ProcessInfo2 Diagnostics IPC Command (#52258)

* Stash the entrypoint assembly path

* Add ep funcs for accessing entrypoint and version
 * TODO: get Mono's entrypoint asm

* Add ProcessInfo2 command
 * command includes everything the first one did + product ver
   and entrypoint asm path
* Add a test too

* Mono build fixes

* fix Mono build

* PR feedback
* fetch mono info from main assembly
* remove ref naming
* remove lazy method

* handle bundled host
* need to test still

* Use assembly name
* simplify access patterns
* change API to utf8
* updated test

* update comment

* PR feedback

* save before I commit this time...

* fix merge conflict

* Update ds-process-protocol.c

add missing break statement from merge conflict fix

* Update src/native/eventpipe/ds-process-protocol.h

* Update ds-process-protocol.c

add missing frees

* PR feedback

10 files changed, 619 insertions, 1 deletions

diff --git a/src/coreclr/vm/eventing/eventpipe/ep-rt-coreclr.h b/src/coreclr/vm/eventing/eventpipe/ep-rt-coreclr.h
index a6400416a4e..38d5598be0b 100644
--- a/src/coreclr/vm/eventing/eventpipe/ep-rt-coreclr.h
+++ b/src/coreclr/vm/eventing/eventpipe/ep-rt-coreclr.h
@@ -12,6 +12,7 @@
 #include "fstream.h"
 #include "typestring.h"
 #include "win32threadpool.h"
+#include "clrversion.h"
 
 #undef EP_ARRAY_SIZE
 #define EP_ARRAY_SIZE(expr) (sizeof(expr) / sizeof ((expr) [0]))
@@ -1161,6 +1162,25 @@ ep_rt_coreclr_config_lock_get (void)
 	return &_ep_rt_coreclr_config_lock_handle;
 }
 
+static
+inline
+const ep_char8_t *
+ep_rt_entrypoint_assembly_name_get_utf8 (void)
+{
+	STATIC_CONTRACT_NOTHROW;
+
+	return reinterpret_cast<const ep_char8_t*>(GetAppDomain ()->GetRootAssembly ()->GetSimpleName ());
+}
+
+static
+const ep_char8_t *
+ep_rt_runtime_version_get_utf8 (void)
+{
+	STATIC_CONTRACT_NOTHROW;
+
+	return reinterpret_cast<const ep_char8_t*>(CLR_PRODUCT_VERSION);
+}
+
 /*
 * Atomics.
 */
diff --git a/src/mono/mono/eventpipe/ep-rt-mono.c b/src/mono/mono/eventpipe/ep-rt-mono.c
index 8416cf0ad8f..f8b85538db0 100644
--- a/src/mono/mono/eventpipe/ep-rt-mono.c
+++ b/src/mono/mono/eventpipe/ep-rt-mono.c
@@ -44,6 +44,7 @@ char *_ep_rt_mono_os_cmd_line = NULL;
 mono_lazy_init_t _ep_rt_mono_managed_cmd_line_init = MONO_LAZY_INIT_STATUS_NOT_INITIALIZED;
 char *_ep_rt_mono_managed_cmd_line = NULL;
 
+
 // Sample profiler.
 static GArray * _ep_rt_mono_sampled_thread_callstacks = NULL;
 static uint32_t _ep_rt_mono_max_sampled_thread_count = 32;
diff --git a/src/mono/mono/eventpipe/ep-rt-mono.h b/src/mono/mono/eventpipe/ep-rt-mono.h
index c048682445c..22bdccdcd7d 100644
--- a/src/mono/mono/eventpipe/ep-rt-mono.h
+++ b/src/mono/mono/eventpipe/ep-rt-mono.h
@@ -20,9 +20,12 @@
 #include <mono/utils/mono-rand.h>
 #include <mono/utils/mono-lazy-init.h>
 #include <mono/utils/w32api.h>
+#include <mono/metadata/assembly.h>
 #include <mono/metadata/w32file.h>
 #include <mono/metadata/w32event.h>
 #include <mono/metadata/environment-internals.h>
+#include <mono/metadata/metadata-internals.h>
+#include <runtime_version.h>
 #include <mono/metadata/profiler.h>
 
 #undef EP_ARRAY_SIZE
@@ -1824,6 +1827,22 @@ ep_rt_diagnostics_command_line_get (void)
 	return cmd_line;
 }
 
