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From:   Vincent Whitchurch <vincent.whitchurch@axis.com>
To:     <linux-kernel@vger.kernel.org>
CC:     <kernel@axis.com>,
        Vincent Whitchurch <vincent.whitchurch@axis.com>,
        <devicetree@vger.kernel.org>, <linux-um@lists.infradead.org>,
        <shuah@kernel.org>, <brendanhiggins@google.com>,
        <linux-kselftest@vger.kernel.org>, <jic23@kernel.org>,
        <linux-iio@vger.kernel.org>, <lgirdwood@gmail.com>,
        <broonie@kernel.org>, <a.zummo@towertech.it>,
        <alexandre.belloni@bootlin.com>, <linux-rtc@vger.kernel.org>,
        <corbet@lwn.net>, <linux-doc@vger.kernel.org>
Subject: [RFC v1 02/10] roadtest: add C backend
Date:   Fri, 11 Mar 2022 17:24:37 +0100
Message-ID: <20220311162445.346685-3-vincent.whitchurch@axis.com>
In-Reply-To: <20220311162445.346685-1-vincent.whitchurch@axis.com>
References: <20220311162445.346685-1-vincent.whitchurch@axis.com>
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Precedence: bulk

Add the C parts of the roadtest framework.  This uses QEMU's
libvhost-user to implement the device side of virtio-user and
virtio-gpio and bridge them to the Python portions of the backend.

The C backend is also responsible for starting UML after the virtio
device implementations are initialized.

Signed-off-by: Vincent Whitchurch <vincent.whitchurch@axis.com>
---
 tools/testing/roadtest/src/backend.c | 884 +++++++++++++++++++++++++++
 1 file changed, 884 insertions(+)
 create mode 100644 tools/testing/roadtest/src/backend.c

diff --git a/tools/testing/roadtest/src/backend.c b/tools/testing/roadtest/src/backend.c
new file mode 100644
index 000000000000..d5ac08b20fd9
--- /dev/null
+++ b/tools/testing/roadtest/src/backend.c
@@ -0,0 +1,884 @@
+// SPDX-License-Identifier: GPL-2.0-only
+// Copyright Axis Communications AB
+
+#define PY_SSIZE_T_CLEAN
+#include <Python.h>
+
+#include <err.h>
+#include <getopt.h>
+#include <stdlib.h>
+#include <sys/epoll.h>
+#include <sys/socket.h>
+#include <sys/types.h>
+#include <sys/uio.h>
+#include <sys/un.h>
+#include <unistd.h>
+#include <stdio.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <linux/virtio_gpio.h>
+#include <linux/virtio_i2c.h>
+#include <linux/kernel.h>
+#include <linux/list.h>
+
+#include "libvhost-user.h"
+
+enum watch_type {
+	LISTEN,
+	SOCKET_WATCH,
+	VU_WATCH,
+};
+
+struct watch {
+	VuDev *dev;
+	enum watch_type type;
+	int fd;
+	void *func;
+	void *data;
+	struct list_head list;
+};
+
+struct vhost_user_i2c {
+	VuDev dev;
+	FILE *control;
+};
+
+struct vhost_user_gpio {
+	VuDev dev;
+	FILE *control;
+	VuVirtqElement *irq_elements[64];
+};
+
+#define dbg(...)                                                               \
+	do {                                                                   \
+		if (0) {                                                       \
+			fprintf(stderr, __VA_ARGS__);                          \
+		}                                                              \
+	} while (0)
+
+static LIST_HEAD(watches);
+
+static int epfd;
+
+static PyObject *py_i2c_read, *py_i2c_write, *py_process_control;
+static PyObject *py_gpio_set_irq_type, *py_gpio_unmask;
+
+static const char *opt_main_script;
