Miscellaneous cleanups.

Factor out redundant code, make some functions `const fn`, and add some
documentation comments.

src/backend/libc/c.rs

@@ -187,26 +187,28 @@ pub(super) unsafe fn prlimit(
     prlimit64(pid, resource, new_limit, old_limit)
 }
 
+// 64-bit offsets on 32-bit platforms are passed in endianness-specific
+// lo/hi pairs. See src/backend/linux_raw/conv.rs for details.
+#[cfg(all(linux_kernel, target_endian = "little", target_pointer_width = "32"))]
+fn lo(x: i64) -> usize {
+    (x >> 32) as usize
+}
+#[cfg(all(linux_kernel, target_endian = "little", target_pointer_width = "32"))]
+fn hi(x: i64) -> usize {
+    x as usize
+}
+#[cfg(all(linux_kernel, target_endian = "big", target_pointer_width = "32"))]
+fn lo(x: i64) -> usize {
+    x as usize
+}
+#[cfg(all(linux_kernel, target_endian = "big", target_pointer_width = "32"))]
+fn hi(x: i64) -> usize {
+    (x >> 32) as usize
+}
+
 #[cfg(target_os = "android")]
 mod readwrite_pv64 {
-    // 64-bit offsets on 32-bit platforms are passed in endianness-specific
-    // lo/hi pairs. See src/backend/linux_raw/conv.rs for details.
-    #[cfg(all(target_endian = "little", target_pointer_width = "32"))]
-    fn lo(x: i64) -> usize {
-        (x >> 32) as usize
-    }
-    #[cfg(all(target_endian = "little", target_pointer_width = "32"))]
-    fn hi(x: i64) -> usize {
-        x as usize
-    }
-    #[cfg(all(target_endian = "big", target_pointer_width = "32"))]
-    fn lo(x: i64) -> usize {
-        x as usize
-    }
-    #[cfg(all(target_endian = "big", target_pointer_width = "32"))]
-    fn hi(x: i64) -> usize {
-        (x >> 32) as usize
-    }
+    use super::*;
 
     pub(in super::super) unsafe fn preadv64(
         fd: libc::c_int,
@@ -320,24 +322,7 @@ pub(super) use readwrite_pv::{preadv, pwritev};
 // glibc added `preadv64v2` and `pwritev64v2` in version 2.26.
 #[cfg(all(target_os = "linux", target_env = "gnu"))]
 mod readwrite_pv64v2 {
-    // 64-bit offsets on 32-bit platforms are passed in endianness-specific
-    // lo/hi pairs. See src/backend/linux_raw/conv.rs for details.
-    #[cfg(all(target_endian = "little", target_pointer_width = "32"))]
-    fn lo(x: i64) -> usize {
-        (x >> 32) as usize
-    }
-    #[cfg(all(target_endian = "little", target_pointer_width = "32"))]
-    fn hi(x: i64) -> usize {
-        x as usize
-    }
-    #[cfg(all(target_endian = "big", target_pointer_width = "32"))]
-    fn lo(x: i64) -> usize {
-        x as usize
-    }
-    #[cfg(all(target_endian = "big", target_pointer_width = "32"))]
-    fn hi(x: i64) -> usize {
-        (x >> 32) as usize
-    }
+    use super::*;
 
     pub(in super::super) unsafe fn preadv64v2(
         fd: libc::c_int,
@@ -439,24 +424,7 @@ pub(super) use readwrite_pv64v2::{preadv64v2 as preadv2, pwritev64v2 as pwritev2
     all(target_os = "linux", not(target_env = "gnu")),
 ))]
 mod readwrite_pv64v2 {
-    // 64-bit offsets on 32-bit platforms are passed in endianness-specific
-    // lo/hi pairs. See src/backend/linux_raw/conv.rs for details.
-    #[cfg(all(target_endian = "little", target_pointer_width = "32"))]
-    fn lo(x: i64) -> usize {
-        (x >> 32) as usize
-    }
-    #[cfg(all(target_endian = "little", target_pointer_width = "32"))]
-    fn hi(x: i64) -> usize {
-        x as usize
-    }
-    #[cfg(all(target_endian = "big", target_pointer_width = "32"))]
-    fn lo(x: i64) -> usize {
-        x as usize
-    }
-    #[cfg(all(target_endian = "big", target_pointer_width = "32"))]
-    fn hi(x: i64) -> usize {
-        (x >> 32) as usize
-    }
+    use super::*;
 
