uucore: handle SIGRTMIN+N and SIGRTMAX-N notation

src/uu/env/src/env.rs

@@ -20,10 +20,7 @@
 #[cfg(unix)]
 use nix::libc;
 #[cfg(unix)]
-use nix::sys::signal::{
-    SigHandler::{SigDfl, SigIgn},
-    SigSet, SigmaskHow, Signal, signal, sigprocmask,
-};
+use nix::sys::signal::{sigprocmask, SigSet, SigmaskHow};
 #[cfg(unix)]
 use nix::unistd::execvp;
 use std::borrow::Cow;
@@ -36,6 +33,7 @@
 use std::io;
 use std::io::Write as _;
 use std::io::stderr;
+use std::mem::zeroed;
 #[cfg(unix)]
 use std::os::unix::ffi::OsStrExt;
 
@@ -294,19 +292,6 @@
     Ok(request)
 }
 
-#[cfg(unix)]
-fn signal_from_value(sig_value: usize) -> UResult<Signal> {
-    Signal::try_from(sig_value as i32).map_err(|_| {
-        USimpleError::new(
-            125,
-            translate!(
-                "env-error-invalid-signal",
-                "signal" => sig_value.to_string().quote()
-            ),
-        )
-    })
-}
-
 fn load_config_file(opts: &mut Options) -> UResult<()> {
     // NOTE: config files are parsed using an INI parser b/c it's available and compatible with ".env"-style files
     //   ... * but support for actual INI files, although working, is not intended, nor claimed
@@ -1072,15 +1057,10 @@
     signal_fn: F,
 ) -> UResult<()>
 where
-    F: Fn(Signal) -> UResult<()>,
+    F: Fn(usize) -> UResult<()>,
 {
     request.for_each_signal(|sig_value, explicit| {
-        // On some platforms ALL_SIGNALS may contain values that are not valid in libc.
-        // Skip those invalid ones and continue (GNU env also ignores undefined signals).
-        let Ok(sig) = signal_from_value(sig_value) else {
-            return Ok(());
-        };
-        signal_fn(sig)?;
+        signal_fn(sig_value)?;
         log.record(sig_value, action_kind, explicit);
 
         // Set environment variable to communicate to Rust child processes
@@ -1096,9 +1076,14 @@
 }
 
 #[cfg(unix)]
-fn ignore_signal(sig: Signal) -> UResult<()> {
+fn ignore_signal(sig: usize) -> UResult<()> {
     // SAFETY: This is safe because we write the handler for each signal only once, and therefore "the current handler is the default", as the documentation requires it.
-    let result = unsafe { signal(sig, SigIgn) };
+    // nix::sys::signal::Signal does not cover real-time signals, so we need to call
+    // libc::signal directly.
+    let result = unsafe {
+        let res = libc::signal(sig as libc::c_int, libc::SIG_IGN);
+        nix::errno::Errno::result(res)
+    };
     if let Err(err) = result {
         return Err(USimpleError::new(
             125,
@@ -1109,8 +1094,13 @@
 }
 
 #[cfg(unix)]
-fn reset_signal(sig: Signal) -> UResult<()> {
-    let result = unsafe { signal(sig, SigDfl) };
+fn reset_signal(sig: usize) -> UResult<()> {
+    // nix::sys::signal::Signal does not cover real-time signals, so we need to call
+    // libc::signal directly.
+    let result = unsafe {
+        let res = libc::signal(sig as libc::c_int, libc::SIG_DFL);
+        nix::errno::Errno::result(res)
+    };
     if let Err(err) = result {
         return Err(USimpleError::new(
             125,
@@ -1121,9 +1111,36 @@
 }
 
