Add trivfs_startup_debug() for easier translator development

Basically it is an automation of this:
http://walfield.org/pub/people/neal/papers/hurd-misc/manual-bootstrap.txt

To launch a storeio translator on FILE:
  $ storeio -d FILE -T TYPE ARG

Message-Id: <20170126213616.26846-1-luca.dariz@gmail.com>

2 files changed, 80 insertions, 0 deletions

diff --git a/libtrivfs/startup.c b/libtrivfs/startup.c
index 56ef02c4..d5767df2 100644
--- a/libtrivfs/startup.c
+++ b/libtrivfs/startup.c
@@ -86,3 +86,72 @@ trivfs_startup(mach_port_t bootstrap, int flags,
 
   return err;
 }
+
+/* Start in debug mode, no need to be called by settrans. Common options are
+   the same as in trivfs_startup. FILE_NAME is the path of the node where the
+   translator is set*/
+error_t
+trivfs_startup_debug(const char *file_name,
+		     struct port_class *control_class,
+		     struct port_bucket *control_bucket,
+		     struct port_class *protid_class,
+		     struct port_bucket *protid_bucket,
+		     struct trivfs_control **control)
+{
+  mach_port_t underlying, right, goaway;
+  struct trivfs_control *fsys;
+  error_t err =
+    trivfs_create_control (MACH_PORT_NULL,
+			   control_class, control_bucket,
+			   protid_class, protid_bucket,
+			   &fsys);
+
+  if (err)
+    return err;
+
+  right = ports_get_send_right (fsys);
+  goaway = ports_get_send_right (fsys);
+
+  /* Start ourselves as transpator instead of replying to settrans */
+  underlying = file_name_lookup(file_name, 0, 0);
+  if (underlying == MACH_PORT_NULL)
+    err = errno;
+  else
+    err = file_set_translator(underlying, 0, FS_TRANS_SET, 0, "", 0,
+			      right, MACH_MSG_TYPE_COPY_SEND);
+  mach_port_deallocate (mach_task_self (), right);
+
+  if (! err)
+    fsys->underlying = underlying;
+
+  ports_port_deref (fsys);
+
+  /* Pass back what we got, unless the caller doesn't want it.  */
+  if (!err && control)
+    *control = fsys;
+
+  /* don't mark us as important and install a SIGTERM handler, so we can be
+   * easily killed by Ctrl-C */
+  void handler_sigterm(int signum)
+  {
+    error_t ee;
+    ee = fsys_goaway(goaway, 0);
+    if (ee == ESUCCESS)
+      {
+	mach_port_deallocate (mach_task_self (), goaway);
+      }
+    else if (ee != EBUSY)
+      {
+	/* Not nice */
+	error(99, err, "fsys_goaway");
+      }
+    /* else the translator is busy, please retry */
+  }
+
+  struct sigaction sa;
+  memset(&sa, 0, sizeof(sa));
+  sa.sa_handler = handler_sigterm;
+  if (sigaction(SIGTERM, &sa, NULL) < 0)
+    err = errno;
+  return err;
+}
diff --git a/libtrivfs/trivfs.h b/libtrivfs/trivfs.h
index c9e5defa..4802f5fc 100644
--- a/libtrivfs/trivfs.h
+++ b/libtrivfs/trivfs.h
@@ -174,6 +174,17 @@ error_t trivfs_startup (mach_port_t bootstrap, int flags,
 			struct port_bucket *protid_bucket,
 			struct trivfs_control **control);
 
+/* Start in debug mode, no need to be called by settrans. Common options are
+   the same as in trivfs_startup. FILE_NAME is the path of the node where the
+   translator is set*/
+error_t
+trivfs_startup_debug(const char *file_name,
+                    struct port_class *control_class,
+                    struct port_bucket *control_bucket,
+                    struct port_class *protid_class,
+                    struct port_bucket *protid_bucket,
+                    struct trivfs_control **control);
+
 /* Create a new trivfs control port, with underlying node UNDERLYING, and
    return it in CONTROL.  CONTROL_CLASS & CONTROL_BUCKET are passed to
    the ports library to create the control port, and PROTID_CLASS &