+static
+inline
+const ep_char8_t *
+ep_rt_entrypoint_assembly_name_get_utf8 (void)
+{
+	return (const ep_char8_t *)m_image_get_assembly_name (mono_assembly_get_main ()->image);
+}
+
+static
+inline
+const ep_char8_t *
+ep_rt_runtime_version_get_utf8 (void)
+{
+	return (const ep_char8_t *)EGLIB_TOSTRING (RuntimeProductVersion);
+}
+
 /*
  * Thread.
  */
diff --git a/src/native/eventpipe/ds-process-protocol.c b/src/native/eventpipe/ds-process-protocol.c
index 2ce9ddc4fc4..75886a79ff3 100644
--- a/src/native/eventpipe/ds-process-protocol.c
+++ b/src/native/eventpipe/ds-process-protocol.c
@@ -55,6 +55,12 @@ process_protocol_helper_get_process_info (
 
 static
 bool
+process_protocol_helper_get_process_info_2 (
+	DiagnosticsIpcMessage *message,
+	DiagnosticsIpcStream *stream);
+
+static
+bool
 process_protocol_helper_get_process_env (
 	DiagnosticsIpcMessage *message,
 	DiagnosticsIpcStream *stream);
@@ -192,6 +198,143 @@ ds_process_info_payload_fini (DiagnosticsProcessInfoPayload *payload)
 }
 
 /*
+ * DiagnosticsProcessInfo2Payload.
+ */
+
+static
+uint16_t
+process_info_2_payload_get_size (DiagnosticsProcessInfo2Payload *payload)
+{
+	// see IPC spec @ https://github.com/dotnet/diagnostics/blob/master/documentation/design-docs/ipc-protocol.md
+	// for definition of serialization format
+
+	// uint64_t ProcessId;  -> 8 bytes
+	// GUID RuntimeCookie;  -> 16 bytes
+	// LPCWSTR CommandLine; -> 4 bytes + strlen * sizeof(WCHAR)
+	// LPCWSTR OS;          -> 4 bytes + strlen * sizeof(WCHAR)
+	// LPCWSTR Arch;        -> 4 bytes + strlen * sizeof(WCHAR)
+	// LPCWSTR managed_entrypoint_assembly_name;	-> 4 bytes + strlen * sizeof(WCHAR)
+	// LPCWSTR clr_product_version; 				-> 4 bytes + strlen * sizeof(WCHAR)
+
+	EP_ASSERT (payload != NULL);
+
+	size_t size = 0;
+	size += sizeof(payload->process_id);
+	size += sizeof(payload->runtime_cookie);
+
+	size += sizeof(uint32_t);
+	size += (payload->command_line != NULL) ?
+		(ep_rt_utf16_string_len (payload->command_line) + 1) * sizeof(ep_char16_t) : 0;
+
+	size += sizeof(uint32_t);
+	size += (payload->os != NULL) ?
+		(ep_rt_utf16_string_len (payload->os) + 1) * sizeof(ep_char16_t) : 0;
+
+	size += sizeof(uint32_t);
+	size += (payload->arch != NULL) ?
+		(ep_rt_utf16_string_len (payload->arch) + 1) * sizeof(ep_char16_t) : 0;
+
+	size += sizeof(uint32_t);
+	size += (payload->managed_entrypoint_assembly_name != NULL) ?
+		(ep_rt_utf16_string_len (payload->managed_entrypoint_assembly_name) + 1) * sizeof(ep_char16_t) : 0;
+
+	size += sizeof(uint32_t);
+	size += (payload->clr_product_version != NULL) ?
+		(ep_rt_utf16_string_len (payload->clr_product_version) + 1) * sizeof(ep_char16_t) : 0;
+
+	EP_ASSERT (size <= UINT16_MAX);
+	return (uint16_t)size;
+}
+
+static
+bool
+process_info_2_payload_flatten (
+	void *payload,
+	uint8_t **buffer,
+	uint16_t *size)
+{
+	DiagnosticsProcessInfo2Payload *process_info = (DiagnosticsProcessInfo2Payload*)payload;
+
+	EP_ASSERT (payload != NULL);
+	EP_ASSERT (buffer != NULL);
+	EP_ASSERT (*buffer != NULL);
+	EP_ASSERT (size != NULL);
+	EP_ASSERT (process_info_2_payload_get_size (process_info) == *size);
+
+	// see IPC spec @ https://github.com/dotnet/diagnostics/blob/master/documentation/design-docs/ipc-protocol.md
+	// for definition of serialization format
+
+	bool success = true;
+
+	// uint64_t ProcessId;
+	memcpy (*buffer, &process_info->process_id, sizeof (process_info->process_id));
+	*buffer += sizeof (process_info->process_id);
+	*size -= sizeof (process_info->process_id);
+
+	// GUID RuntimeCookie;
+	memcpy(*buffer, &process_info->runtime_cookie, sizeof (process_info->runtime_cookie));
+	*buffer += sizeof (process_info->runtime_cookie);
+	*size -= sizeof (process_info->runtime_cookie);
+
+	// LPCWSTR CommandLine;
+	success &= ds_ipc_message_try_write_string_utf16_t (buffer, size, process_info->command_line);
+
+	// LPCWSTR OS;
+	if (success)
+		success &= ds_ipc_message_try_write_string_utf16_t (buffer, size, process_info->os);
+
+	// LPCWSTR Arch;
+	if (success)
+		success &= ds_ipc_message_try_write_string_utf16_t (buffer, size, process_info->arch);
+
+	// LPCWSTR managed_entrypoint_assembly_name;
+	if (success)
+		success &= ds_ipc_message_try_write_string_utf16_t (buffer, size, process_info->managed_entrypoint_assembly_name);
+
+	// LPCWSTR clr_product_version;
+	if (success)
+		success &= ds_ipc_message_try_write_string_utf16_t (buffer, size, process_info->clr_product_version);
+
+	// Assert we've used the whole buffer we were given
+	EP_ASSERT(*size == 0);
+
+	return success;
+}
+
+DiagnosticsProcessInfo2Payload *
+ds_process_info_2_payload_init (
+	DiagnosticsProcessInfo2Payload *payload,
+	const ep_char16_t *command_line,
+	const ep_char16_t *os,
+	const ep_char16_t *arch,
+	uint32_t process_id,
+	const uint8_t *runtime_cookie,
+	const ep_char16_t *managed_entrypoint_assembly_name,
+	const ep_char16_t *clr_product_version)
+{
+	ep_return_null_if_nok (payload != NULL);
+
+	payload->command_line = command_line;
+	payload->os = os;
+	payload->arch = arch;
+	payload->process_id = process_id;
+	payload->managed_entrypoint_assembly_name = managed_entrypoint_assembly_name;
+	payload->clr_product_version = clr_product_version;
+
+	if (runtime_cookie)
+		memcpy (&payload->runtime_cookie, runtime_cookie, EP_GUID_SIZE);
+
+	return payload;
+}
+
+void
+ds_process_info_2_payload_fini (DiagnosticsProcessInfo2Payload *payload)
+{
+	;
+}
+
+
+/*
  * DiagnosticsEnvironmentInfoPayload.
  */
 