+static char *opt_gpio_socket;
+static char *opt_i2c_socket;
+
+static struct vhost_user_gpio gpio;
+static struct vhost_user_i2c i2c;
+
+static void dump_iov(const char *what, struct iovec *iovec, unsigned int count)
+{
+	int i;
+
+	dbg("dumping %s with count %u\n", what, count);
+
+	for (i = 0; i < count; i++) {
+		struct iovec *iov = &iovec[0];
+
+		dbg("i %d base %p len %zu\n", i, iov->iov_base, iov->iov_len);
+	}
+}
+
+static bool i2c_read(struct vhost_user_i2c *vi, uint16_t addr, void *data,
+		     size_t len)
+{
+	PyObject *pArgs, *pValue;
+
+	dbg("i2c read addr %#x len %zu\n", addr, len);
+
+	pArgs = PyTuple_New(1);
+	pValue = PyLong_FromLong(len);
+	PyTuple_SetItem(pArgs, 0, pValue);
+
+	pValue = PyObject_CallObject(py_i2c_read, pArgs);
+	Py_DECREF(pArgs);
+	if (!pValue) {
+		PyErr_Print();
+		return false;
+	}
+
+	unsigned char *buffer;
+	Py_ssize_t length;
+
+	if (PyBytes_AsStringAndSize(pValue, (char **)&buffer, &length) < 0) {
+		PyErr_Print();
+		errx(1, "invalid result from i2c.read()");
+	}
+	if (length != len) {
+		errx(1,
+		     "unexpected length from i2c.read(), expected %zu, got %zu",
+		     len, length);
+	}
+
+	memcpy(data, buffer, len);
+
+	return true;
+}
+
+static bool i2c_write(struct vhost_user_i2c *vi, uint16_t addr,
+		      const void *data, size_t len)
+{
+	PyObject *pArgs, *pValue;
+
+	dbg("i2c write addr %#x len %zu\n", addr, len);
+
+	pArgs = PyTuple_New(1);
+	pValue = PyBytes_FromStringAndSize(data, len);
+	PyTuple_SetItem(pArgs, 0, pValue);
+
+	pValue = PyObject_CallObject(py_i2c_write, pArgs);
+	Py_DECREF(pArgs);
+	if (!pValue) {
+		PyErr_Print();
+		return false;
+	}
+
+	return true;
+}
+
+static void gpio_send_irq_response(struct vhost_user_gpio *gpio,
+				   unsigned int pin, unsigned int status);
+
+static PyObject *cbackend_trigger_gpio_irq(PyObject *self, PyObject *args)
+{
+	unsigned int pin;
+
+	if (!PyArg_ParseTuple(args, "I", &pin))
+		return NULL;
+
+	dbg("trigger gpio %u irq\n", pin);
+
+	gpio_send_irq_response(&gpio, pin, VIRTIO_GPIO_IRQ_STATUS_VALID);
+
+	Py_RETURN_NONE;
+}
+
+static PyMethodDef EmbMethods[] = {
+	{ "trigger_gpio_irq", cbackend_trigger_gpio_irq, METH_VARARGS,
+	  "Return the number of arguments received by the process." },
+	{ NULL, NULL, 0, NULL }
+};
+
+static PyModuleDef EmbModule = { PyModuleDef_HEAD_INIT,
+				 "cbackend",
+				 NULL,
+				 -1,
+				 EmbMethods,
+				 NULL,
+				 NULL,
+				 NULL,
+				 NULL };
+
+static PyObject *PyInit_cbackend(void)
+{
+	return PyModule_Create(&EmbModule);
+}
+
+static void init_python_i2c(PyObject *backend)
+{
+	PyObject *i2c = PyObject_GetAttrString(backend, "i2c");
+
+	if (!i2c) {
+		PyErr_Print();
+		errx(1, "Error getting backend.i2c");
+	}
+
+	py_i2c_read = PyObject_GetAttrString(i2c, "read");
+	if (!py_i2c_read) {
+		PyErr_Print();
+		errx(1, "Error getting i2c.read");
+	}
+
+	py_i2c_write = PyObject_GetAttrString(i2c, "write");
+	if (!py_i2c_write) {
+		PyErr_Print();
+		errx(1, "Error getting i2c.write");
+	}
+}
+
+static void init_python_gpio(PyObject *backend)
+{
+	PyObject *gpio = PyObject_GetAttrString(backend, "gpio");
+
+	if (!gpio) {
+		PyErr_Print();
+		errx(1, "error getting backend.gpio");
+	}
+
+	py_gpio_set_irq_type = PyObject_GetAttrString(gpio, "set_irq_type");
