Linux: ProcessName: return script name instead of interpreter program (#37294)

* Linux: ProcessName: return script name instead of interpreter program

Fixes https://github.com/dotnet/corefx/issues/37198
Regression by #37144

* Add ProcessNameMatchesScriptName test

* ProcessNameMatchesScriptName: don't run on OSX

* LongProcessNamesAreSupported: don't run on Alpine

* Remove ActiveIssue attributes

Author: tmds

src/Common/src/Interop/Linux/procfs/Interop.ProcFsStat.cs

@@ -33,7 +33,7 @@ internal struct ParsedStat
             // the MoveNext() with the appropriate ParseNext* call and assignment.
 
             internal int pid;
-            // internal string comm;
+            internal string comm;
             internal char state;
             internal int ppid;
             //internal int pgrp;
@@ -238,7 +238,7 @@ internal static bool TryParseStatFile(string statFilePath, out ParsedStat result
             var results = default(ParsedStat);
 
             results.pid = parser.ParseNextInt32();
-            parser.MoveAndExtractNextInOuterParens(extractValue: false); // comm
+            results.comm = parser.MoveAndExtractNextInOuterParens();
             results.state = parser.ParseNextChar();
             results.ppid = parser.ParseNextInt32();
             parser.MoveNextOrFail(); // pgrp

src/Common/src/System/IO/StringParser.cs

@@ -98,7 +98,7 @@ public string MoveAndExtractNext()
         /// in the string.  The extracted value will be everything between (not including) those parentheses.
         /// </summary>
         /// <returns></returns>
-        public string MoveAndExtractNextInOuterParens(bool extractValue = true)
+        public string MoveAndExtractNextInOuterParens()
         {
             // Move to the next position
             MoveNextOrFail();
@@ -118,7 +118,7 @@ public string MoveAndExtractNextInOuterParens(bool extractValue = true)
             }
 
             // Extract the contents of the parens, then move our ending position to be after the paren
-            string result = extractValue ? _buffer.Substring(_startIndex + 1, lastParen - _startIndex - 1) : null;
+            string result = _buffer.Substring(_startIndex + 1, lastParen - _startIndex - 1);
             _endIndex = lastParen + 1;
 
             return result;

src/Common/tests/Tests/Interop/procfsTests.cs

@@ -49,6 +49,7 @@ public static void ParseValidStatFiles_Success(
                 Assert.True(Interop.procfs.TryParseStatFile(path, out result, new ReusableTextReader()));
 
                 Assert.Equal(expectedPid, result.pid);
+                Assert.Equal(expectedComm, result.comm);
                 Assert.Equal(expectedState, result.state);
                 Assert.Equal(expectedSession, result.session);
                 Assert.Equal(expectedUtime, result.utime);

src/System.Diagnostics.Process/src/System/Diagnostics/Process.Linux.cs

@@ -30,9 +30,11 @@ public static Process[] GetProcessesByName(string processName, string machineNam
             var processes = new List<Process>();
             foreach (int pid in ProcessManager.EnumerateProcessIds())
             {
-                if (string.Equals(processName, Process.GetProcessName(pid), StringComparison.OrdinalIgnoreCase))
+                Interop.procfs.ParsedStat parsedStat;
+                if (Interop.procfs.TryReadStatFile(pid, out parsedStat, reusableReader) &&
+                    string.Equals(processName, Process.GetUntruncatedProcessName(ref parsedStat), StringComparison.OrdinalIgnoreCase))
                 {
-                    ProcessInfo processInfo = ProcessManager.CreateProcessInfo(pid, reusableReader, processName);
+                    ProcessInfo processInfo = ProcessManager.CreateProcessInfo(ref parsedStat, reusableReader, processName);
                     processes.Add(new Process(machineName, false, processInfo.ProcessId, processInfo));
                 }
             }
@@ -256,12 +258,10 @@ internal static string GetExePath(int processId = -1)
         }
 
