From 2501a858743ba41fba5db967c925fe3eb6d966d3 Mon Sep 17 00:00:00 2001
From: Mark Poliakov <mark@alnyan.me>
Date: Wed, 16 Jul 2025 11:00:47 +0300
Subject: [PATCH] runtime: move pidfd support to yggdrasil-rt

---
 lib/runtime/src/io/mod.rs                    | 14 ++++++++++-
 userspace/lib/cross/src/sys/yggdrasil/pid.rs | 25 +++++++++++++-------
 2 files changed, 30 insertions(+), 9 deletions(-)

diff --git a/lib/runtime/src/io/mod.rs b/lib/runtime/src/io/mod.rs
index a254a341..5bef99d7 100644
--- a/lib/runtime/src/io/mod.rs
+++ b/lib/runtime/src/io/mod.rs
@@ -19,7 +19,19 @@ pub use paths::*;
 
 use core::mem::MaybeUninit;
 
-use abi::{error::Error, option::OptionValue};
+use abi::{error::Error, option::OptionValue, process::ProcessId};
+
+pub fn read_pid_fd(fd: RawFd) -> Result<(ProcessId, i32), Error> {
+    let mut buffer = [0; size_of::<u32>() + size_of::<i32>()];
+    let len = unsafe { crate::sys::read(fd, &mut buffer) }?;
+    assert_eq!(len, buffer.len());
+    let mut word = [0; size_of::<u32>()];
+    word.copy_from_slice(&buffer[0..4]);
+    let pid = unsafe { ProcessId::from_raw(u32::from_ne_bytes(word)) };
+    word.copy_from_slice(&buffer[4..8]);
+    let status = i32::from_ne_bytes(word);
+    Ok((pid, status))
+}
 
 pub fn remove_file(at: Option<RawFd>, path: &str) -> Result<(), Error> {
     unsafe { crate::sys::remove(at, path, RemoveFlags::empty()) }
diff --git a/userspace/lib/cross/src/sys/yggdrasil/pid.rs b/userspace/lib/cross/src/sys/yggdrasil/pid.rs
index d7ba2f2e..3a88ba24 100644
--- a/userspace/lib/cross/src/sys/yggdrasil/pid.rs
+++ b/userspace/lib/cross/src/sys/yggdrasil/pid.rs
@@ -1,28 +1,37 @@
 use std::{
     io,
-    os::{
-        fd::{AsRawFd, RawFd},
-        yggdrasil::io::pid::{PidFd as YggPidFd, ProcessId},
-    },
+    os::fd::{AsRawFd, FromRawFd, OwnedFd, RawFd},
+};
+
+use runtime::rt::{
+    process::{ProcessId, ProcessWait, WaitFlags},
+    sys as syscall,
 };
 
 use crate::sys::PidFd;
 
-pub struct PidFdImpl(YggPidFd);
+pub struct PidFdImpl {
+    fd: OwnedFd,
+}
 
 impl PidFd for PidFdImpl {
     fn new(pid: u32) -> io::Result<Self> {
         let pid = unsafe { ProcessId::from_raw(pid) };
-        YggPidFd::child(pid, false).map(Self)
+        let target = ProcessWait::Process(pid);
+        let fd = unsafe { syscall::create_pid(&target, WaitFlags::NON_BLOCKING) }
+            .map_err(io::Error::from)?;
+        let fd = unsafe { OwnedFd::from_raw_fd(fd) };
+        Ok(Self { fd })
     }
 
     fn exit_status(&self) -> io::Result<i32> {
-        self.0.status()
+        let (_, code) = runtime::rt::io::read_pid_fd(self.fd.as_raw_fd())?;
+        Ok(code)
     }
 }
 
 impl AsRawFd for PidFdImpl {
     fn as_raw_fd(&self) -> RawFd {
-        self.0.as_raw_fd()
+        self.fd.as_raw_fd()
     }
 }