     pub(in super::super) unsafe fn preadv64v2(
         fd: libc::c_int,

src/backend/libc/event/epoll.rs

@@ -323,13 +323,13 @@ pub union EventData {
 impl EventData {
     /// Construct a new value containing a `u64`.
     #[inline]
-    pub fn new_u64(value: u64) -> Self {
+    pub const fn new_u64(value: u64) -> Self {
         Self { as_u64: value }
     }
 
     /// Construct a new value containing a `*mut c_void`.
     #[inline]
-    pub fn new_ptr(value: *mut c_void) -> Self {
+    pub const fn new_ptr(value: *mut c_void) -> Self {
         Self {
             sixty_four_bit_pointer: SixtyFourBitPointer {
                 pointer: value,

src/backend/libc/mm/syscalls.rs

@@ -215,7 +215,7 @@ pub(crate) unsafe fn munlock(addr: *mut c::c_void, length: usize) -> io::Result<
 pub(crate) unsafe fn userfaultfd(flags: UserfaultfdFlags) -> io::Result<OwnedFd> {
     syscall! {
         fn userfaultfd(
-            flags: libc::c_int
+            flags: c::c_int
         ) via SYS_userfaultfd -> c::c_int
     }
     ret_owned_fd(userfaultfd(bitflags_bits!(flags)))

src/backend/libc/pty/syscalls.rs

@@ -32,8 +32,7 @@ pub(crate) fn ptsname(fd: BorrowedFd, mut buffer: Vec<u8>) -> io::Result<CString
     loop {
         // On platforms with `ptsname_r`, use it.
         #[cfg(any(target_os = "freebsd", linux_like, target_os = "fuchsia"))]
-        let r =
-            unsafe { libc::ptsname_r(borrowed_fd(fd), buffer.as_mut_ptr().cast(), buffer.len()) };
+        let r = unsafe { c::ptsname_r(borrowed_fd(fd), buffer.as_mut_ptr().cast(), buffer.len()) };
 
         // MacOS 10.13.4 has `ptsname_r`; use it if we have it, otherwise fall
         // back to calling the underlying ioctl directly.
@@ -46,7 +45,7 @@ pub(crate) fn ptsname(fd: BorrowedFd, mut buffer: Vec<u8>) -> io::Result<CString
             } else {
                 // The size declared in the `TIOCPTYGNAME` macro in sys/ttycom.h is 128.
                 let mut name: [u8; 128] = [0_u8; 128];
-                match libc::ioctl(borrowed_fd(fd), libc::TIOCPTYGNAME as u64, &mut name) {
+                match c::ioctl(borrowed_fd(fd), c::TIOCPTYGNAME as u64, &mut name) {
                     0 => {
                         let len = CStr::from_ptr(name.as_ptr().cast()).to_bytes().len();
                         std::ptr::copy_nonoverlapping(name.as_ptr(), buffer.as_mut_ptr(), len + 1);
@@ -60,7 +59,7 @@ pub(crate) fn ptsname(fd: BorrowedFd, mut buffer: Vec<u8>) -> io::Result<CString
         if r == 0 {
             return Ok(unsafe { CStr::from_ptr(buffer.as_ptr().cast()).to_owned() });
         }
-        if r != libc::ERANGE {
+        if r != c::ERANGE {
             return Err(io::Errno::from_raw_os_error(r));
         }
 