@@ -388,6 +531,78 @@ ep_on_error:
 
 static
 bool
+process_protocol_helper_get_process_info_2 (
+	DiagnosticsIpcMessage *message,
+	DiagnosticsIpcStream *stream)
+{
+	EP_ASSERT (message != NULL);
+	EP_ASSERT (stream != NULL);
+
+	bool result = false;
+	ep_char16_t *command_line = NULL;
+	ep_char16_t *os_info = NULL;
+	ep_char16_t *arch_info = NULL;
+	ep_char16_t *managed_entrypoint_assembly_name = NULL;
+	ep_char16_t *clr_product_version = NULL;
+	DiagnosticsProcessInfo2Payload payload;
+	DiagnosticsProcessInfo2Payload *process_info_2_payload = NULL;
+
+	command_line = ep_rt_utf8_to_utf16_string (ep_rt_diagnostics_command_line_get (), -1);
+	ep_raise_error_if_nok (command_line != NULL);
+
+	os_info = ep_rt_utf8_to_utf16_string (ep_event_source_get_os_info (), -1);
+	ep_raise_error_if_nok (os_info != NULL);
+
+	arch_info = ep_rt_utf8_to_utf16_string (ep_event_source_get_arch_info (), -1);
+	ep_raise_error_if_nok (arch_info != NULL);
+
+	managed_entrypoint_assembly_name = ep_rt_utf8_to_utf16_string (ep_rt_entrypoint_assembly_name_get_utf8 (), -1);
+	ep_raise_error_if_nok (managed_entrypoint_assembly_name != NULL);
+
+	clr_product_version = ep_rt_utf8_to_utf16_string (ep_rt_runtime_version_get_utf8 (), -1);
+	ep_raise_error_if_nok (clr_product_version != NULL);
+
+	process_info_2_payload = ds_process_info_2_payload_init (
+		&payload,
+		command_line,
+		os_info,
+		arch_info,
+		ep_rt_current_process_get_id (),
+		ds_ipc_advertise_cookie_v1_get (),
+		managed_entrypoint_assembly_name,
+		clr_product_version);
+	ep_raise_error_if_nok (process_info_2_payload != NULL);
+
+	ep_raise_error_if_nok (ds_ipc_message_initialize_buffer (
+		message,
+		ds_ipc_header_get_generic_success (),
+		(void *)process_info_2_payload,
+		process_info_2_payload_get_size (process_info_2_payload),
+		process_info_2_payload_flatten));
+
+	ep_raise_error_if_nok (ds_ipc_message_send (message, stream));
+
+	result = true;
+
+ep_on_exit:
+	ds_process_info_2_payload_fini (process_info_2_payload);
+	ep_rt_utf16_string_free (arch_info);
+	ep_rt_utf16_string_free (os_info);
+	ep_rt_utf16_string_free (command_line);
+	ep_rt_utf16_string_free (managed_entrypoint_assembly_name);
+	ep_rt_utf16_string_free (clr_product_version);
+	ds_ipc_stream_free (stream);
+	return result;
+
+ep_on_error:
+	EP_ASSERT (!result);
+	ds_ipc_message_send_error (stream, DS_IPC_E_FAIL);
+	DS_LOG_WARNING_0 ("Failed to send DiagnosticsIPC response");
+	ep_exit_error_handler ();
+}
+
+static
+bool
 process_protocol_helper_get_process_env (
 	DiagnosticsIpcMessage *message,
 	DiagnosticsIpcStream *stream)
@@ -566,6 +781,9 @@ ds_process_protocol_helper_handle_ipc_message (
 		break;
 	case DS_PROCESS_COMMANDID_SET_ENV_VAR:
 		result = process_protocol_helper_set_environment_variable (message, stream);
+        break;
+	case DS_PROCESS_COMMANDID_GET_PROCESS_INFO_2:
+		result = process_protocol_helper_get_process_info_2 (message, stream);
 		break;
 	default:
 		result = process_protocol_helper_unknown_command (message, stream);
diff --git a/src/native/eventpipe/ds-process-protocol.h b/src/native/eventpipe/ds-process-protocol.h
index 1b2c279aeee..ac145c0bd1d 100644
--- a/src/native/eventpipe/ds-process-protocol.h
+++ b/src/native/eventpipe/ds-process-protocol.h
@@ -59,6 +59,56 @@ void
 ds_process_info_payload_fini (DiagnosticsProcessInfoPayload *payload);
 
