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>

3 files changed, 117 insertions, 9 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 &
diff --git a/storeio/storeio.c b/storeio/storeio.c
index 872b388f..5b8db0d3 100644
--- a/storeio/storeio.c
+++ b/storeio/storeio.c
@@ -24,6 +24,7 @@
 #include <argp.h>
 #include <argz.h>
 #include <sys/sysmacros.h>
+#include <stdbool.h>
 
 #include <hurd.h>
 #include <hurd/ports.h>
@@ -42,6 +43,8 @@ static struct argp_option options[] =
   {"no-file-io", 'F', 0,  0,"Never perform io via plain file io RPCs"},
   {"no-fileio",  0,   0, OPTION_ALIAS | OPTION_HIDDEN},
   {"enforced",  'e', 0,	  0,"Never reveal underlying devices, even to root"},
+  {"debug",	'd', "PATH",	0,
+   "Launch a standalone translator, for debug purposes"},
   {"rdev",     'n', "ID", 0,
    "The stat rdev number for this node; may be either a"
    " single integer, or of the form MAJOR,MINOR"},
@@ -50,7 +53,10 @@ static struct argp_option options[] =
 static const char doc[] = "Translator for devices and other stores";
 
 const char *argp_program_version = STANDARD_HURD_VERSION (storeio);
-
+
+static bool debug=false;
+static char *debug_fname=NULL;
+
 /* Desired store parameters specified by the user.  */
 struct storeio_argp_params
 {
@@ -97,6 +103,16 @@ parse_opt (int key, char *arg, struct argp_state *state)
       }
       break;
 
+    case 'd':
+      {
+	debug=true;
+	char *new = strdup (arg);
+	if (new == NULL)
+	  return ENOMEM;
+	debug_fname = new;
+      }
+      break;
+
     case ARGP_KEY_INIT:
       /* Now store_argp's parser will get to initialize its state.
 	 The default_type member is our input parameter to it.  */
@@ -135,14 +151,26 @@ main (int argc, char *argv[])
   params.dev = &device;
   argp_parse (&argp, argc, argv, 0, 0, &params);
 
-  task_get_bootstrap_port (mach_task_self (), &bootstrap);
-  if (bootstrap == MACH_PORT_NULL)
-    error (2, 0, "Must be started as a translator");
-
-  /* Reply to our parent */
-  err = trivfs_startup (bootstrap, 0, 0, 0, 0, 0, &storeio_fsys);
-  if (err)
-    error (3, err, "trivfs_startup");
+  if (debug)
+    {
+      if (debug_fname)
+	err = trivfs_startup_debug (debug_fname, 0, 0, 0, 0, &storeio_fsys);
+      else
+	error (3, err, "missing translated node");
+      if (err)
+	error (3, err, "trivfs_startup_debug failed");
+    }
+  else
+    {
+      task_get_bootstrap_port (mach_task_self (), &bootstrap);
+      if (bootstrap == MACH_PORT_NULL)
+	error (2, 0, "Must be started as a translator");
+
+      /* Reply to our parent */
+      err = trivfs_startup (bootstrap, 0, 0, 0, 0, 0, &storeio_fsys);
+      if (err)
+	error (3, err, "trivfs_startup");
+    }
 
   storeio_fsys->hook = &device;