+	if (!py_gpio_set_irq_type) {
+		PyErr_Print();
+		errx(1, "error getting gpio.set_irq_type");
+	}
+
+	py_gpio_unmask = PyObject_GetAttrString(gpio, "unmask");
+	if (!py_gpio_unmask) {
+		PyErr_Print();
+		errx(1, "error getting gpio.unmask");
+	}
+}
+
+static void init_python(void)
+{
+	PyObject *mainmod, *backend;
+	FILE *file;
+
+	PyImport_AppendInittab("cbackend", &PyInit_cbackend);
+
+	Py_Initialize();
+
+	file = fopen(opt_main_script, "r");
+	if (!file)
+		err(1, "open %s", opt_main_script);
+
+	if (PyRun_SimpleFile(file, "main.py") < 0) {
+		PyErr_Print();
+		errx(1, "error running %s", opt_main_script);
+	}
+	fclose(file);
+
+	mainmod = PyImport_AddModule("__main__");
+	if (!mainmod) {
+		PyErr_Print();
+		errx(1, "error getting __main__");
+	}
+
+	backend = PyObject_GetAttrString(mainmod, "backend");
+	if (!backend) {
+		PyErr_Print();
+		errx(1, "error getting backend");
+	}
+
+	py_process_control = PyObject_GetAttrString(backend, "process_control");
+	if (!py_process_control) {
+		PyErr_Print();
+		errx(1, "error getting backend.process_control");
+	}
+
+	init_python_i2c(backend);
+	init_python_gpio(backend);
+}
+
+static void i2c_handle_cmdq(VuDev *dev, int qidx)
+{
+	struct vhost_user_i2c *vi =
+		container_of(dev, struct vhost_user_i2c, dev);
+	VuVirtq *vq = vu_get_queue(dev, qidx);
+	VuVirtqElement *elem;
+
+	for (;;) {
+		struct virtio_i2c_out_hdr *hdr;
+		struct iovec *resultv;
+		size_t used = 0;
+		bool ok = true;
+
+		elem = vu_queue_pop(dev, vq, sizeof(VuVirtqElement));
+		if (!elem)
+			break;
+
+		dbg("elem %p index %u out_num %u in_num %u\n", elem,
+		    elem->index, elem->out_num, elem->in_num);
+		dump_iov("out", elem->out_sg, elem->out_num);
+		dump_iov("in", elem->in_sg, elem->in_num);
+
+		assert(elem->out_sg[0].iov_len == sizeof(*hdr));
+		hdr = elem->out_sg[0].iov_base;
+
+		if (elem->out_num == 2 && elem->in_num == 1) {
+			struct iovec *data = &elem->out_sg[1];
+
+			ok = i2c_write(vi, hdr->addr, data->iov_base,
+				       data->iov_len);
+			resultv = &elem->in_sg[0];
+		} else if (elem->out_num == 1 && elem->in_num == 2) {
+			struct iovec *data = &elem->in_sg[0];
+
+			ok = i2c_read(vi, hdr->addr, data->iov_base,
+				      data->iov_len);
+			resultv = &elem->in_sg[1];
+			used += data->iov_len;
+		} else {
+			assert(false);
+		}
+
+		struct virtio_i2c_in_hdr *inhdr = resultv->iov_base;
+
+		inhdr->status = ok ? VIRTIO_I2C_MSG_OK : VIRTIO_I2C_MSG_ERR;
+
+		used += sizeof(*inhdr);
+		vu_queue_push(dev, vq, elem, used);
+		free(elem);
+	}
+
+	vu_queue_notify(&vi->dev, vq);
+}
+
+static void i2c_queue_set_started(VuDev *dev, int qidx, bool started)
+{
+	VuVirtq *vq = vu_get_queue(dev, qidx);
+
+	dbg("queue started %d:%d\n", qidx, started);
+
+	vu_set_queue_handler(dev, vq, started ? i2c_handle_cmdq : NULL);
+}
+
+static bool i2cquit;
+static bool gpioquit;
+
+static void remove_watch(VuDev *dev, int fd);
+
+static int i2c_process_msg(VuDev *dev, VhostUserMsg *vmsg, int *do_reply)
+{
+	if (vmsg->request == VHOST_USER_NONE) {
+		dbg("i2c disconnect");
+		remove_watch(dev, -1);
+		i2cquit = true;
+		return true;
+	}
+	return false;
+}
+static int gpio_process_msg(VuDev *dev, VhostUserMsg *vmsg, int *do_reply)
+{
+	if (vmsg->request == VHOST_USER_NONE) {
