relibc: full eventfd() implementation + no-stubs policy in AGENTS.md

Replaced P3-sys-eventfd-create.patch (constants-only stub) with:
- P3-eventfd-impl.patch: full eventfd() opening /scheme/event/eventfd
- P3-bits-eventfd.patch: eventfd_t type
- P3-eventfd-cbindgen.patch: generates sys/eventfd.h C header
- P3-bits-eventfd-mod.patch: wires bits_eventfd into header/mod.rs

libwayland: removed eventfd stub from redox.patch — relibc provides it now.
Only meson.build fix + wl_proxy null guards + MSG_NOSIGNAL guard remain.

Documented zero-tolerance stub policy at top of local/AGENTS.md.

local/AGENTS.md

@@ -3,6 +3,35 @@
 This directory contains ALL custom work on top of mainline Redox. When mainline Redox
 updates (`git pull` on the build system repo), this directory is untouched.
 
+## STUB AND WORKAROUND POLICY — ZERO TOLERANCE
+
+**Red Bear OS has zero tolerance for stubs, workarounds, `#ifdef`-guarded no-ops, fake headers,
+shell-script patches, sed/awk hacks, `LD_PRELOAD` tricks, rename-to-.disabled wrappers, or any
+other "make it compile" shortcut.**
+
+If something doesn't build because of a missing implementation, the ONLY acceptable response is
+to implement the missing functionality in the correct component:
+
+| Problem | Correct Fix |
+|---------|-------------|
+| `eventfd()` not found | Implement `eventfd()` in relibc, generate `sys/eventfd.h` via cbindgen |
+| `signalfd()` not found | Implement `signalfd()` in relibc, generate `sys/signalfd.h` via cbindgen |
+| Missing POSIX type | Add it to the relibc header it belongs to, with proper `stdint.h` include chain |
+| Compiler can't find header | Fix the include path in the recipe's sysroot/cookbook, NOT by adding `-I` hacks |
+| CMake can't find dependency | Implement the dependency or fix pkg-config, NOT with `-DFEATURE_x=OFF` |
+| Qt needs `open_memstream` | Implement it in relibc — never add a static stub in Qt or libwayland source |
+
+**Any stub found in the tree is a bug to be fixed, not a precedent to follow.**
+
+When relibc gains a function or type that obsoletes a previously-needed local stub, the stub
+MUST be removed and the dependency switched to relibc's implementation. Coexistence of stubs
+with real implementations causes header conflicts, linker errors, and silent ABI mismatches.
+
+This applies to: relibc functions, kernel syscalls, C headers, CMake modules, pkg-config `.pc`
+files, Wayland protocol stubs, D-Bus service stubs, and any other layer of the stack.
+
+**No exceptions. No "temporary." No "until we fix it properly."**
+
 ## DESIGN PRINCIPLE
 
 Red Bear OS is a **full fork** based on frozen Redox OS snapshots:

local/patches/relibc/P3-bits-eventfd-mod.patch

@@ -0,0 +1,10 @@
+--- a/src/header/mod.rs
++++ b/src/header/mod.rs
+@@ -5,6 +5,7 @@
+ pub mod arpa_inet;
+ pub mod assert;
+ pub mod bits_arpainet;
++pub mod bits_eventfd;
+ pub mod bits_iovec;
+ #[path = "bits_locale-t/mod.rs"]
+ pub mod bits_locale_t;

local/patches/relibc/P3-bits-eventfd.patch

@@ -0,0 +1,7 @@
+--- /dev/null	2026-05-03 20:55:05.750445686 +0100
++++ b/src/header/bits_eventfd/mod.rs
+@@ -0,0 +1,4 @@
++//! `bits/eventfd.h` — eventfd counter type.
++
++use crate::platform::types::uint64_t;
++pub type eventfd_t = uint64_t;

local/patches/relibc/P3-eventfd-cbindgen.patch

@@ -0,0 +1,19 @@
+diff --git a/src/header/sys_eventfd/cbindgen.toml b/src/header/sys_eventfd/cbindgen.toml
+new file mode 100644
+index 00000000..c47f467f
+--- /dev/null
++++ b/src/header/sys_eventfd/cbindgen.toml
+@@ -0,0 +1,13 @@
++sys_includes = ["stdint.h"]
++after_includes = """
++typedef uint64_t eventfd_t;
++int eventfd(unsigned int initval, int flags);
++"""
++include_guard = "_SYS_EVENTFD_H"
++language = "C"
++style = "Tag"
++no_includes = true
++cpp_compat = true
++
++[enum]
++prefix_with_name = true

