[mxio][launchpad] loader-service moves to launchpad

This is the logical place for it to live and paves the way to migrate
it away from the soon-to-be-no-more mxio dispatcher.

Tidied up the API, de-mxio'd it, put it behind a common loader_service_
prefix, and broke some swiss-army-knife interfaces into more standalone
pieces, hopefully easier to understand.

Change-Id: I91acd79a44c5dcc72412484bd6e151a54d52c8a1

system/core/devmgr/devmgr.c

@@ -12,13 +12,14 @@
 #include <unistd.h>
 
 #include <launchpad/launchpad.h>
+#include <launchpad/loader-service.h>
 #include <magenta/dlfcn.h>
 #include <magenta/process.h>
 #include <magenta/processargs.h>
 #include <magenta/syscalls.h>
 #include <magenta/syscalls/object.h>
 #include <magenta/status.h>
-#include <mxio/loader-service.h>
+
 #include <mxio/util.h>
 
 #include "devmgr.h"
@@ -370,7 +371,7 @@ int main(int argc, char** argv) {
 
     // Ensure that devmgr doesn't try to connect to the global
     // loader sevice (as this leads to deadlocks in devhost v2)
-    mxio_force_local_loader_service();
+    loader_service_force_local();
 
     devmgr_io_init();
 

system/core/devmgr/dmctl.c

@@ -13,11 +13,11 @@
 #include "devcoordinator.h"
 
 #include <magenta/device/dmctl.h>
-#include <mxio/loader-service.h>
+#include <launchpad/loader-service.h>
 
 static mx_device_t* dmctl_dev;
 
-static mxio_multiloader_t* multiloader;
+static loader_service_t* loader_svc;
 
 static mx_status_t dmctl_cmd(uint32_t op, const char* cmd, size_t cmdlen, mx_handle_t h) {
     dc_msg_t msg;
@@ -50,13 +50,13 @@ static mx_status_t dmctl_ioctl(void* ctx, uint32_t op,
         if (in_len != 0 || out_buf == NULL || out_len != sizeof(mx_handle_t)) {
             return MX_ERR_INVALID_ARGS;
         }
-        if (multiloader == NULL) {
+        if (loader_svc == NULL) {
             // The allocation in dmctl_init() failed.
             return MX_ERR_NO_MEMORY;
         }
         // Create a new channel on the multiloader.
         mx_handle_t out_channel;
-        mx_status_t status = mxio_multiloader_new_service(multiloader, &out_channel);
+        mx_status_t status = loader_service_connect(loader_svc, &out_channel);
         if (status < 0) {
             return status;
         }
@@ -106,7 +106,7 @@ mx_status_t dmctl_bind(void* ctx, mx_device_t* parent, void** cookie) {
     // Don't try to ioctl to ourselves when this process loads libraries.
     // Call this before the device has been created; mxio_loader_service()
     // uses the device's presence as an invitation to use it.
-    mxio_force_local_loader_service();
+    loader_service_force_local();
 
     device_add_args_t args = {
         .version = DEVICE_ADD_ARGS_VERSION,
@@ -120,7 +120,7 @@ mx_status_t dmctl_bind(void* ctx, mx_device_t* parent, void** cookie) {
     }
 
     // Loader service init.
-    if ((status = mxio_multiloader_create("dmctl-multiloader", &multiloader)) < 0) {
+    if ((status = loader_service_create("dmctl-multiloader", &loader_svc)) < 0) {
         // If this fails, IOCTL_DMCTL_GET_LOADER_SERVICE_CHANNEL will fail
         // and processes will fall back to using a local loader.
         // TODO: Make this fatal?

system/core/devmgr/rules.mk

@@ -96,6 +96,6 @@ MODULE_SRCS := \
 
 MODULE_STATIC_LIBS := system/ulib/ddk system/ulib/port
 
-MODULE_LIBS := system/ulib/driver system/ulib/mxio system/ulib/magenta system/ulib/c
+MODULE_LIBS := system/ulib/driver system/ulib/launchpad system/ulib/mxio system/ulib/magenta system/ulib/c
 