 /*
+* DiagnosticsProcessInfo2Payload
+*/
+
+// command = 0x0400
+#if defined(DS_INLINE_GETTER_SETTER) || defined(DS_IMPL_PROCESS_PROTOCOL_GETTER_SETTER)
+struct _DiagnosticsProcessInfo2Payload {
+#else
+struct _DiagnosticsProcessInfo2Payload_Internal {
+#endif
+	// The protocol buffer is defined as:
+	// X, Y, Z means encode bytes for X followed by bytes for Y followed by bytes for Z
+	// uint = 4 little endian bytes
+	// long = 8 little endian bytes
+	// GUID = 16 little endian bytes
+	// wchar = 2 little endian bytes, UTF16 encoding
+	// array<T> = uint length, length # of Ts
+	// string = (array<char> where the last char must = 0) or (length = 0)
+
+	// ProcessInfo = long pid, GUID runtimeCookie, string cmdline, string OS, string arch, string managed entrypoint assembly path, string clr product version
+	uint64_t process_id;
+	const ep_char16_t *command_line;
+	const ep_char16_t *os;
+	const ep_char16_t *arch;
+	uint8_t runtime_cookie [EP_GUID_SIZE];
+	const ep_char16_t *managed_entrypoint_assembly_name;
+	const ep_char16_t *clr_product_version;
+
+};
+
+#if !defined(DS_INLINE_GETTER_SETTER) && !defined(DS_IMPL_PROCESS_PROTOCOL_GETTER_SETTER)
+struct _DiagnosticsProcessInfo2Payload {
+	uint8_t _internal [sizeof (struct _DiagnosticsProcessInfo2Payload_Internal)];
+};
+#endif
+
+DiagnosticsProcessInfo2Payload *
+ds_process_info_2_payload_init (
+	DiagnosticsProcessInfo2Payload *payload,
+	const ep_char16_t *command_line,
+	const ep_char16_t *os,
+	const ep_char16_t *arch,
+	uint32_t process_id,
+	const uint8_t *runtime_cookie,
+	const ep_char16_t *managed_entrypoint_assembly_name,
+	const ep_char16_t *clr_product_version);
+
+void
+ds_process_info_2_payload_fini (DiagnosticsProcessInfo2Payload *payload);
+
+/*
 * DiagnosticsEnvironmentInfoPayload
 */
 
