From 59b7a6d78d4d9771787a4a4afad13874154f9941 Mon Sep 17 00:00:00 2001
From: Jonathan <jonathanwoollettlight@gmail.com>
Date: Thu, 17 Nov 2022 00:10:09 +0000
Subject: [PATCH] pidfd_send_signal

---
 CHANGELOG.md     |  2 ++
 src/sys/mod.rs   |  2 +-
 src/sys/pidfd.rs | 37 +++++++++++++++++++++++++++++++++++++
 3 files changed, 40 insertions(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2b81ca23b8..9b11cb783a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,8 @@ This project adheres to [Semantic Versioning](https://semver.org/).
 ## [Unreleased] - ReleaseDate
 ### Added
 
+- Added `pidfd_send_signal` on Linux.
+  ([#1868](https://github.com/nix-rust/nix/pull/1868))
 - Added `pid_open` on Linux.
   ([#1868](https://github.com/nix-rust/nix/pull/1868))
 - Added `pidfd_getfd` on Linux.
diff --git a/src/sys/mod.rs b/src/sys/mod.rs
index e34a5a7e90..1f90ab0b8a 100644
--- a/src/sys/mod.rs
+++ b/src/sys/mod.rs
@@ -227,6 +227,6 @@ feature! {
     pub mod timer;
 }
 
-#[cfg(all(target_os = "linux", feature = "process"))]
+#[cfg(all(target_os = "linux", feature = "signal", feature = "process"))]
 /// pidfd related functionality
 pub mod pidfd;
diff --git a/src/sys/pidfd.rs b/src/sys/pidfd.rs
index f4229a8908..16911e87b8 100644
--- a/src/sys/pidfd.rs
+++ b/src/sys/pidfd.rs
@@ -1,4 +1,5 @@
 use crate::errno::Errno;
+use crate::sys::signal::Signal;
 use crate::unistd::Pid;
 use crate::Result;
 use std::convert::TryFrom;
@@ -58,3 +59,39 @@ pub fn pid_open(pid_t: Pid, pidfd_nonblock: bool) -> Result<RawFd> {
         _ => unreachable!(),
     }
 }
+
+/// Sends the signal `sig` to the target process referred to by `pidfd`, a PID file descriptor that
+/// refers to a process.
+///
+/// If the info argument is some [`libc::siginfo_t`] buffer, that buffer should be populated as
+/// described in [rt_sigqueueinfo(2)](https://man7.org/linux/man-pages/man2/rt_sigqueueinfo.2.html).
+///
+/// If the info argument is `None`, this is equivalent to specifying a pointer to a `siginfo_t`
+/// buffer whose fields match the values that are implicitly supplied when a signal is sent using
+/// [`crate::sys::signal::kill`]:
+///
+/// -  `si_signo` is set to the signal number;
+/// -  `si_errno` is set to 0;
+/// -  `si_code` is set to SI_USER;
+/// -  `si_pid` is set to the caller's PID; and
+/// -  `si_uid` is set to the caller's real user ID.
+///
+/// The calling process must either be in the same PID namespace as the process referred to by
+/// pidfd, or be in an ancestor of that namespace.
+pub fn pidfd_send_signal(
+    pidfd: RawFd,
+    sig: Signal,
+    info: Option<libc::siginfo_t>,
+) -> Result<()> {
+    let info = match info {
+        Some(i) => &i,
+        None => std::ptr::null(),
+    };
+    match unsafe {
+        libc::syscall(libc::SYS_pidfd_send_signal, pidfd, sig as i32, info)
+    } {
+        -1 => Err(Errno::last()),
+        0 => Ok(()),
+        _ => unreachable!(),
+    }
+}