Get rid of unsafe for procfs get methods

src/libraries/Common/src/Interop/SunOS/procfs/Interop.ProcFs.Definitions.cs

@@ -1,9 +1,15 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
+using System;
 using System.Runtime.InteropServices;
 
-// The const int PRARGSZ show up as unused.  Not sure why.
+// C# equivalents for <sys/procfs.h> structures. See: struct lwpsinfo, struct psinfo.
+// We read directly onto these from procfs, so the layouts and sizes of these structures
+// must _exactly_ match those in <sys/procfs.h>
+
+// analyzer incorrectly flags fixed buffer length const
+// (https://github.com/dotnet/roslyn/issues/37593)
 #pragma warning disable CA1823
 
 internal static partial class Interop
@@ -28,6 +34,7 @@ internal struct @timestruc_t
         }
 
         // lwp ps(1) information file.  /proc/<pid>/lwp/<lwpid>/lwpsinfo
+        // Equivalent to sys/procfs.h struct lwpsinfo
         // "unsafe" because it has fixed sized arrays.
         [StructLayout(LayoutKind.Sequential)]
         internal unsafe struct @lwpsinfo
@@ -56,8 +63,10 @@ internal unsafe struct @lwpsinfo
             private     int     pr_lgrp;        /* lwp home lgroup */
             private     fixed int       pr_filler[4];   /* reserved for future use */
         }
+        private const int PR_LWPSINFO_SIZE = 128; // for debug assertions
 
         // process ps(1) information file.  /proc/<pid>/psinfo
+        // Equivalent to sys/procfs.h struct psinfo
         // "unsafe" because it has fixed sized arrays.
         [StructLayout(LayoutKind.Sequential)]
         internal unsafe struct @psinfo
@@ -98,7 +107,12 @@ internal unsafe struct @psinfo
             public      int     pr_contract;    /* process contract */
             private     fixed int pr_filler[1]; /* reserved for future use */
             public      lwpsinfo pr_lwp;        /* information for representative lwp */
+            // C# magic: Accessor method to get a Span for pr_psargs[]
+            // Does not affect the size or layout of this struct.
+            internal     ReadOnlySpan<byte> PsArgsSpan =>
+                MemoryMarshal.CreateReadOnlySpan(ref pr_psargs[0], PRARGSZ);
         }
+        private const int PR_PSINFO_SIZE = 416; // for debug assertions
 
         // Ouput type for TryGetThreadInfoById()
         internal struct ThreadInfo

src/libraries/Common/src/Interop/SunOS/procfs/Interop.ProcFs.TryGetProcessInfoById.cs

@@ -7,6 +7,7 @@
 using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
 using System.IO;
+using System.Text;
 
 internal static partial class Interop
 {
@@ -23,8 +24,7 @@ internal static partial class @procfs
         /// </returns>
 
         // ProcessManager.SunOS.cs calls this
-        // "unsafe" due to use of fixed-size buffers
-        internal static unsafe bool TryGetProcessInfoById(int pid, out ProcessInfo result)
+        internal static bool TryGetProcessInfoById(int pid, out ProcessInfo result)
         {
             result = default;
 
@@ -34,7 +34,10 @@ internal static unsafe bool TryGetProcessInfoById(int pid, out ProcessInfo resul
                 using FileStream fs = new FileStream(fileName, FileMode.Open, FileAccess.Read);
                 psinfo pr;
                 Unsafe.SkipInit(out pr);
-                fs.ReadExactly(MemoryMarshal.AsBytes(new Span<psinfo>(ref pr)));
+                Span<byte> prspan = MemoryMarshal.AsBytes(new Span<psinfo>(ref pr));
+                Debug.Assert(prspan.Length == PR_PSINFO_SIZE,
+                    $"psinfo struct size {prspan.Length} bytes not {PR_PSINFO_SIZE}.");
+                fs.ReadExactly(prspan);
 
                 result.Pid = pr.pr_pid;
                 result.ParentPid = pr.pr_ppid;
@@ -45,7 +48,12 @@ internal static unsafe bool TryGetProcessInfoById(int pid, out ProcessInfo resul
                 result.StartTime.TvNsec = pr.pr_start.tv_nsec;
                 result.CpuTotalTime.TvSec = pr.pr_time.tv_sec;
                 result.CpuTotalTime.TvNsec = pr.pr_time.tv_nsec;
-                result.Args = Marshal.PtrToStringUTF8((IntPtr)pr.pr_psargs);
+
+                // Get Args as a managed string, using accessor for pr_psargs[]
+                ReadOnlySpan<byte> argspan = pr.PsArgsSpan;
+                int argslen = argspan.IndexOf((byte)0);
+                argslen = (argslen >= 0) ? argslen : argspan.Length;
+                result.Args = Encoding.UTF8.GetString(argspan.Slice(0, argslen));
 
                 // A couple things from pr_lwp
                 result.Priority = pr.pr_lwp.pr_pri;

src/libraries/Common/src/Interop/SunOS/procfs/Interop.ProcFs.TryGetThreadInfoById.cs

@@ -24,8 +24,7 @@ internal static partial class @procfs
         /// </returns>
 
         // ProcessManager.SunOS.cs calls this
-        // "unsafe" due to use of fixed-size buffers
-        internal static unsafe bool TryGetThreadInfoById(int pid, int tid, out ThreadInfo result)
+        internal static bool TryGetThreadInfoById(int pid, int tid, out ThreadInfo result)
         {
             result = default;
 
@@ -35,7 +34,10 @@ internal static unsafe bool TryGetThreadInfoById(int pid, int tid, out ThreadInf
                 using FileStream fs = new FileStream(fileName, FileMode.Open, FileAccess.Read);
                 lwpsinfo pr;
                 Unsafe.SkipInit(out pr);
-                fs.ReadExactly(MemoryMarshal.AsBytes(new Span<lwpsinfo>(ref pr)));
+                Span<byte> prspan = MemoryMarshal.AsBytes(new Span<lwpsinfo>(ref pr));
+                Debug.Assert(prspan.Length == PR_LWPSINFO_SIZE,
+                    $"psinfo struct size {prspan.Length} bytes not {PR_LWPSINFO_SIZE}.");
+                fs.ReadExactly(prspan);
 
                 result.Tid = pr.pr_lwpid;
                 result.Priority = pr.pr_pri;