@@ -125,4 +175,3 @@ ds_process_protocol_helper_handle_ipc_message (
 
 #endif /* ENABLE_PERFTRACING */
 #endif /* __DIAGNOSTICS_PROCESS_PROTOCOL_H__ */
-
diff --git a/src/native/eventpipe/ds-types.h b/src/native/eventpipe/ds-types.h
index 243951d243d..fc5d3e1a2ec 100644
--- a/src/native/eventpipe/ds-types.h
+++ b/src/native/eventpipe/ds-types.h
@@ -29,6 +29,7 @@ typedef struct _DiagnosticsPort DiagnosticsPort;
 typedef struct _DiagnosticsPortBuilder DiagnosticsPortBuilder;
 typedef struct _DiagnosticsPortVtable DiagnosticsPortVtable;
 typedef struct _DiagnosticsProcessInfoPayload DiagnosticsProcessInfoPayload;
+typedef struct _DiagnosticsProcessInfo2Payload DiagnosticsProcessInfo2Payload;
 typedef struct _EventPipeCollectTracingCommandPayload EventPipeCollectTracingCommandPayload;
 typedef struct _EventPipeCollectTracing2CommandPayload EventPipeCollectTracing2CommandPayload;
 typedef struct _EventPipeStopTracingCommandPayload EventPipeStopTracingCommandPayload;
@@ -67,6 +68,7 @@ typedef enum {
 	DS_PROCESS_COMMANDID_RESUME_RUNTIME = 0x01,
 	DS_PROCESS_COMMANDID_GET_PROCESS_ENV = 0x02,
 	DS_PROCESS_COMMANDID_SET_ENV_VAR = 0x03,
+	DS_PROCESS_COMMANDID_GET_PROCESS_INFO_2 = 0x04
 	// future
 } DiagnosticsProcessCommandId;
 
diff --git a/src/native/eventpipe/ep-rt.h b/src/native/eventpipe/ep-rt.h
index 405bb4fb038..d043710f46c 100644
--- a/src/native/eventpipe/ep-rt.h
+++ b/src/native/eventpipe/ep-rt.h
@@ -600,6 +600,14 @@ static
 void
 ep_rt_os_environment_get_utf16 (ep_rt_env_array_utf16_t *env_array);
 
+static
+const ep_char8_t *
+ep_rt_entrypoint_assembly_name_get_utf8 (void);
+
+static
+const ep_char8_t *
+ep_rt_runtime_version_get_utf8 (void);
+
 /*
 * Lock
 */
diff --git a/src/tests/tracing/eventpipe/common/IpcUtils.cs b/src/tests/tracing/eventpipe/common/IpcUtils.cs
index 6f60368894d..b3448f704f2 100644
--- a/src/tests/tracing/eventpipe/common/IpcUtils.cs
+++ b/src/tests/tracing/eventpipe/common/IpcUtils.cs
@@ -339,6 +339,53 @@ namespace Tracing.Tests.Common
         }
     }
 