src/backend/linux_raw/arch/mod.rs

@@ -133,8 +133,8 @@ macro_rules! syscall {
     };
 }
 
-// Macro to invoke a syscall that always uses direct assembly, rather than the vdso. Useful when
-// still finding the vdso.
+// Macro to invoke a syscall that always uses direct assembly, rather than the
+// vDSO. Useful when still finding the vDSO.
 #[allow(unused_macros)]
 macro_rules! syscall_always_asm {
     ($nr:ident) => {

src/backend/linux_raw/event/epoll.rs

@@ -299,13 +299,13 @@ pub union EventData {
 impl EventData {
     /// Construct a new value containing a `u64`.
     #[inline]
-    pub fn new_u64(value: u64) -> Self {
+    pub const fn new_u64(value: u64) -> Self {
         Self { as_u64: value }
     }
 
     /// Construct a new value containing a `*mut c_void`.
     #[inline]
-    pub fn new_ptr(value: *mut c_void) -> Self {
+    pub const fn new_ptr(value: *mut c_void) -> Self {
         Self {
             sixty_four_bit_pointer: SixtyFourBitPointer {
                 pointer: value,

src/backend/linux_raw/fs/dir.rs

@@ -101,7 +101,7 @@ impl Dir {
             .iter()
             .position(|x| *x == b'\0')
             .unwrap();
-        let name = CStr::from_bytes_with_nul(&self.buf[name_start..][..name_len + 1]).unwrap();
+        let name = CStr::from_bytes_with_nul(&self.buf[name_start..][..=name_len]).unwrap();
         let name = name.to_owned();
         assert!(name.as_bytes().len() <= self.buf.len() - name_start);
 

src/backend/linux_raw/fs/syscalls.rs

@@ -853,7 +853,7 @@ fn statfs_to_statvfs(statfs: StatFs) -> StatVfs {
         f_files: statfs.f_files as u64,
         f_ffree: statfs.f_ffree as u64,
         f_favail: statfs.f_ffree as u64,
-        f_fsid: f_fsid_val0 as u32 as u64 | ((f_fsid_val1 as u32 as u64) << 32),
+        f_fsid: u64::from(f_fsid_val0 as u32) | u64::from(f_fsid_val1 as u32) << 32,
         f_flag: StatVfsMountFlags::from_bits_retain(statfs.f_flags as u64),
         f_namemax: statfs.f_namelen as u64,
     }

src/backend/linux_raw/param/auxv.rs

@@ -10,7 +10,6 @@ use crate::backend::elf::*;
 use crate::fd::OwnedFd;
 #[cfg(feature = "param")]
 use crate::ffi::CStr;
-#[cfg(not(target_vendor = "mustang"))]
 use crate::fs::{Mode, OFlags};
 use crate::utils::{as_ptr, check_raw_pointer};
 use alloc::vec::Vec;
@@ -130,7 +129,6 @@ static PHDR: AtomicPtr<Elf_Phdr> = AtomicPtr::new(null_mut());
 static PHNUM: AtomicUsize = AtomicUsize::new(0);
 static EXECFN: AtomicPtr<c::c_char> = AtomicPtr::new(null_mut());
 
-#[cfg(not(target_vendor = "mustang"))]
 fn pr_get_auxv() -> crate::io::Result<Vec<u8>> {
     use super::super::conv::{c_int, pass_usize, ret_usize};
     const PR_GET_AUXV: c::c_int = 0x41555856;
@@ -160,9 +158,9 @@ fn pr_get_auxv() -> crate::io::Result<Vec<u8>> {
     return Ok(buffer);
 }
 
-/// On non-Mustang platforms, we read the aux vector via the prctl PR_GET_AUXV, with a fallback to
-/// /proc/self/auxv for kernels that don't support PR_GET_AUXV.
-#[cfg(not(target_vendor = "mustang"))]
+/// On non-Mustang platforms, we read the aux vector via the `prctl`
+/// `PR_GET_AUXV`, with a fallback to /proc/self/auxv for kernels that don't
+/// support `PR_GET_AUXV`.
 fn init_auxv() {
     match pr_get_auxv() {
         Ok(buffer) => {
@@ -186,11 +184,6 @@ fn init_auxv() {
     let _ = init_from_auxv_file(file);
 }
 
-#[cfg(target_vendor = "mustang")]
-fn init_auxv() {
-    panic!("mustang should have initialized the auxv values");
-}
-
 /// Process auxv entries from the open file `auxv`.
 fn init_from_auxv_file(auxv: OwnedFd) -> Option<()> {
     let mut buffer = Vec::<u8>::with_capacity(512);

src/event/kqueue.rs

@@ -1,6 +1,6 @@
 //! An API for interfacing with `kqueue`.
 