 include make/module.mk

system/uapp/launch/launch.c

@@ -4,13 +4,14 @@
 
 #include <assert.h>
 #include <launchpad/launchpad.h>
+#include <launchpad/loader-service.h>
 #include <launchpad/vmo.h>
 #include <magenta/process.h>
 #include <magenta/processargs.h>
 #include <magenta/syscalls.h>
 #include <magenta/syscalls/object.h>
 #include <magenta/syscalls/policy.h>
-#include <mxio/loader-service.h>
+
 #include <mxio/io.h>
 #include <stdbool.h>
 #include <stdio.h>
@@ -226,7 +227,7 @@ int main(int argc, char** argv) {
         bool already_sending = launchpad_send_loader_message(lp, true);
         if (!already_sending) {
             mx_handle_t loader_svc;
-            status = mxio_loader_service(NULL, NULL, &loader_svc);
+            status = loader_service_get_default(&loader_svc);
             check("mxio_loader_service", status);
             mx_handle_t old = launchpad_use_loader_service(lp, loader_svc);
             check("launchpad_use_loader_service", old);
@@ -240,7 +241,7 @@ int main(int argc, char** argv) {
 
     if (pass_loader_handle) {
         mx_handle_t loader_svc;
-        status = mxio_loader_service(NULL, NULL, &loader_svc);
+        status = loader_service_get_default(&loader_svc);
         check("mxio_loader_service", status);
         status = launchpad_add_handle(lp, loader_svc, PA_SVC_LOADER);
         check("launchpad_add_handle", status);

system/ulib/launchpad/include/launchpad/loader-service.h

@@ -0,0 +1,67 @@
+// Copyright 2017 The Fuchsia Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#pragma once
+
+#include <magenta/types.h>
+#include <magenta/compiler.h>
+
+__BEGIN_CDECLS
+
+// These routines provide loader service implementations that
+// some users of liblaunchpad may need.  They are compatible with
+// dl_set_loader_service() and are primarily used by devmgr (to
+// provide the default system loader service) and clients of
+// launchpad that need a specialized variant loader.
+//
+// Terms:
+// "loader service": A channel that speaks the protocol expected by
+//     dl_set_loader_service(). The service behind the channel receives
+//     load requests (e.g., "libhid.so") and returns VMOs that contain
+//     the data associated with that name.
+// "local loader service": An in-process loader service.
+// "system loader service": A loader service, provided by the system,
+//     that is shared by multiple processes.
+
+// Type of the hook for loader_service.  The first argument is
+// the one passed to loader_service_simple(), and the second specifies
+// which load service was requested (the opcode from mx_loader_svc_msg_t).
+// The remaining arguments' meaning depends on the opcode.
+typedef mx_status_t (*loader_service_fn_t)(void* loader_arg, uint32_t load_cmd,
+                                           mx_handle_t request_handle, const char* file,
+                                           mx_handle_t* out);
+
+
+// Obtain a handle to the system loader service, if possible
+mx_status_t loader_service_get_system(mx_handle_t* out);
+
+// Obtain the default loader service for this process
+// Normally it attempts to use the system loader service, and
+// if that fails attempts to create a process-local service
+// (which depends on the process having filesystem access
+// to executables and libraries needing loading)
+mx_status_t loader_service_get_default(mx_handle_t* out);
+
+// After this function returns, loader_service_get_default will no
+// longer attempt to use the system loader service for the current
+// process. Should only be used by the system loader service itself.
+void loader_service_force_local(void);
+
+
+// Create a simple single-threaded loader service, which
+// will use the provided service_fn to process load commands
+mx_status_t loader_service_simple(loader_service_fn_t loader,
+                                  void* loader_arg, mx_handle_t* out);
+
+
+typedef struct loader_service loader_service_t;
+
+// Create a new file-system backed loader service capable of handling
+// any number of clients.
+mx_status_t loader_service_create(const char* name, loader_service_t** out);
+
+// Returns a new dl_set_loader_service-compatible loader service channel.
+mx_status_t loader_service_connect(loader_service_t* svc, mx_handle_t* out);
+
+__END_CDECLS

system/ulib/launchpad/launchpad.c

@@ -11,7 +11,7 @@
 #include <magenta/processargs.h>
 #include <magenta/stack.h>
 #include <magenta/syscalls.h>
-#include <mxio/loader-service.h>
+#include <launchpad/loader-service.h>
 #include <mxio/io.h>
 #include <assert.h>
 #include <stdatomic.h>
@@ -475,7 +475,7 @@ static mx_status_t setup_loader_svc(launchpad_t* lp) {
         return MX_OK;
 
     mx_handle_t loader_svc;
-    mx_status_t status = mxio_loader_service(NULL, NULL, &loader_svc);
+    mx_status_t status = loader_service_get_default(&loader_svc);
     if (status < 0)
         return status;