         /// <summary>Gets the name that was used to start the process, or null if it could not be retrieved.</summary>
-        /// <param name="processId">The pid for the target process, or -1 for the current process.</param>
-        internal static string GetProcessName(int processId = -1)
+        /// <param name="stat">The stat for the target process.</param>
+        internal static string GetUntruncatedProcessName(ref Interop.procfs.ParsedStat stat)
         {
-            string cmdLineFilePath = processId == -1 ?
-                Interop.procfs.SelfCmdLineFilePath :
-                Interop.procfs.GetCmdLinePathForProcess(processId);
+            string cmdLineFilePath = Interop.procfs.GetCmdLinePathForProcess(stat.pid);
 
             byte[] rentedArray = null;
             try
@@ -282,7 +282,7 @@ internal static string GetProcessName(int processId = -1)
                             buffer.CopyTo(tmp);
                             byte[] toReturn = rentedArray;
                             buffer = rentedArray = tmp;
-                            if (rentedArray != null)
+                            if (toReturn != null)
                             {
                                 ArrayPool<byte>.Shared.Return(toReturn);
                             }
@@ -293,26 +293,40 @@ internal static string GetProcessName(int processId = -1)
                         bytesRead += n;
 
                         // cmdline contains the argv array separated by '\0' bytes.
-                        // we determine the process name using argv[0].
-                        int argv0End = buffer.Slice(0, bytesRead).IndexOf((byte)'\0');
-                        if (argv0End != -1)
+                        // stat.comm contains a possibly truncated version of the process name.
+                        // When the program is a native executable, the process name will be in argv[0].
+                        // When the program is a script, argv[0] contains the interpreter, and argv[1] contains the script name.
+                        Span<byte> argRemainder = buffer.Slice(0, bytesRead);
+                        int argEnd = argRemainder.IndexOf((byte)'\0');
+                        if (argEnd != -1)
                         {
-                            // Strip directory names from argv[0].
-                            int nameStart = buffer.Slice(0, argv0End).LastIndexOf((byte)'/') + 1;
+                            // Check if argv[0] has the process name.
+                            string name = GetUntruncatedNameFromArg(argRemainder.Slice(0, argEnd), prefix: stat.comm);
+                            if (name != null)
+                            {
+                                return name;
+                            }
 
-                            return Encoding.UTF8.GetString(buffer.Slice(nameStart, argv0End - nameStart));
+                            // Check if argv[1] has the process name.
+                            argRemainder = argRemainder.Slice(argEnd + 1);
+                            argEnd = argRemainder.IndexOf((byte)'\0');
+                            if (argEnd != -1)
+                            {
+                                name = GetUntruncatedNameFromArg(argRemainder.Slice(0, argEnd), prefix: stat.comm);
+                                return name ?? stat.comm;
+                            }
                         }
 
                         if (n == 0)
                         {
-                            return null;
+                            return stat.comm;
                         }
                     }
                 }
             }
             catch (IOException)
             {
-                return null;
+                return stat.comm;
             }
             finally
             {
@@ -321,6 +335,22 @@ internal static string GetProcessName(int processId = -1)
                     ArrayPool<byte>.Shared.Return(rentedArray);
                 }
             }
+
+            string GetUntruncatedNameFromArg(Span<byte> arg, string prefix)
+            {
+                // Strip directory names from arg.
+                int nameStart = arg.LastIndexOf((byte)'/') + 1;
+                string argString = Encoding.UTF8.GetString(arg.Slice(nameStart));
+
+                if (argString.StartsWith(prefix, StringComparison.OrdinalIgnoreCase))
+                {
+                    return argString;
+                }
+                else
+                {
+                    return null;
+                }
+            }
         }
 
         // ----------------------------------

src/System.Diagnostics.Process/src/System/Diagnostics/ProcessManager.Linux.cs

@@ -108,7 +108,7 @@ internal static ProcessModuleCollection GetModules(int processId)
         /// <summary>
         /// Creates a ProcessInfo from the specified process ID.
         /// </summary>
-        internal static ProcessInfo CreateProcessInfo(int pid, ReusableTextReader reusableReader = null, string processName = null)
+        internal static ProcessInfo CreateProcessInfo(int pid, ReusableTextReader reusableReader = null)
         {
             if (reusableReader == null)
             {
@@ -117,21 +117,21 @@ internal static ProcessInfo CreateProcessInfo(int pid, ReusableTextReader reusab
 