+		dbg("gpio disconnect");
+		remove_watch(dev, -1);
+		gpioquit = true;
+		return true;
+	}
+	return false;
+}
+
+static uint64_t i2c_get_features(VuDev *dev)
+{
+	return 1ull << VIRTIO_I2C_F_ZERO_LENGTH_REQUEST;
+}
+
+static const VuDevIface i2c_iface = {
+	.get_features = i2c_get_features,
+	.queue_set_started = i2c_queue_set_started,
+	.process_msg = i2c_process_msg,
+};
+
+static void gpio_send_irq_response(struct vhost_user_gpio *gpio,
+				   unsigned int pin, unsigned int status)
+{
+	assert(pin < ARRAY_SIZE(gpio->irq_elements));
+
+	VuVirtqElement *elem = gpio->irq_elements[pin];
+	VuVirtq *vq = vu_get_queue(&gpio->dev, 1);
+
+	if (!elem) {
+		dbg("no irq buf for pin %d\n", pin);
+		assert(status != VIRTIO_GPIO_IRQ_STATUS_VALID);
+		return;
+	}
+
+	struct virtio_gpio_irq_response *resp;
+
+	assert(elem->out_num == 1);
+	assert(elem->in_sg[0].iov_len == sizeof(*resp));
+
+	resp = elem->in_sg[0].iov_base;
+	resp->status = status;
+
+	vu_queue_push(&gpio->dev, vq, elem, sizeof(*resp));
+	gpio->irq_elements[pin] = NULL;
+	free(elem);
+
+	vu_queue_notify(&gpio->dev, vq);
+}
+
+static void gpio_set_irq_type(struct vhost_user_gpio *gpio, unsigned int pin,
+			      unsigned int type)
+{
+	PyObject *pArgs, *pValue;
+
+	pArgs = PyTuple_New(2);
+	pValue = PyLong_FromLong(pin);
+	PyTuple_SetItem(pArgs, 0, pValue);
+
+	pValue = PyLong_FromLong(type);
+	PyTuple_SetItem(pArgs, 1, pValue);
+
+	pValue = PyObject_CallObject(py_gpio_set_irq_type, pArgs);
+	if (!pValue) {
+		PyErr_Print();
+		errx(1, "error from gpio.set_irq_type()");
+	}
+	Py_DECREF(pArgs);
+
+	if (type == VIRTIO_GPIO_IRQ_TYPE_NONE) {
+		gpio_send_irq_response(gpio, pin,
+				       VIRTIO_GPIO_IRQ_STATUS_INVALID);
+	}
+}
+
+static void gpio_unmask(struct vhost_user_gpio *vi, unsigned int gpio)
+{
+	PyObject *pArgs, *pValue;
+
+	pArgs = PyTuple_New(1);
+	pValue = PyLong_FromLong(gpio);
+	PyTuple_SetItem(pArgs, 0, pValue);
+
+	pValue = PyObject_CallObject(py_gpio_unmask, pArgs);
+	if (!pValue) {
+		PyErr_Print();
+		errx(1, "error from gpio.unmask()");
+	}
+	Py_DECREF(pArgs);
+}
+
+static void gpio_handle_cmdq(VuDev *dev, int qidx)
+{
+	struct vhost_user_gpio *vi =
+		container_of(dev, struct vhost_user_gpio, dev);
+	VuVirtq *vq = vu_get_queue(dev, qidx);
+	VuVirtqElement *elem;
+
+	while (1) {
+		struct virtio_gpio_request *req;
+		struct virtio_gpio_response *resp;
+
+		elem = vu_queue_pop(dev, vq, sizeof(VuVirtqElement));
+		if (!elem)
+			break;
+
+		dbg("elem %p index %u out_num %u in_num %u\n", elem,
+		    elem->index, elem->out_num, elem->in_num);
+
+		dump_iov("out", elem->out_sg, elem->out_num);
+		dump_iov("in", elem->in_sg, elem->in_num);
+
+		assert(elem->out_num == 1);
+		assert(elem->in_num == 1);
+
+		assert(elem->out_sg[0].iov_len == sizeof(*req));
+		assert(elem->in_sg[0].iov_len == sizeof(*resp));
+
+		req = elem->out_sg[0].iov_base;
+		resp = elem->in_sg[0].iov_base;
+
+		dbg("req type %#x gpio %#x value %#x\n", req->type, req->gpio,
+		    req->value);
+
+		switch (req->type) {
+		case VIRTIO_GPIO_MSG_IRQ_TYPE:
+			gpio_set_irq_type(vi, req->gpio, req->value);
+			break;
+		default:
+			/*
+			 * The other types couldhooked up to Python later for
+			 * testing of drivers' control of GPIOs.