+    public class ProcessInfo2
+    {
+        // uint64_t ProcessId;
+        // GUID RuntimeCookie;
+        // LPCWSTR CommandLine;
+        // LPCWSTR OS;
+        // LPCWSTR Arch;
+        public UInt64 ProcessId;
+        public Guid RuntimeCookie;
+        public string Commandline;
+        public string OS;
+        public string Arch;
+        public string ManagedEntrypointAssemblyName;
+        public string ClrProductVersion;
+
+        public static ProcessInfo2 TryParse(byte[] buf)
+        {
+            var info = new ProcessInfo2();
+            int start = 0;
+            int end = 8; /* sizeof(uint64_t) */
+            info.ProcessId = BitConverter.ToUInt64(buf[start..end]);
+
+            start = end;
+            end = start + 16; /* sizeof(guid) */
+            info.RuntimeCookie = new Guid(buf[start..end]);
+
+            string ParseString(ref int start, ref int end)
+            {
+                start = end;
+                end = start + 4; /* sizeof(uint32_t) */
+                uint nChars = BitConverter.ToUInt32(buf[start..end]);
+
+                start = end;
+                end = start + ((int)nChars * sizeof(char));
+                return System.Text.Encoding.Unicode.GetString(buf[start..end]).TrimEnd('\0');
+            }
+
+            info.Commandline = ParseString(ref start, ref end);
+            info.OS = ParseString(ref start, ref end);
+            info.Arch = ParseString(ref start, ref end);
+            info.ManagedEntrypointAssemblyName = ParseString(ref start, ref end);
+            info.ClrProductVersion = ParseString(ref start, ref end);
+
+            return info;
+        }
+    }
+
     public class IpcClient
     {
         public static IpcMessage SendMessage(Stream stream, IpcMessage message)
diff --git a/src/tests/tracing/eventpipe/processinfo2/processinfo2.cs b/src/tests/tracing/eventpipe/processinfo2/processinfo2.cs
new file mode 100644
index 00000000000..08a10821041
--- /dev/null
+++ b/src/tests/tracing/eventpipe/processinfo2/processinfo2.cs
@@ -0,0 +1,235 @@
+// 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.Collections.Generic;
+using System.Diagnostics.Tracing;
+using System.Diagnostics;
+using System.IO;
+using System.Linq;
+using System.Runtime.InteropServices;
+using System.Reflection;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.Diagnostics.Tools.RuntimeClient;
+using Microsoft.Diagnostics.Tracing;
+using Tracing.Tests.Common;
+
+namespace Tracing.Tests.ProcessInfoValidation
+{
+    public class ProcessInfoValidation
+    {
+        public static string NormalizeCommandLine(string cmdline)
+        {
+            // ASSUMPTION: double quotes (") and single quotes (') are used for paths with spaces
+            // ASSUMPTION: This test will only have two parts to the commandline
+
+            // check for quotes in first part
+            var parts = new List<string>();
+            bool isQuoted = false;
+            int start = 0;
+
+            for (int i = 0; i < cmdline.Length; i++)
+            {
+                if (isQuoted)
+                {
+                    if (cmdline[i] == '"' || cmdline[i] == '\'')
+                    {
+                        parts.Add(cmdline.Substring(start, i - start));
+                        isQuoted = false;
+                        start = i + 1;
+                    }
+                }
+                else if (cmdline[i] == '"' || cmdline[i] == '\'')
+                {
+                    isQuoted = true;
+                    start = i + 1;
+                }
+                else if (cmdline[i] == ' ')
+                {
+                    parts.Add(cmdline.Substring(start, i - start));
+                    start = i + 1;
+                }
+                else if (i == cmdline.Length - 1)
+                {
+                    parts.Add(cmdline.Substring(start));
+                }
+            }
+
+            string normalizedCommandLine = parts
+                .Where(part => !string.IsNullOrWhiteSpace(part))
+                .Select(part => (new FileInfo(part)).FullName)
+                .Aggregate((s1, s2) => string.Join(' ', s1, s2));
+
+            // Tests are run out of /tmp on Mac and linux, but on Mac /tmp is actually a symlink that points to /private/tmp.
+            // This isn't represented in the output from FileInfo.FullName unfortunately, so we'll fake that completion in that case.
+            if (RuntimeInformation.IsOSPlatform(OSPlatform.OSX) && normalizedCommandLine.StartsWith("/tmp/"))
+                normalizedCommandLine = "/private" + normalizedCommandLine;
+
+            return normalizedCommandLine;
+        }
+
+        public static int Main(string[] args)
+        {
+
+            Process currentProcess = Process.GetCurrentProcess();
+            int pid = currentProcess.Id;
+            Logger.logger.Log($"Test PID: {pid}");
+
+            Stream stream = ConnectionHelper.GetStandardTransport(pid);
+
+            // 0x04 = ProcessCommandSet, 0x04 = ProcessInfo2
+            var processInfoMessage = new IpcMessage(0x04, 0x04);
+            Logger.logger.Log($"Wrote: {processInfoMessage}");