 #[cfg(unix)]
-fn block_signal(sig: Signal) -> UResult<()> {
-    let mut set = SigSet::empty();
-    set.add(sig);
+fn block_signal(sig: usize) -> UResult<()> {
+    // nix::sys::signal::Signal does not cover real time signals, so we need to build
+    // sigset_t manually using libc.
+    let set = unsafe {
+        let mut sigset: libc::sigset_t = zeroed();
+
+        if let Err(err) = nix::errno::Errno::result(libc::sigemptyset(&mut sigset)) {
+            return Err(USimpleError::new(
+                125,
+                translate!(
+                    "env-error-failed-set-signal-action",
+                    "signal" => (sig as i32),
+                    "error" => err.desc()
+                ),
+            ));
+        }
+        if let Err(err) = nix::errno::Errno::result(libc::sigaddset(&mut sigset, sig as libc::c_int))
+        {
+            return Err(USimpleError::new(
+                125,
+                translate!(
+                    "env-error-failed-set-signal-action",
+                    "signal" => (sig as i32),
+                    "error" => err.desc()
+                ),
+            ));
+        }
+        SigSet::from_sigset_t_unchecked(sigset)
+    };
+
     if let Err(err) = sigprocmask(SigmaskHow::SIG_BLOCK, Some(&set), None) {
         return Err(USimpleError::new(
             125,
@@ -1148,7 +1165,7 @@
             SignalActionKind::Ignore => "IGNORE",
             SignalActionKind::Block => "BLOCK",
         };
-        let signal_name = signal_name_by_value(sig_value).unwrap_or("?");
+        let signal_name = signal_name_by_value(sig_value).unwrap_or("?".to_string());
         eprintln!("{signal_name:<10} ({}): {action}", sig_value as i32);
     }
 }

src/uu/kill/src/kill.rs

@@ -6,16 +6,16 @@
 // spell-checker:ignore (ToDO) signalname pids killpg
 
 use clap::{Arg, ArgAction, Command};
-use nix::sys::signal::{self, Signal};
-use nix::unistd::Pid;
+use nix::libc;
+use nix::errno::Errno;
 use std::io::Error;
 use uucore::display::Quotable;
 use uucore::error::{FromIo, UResult, USimpleError};
 use uucore::translate;
 
 use uucore::signals::{
     signal_by_name_or_value, signal_list_name_by_value, signal_list_value_by_name_or_number,
-    signal_name_by_value, signal_number_upper_bound,
+    signal_number_upper_bound,
 };
 use uucore::{format_usage, show};
 
@@ -68,18 +68,6 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
                 15_usize //SIGTERM
             };
 
-            let sig_name = signal_name_by_value(sig);
-            // Signal does not support converting from EXIT
-            // Instead, nix::signal::kill expects Option::None to properly handle EXIT
-            let sig: Option<Signal> = if sig_name.is_some_and(|name| name == "EXIT") {
-                None
-            } else {
-                let sig = (sig as i32)
-                    .try_into()
-                    .map_err(|e| Error::from_raw_os_error(e as i32))?;
-                Some(sig)
-            };
-
             let pids = parse_pids(&pids_or_signals)?;
             if pids.is_empty() {
                 Err(USimpleError::new(1, translate!("kill-error-no-process-id")))
@@ -250,9 +238,14 @@ fn parse_pids(pids: &[String]) -> UResult<Vec<i32>> {
         .collect()
 }
 
-fn kill(sig: Option<Signal>, pids: &[i32]) {
+fn kill(sig: usize, pids: &[i32]) {
     for &pid in pids {
-        if let Err(e) = signal::kill(Pid::from_raw(pid), sig) {
+        let result = unsafe {
+            let res = libc::kill(pid, sig as libc::c_int);
+            Errno::result(res)
+        };
+
+        if let Err(e) = result {
             show!(
                 Error::from_raw_os_error(e as i32)
                     .map_err_context(|| { translate!("kill-error-sending-signal", "pid" => pid) })

src/uucore/src/lib/features/signals.rs

@@ -399,31 +399,67 @@ pub fn signal_by_name_or_value(signal_name_or_value: &str) -> Option<usize> {
         if is_signal(value) {
             return Some(value);
         }
-        return realtime_signal_bounds()
-            .filter(|&(rtmin, rtmax)| value >= rtmin && value <= rtmax)
-            .map(|_| value);
     }
     let signal_name = signal_name_upcase.trim_start_matches("SIG");
 
     if let Some(pos) = ALL_SIGNALS.iter().position(|&s| s == signal_name) {
         return Some(pos);
     }
 