+			 */
+			break;
+		}
+
+		resp->status = VIRTIO_GPIO_STATUS_OK;
+		resp->value = 0;
+
+		vu_queue_push(dev, vq, elem, sizeof(*resp));
+		free(elem);
+	}
+
+	vu_queue_notify(&vi->dev, vq);
+}
+
+static void gpio_handle_eventq(VuDev *dev, int qidx)
+{
+	struct vhost_user_gpio *vi =
+		container_of(dev, struct vhost_user_gpio, dev);
+	VuVirtq *vq = vu_get_queue(dev, qidx);
+	VuVirtqElement *elem;
+
+	for (;;) {
+		struct virtio_gpio_irq_request *req;
+		struct virtio_gpio_irq_response *resp;
+
+		elem = vu_queue_pop(dev, vq, sizeof(VuVirtqElement));
+		if (!elem)
+			break;
+
+		dbg("elem %p index %u out_num %u in_num %u\n", elem,
+		    elem->index, elem->out_num, elem->in_num);
+
+		dump_iov("out", elem->out_sg, elem->out_num);
+		dump_iov("in", elem->in_sg, elem->in_num);
+
+		assert(elem->out_num == 1);
+		assert(elem->in_num == 1);
+
+		assert(elem->out_sg[0].iov_len == sizeof(*req));
+		assert(elem->in_sg[0].iov_len == sizeof(*resp));
+
+		req = elem->out_sg[0].iov_base;
+		resp = elem->in_sg[0].iov_base;
+
+		dbg("irq req gpio %#x\n", req->gpio);
+
+		assert(req->gpio < ARRAY_SIZE(vi->irq_elements));
+		assert(vi->irq_elements[req->gpio] == NULL);
+
+		vi->irq_elements[req->gpio] = elem;
+
+		gpio_unmask(vi, req->gpio);
+	}
+}
+
+static void gpio_queue_set_started(VuDev *dev, int qidx, bool started)
+{
+	VuVirtq *vq = vu_get_queue(dev, qidx);
+
+	dbg("%s %d:%d\n", __func__, qidx, started);
+
+	if (qidx == 0)
+		vu_set_queue_handler(dev, vq,
+				     started ? gpio_handle_cmdq : NULL);
+	if (qidx == 1)
+		vu_set_queue_handler(dev, vq,
+				     started ? gpio_handle_eventq : NULL);
+}
+
+static int gpio_get_config(VuDev *dev, uint8_t *config, uint32_t len)
+{
+	struct vhost_user_gpio *gpio =
+		container_of(dev, struct vhost_user_gpio, dev);
+	static struct virtio_gpio_config gpioconfig = {
+		.ngpio = ARRAY_SIZE(gpio->irq_elements),
+	};
+
+	dbg("%s: len %u\n", __func__, len);
+
+	if (len > sizeof(struct virtio_gpio_config))
+		return -1;
+
+	memcpy(config, &gpioconfig, len);
+
+	return 0;
+}
+
+static uint64_t gpio_get_protocol_features(VuDev *dev)
+{
+	return 1ull << VHOST_USER_PROTOCOL_F_CONFIG;
+}
+
+static uint64_t gpio_get_features(VuDev *dev)
+{
+	return 1ull << VIRTIO_GPIO_F_IRQ;
+}
+
+static const VuDevIface gpio_vuiface = {
+	.get_features = gpio_get_features,
+	.queue_set_started = gpio_queue_set_started,
+	.process_msg = gpio_process_msg,
+	.get_config = gpio_get_config,
+	.get_protocol_features = gpio_get_protocol_features,
+};
+
+static void panic(VuDev *dev, const char *err)
+{
+	fprintf(stderr, "panicking!");
+	abort();
+}
+
+static struct watch *new_watch(struct VuDev *dev, int fd, enum watch_type type,
+			       void *func, void *data)
+{
+	struct watch *watch = malloc(sizeof(*watch));
+