+            IpcMessage response = IpcClient.SendMessage(stream, processInfoMessage);
+            Logger.logger.Log($"Received: <omitted>");
+
+            Utils.Assert(response.Header.CommandSet == 0xFF, $"Response must have Server command set. Expected: 0xFF, Received: 0x{response.Header.CommandSet:X2}"); // server
+            Utils.Assert(response.Header.CommandId == 0x00, $"Response must have OK command id. Expected: 0x00, Received: 0x{response.Header.CommandId:X2}"); // OK
+
+            // Parse payload
+            // uint64_t ProcessId;
+            // GUID RuntimeCookie;
+            // LPCWSTR CommandLine;
+            // LPCWSTR OS;
+            // LPCWSTR Arch;
+
+            int totalSize = response.Payload.Length;
+            Logger.logger.Log($"Total size of Payload = {totalSize} bytes");
+
+            // VALIDATE PID
+            int start = 0;
+            int end = start + 8 /* sizeof(uint63_t) */;
+            UInt64 processId = BitConverter.ToUInt64(response.Payload[start..end]);
+            Utils.Assert((int)processId == pid, $"PID in process info must match. Expected: {pid}, Received: {processId}");
+            Logger.logger.Log($"pid: {processId}");
+
+            // VALIDATE RUNTIME COOKIE
+            start = end;
+            end = start + 16 /* sizeof(GUID) */;
+            Guid runtimeCookie = new Guid(response.Payload[start..end]);
+            Logger.logger.Log($"runtimeCookie: {runtimeCookie}");
+
+            // VALIDATE COMMAND LINE
+            start = end;
+            end = start + 4 /* sizeof(uint32_t) */;
+            UInt32 commandLineLength = BitConverter.ToUInt32(response.Payload[start..end]);
+            Logger.logger.Log($"commandLineLength: {commandLineLength}");
+
+            start = end;
+            end = start + ((int)commandLineLength * sizeof(char));
+            Utils.Assert(end <= totalSize, $"String end can't exceed payload size. Expected: <{totalSize}, Received: {end} (decoded length: {commandLineLength})");
+            Logger.logger.Log($"commandLine bytes: [ {response.Payload[start..end].Select(b => b.ToString("X2") + " ").Aggregate(string.Concat)}]");
+            string commandLine = System.Text.Encoding.Unicode.GetString(response.Payload[start..end]).TrimEnd('\0');
+            Logger.logger.Log($"commandLine: \"{commandLine}\"");
+
+            // The following logic is tailored to this specific test where the cmdline _should_ look like the following:
+            // /path/to/corerun /path/to/processinfo.dll
+            // or
+            // "C:\path\to\CoreRun.exe" C:\path\to\processinfo.dll
+            string currentProcessCommandLine = $"{currentProcess.MainModule.FileName} {System.Reflection.Assembly.GetExecutingAssembly().Location}";
+            string receivedCommandLine = NormalizeCommandLine(commandLine);
+
+            Utils.Assert(currentProcessCommandLine.Equals(receivedCommandLine, StringComparison.OrdinalIgnoreCase), $"CommandLine must match current process. Expected: {currentProcessCommandLine}, Received: {receivedCommandLine} (original: {commandLine})");
+
+            // VALIDATE OS
+            start = end;
+            end = start + 4 /* sizeof(uint32_t) */;
+            UInt32 OSLength = BitConverter.ToUInt32(response.Payload[start..end]);
+            Logger.logger.Log($"OSLength: {OSLength}");
+
+            start = end;
+            end = start + ((int)OSLength * sizeof(char));
+            Utils.Assert(end <= totalSize, $"String end can't exceed payload size. Expected: <{totalSize}, Received: {end} (decoded length: {OSLength})");
+            Logger.logger.Log($"OS bytes: [ {response.Payload[start..end].Select(b => b.ToString("X2") + " ").Aggregate(string.Concat)}]");
+            string OS = System.Text.Encoding.Unicode.GetString(response.Payload[start..end]).TrimEnd('\0');
+            Logger.logger.Log($"OS: \"{OS}\"");
+
+            // see eventpipeeventsource.cpp for these values
+            string expectedOSValue = null;
+            if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
+            {
+                expectedOSValue = "Windows";
+            }
+            else if (RuntimeInformation.IsOSPlatform(OSPlatform.OSX))
+            {
+                expectedOSValue = "macOS";
+            }
+            else if (RuntimeInformation.IsOSPlatform(OSPlatform.Linux))
+            {
+                expectedOSValue = "Linux";
+            }
+            else
+            {
+                expectedOSValue = "Unknown";
+            }
+
+            Utils.Assert(expectedOSValue.Equals(OS), $"OS must match current Operating System. Expected: \"{expectedOSValue}\", Received: \"{OS}\"");
+
+            // VALIDATE ARCH
+            start = end;
+            end = start + 4 /* sizeof(uint32_t) */;
+            UInt32 archLength = BitConverter.ToUInt32(response.Payload[start..end]);
+            Logger.logger.Log($"archLength: {archLength}");
+
+            start = end;
+            end = start + ((int)archLength * sizeof(char));
+            Utils.Assert(end <= totalSize, $"String end can't exceed payload size. Expected: <{totalSize}, Received: {end} (decoded length: {archLength})");