local/patches/relibc/P3-eventfd-impl.patch

@@ -0,0 +1,40 @@
+--- /dev/null	2026-05-03 20:55:05.750445686 +0100
++++ b/src/header/sys_eventfd/mod.rs
+@@ -0,0 +1,37 @@
++//! `sys/eventfd.h` implementation — eventfd() with EFD_SEMAPHORE/CLOEXEC/NONBLOCK.
++
++use alloc::format;
++use crate::c_str::{CStr, CString};
++use crate::error::{Errno, ResultExt};
++use crate::header::fcntl::{O_CLOEXEC, O_NONBLOCK, O_RDWR};
++use crate::header::errno::EINVAL;
++use crate::platform::{Pal, Sys, types::{c_int, c_uint}};
++
++pub const EFD_SEMAPHORE: c_int = 1;
++pub const EFD_CLOEXEC: c_int = 0x80000;
++pub const EFD_NONBLOCK: c_int = 0x800;
++
++pub type eventfd_t = u64;
++
++#[unsafe(no_mangle)]
++pub extern "C" fn eventfd(initval: c_uint, flags: c_int) -> c_int {
++    let supported = EFD_CLOEXEC | EFD_NONBLOCK | EFD_SEMAPHORE;
++    if flags & !supported != 0 {
++        return Err::<c_int, _>(Errno(EINVAL)).or_minus_one_errno();
++    }
++    let sem = if flags & EFD_SEMAPHORE != 0 { 1 } else { 0 };
++    let path = format!("/scheme/event/eventfd/{}/{}", initval, sem);
++    let cpath = match CString::new(path) {
++        Ok(p) => p,
++        Err(_) => return Err::<c_int, _>(Errno(EINVAL)).or_minus_one_errno(),
++    };
++
++    let mut oflag = O_RDWR;
++    if flags & EFD_CLOEXEC == EFD_CLOEXEC {
++        oflag |= O_CLOEXEC;
++    }
++    if flags & EFD_NONBLOCK == EFD_NONBLOCK {
++        oflag |= O_NONBLOCK;
++    }
++    Sys::open(CStr::borrow(&cpath), oflag, 0).or_minus_one_errno()
++}

recipes/core/relibc/P3-bits-eventfd-mod.patch

@@ -0,0 +1 @@
+../../../local/patches/relibc/P3-bits-eventfd-mod.patch

recipes/core/relibc/P3-bits-eventfd.patch

@@ -0,0 +1 @@
+../../../local/patches/relibc/P3-bits-eventfd.patch

recipes/core/relibc/P3-eventfd-cbindgen.patch

@@ -0,0 +1 @@
+../../../local/patches/relibc/P3-eventfd-cbindgen.patch

recipes/core/relibc/P3-eventfd-impl.patch

@@ -0,0 +1 @@
+../../../local/patches/relibc/P3-eventfd-impl.patch

recipes/core/relibc/recipe.toml

@@ -2,10 +2,15 @@
 git = "https://gitlab.redox-os.org/redox-os/relibc.git"
 rev = "861bbb0"
 patches = [
-    # Module declarations (pub mod sys_eventfd/signalfd/timerfd in header/mod.rs)
     "P3-eventfd-mod.patch",
-    # sys_eventfd module (constants only — libwayland has its own eventfd())
-    "P3-sys-eventfd-create.patch",
+    # Add pub mod bits_eventfd to header/mod.rs
+    "P3-bits-eventfd-mod.patch",
+    # bits_eventfd module (eventfd_t type)
+    "P3-bits-eventfd.patch",
+    # sys_eventfd module — FULL eventfd() implementation (opens /scheme/event/eventfd)
+    "P3-eventfd-impl.patch",
+    # cbindgen.toml for sys/eventfd.h C header generation
+    "P3-eventfd-cbindgen.patch",
     # sys_signalfd module (cbindgen.toml + mod.rs with cbindgen exports)
     "P3-signalfd-header.patch",
     # signalfd implementation (signal/signalfd.rs + signal/mod.rs wiring)