+	assert(watch);
+
+	watch->dev = dev;
+	watch->fd = fd;
+	watch->func = func;
+	watch->data = data;
+	watch->type = type;
+
+	list_add(&watch->list, &watches);
+
+	return watch;
+}
+
+static void set_watch(VuDev *dev, int fd, int condition, vu_watch_cb cb,
+		      void *data)
+{
+	struct watch *watch = new_watch(dev, fd, VU_WATCH, cb, data);
+	int ret;
+
+	struct epoll_event ev = {
+		.events = EPOLLIN,
+		.data.ptr = watch,
+	};
+
+	dbg("set watch epfd %d fd %d condition %d cb %p\n", epfd, fd, condition,
+	    cb);
+
+	epoll_ctl(epfd, EPOLL_CTL_DEL, fd, NULL);
+
+	ret = epoll_ctl(epfd, EPOLL_CTL_ADD, fd, &ev);
+	if (ret < 0)
+		err(1, "epoll_ctl");
+}
+
+static void remove_watch(VuDev *dev, int fd)
+{
+	struct watch *watch, *tmp;
+
+	list_for_each_entry_safe(watch, tmp, &watches, list) {
+		if (watch->dev != dev)
+			continue;
+		if (fd >= 0 && watch->fd != fd)
+			continue;
+
+		epoll_ctl(epfd, EPOLL_CTL_DEL, watch->fd, NULL);
+
+		list_del(&watch->list);
+		free(watch);
+	}
+}
+
+static int unix_listen(const char *path)
+{
+	struct sockaddr_un un = {
+		.sun_family = AF_UNIX,
+	};
+	int sock;
+	int ret;
+
+	unlink(path);
+
+	sock = socket(PF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, 0);
+	if (sock < 0)
+		err(1, "socket");
+
+	memcpy(&un.sun_path, path, strlen(path));
+
+	ret = bind(sock, (struct sockaddr *)&un, sizeof(un));
+	if (ret < 0)
+		err(1, "bind");
+
+	ret = listen(sock, 1);
+	if (ret < 0)
+		err(1, "listen");
+
+	return sock;
+}
+
+static void dev_add_watch(int epfd, struct watch *watch)
+{
+	struct epoll_event event = {
+		.events = EPOLLIN | EPOLLONESHOT,
+		.data.ptr = watch,
+	};
+	int ret;
+
+	ret = epoll_ctl(epfd, EPOLL_CTL_ADD, watch->fd, &event);
+	if (ret < 0)
+		err(1, "EPOLL_CTL_ADD");
+}
+
+static VuDev *gpio_init(int epfd, const char *path)
+{
+	struct watch *watch;
+	VuDev *dev;
+	int lsock;
+	bool rc;
+
+	lsock = unix_listen(path);
+	if (lsock < 0)
+		err(1, "listen %s", path);
+
+	rc = vu_init(&gpio.dev, 2, lsock, panic, NULL, set_watch,
+		     remove_watch, &gpio_vuiface);
+	assert(rc == true);
+
+	dev = &gpio.dev;
+	watch = new_watch(dev, lsock, LISTEN, vu_dispatch, dev);
+
+	dev_add_watch(epfd, watch);
+
+	return dev;
+}
+
+static VuDev *i2c_init(int epfd, const char *path)
+{
+	static struct vhost_user_i2c i2c = {};
+	VuDev *dev = &i2c.dev;
+	struct watch *watch;
+	int lsock;
+	bool rc;
+
+	lsock = unix_listen(path);
+	if (lsock < 0)
+		err(1, "listen %s", path);
+
+	rc = vu_init(dev, 1, lsock, panic, NULL, set_watch,
+		     remove_watch, &i2c_iface);
+	assert(rc == true);
+
+	watch = new_watch(dev, lsock, LISTEN, vu_dispatch, dev);
+
+	dev_add_watch(epfd, watch);
+
+	return dev;
+}
+
+static pid_t run_uml(char **argv)
+{
+	int log, null, ret;
+	pid_t pid;
+
+	pid = fork();
