Implement SafeProcessHandle.Kill and Signal

src/libraries/System.Diagnostics.Process/ref/System.Diagnostics.Process.cs

@@ -15,6 +15,14 @@ public SafeProcessHandle(System.IntPtr existingHandle, bool ownsHandle) : base (
         [System.Runtime.Versioning.UnsupportedOSPlatformAttribute("ios")]
         [System.Runtime.Versioning.UnsupportedOSPlatformAttribute("tvos")]
         [System.Runtime.Versioning.SupportedOSPlatformAttribute("maccatalyst")]
+        public void Kill() { }
+        [System.Runtime.Versioning.UnsupportedOSPlatformAttribute("ios")]
+        [System.Runtime.Versioning.UnsupportedOSPlatformAttribute("tvos")]
+        [System.Runtime.Versioning.SupportedOSPlatformAttribute("maccatalyst")]
+        public bool Signal(System.Runtime.InteropServices.PosixSignal signal) { throw null; }
+        [System.Runtime.Versioning.UnsupportedOSPlatformAttribute("ios")]
+        [System.Runtime.Versioning.UnsupportedOSPlatformAttribute("tvos")]
+        [System.Runtime.Versioning.SupportedOSPlatformAttribute("maccatalyst")]
         public static Microsoft.Win32.SafeHandles.SafeProcessHandle Start(System.Diagnostics.ProcessStartInfo startInfo) { throw null; }
     }
 }

src/libraries/System.Diagnostics.Process/src/Microsoft/Win32/SafeHandles/SafeProcessHandle.Unix.cs

@@ -59,6 +59,31 @@ protected override bool ReleaseHandle()
         // On Unix, we don't use process descriptors yet, so we can't get PID.
         private static int GetProcessIdCore() => throw new PlatformNotSupportedException();
 
+        private bool SignalCore(PosixSignal signal)
+        {
+            int signalNumber = Interop.Sys.GetPlatformSignalNumber(signal);
+            if (signalNumber == 0)
+            {
+                throw new PlatformNotSupportedException();
+            }
+
+            int killResult = Interop.Sys.Kill(ProcessId, (Interop.Sys.Signals)signalNumber);
+            if (killResult != 0)
+            {
+                Interop.ErrorInfo errorInfo = Interop.Sys.GetLastErrorInfo();
+
+                // Return false if the process has already exited (or never existed).
+                if (errorInfo.Error == Interop.Error.ESRCH)
+                {
+                    return false;
+                }
+
+                throw new Win32Exception(errorInfo.RawErrno); // same exception as on Windows
+            }
+
+            return true;
+        }
+
         private static SafeProcessHandle StartCore(ProcessStartInfo startInfo, SafeFileHandle? stdinHandle, SafeFileHandle? stdoutHandle, SafeFileHandle? stderrHandle)
         {
             SafeProcessHandle startedProcess = StartCore(startInfo, stdinHandle, stdoutHandle, stderrHandle, out ProcessWaitState.Holder? waitStateHolder);

src/libraries/System.Diagnostics.Process/src/Microsoft/Win32/SafeHandles/SafeProcessHandle.Windows.cs

@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System;
+using System.ComponentModel;
 using System.Diagnostics;
 using System.Runtime.InteropServices;
 using System.Security;
@@ -282,5 +283,31 @@ ref processInfo      // pointer to PROCESS_INFORMATION
         }
 
         private int GetProcessIdCore() => Interop.Kernel32.GetProcessId(this);
+
+        private bool SignalCore(PosixSignal signal)
+        {
+            // On Windows, only SIGKILL is supported, mapped to TerminateProcess.
+            if (signal != PosixSignal.SIGKILL)
+            {
+                throw new PlatformNotSupportedException();
+            }
+
+            if (!Interop.Kernel32.TerminateProcess(this, -1))
+            {
+                int errorCode = Marshal.GetLastWin32Error();
+
+                // Return false if the process has already exited.
+                if (errorCode == Interop.Errors.ERROR_ACCESS_DENIED &&
+                    Interop.Kernel32.GetExitCodeProcess(this, out int exitCode) &&
+                    exitCode != Interop.Kernel32.HandleOptions.STILL_ACTIVE)
+                {
+                    return false;
+                }
+
+                throw new Win32Exception(errorCode);
+            }
+
+            return true;
+        }
     }
 }

src/libraries/System.Diagnostics.Process/src/Microsoft/Win32/SafeHandles/SafeProcessHandle.cs

@@ -14,6 +14,7 @@
 using System.Diagnostics;
 using System.Runtime.Serialization;
 using System.Runtime.Versioning;
+using System.Runtime.InteropServices;
 
 namespace Microsoft.Win32.SafeHandles
 {
@@ -120,6 +121,47 @@ public static SafeProcessHandle Start(ProcessStartInfo startInfo)
             return StartCore(startInfo, childInputHandle, childOutputHandle, childErrorHandle);
         }
 