+            Logger.logger.Log($"arch bytes: [ {response.Payload[start..end].Select(b => b.ToString("X2") + " ").Aggregate(string.Concat)}]");
+            string arch = System.Text.Encoding.Unicode.GetString(response.Payload[start..end]).TrimEnd('\0');
+            Logger.logger.Log($"arch: \"{arch}\"");
+
+            // see eventpipeeventsource.cpp for these values
+            string expectedArchValue = RuntimeInformation.ProcessArchitecture switch
+            {
+                Architecture.X86 => "x86",
+                Architecture.X64 => "x64",
+                Architecture.Arm => "arm32",
+                Architecture.Arm64 => "arm64",
+                _ => "Unknown"
+            };
+
+            Utils.Assert(expectedArchValue.Equals(arch), $"OS must match current Operating System. Expected: \"{expectedArchValue}\", Received: \"{arch}\"");
+
+            // VALIDATE ManagedEntrypointAssemblyName
+            start = end;
+            end = start + 4 /* sizeof(uint32_t) */;
+            UInt32 managedEntrypointAssemblyNameLength = BitConverter.ToUInt32(response.Payload[start..end]);
+            Logger.logger.Log($"managedEntrypointAssemblyNameLength: {managedEntrypointAssemblyNameLength}");
+
+            start = end;
+            end = start + ((int)managedEntrypointAssemblyNameLength * sizeof(char));
+            Utils.Assert(end <= totalSize, $"String end can't exceed payload size. Expected: <{totalSize}, Received: {end} (decoded length: {managedEntrypointAssemblyNameLength})");
+            Logger.logger.Log($"ManagedEntrypointAssemblyName bytes: [ {response.Payload[start..end].Select(b => b.ToString("X2") + " ").Aggregate(string.Concat)}]");
+            string managedEntrypointAssemblyName = System.Text.Encoding.Unicode.GetString(response.Payload[start..end]).TrimEnd('\0');
+            Logger.logger.Log($"ManagedEntrypointAssemblyName: \"{managedEntrypointAssemblyName}\"");
+
+            string expectedManagedEntrypointAssemblyName = System.Reflection.Assembly.GetExecutingAssembly().GetName().Name;
+
+            Utils.Assert(expectedManagedEntrypointAssemblyName.Equals(managedEntrypointAssemblyName), $"ManagedEntrypointAssemblyName must match. Expected: \"{expectedManagedEntrypointAssemblyName}\", received: \"{managedEntrypointAssemblyName}\"");
+
+            // VALIDATE ClrProductVersion
+            start = end;
+            end = start + 4 /* sizeof(uint32_t) */;
+            UInt32 clrProductVersionSize = BitConverter.ToUInt32(response.Payload[start..end]);
+            Logger.logger.Log($"clrProductVersionSize: {clrProductVersionSize}");
+
+            start = end;
+            end = start + ((int)clrProductVersionSize * sizeof(char));
+            Utils.Assert(end <= totalSize, $"String end can't exceed payload size. Expected: <{totalSize}, Received: {end} (decoded length: {clrProductVersionSize})");
+            Logger.logger.Log($"ClrProductVersion bytes: [ {response.Payload[start..end].Select(b => b.ToString("X2") + " ").Aggregate(string.Concat)}]");
+            string clrProductVersion = System.Text.Encoding.Unicode.GetString(response.Payload[start..end]).TrimEnd('\0');
+            Logger.logger.Log($"ClrProductVersion: \"{clrProductVersion}\"");
+
+            string expectedClrProductVersion = typeof(object).Assembly.GetCustomAttribute<AssemblyInformationalVersionAttribute>()?.InformationalVersion;
+
+            Utils.Assert(expectedClrProductVersion.Equals(clrProductVersion), $"ClrProductVersion must match. Expected: \"{expectedClrProductVersion}\", received: \"{clrProductVersion}\"");
+
+            Utils.Assert(end == totalSize, $"Full payload should have been read. Expected: {totalSize}, Received: {end}");
+
+            Logger.logger.Log($"\n{{\n\tprocessId: {processId},\n\truntimeCookie: {runtimeCookie},\n\tcommandLine: {commandLine},\n\tOS: {OS},\n\tArch: {arch},\n\tManagedEntrypointAssemblyName: {managedEntrypointAssemblyName},\n\tClrProductVersion: {clrProductVersion}\n}}");
+
+            return 100;
+        }
+    }
+}
\ No newline at end of file
diff --git a/src/tests/tracing/eventpipe/processinfo2/processinfo2.csproj b/src/tests/tracing/eventpipe/processinfo2/processinfo2.csproj
new file mode 100644
index 00000000000..69e7a9fba00
--- /dev/null
+++ b/src/tests/tracing/eventpipe/processinfo2/processinfo2.csproj
@@ -0,0 +1,19 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <TargetFrameworkIdentifier>.NETCoreApp</TargetFrameworkIdentifier>
+    <OutputType>exe</OutputType>
+    <CLRTestKind>BuildAndRun</CLRTestKind>
+    <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
+    <CLRTestPriority>0</CLRTestPriority>
+    <UnloadabilityIncompatible>true</UnloadabilityIncompatible>
+    <JitOptimizationSensitive>true</JitOptimizationSensitive>
+    <!-- ilasm round-trip testing doesn't work, as test expects unchanged assembly name.
+         Issue: https://github.com/dotnet/runtime/issues/39935
+    -->
+    <IlasmRoundTripIncompatible>true</IlasmRoundTripIncompatible>
+  </PropertyGroup>
+  <ItemGroup>
+    <Compile Include="$(MSBuildProjectName).cs" />
+    <ProjectReference Include="../common/common.csproj" />
+  </ItemGroup>
+</Project>