[EventPipe] Add dotnet_ipc_created mapping

src/native/eventpipe/configure.cmake

@@ -28,6 +28,11 @@ check_include_file(
     HAVE_SYS_IOCTL_H
 )
 
+check_include_file(
+    sys/syscall.h
+    HAVE_SYS_SYSCALL_H
+)
+
 check_include_file(
     unistd.h
     HAVE_UNISTD_H
@@ -43,6 +48,17 @@ check_include_file(
     HAVE_ERRNO_H
 )
 
+check_include_file(
+    sys/mman.h
+    HAVE_SYS_MMAN_H
+)
+
+check_symbol_exists(
+    __NR_memfd_create
+    sys/syscall.h
+    HAVE_MEMFD_CREATE
+)
+
 if (NOT DEFINED EP_GENERATED_HEADER_PATH)
     message(FATAL_ERROR "Required configuration EP_GENERATED_HEADER_PATH not set.")
 endif (NOT DEFINED EP_GENERATED_HEADER_PATH)

src/native/eventpipe/ds-ipc.c

@@ -10,6 +10,15 @@
 #include "ep.h"
 #include "ds-rt.h"
 
+#if HAVE_SYS_MMAN_H && HAVE_MEMFD_CREATE && HAVE_UNISTD_H
+#include <sys/mman.h>
+#include <sys/syscall.h>
+#include <unistd.h>
+#ifndef MFD_CLOEXEC
+#define MFD_CLOEXEC 0x0001U
+#endif
+#endif
+
 /*
  * Globals and volatile access functions.
  */
@@ -342,6 +351,19 @@ ds_ipc_stream_factory_configure (ds_ipc_error_callback_func callback)
 	DS_LOG_DEBUG_0 ("ds_ipc_stream_factory_configure - Ignoring default LISTEN port");
 #endif
 
+#if HAVE_SYS_MMAN_H && HAVE_MEMFD_CREATE && HAVE_UNISTD_H
+	// Create a mapping to signal that the diagnostic server IPC is available.
+	// External tools can use this to detect when the runtime is ready to accept diagnostic commands.
+	// The mapping's lifetime is tied to the process, so tools that start after the .NET process can still detect it.
+	if (ds_ipc_stream_factory_any_listen_ports ()) {
+		int fd = (int)syscall (__NR_memfd_create, "dotnet_ipc_created", (unsigned int)MFD_CLOEXEC);
+		if (fd >= 0) {
+			mmap (NULL, 1, PROT_EXEC | PROT_READ, MAP_PRIVATE, fd, 0);
+			close (fd);
+		}
+	}
+#endif
+
 	return result;
 }
 
@@ -479,6 +501,17 @@ ds_ipc_stream_factory_resume_current_port (void)
 		_ds_current_port->has_resumed_runtime = true;
 }
 
+bool
+ds_ipc_stream_factory_any_listen_ports (void)
+{
+	bool any_listen_ports = false;
+	DN_VECTOR_PTR_FOREACH_BEGIN (DiagnosticsPort *, port, _ds_port_array) {
+		any_listen_ports |= (port->type == DS_PORT_TYPE_LISTEN);
+	} DN_VECTOR_PTR_FOREACH_END;
+
+	return any_listen_ports;
+}
+
 bool
 ds_ipc_stream_factory_any_suspended_ports (void)
 {

src/native/eventpipe/ds-ipc.h

@@ -32,6 +32,9 @@ ds_ipc_stream_factory_get_next_available_stream (ds_ipc_error_callback_func call
 void
 ds_ipc_stream_factory_resume_current_port (void);
 
+bool
+ds_ipc_stream_factory_any_listen_ports (void);
+
 bool
 ds_ipc_stream_factory_any_suspended_ports (void);
 

src/native/eventpipe/ep-shared-config.h.in

@@ -2,6 +2,8 @@
 #define EP_SHARED_CONFIG_H_INCLUDED
 
 #cmakedefine01 HAVE_ERRNO_H
+#cmakedefine01 HAVE_SYS_MMAN_H
+#cmakedefine01 HAVE_MEMFD_CREATE
 #cmakedefine01 HAVE_LINUX_USER_EVENTS_H
 #cmakedefine01 HAVE_SYS_IOCTL_H
 #cmakedefine01 HAVE_SYS_SOCKET_H