-    realtime_signal_bounds().and_then(|(rtmin, rtmax)| match signal_name {
-        "RTMIN" => Some(rtmin),
-        "RTMAX" => Some(rtmax),
-        _ => None,
+    realtime_signal_bounds().and_then(|(rtmin, rtmax)| {
+        if signal_name.starts_with("RTMIN+") {
+            if let Ok(n) = signal_name.trim_start_matches("RTMIN+").parse::<usize>() {
+                let value = rtmin + n;
+                return (value >= rtmin && value <= rtmax).then_some(value);
+            }
+        }
+
+        if signal_name.starts_with("RTMAX-") {
+            if let Ok(n) = signal_name.trim_start_matches("RTMAX-").parse::<usize>() {
+                let value = rtmax - n;
+                return (value >= rtmin && value <= rtmax).then_some(value);
+            }
+        }
+
+        match signal_name {
+            "RTMIN" => Some(rtmin),
+            "RTMAX" => Some(rtmax),
+            _ => None,
+        }
     })
 }
 
 /// Returns true if the given number is a valid signal number.
 pub fn is_signal(num: usize) -> bool {
-    num < ALL_SIGNALS.len()
+    if num < ALL_SIGNALS.len() {
+        return true;
+    }
+
+    if let Some((rtmin, rtmax)) = realtime_signal_bounds() {
+        return num >= rtmin && num <= rtmax;
+    }
+
+    false
 }
 
 /// Returns the signal name for a given signal value.
-pub fn signal_name_by_value(signal_value: usize) -> Option<&'static str> {
-    ALL_SIGNALS.get(signal_value).copied()
+pub fn signal_name_by_value(signal_value: usize) -> Option<String> {
+    if let Some(name) = ALL_SIGNALS.get(signal_value).copied() {
+        return Some(name.to_string());
+    }
+
+    realtime_signal_bounds().and_then(|(rtmin, rtmax)| {
+        if signal_value == rtmin {
+            Some("RTMIN".to_string())
+        } else if signal_value == rtmax {
+            Some("RTMAX".to_string())
+        } else if signal_value > rtmin && signal_value < rtmax {
+            let n = signal_value - rtmin;
+            Some(format!("RTMIN+{n}"))
+        } else {
+            None
+        }
+    })
 }
 
 #[cfg(any(target_os = "linux", target_os = "android"))]
@@ -449,7 +485,7 @@ pub fn signal_number_upper_bound() -> usize {
 /// Returns the signal name for list-style interfaces.
 pub fn signal_list_name_by_value(signal_value: usize) -> Option<String> {
     if let Some(signal_name) = signal_name_by_value(signal_value) {
-        return Some(signal_name.to_string());
+        return Some(signal_name);
     }
 
     realtime_signal_bounds().and_then(|(rtmin, rtmax)| {
@@ -719,7 +755,7 @@ fn signal_by_long_name() {
 #[test]
 fn name() {
     for (value, signal) in ALL_SIGNALS.iter().enumerate() {
-        assert_eq!(signal_name_by_value(value), Some(*signal));
+        assert_eq!(signal_name_by_value(value), Some(signal.to_string()));
     }
 }
 
@@ -783,11 +819,35 @@ fn linux_realtime_signals_resolve_by_name_or_value() {
 
     // By name
     assert_eq!(signal_by_name_or_value("RTMIN"), Some(rtmin));
+    for i in 1..rtmax - rtmin - 1 {
+        assert_eq!(
+            signal_by_name_or_value(&format!("RTMIN+{i}")),
+            Some(rtmin + i)
+        );
+        assert_eq!(
+            signal_by_name_or_value(&format!("RTMAX-{i}")),
+            Some(rtmax - i)
+        );
+    }
     assert_eq!(signal_by_name_or_value("RTMAX"), Some(rtmax));
     assert_eq!(signal_by_name_or_value("SIGRTMIN"), Some(rtmin));
+    for i in 1..rtmax - rtmin - 1 {
+        assert_eq!(
+            signal_by_name_or_value(&format!("SIGRTMIN+{i}")),
+            Some(rtmin + i)
+        );
+        assert_eq!(
+            signal_by_name_or_value(&format!("SIGRTMAX-{i}")),
+            Some(rtmax - i)
+        );
+    }
     assert_eq!(signal_by_name_or_value("SIGRTMAX"), Some(rtmax));
 
     // By numeric value
     assert_eq!(signal_by_name_or_value(&rtmin.to_string()), Some(rtmin));
+    for i in 1..rtmax - rtmin - 1 {
+        let value = rtmin + i;
+        assert_eq!(signal_by_name_or_value(&value.to_string()), Some(value));
+    }
     assert_eq!(signal_by_name_or_value(&rtmax.to_string()), Some(rtmax));
 }