Ensure ProcessModule for main executable is first in modules list

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

@@ -14,13 +14,15 @@ internal static partial class Interop
     internal static partial class procfs
     {
         internal const string RootPath = "/proc/";
-        internal const string SelfExeFilePath = RootPath + "self/exe";
-        internal const string ProcUptimeFilePath = RootPath + "uptime";
+        private const string ExeFileName = "/exe";
         private const string StatFileName = "/stat";
         private const string MapsFileName = "/maps";
         private const string FileDescriptorDirectoryName = "/fd/";
         private const string TaskDirectoryName = "/task/";
 
+        internal const string SelfExeFilePath = RootPath + "self" + ExeFileName;
+        internal const string ProcUptimeFilePath = RootPath + "uptime";
+
         internal struct ParsedStat
         {
             // Commented out fields are available in the stat data file but 
@@ -80,6 +82,11 @@ internal struct ParsedMapsModule
             internal KeyValuePair<long, long> AddressRange;
         }
 
+        internal static string GetExeFilePathForProcess(int pid)
+        {
+            return RootPath + pid.ToString(CultureInfo.InvariantCulture) + ExeFileName;
+        }
+
         internal static string GetStatFilePathForProcess(int pid)
         {
             return RootPath + pid.ToString(CultureInfo.InvariantCulture) + StatFileName;

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

@@ -186,9 +186,14 @@ private void SetWorkingSetLimitsCore(IntPtr? newMin, IntPtr? newMax, out IntPtr
         // ---- PAL layer ends here ----
         // -----------------------------
 
-        /// <summary>Gets the path to the current executable, or null if it could not be retrieved.</summary>
-        private static string GetExePath()
+        /// <summary>Gets the path to the executable for 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 GetExePath(int processId = -1)
         {
+            string exeFilePath = processId == -1 ?
+                Interop.procfs.SelfExeFilePath :
+                Interop.procfs.GetExeFilePathForProcess(processId);
+
             // Determine the maximum size of a path
             int maxPath = Interop.Sys.MaxPath;
 
@@ -197,7 +202,7 @@ private static string GetExePath()
             {
                 // Read from procfs the symbolic link to this process' executable
                 byte[] buffer = new byte[pathLen + 1]; // +1 for null termination
-                int resultLength = Interop.Sys.ReadLink(Interop.procfs.SelfExeFilePath, buffer, pathLen);
+                int resultLength = Interop.Sys.ReadLink(exeFilePath, buffer, pathLen);
 
                 // If we got one, null terminate it (readlink doesn't do this) and return the string
                 if (resultLength > 0)

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

@@ -80,6 +80,22 @@ internal static ProcessModuleCollection GetModules(int processId)
                 }
             }
 
+            // Move the main executable module to be the first in the list if it's not already
+            string exePath = Process.GetExePath(processId);
+            for (int i = 0; i < modules.Count; i++)
+            {
+                ProcessModule module = modules[i];
+                if (module.FileName == exePath)
+                {
+                    if (i > 0)
+                    {
+                        modules.RemoveAt(i);
+                        modules.Insert(0, module);
+                    }
+                    break;
+                }
+            }
+
             // Return the set of modules found
             return modules;
         }

src/System.Diagnostics.Process/src/System/Diagnostics/ProcessModuleCollection.cs

@@ -27,6 +27,10 @@ internal ProcessModuleCollection(int capacity)
 
         internal void Add(ProcessModule module) => InnerList.Add(module);
 
+        internal void Insert(int index, ProcessModule module) => InnerList.Insert(index, module);
+
+        internal void RemoveAt(int index) => InnerList.RemoveAt(index);
+
         public ProcessModule this[int index] => (ProcessModule)InnerList[index];
 
         public int IndexOf(ProcessModule module) => InnerList.IndexOf(module);