absorb: 27 orphaned relibc patches re-applied (Phase 1.0A)

Per local/docs/PATCH-PRESERVATION-AUDIT-2026-07-12.md the relibc
fork was carrying only 34 of 90 patches in local/patches/relibc/.
The other 56 patches' content was silently missing from the fork.

This commit re-applies 27 patches that genuinely still apply
cleanly. Recovery covers:

- eventfd implementation (sys/eventfd.h + eventfd.rs)
- signalfd implementation (sys/signalfd.h + signalfd.rs)
- timerfd implementation (sys/timerfd.h + timerfd.rs)
- bits/eventfd.h header
- spawn() function: cbindgen + stdint fix
- P3-timerfd-cbindgen-fix
- cbindgen language=C fixes for sys/{timerfd,semaphore}
- stdint include chain fixes
- strtold implementation
- dns aaaa getaddrinfo ipv6
- various stack/threading/header threading fixes
- dup3 syscalls
- waitid implementation
- bits/timespec reverse_from
- open_memstream integration

24 files changed.

src/header/sys_timerfd/mod.rs

@@ -0,0 +1,138 @@
+//! `sys/timerfd.h` implementation.
+//!
+//! Non-POSIX, see <https://man7.org/linux/man-pages/man2/timerfd_create.2.html>.
+
+use alloc::{collections::BTreeMap, format};
+use core::{mem, slice, sync::atomic::{AtomicBool, Ordering}};
+
+use crate::{
+    c_str::{CStr, CString},
+    error::{Errno, ResultExt},
+    header::{
+        bits_timespec::timespec,
+        errno::{EBADF, EFAULT, EINVAL, EIO},
+        fcntl::{O_CLOEXEC, O_NONBLOCK, O_RDWR},
+    },
+    out::Out,
+    platform::{
+        Pal, Sys,
+        types::{c_int, clockid_t},
+    },
+    sync::Mutex,
+};
+
+pub use crate::header::time::itimerspec;
+
+pub const TFD_CLOEXEC: c_int = 0x80000;
+pub const TFD_NONBLOCK: c_int = 0x800;
+pub const TFD_TIMER_ABSTIME: c_int = 0x1;
+pub const TFD_TIMER_CANCEL_ON_SET: c_int = 0x2;
+
+const NSEC_PER_SEC: i64 = 1_000_000_000;
+
+static MAP_INIT: AtomicBool = AtomicBool::new(false);
+static TIMERFD_CLOCKIDS: Mutex<Option<BTreeMap<c_int, clockid_t>>> = Mutex::new(None);
+
+fn with_map<R>(f: impl FnOnce(&mut BTreeMap<c_int, clockid_t>) -> R) -> R {
+    let mut guard = TIMERFD_CLOCKIDS.lock();
+    if !MAP_INIT.load(Ordering::Acquire) {
+        *guard = Some(BTreeMap::new());
+        MAP_INIT.store(true, Ordering::Release);
+    }
+    f(guard.as_mut().unwrap())
+}
+
+fn add_timespec(a: &timespec, b: &timespec) -> timespec {
+    let total_nsec = a.tv_nsec as i64 + b.tv_nsec as i64;
+    let mut sec = a.tv_sec + b.tv_sec + (total_nsec / NSEC_PER_SEC) as i64;
+    let mut nsec = (total_nsec % NSEC_PER_SEC) as i64;
+    if nsec < 0 {
+        sec -= 1;
+        nsec += NSEC_PER_SEC;
+    }
+    timespec { tv_sec: sec, tv_nsec: nsec }
+}
+
+fn read_exact(fd: c_int, buf: &mut [u8]) -> Result<(), Errno> {
+    match Sys::read(fd, buf)? {
+        n if n == buf.len() => Ok(()),
+        _ => Err(Errno(EIO)),
+    }
+}
+
+fn write_exact(fd: c_int, buf: &[u8]) -> Result<(), Errno> {
+    match Sys::write(fd, buf)? {
+        n if n == buf.len() => Ok(()),
+        _ => Err(Errno(EIO)),
+    }
+}
+
+#[unsafe(no_mangle)]
+pub extern "C" fn timerfd_create(clockid: clockid_t, flags: c_int) -> c_int {
+    let supported = TFD_CLOEXEC | TFD_NONBLOCK;
+    if flags & !supported != 0 {
+        return Err::<c_int, _>(Errno(EINVAL)).or_minus_one_errno();
+    }
+
+    let mut oflag = O_RDWR;
+    if flags & TFD_CLOEXEC == TFD_CLOEXEC {
+        oflag |= O_CLOEXEC;
+    }
+    if flags & TFD_NONBLOCK == TFD_NONBLOCK {
+        oflag |= O_NONBLOCK;
+    }
+
+    let path = match CString::new(format!("/scheme/time/{clockid}")) {
+        Ok(path) => path,
+        Err(_) => return Err::<c_int, _>(Errno(EINVAL)).or_minus_one_errno(),
+    };
+    let fd = match Sys::open(CStr::borrow(&path), oflag, 0) {
+        Ok(fd) => fd,
+        Err(Errno(e)) => { return Err::<c_int, _>(Errno(e)).or_minus_one_errno(); }
+    };
+
+    // Register the clockid for this fd so timerfd_settime can convert relative times
+    with_map(|map| { map.insert(fd, clockid); });
+
+    fd
+}
+
+#[unsafe(no_mangle)]
+pub unsafe extern "C" fn timerfd_settime(fd: c_int, flags: c_int, new: *const itimerspec, old: *mut itimerspec) -> c_int {
+    let supported = TFD_TIMER_ABSTIME | TFD_TIMER_CANCEL_ON_SET;
+    if flags & !supported != 0 {
+        return Err::<c_int, _>(Errno(EINVAL)).or_minus_one_errno();
+    }
+    if new.is_null() {
+        return Err::<c_int, _>(Errno(EFAULT)).or_minus_one_errno();
+    }
+    if !old.is_null() && unsafe { timerfd_gettime(fd, old) } < 0 {
+        return -1;
+    }
+    let spec = unsafe { &*new };
+    let mut value = spec.it_value.clone();
+
+    // Convert relative time to absolute if TFD_TIMER_ABSTIME is not set
+    if flags & TFD_TIMER_ABSTIME == 0 {
+        let clockid = with_map(|map| map.get(&fd).copied()).unwrap_or(0);
+        let mut now = timespec::default();
+        if Sys::clock_gettime(clockid, Out::from_mut(&mut now)).is_err() {
+            return Err::<c_int, _>(Errno(EBADF)).or_minus_one_errno();
+        }
+        value = add_timespec(&now, &value);
+    }
+
+    let buf = unsafe { slice::from_raw_parts((&raw const value).cast::<u8>(), mem::size_of::<timespec>()) };
+    write_exact(fd, buf).map(|()| 0).or_minus_one_errno()
+}
+
+#[unsafe(no_mangle)]
+pub unsafe extern "C" fn timerfd_gettime(fd: c_int, curr: *mut itimerspec) -> c_int {
+    if curr.is_null() {
+        return Err::<c_int, _>(Errno(EFAULT)).or_minus_one_errno();
+    }
+    let curr = unsafe { &mut *curr };
+    curr.it_interval = timespec::default();
+    let buf = unsafe { slice::from_raw_parts_mut((&raw mut curr.it_value).cast::<u8>(), mem::size_of::<timespec>()) };
+    read_exact(fd, buf).map(|()| 0).or_minus_one_errno()
+}