+        /// <summary>
+        /// Sends a request to the OS to terminate the process.
+        /// </summary>
+        /// <remarks>
+        /// This method does not throw if the process has already exited.
+        /// On Unix, this sends <c>SIGKILL</c> to the process.
+        /// </remarks>
+        /// <exception cref="InvalidOperationException">The handle is invalid.</exception>
+        /// <exception cref="System.ComponentModel.Win32Exception">The process could not be terminated.</exception>
+        [UnsupportedOSPlatform("ios")]
+        [UnsupportedOSPlatform("tvos")]
+        [SupportedOSPlatform("maccatalyst")]
+        public void Kill()
+        {
+            Validate();
+            SignalCore(PosixSignal.SIGKILL);
+        }
+
+        /// <summary>
+        /// Sends a signal to the process.
+        /// </summary>
+        /// <param name="signal">The signal to send.</param>
+        /// <returns>
+        /// <see langword="true"/> if the signal was sent successfully;
+        /// <see langword="false"/> if the process has already exited (or never existed) and the signal was not delivered.
+        /// </returns>
+        /// <remarks>
+        /// On Windows, only <see cref="PosixSignal.SIGKILL"/> is supported and is mapped to <see cref="Kill"/>.
+        /// </remarks>
+        /// <exception cref="InvalidOperationException">The handle is invalid.</exception>
+        /// <exception cref="PlatformNotSupportedException">The specified signal is not supported on this platform.</exception>
+        /// <exception cref="System.ComponentModel.Win32Exception">The signal could not be sent.</exception>
+        [UnsupportedOSPlatform("ios")]
+        [UnsupportedOSPlatform("tvos")]
+        [SupportedOSPlatform("maccatalyst")]
+        public bool Signal(PosixSignal signal)
+        {
+            Validate();
+            return SignalCore(signal);
+        }
+
         private void Validate()
         {
             if (IsInvalid)

src/libraries/System.Diagnostics.Process/src/System.Diagnostics.Process.csproj

@@ -264,6 +264,8 @@
              Link="Common\Interop\Unix\Interop.InitializeTerminalAndSignalHandling.cs" />
     <Compile Include="$(CommonPath)Interop\Unix\System.Native\Interop.Kill.cs"
              Link="Common\Interop\Unix\Interop.Kill.cs" />
+    <Compile Include="$(CommonPath)Interop\Unix\System.Native\Interop.PosixSignal.cs"
+             Link="Common\Interop\Unix\System.Native\Interop.PosixSignal.cs" />
     <Compile Include="$(CommonPath)Interop\Unix\System.Native\Interop.ReadLink.cs"
              Link="Common\Interop\Unix\Interop.ReadLink.cs" />
     <Compile Include="$(CommonPath)Interop\Unix\System.Native\Interop.RegisterForSigChld.cs"

src/libraries/System.Diagnostics.Process/tests/ProcessTests.Unix.cs

@@ -15,6 +15,7 @@
 using Xunit;
 using Microsoft.DotNet.RemoteExecutor;
 using Microsoft.DotNet.XUnitExtensions;
+using Microsoft.Win32.SafeHandles;
 
 namespace System.Diagnostics.Tests
 {
@@ -1114,8 +1115,8 @@ public void ChildProcess_WithParentSignalHandler_CanReceiveSignals()
 
                 AssertRemoteProcessStandardOutputLine(childHandle, ChildReadyMessage, WaitInMS);
 
-                // Send SIGCONT to the child process
-                SendSignal(PosixSignal.SIGCONT, childHandle.Process.Id);
+                // Send SIGCONT to the child process using SafeProcessHandle.Signal
+                Assert.True(childHandle.Process.SafeHandle.Signal(PosixSignal.SIGCONT));
 
                 Assert.True(childHandle.Process.WaitForExit(WaitInMS));
                 Assert.Equal(RemotelyInvokable.SuccessExitCode, childHandle.Process.ExitCode);

src/libraries/System.Diagnostics.Process/tests/SafeProcessHandleTests.cs

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System.IO;
+using System.Runtime.InteropServices;
+using System.Threading;
 using Microsoft.DotNet.RemoteExecutor;
 using Microsoft.Win32.SafeHandles;
 using Xunit;
@@ -94,5 +96,123 @@ public void Start_WithRedirectedStreams_ThrowsInvalidOperationException(
 