             Interop.procfs.ParsedStat stat;
             return Interop.procfs.TryReadStatFile(pid, out stat, reusableReader) ?
-                CreateProcessInfo(stat, reusableReader, processName) :
+                CreateProcessInfo(ref stat, reusableReader) :
                 null;
         }
 
         /// <summary>
         /// Creates a ProcessInfo from the data parsed from a /proc/pid/stat file and the associated tasks directory.
         /// </summary>
-        internal static ProcessInfo CreateProcessInfo(Interop.procfs.ParsedStat procFsStat, ReusableTextReader reusableReader, string processName)
+        internal static ProcessInfo CreateProcessInfo(ref Interop.procfs.ParsedStat procFsStat, ReusableTextReader reusableReader, string processName = null)
         {
             int pid = procFsStat.pid;
 
             var pi = new ProcessInfo()
             {
                 ProcessId = pid,
-                ProcessName = processName ?? Process.GetProcessName(pid) ?? string.Empty,
+                ProcessName = processName ?? Process.GetUntruncatedProcessName(ref procFsStat) ?? string.Empty,
                 BasePriority = (int)procFsStat.nice,
                 VirtualBytes = (long)procFsStat.vsize,
                 WorkingSet = procFsStat.rss * Environment.SystemPageSize,

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

@@ -124,7 +124,6 @@ public void ProcessStart_UseShellExecute_OnUnix_OpenMissingFile_DoesNotThrow()
             }
         }
 
-        [ActiveIssue(37198)]
         [Theory, InlineData(true), InlineData(false)]
         [OuterLoop("Opens program")]
         public void ProcessStart_UseShellExecute_OnUnix_SuccessWhenProgramInstalled(bool isFolder)
@@ -157,6 +156,31 @@ public void ProcessStart_UseShellExecute_OnUnix_SuccessWhenProgramInstalled(bool
             }
         }
 
+        [Fact]
+        [PlatformSpecific(~TestPlatforms.OSX)] // On OSX, ProcessName returns the script interpreter.
+        public void ProcessNameMatchesScriptName()
+        {
+            string scriptName = GetTestFileName();
+            string filename = Path.Combine(TestDirectory, scriptName);
+            File.WriteAllText(filename, $"#!/bin/sh\nsleep 600\n"); // sleep 10 min.
+            // set x-bit
+            int mode = Convert.ToInt32("744", 8);
+            Assert.Equal(0, chmod(filename, mode));
+
+            using (var process = Process.Start(new ProcessStartInfo { FileName = filename }))
+            {
+                try
+                {
+                    Assert.Equal(scriptName, process.ProcessName);
+                }
+                finally
+                {
+                    process.Kill();
+                    process.WaitForExit();
+                }
+            }
+        }
+
         [Fact]
         [PlatformSpecific(TestPlatforms.Linux)] // s_allowedProgramsToRun is Linux specific
         public void ProcessStart_UseShellExecute_OnUnix_FallsBackWhenNotRealExecutable()
@@ -294,7 +318,6 @@ public void ProcessStart_OpenFileOnLinux_UsesSpecifiedProgram(string programToOp
             }
         }
 
-        [ActiveIssue(37198)]
         [Theory, InlineData("vi")]
         [PlatformSpecific(TestPlatforms.Linux)]
         [OuterLoop("Opens program")]

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

@@ -1921,15 +1921,16 @@ public void TestLongProcessIsWorking()
             Assert.True(p.HasExited);
         }
 
-        [ActiveIssue(37198)]
         [PlatformSpecific(TestPlatforms.AnyUnix)]
         [ActiveIssue(37054, TestPlatforms.OSX)]
         [Fact]
         public void LongProcessNamesAreSupported()
         {
+            // Alpine implements sleep as a symlink to the busybox executable.
+            // If we rename it, the program will no longer sleep.
             if (PlatformDetection.IsAlpine)
             {
-                return; // https://github.com/dotnet/corefx/issues/37054
+                return;
             }
 
             string programPath = GetProgramPath("sleep");