags: MountFlags,
+    data: Option<&CStr>,
+) -> io::Result<()> {
+    option_into_with_c_str(source, |source| {
+        target.into_with_c_str(|target| {
+            option_into_with_c_str(file_system_type, |file_system_type| {
+                backend::mount::syscalls::mount(
+                    source,
+                    target,
+                    file_system_type,
+                    MountFlagsArg(flags.bits()),
+                    data,
+                )
+            })
+        })
+    })
+}
+
 /// `mount(NULL, target, NULL, MS_REMOUNT | mountflags, data)`
 ///
 /// # References

src/path/arg.rs

@@ -89,6 +89,19 @@ pub trait Arg {
         F: FnOnce(&CStr) -> io::Result<T>;
 }
 
+/// Runs a closure on `arg` where `A` is mapped to a `&CStr`
+pub fn option_into_with_c_str<T, F, A: Arg>(arg: Option<A>, f: F) -> io::Result<T>
+where
+    A: Sized,
+    F: FnOnce(Option<&CStr>) -> io::Result<T>,
+{
+    if let Some(arg) = arg {
+        arg.into_with_c_str(|p| f(Some(p)))
+    } else {
+        f(None)
+    }
+}
+
 impl Arg for &str {
     #[inline]
     fn as_str(&self) -> io::Result<&str> {

src/path/mod.rs

@@ -4,7 +4,7 @@ mod arg;
 #[cfg(feature = "itoa")]
 mod dec_int;
 
-pub use arg::Arg;
+pub use arg::{option_into_with_c_str, Arg};
 #[cfg(feature = "itoa")]
 #[cfg_attr(doc_cfg, doc(cfg(feature = "itoa")))]
 pub use dec_int::DecInt;