             Assert.Throws<InvalidOperationException>(() => SafeProcessHandle.Start(startInfo));
         }
+
+        [Fact]
+        public void Kill_InvalidHandle_ThrowsInvalidOperationException()
+        {
+            using SafeProcessHandle invalidHandle = new SafeProcessHandle();
+            Assert.Throws<InvalidOperationException>(() => invalidHandle.Kill());
+        }
+
+        [Fact]
+        public void Signal_InvalidHandle_ThrowsInvalidOperationException()
+        {
+            using SafeProcessHandle invalidHandle = new SafeProcessHandle();
+            Assert.Throws<InvalidOperationException>(() => invalidHandle.Signal(PosixSignal.SIGKILL));
+        }
+
+        [ConditionalFact(typeof(RemoteExecutor), nameof(RemoteExecutor.IsSupported))]
+        public void Kill_RunningProcess_Terminates()
+        {
+            Process process = CreateProcess(static () =>
+            {
+                Thread.Sleep(Timeout.Infinite);
+                return RemoteExecutor.SuccessExitCode;
+            });
+
+            using SafeProcessHandle processHandle = SafeProcessHandle.Start(process.StartInfo);
+            using Process fetchedProcess = Process.GetProcessById(processHandle.ProcessId);
+
+            processHandle.Kill();
+
+            Assert.True(fetchedProcess.WaitForExit(WaitInMS));
+        }
+
+        [ConditionalFact(typeof(RemoteExecutor), nameof(RemoteExecutor.IsSupported))]
+        public void Kill_AlreadyExited_DoesNotThrow()
+        {
+            Process process = CreateProcess(static () => RemoteExecutor.SuccessExitCode);
+            process.Start();
+            SafeProcessHandle handle = process.SafeHandle;
+
+            Assert.True(process.WaitForExit(WaitInMS));
+
+            // Kill after the process has exited should not throw.
+            handle.Kill();
+        }
+
+        [ConditionalFact(typeof(RemoteExecutor), nameof(RemoteExecutor.IsSupported))]
+        public void Signal_SIGKILL_RunningProcess_ReturnsTrue()
+        {
+            Process process = CreateProcess(static () =>
+            {
+                Thread.Sleep(Timeout.Infinite);
+                return RemoteExecutor.SuccessExitCode;
+            });
+
+            using SafeProcessHandle processHandle = SafeProcessHandle.Start(process.StartInfo);
+            using Process fetchedProcess = Process.GetProcessById(processHandle.ProcessId);
+
+            bool delivered = processHandle.Signal(PosixSignal.SIGKILL);
+
+            Assert.True(delivered);
+            Assert.True(fetchedProcess.WaitForExit(WaitInMS));
+        }
+
+        [ConditionalFact(typeof(RemoteExecutor), nameof(RemoteExecutor.IsSupported))]
+        public void Signal_SIGKILL_AlreadyExited_ReturnsFalse()
+        {
+            Process process = CreateProcess(static () => RemoteExecutor.SuccessExitCode);
+            process.Start();
+            SafeProcessHandle handle = process.SafeHandle;
+
+            Assert.True(process.WaitForExit(WaitInMS));
+
+            // Signal after the process has exited should return false.
+            Assert.False(handle.Signal(PosixSignal.SIGKILL));
+        }
+
+        [ConditionalFact(typeof(RemoteExecutor), nameof(RemoteExecutor.IsSupported))]
+        [PlatformSpecific(TestPlatforms.Windows)]
+        public void Signal_NonSIGKILL_OnWindows_ThrowsPlatformNotSupportedException()
+        {
+            Process process = CreateProcess(static () =>
+            {
+                Thread.Sleep(Timeout.Infinite);
+                return RemoteExecutor.SuccessExitCode;
+            });
+
+            using SafeProcessHandle processHandle = SafeProcessHandle.Start(process.StartInfo);
+            using Process fetchedProcess = Process.GetProcessById(processHandle.ProcessId);
+
+            try
+            {
+                Assert.Throws<PlatformNotSupportedException>(() => processHandle.Signal(PosixSignal.SIGTERM));
+            }
+            finally
+            {
+                processHandle.Kill();
+                fetchedProcess.WaitForExit(WaitInMS);
+            }
+        }
+
+        [ConditionalFact(typeof(RemoteExecutor), nameof(RemoteExecutor.IsSupported))]
+        [SkipOnPlatform(TestPlatforms.Windows, "SIGTERM is not supported on Windows.")]
+        public void Signal_SIGTERM_RunningProcess_ReturnsTrue()
+        {
+            Process process = CreateProcess(static () =>
+            {
+                Thread.Sleep(Timeout.Infinite);
+                return RemoteExecutor.SuccessExitCode;
+            });
+
+            using SafeProcessHandle processHandle = SafeProcessHandle.Start(process.StartInfo);
+            using Process fetchedProcess = Process.GetProcessById(processHandle.ProcessId);
+
+            bool delivered = processHandle.Signal(PosixSignal.SIGTERM);
+
+            Assert.True(delivered);
+            Assert.True(fetchedProcess.WaitForExit(WaitInMS));
+        }
     }
 }