+	if (pid < 0)
+		err(1, "fork");
+	if (pid > 0)
+		return pid;
+
+	chdir(getenv("ROADTEST_WORK_DIR"));
+
+	log = open("uml.txt", O_WRONLY | O_TRUNC | O_APPEND | O_CREAT, 0600);
+	if (log < 0)
+		err(1, "open uml.txt");
+
+	null = open("/dev/null", O_RDONLY);
+	if (null < 0)
+		err(1, "open null");
+
+	ret = dup2(null, 0);
+	if (ret < 0)
+		err(1, "dup2");
+
+	ret = dup2(log, 1);
+	if (ret < 0)
+		err(1, "dup2");
+
+	ret = dup2(log, 2);
+	if (ret < 0)
+		err(1, "dup2");
+
+	execvpe(argv[0], argv, environ);
+	err(1, "execve");
+
+	return -1;
+}
+
+int main(int argc, char *argv[])
+{
+	static struct option long_option[] = {
+		{ "main-script", required_argument, 0, 'm' },
+		{ "gpio-socket", required_argument, 0, 'g' },
+		{ "i2c-socket", required_argument, 0, 'i' },
+	};
+
+	while (1) {
+		int c = getopt_long(argc, argv, "", long_option, NULL);
+
+		if (c == -1)
+			break;
+
+		switch (c) {
+		case 'm':
+			opt_main_script = optarg;
+			break;
+
+		case 'g':
+			opt_gpio_socket = optarg;
+			break;
+
+		case 'i':
+			opt_i2c_socket = optarg;
+			break;
+
+		default:
+			errx(1, "getopt");
+		}
+	}
+
+	if (!opt_main_script || !opt_gpio_socket || !opt_i2c_socket)
+		errx(1, "Invalid arguments");
+
+	epfd = epoll_create1(EPOLL_CLOEXEC);
+	if (epfd < 0)
+		err(1, "epoll_create1");
+
+	init_python();
+
+	gpio_init(epfd, opt_gpio_socket);
+	i2c_init(epfd, opt_i2c_socket);
+
+	run_uml(&argv[optind]);
+
+	while (1) {
+		struct epoll_event events[10];
+		int nfds;
+		int i;
+
+		nfds = epoll_wait(epfd, events, ARRAY_SIZE(events), -1);
+		if (nfds < 0) {
+			if (errno == EINTR) {
+				continue;
+
+				err(1, "epoll_wait");
+			}
+		}
+
+		if (!PyObject_CallObject(py_process_control, NULL)) {
+			PyErr_Print();
+			errx(1, "error from backend.process_control");
+		}
+
+		for (i = 0; i < nfds; i++) {
+			struct epoll_event *event = &events[i];
+			struct watch *watch = event->data.ptr;
+			int fd;
+
+			switch (watch->type) {
+			case LISTEN:
+				fd = accept(watch->fd, NULL, NULL);
+				close(watch->fd);
+				if (fd == -1)
+					err(1, "accept");
+
+				watch->dev->sock = fd;
+				watch->fd = fd;
+				watch->type = SOCKET_WATCH;
+
+				struct epoll_event event = {
+					.events = EPOLLIN,
+					.data.ptr = watch,
+				};
+
+				int ret = epoll_ctl(epfd, EPOLL_CTL_ADD, fd,
+						    &event);
+				if (ret < 0)
+					err(1, "epoll_ctl");
+
+				break;
+			case SOCKET_WATCH:
+				vu_dispatch(watch->dev);
+				break;
+			case VU_WATCH:
+				((vu_watch_cb)(watch->func))(watch->dev, POLLIN,
+							     watch->data);
+				break;
+			default:
+				fprintf(stderr, "abort!");
+				abort();
+			}
+		}
+
+		if (i2cquit && gpioquit)
+			break;
+	}
+
+	vu_deinit(&i2c.dev);
+	vu_deinit(&gpio.dev);
+
+	Py_Finalize();
+
+	return 0;
+}
-- 
2.34.1