-use crate::fd::{AsFd, AsRawFd, OwnedFd, RawFd};
+use crate::fd::{AsFd, OwnedFd, RawFd};
 use crate::pid::Pid;
 use crate::signal::Signal;
 use crate::{backend, io};
@@ -26,13 +26,11 @@ impl Event {
     #[allow(clippy::needless_update)]
     pub fn new(filter: EventFilter, flags: EventFlags, udata: isize) -> Event {
         let (ident, data, filter, fflags) = match filter {
-            EventFilter::Read(fd) => (fd.as_raw_fd() as uintptr_t, 0, c::EVFILT_READ, 0),
-            EventFilter::Write(fd) => (fd.as_raw_fd() as _, 0, c::EVFILT_WRITE, 0),
+            EventFilter::Read(fd) => (fd as uintptr_t, 0, c::EVFILT_READ, 0),
+            EventFilter::Write(fd) => (fd as _, 0, c::EVFILT_WRITE, 0),
             #[cfg(target_os = "freebsd")]
-            EventFilter::Empty(fd) => (fd.as_raw_fd() as _, 0, c::EVFILT_EMPTY, 0),
-            EventFilter::Vnode { vnode, flags } => {
-                (vnode.as_raw_fd() as _, 0, c::EVFILT_VNODE, flags.bits())
-            }
+            EventFilter::Empty(fd) => (fd as _, 0, c::EVFILT_EMPTY, 0),
+            EventFilter::Vnode { vnode, flags } => (vnode as _, 0, c::EVFILT_VNODE, flags.bits()),
             EventFilter::Proc { pid, flags } => {
                 (Pid::as_raw(Some(pid)) as _, 0, c::EVFILT_PROC, flags.bits())
             }

src/net/socket_addr_any.rs

@@ -1,7 +1,7 @@
 //! A socket address for any kind of socket.
 //!
 //! This is similar to [`std::net::SocketAddr`], but also supports Unix-domain
-//! socket addresses.
+//! socket addresses on Unix.
 //!
 //! # Safety
 //!

src/net/socketpair.rs

@@ -2,7 +2,8 @@ use crate::fd::OwnedFd;
 use crate::net::{AddressFamily, Protocol, SocketFlags, SocketType};
 use crate::{backend, io};
 
-/// `socketpair(domain, type_ | accept_flags, protocol)`
+/// `socketpair(domain, type_ | accept_flags, protocol)`—Create a pair of
+/// sockets that are connected to each other.
 ///
 /// # References
 ///  - [POSIX]

src/termios/types.rs

@@ -948,7 +948,7 @@ pub mod speed {
     }
 }
 
-/// An array indexed by `SpecialCodeIndex` indicating the current values
+/// An array indexed by [`SpecialCodeIndex`] indicating the current values
 /// of various special control codes.
 #[repr(transparent)]
 #[derive(Clone, Debug)]
@@ -968,7 +968,7 @@ impl core::ops::IndexMut<SpecialCodeIndex> for SpecialCodes {
     }
 }
 
-/// Indices for use with `Termios::special_codes`.
+/// Indices for use with [`Termios::special_codes`].
 pub struct SpecialCodeIndex(usize);
 
 #[rustfmt::skip]

src/timespec.rs

@@ -1,3 +1,6 @@
+//! `Timespec` and related types, which are used by multiple public API
+//! modules.
+
 use crate::backend::c;
 
 /// `struct timespec`