Add initial RTT support

Real Time Transfer (RTT) is an interface specified by SEGGER based on
basic memory reads and writes to transfer data bidirectionally between
target and host.
Every target that supports so called "background memory access", which
means that the target memory can be accessed by the debugger while the
target is running, can be used.

RTT is especially of interest for targets which do not support Serial
Wire Output (SWO) (e.g. ARM Cortex-M0) or where using semihosting is
not possible (e.g. real-time applications) [1].

The data transfer is organized in channels where each channel consists
of an up- and/or down-channel. See [2] for more details.

Channels are exposed via TCP connections. One or more RTT server can be
assigned to each channel to make them accessible to an unlimited number
of TCP connections.

The current implementation does not respect buffer flags which are used
to determine what happens when writing to a full buffer.

Note that the implementation is designed in a way that the RTT
operations can be directly performed by an adapter (e.g. J-Link).

[1] https://devzone.nordicsemi.com/tutorials/6/
[2] https://www.segger.com/jlink-rtt.html

Change-Id: I8bc8a1b381fb74e08b8752d5cf53804cc573c1e0
Signed-off-by: Marc Schink <dev@zapb.de>
Reviewed-on: http://openocd.zylin.com/4055
Tested-by: jenkins
Reviewed-by: Tomas Vanek <vanekt@fbl.cz>
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>

1 files changed, 424 insertions, 0 deletions

diff --git a/src/target/rtt.c b/src/target/rtt.c
new file mode 100644
index 0000000..7e556e1
--- /dev/null
+++ b/src/target/rtt.c
@@ -0,0 +1,424 @@
+/*
+ * Copyright (C) 2016-2020 by Marc Schink <dev@zapb.de>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <stddef.h>
+#include <stdint.h>
+#include <helper/log.h>
+#include <helper/binarybuffer.h>
+#include <helper/command.h>
+#include <rtt/rtt.h>
+
+#include "target.h"
+
+static int read_rtt_channel(struct target *target,
+		const struct rtt_control *ctrl, unsigned int channel_index,
+		enum rtt_channel_type type, struct rtt_channel *channel)
+{
+	int ret;
+	uint8_t buf[RTT_CHANNEL_SIZE];
+	target_addr_t address;
+
+	address = ctrl->address + RTT_CB_SIZE + (channel_index * RTT_CHANNEL_SIZE);
+
+	if (type == RTT_CHANNEL_TYPE_DOWN)
+		address += ctrl->num_up_channels * RTT_CHANNEL_SIZE;
+
+	ret = target_read_buffer(target, address, RTT_CHANNEL_SIZE, buf);
+
+	if (ret != ERROR_OK)
+		return ret;
+
+	channel->address = address;
+	channel->name_addr = buf_get_u32(buf + 0, 0, 32);
+	channel->buffer_addr = buf_get_u32(buf + 4, 0, 32);
+	channel->size = buf_get_u32(buf + 8, 0, 32);
+	channel->write_pos = buf_get_u32(buf + 12, 0, 32);
+	channel->read_pos = buf_get_u32(buf + 16, 0, 32);
+	channel->flags = buf_get_u32(buf + 20, 0, 32);
+
+	return ERROR_OK;
+}
+
+int target_rtt_start(struct target *target, const struct rtt_control *ctrl,
+		void *user_data)
+{
+	return ERROR_OK;
+}
+
+int target_rtt_stop(struct target *target, void *user_data)
+{
+	return ERROR_OK;
+}
+
+static int read_channel_name(struct target *target, target_addr_t address,
+		char *name, size_t length)
+{
+	size_t offset;
+
+	offset = 0;
+
+	while (offset < length) {
+		int ret;
+		size_t read_length;
+
+		read_length = MIN(32, length - offset);
+		ret = target_read_buffer(target, address + offset, read_length,
+			(uint8_t *)name + offset);
+
+		if (ret != ERROR_OK)
+			return ret;
+
+		if (memchr(name + offset, '\0', read_length))
+			return ERROR_OK;
+
+		offset += read_length;
+	}
+
+	name[length - 1] = '\0';
+
+	return ERROR_OK;
+}
+
+static int write_to_channel(struct target *target,
+		const struct rtt_channel *channel, const uint8_t *buffer,
+		size_t *length)
+{
+	int ret;
+	uint32_t len;
+
+	if (!*length)
+		return ERROR_OK;
+
+	if (channel->write_pos == channel->read_pos) {
+		uint32_t first_length;
+
+		len = MIN(*length, channel->size - 1);
+		first_length = MIN(len, channel->size - channel->write_pos);
+
+		ret = target_write_buffer(target,
+			channel->buffer_addr + channel->write_pos, first_length,
+			buffer);
+
+		if (ret != ERROR_OK)
+			return ret;
+
+		ret = target_write_buffer(target, channel->buffer_addr,
+			len - first_length, buffer + first_length);
+
+		if (ret != ERROR_OK)
+			return ret;
+	} else if (channel->write_pos < channel->read_pos) {
+		len = MIN(*length, channel->read_pos - channel->write_pos - 1);
+
+		if (!len) {
+			*length = 0;
+			return ERROR_OK;
+		}
+
+		ret = target_write_buffer(target,
+			channel->buffer_addr + channel->write_pos, len, buffer);
+
+		if (ret != ERROR_OK)
+			return ret;
+	} else {
+		uint32_t first_length;
+
+		len = MIN(*length,
+			channel->size - channel->write_pos + channel->read_pos - 1);
+
+		if (!len) {
+			*length = 0;
+			return ERROR_OK;
+		}
+
+		first_length = MIN(len, channel->size - channel->write_pos);
+
+		ret = target_write_buffer(target,
+			channel->buffer_addr + channel->write_pos, first_length,
+			buffer);
+
+		if (ret != ERROR_OK)
+			return ret;
+
+		buffer = buffer + first_length;
+
+		ret = target_write_buffer(target, channel->buffer_addr,
+			len - first_length, buffer);
+
+		if (ret != ERROR_OK)
+			return ret;
+	}
+
+	ret = target_write_u32(target, channel->address + 12,
+		(channel->write_pos + len) % channel->size);
+
+	if (ret != ERROR_OK)
+		return ret;
+
+	*length = len;
+
+	return ERROR_OK;
+}
+
+static bool channel_is_active(const struct rtt_channel *channel)
+{
+	if (!channel)
+		return false;
+
+	if (!channel->size)
+		return false;
+
+	return true;
+}
+
+int target_rtt_write_callback(struct target *target, struct rtt_control *ctrl,
+		unsigned int channel_index, const uint8_t *buffer, size_t *length,
+		void *user_data)
+{
+	int ret;
+	struct rtt_channel channel;
+
+	ret = read_rtt_channel(target, ctrl, channel_index,
+		RTT_CHANNEL_TYPE_DOWN, &channel);
+
+	if (ret != ERROR_OK) {
+		LOG_ERROR("rtt: Failed to read down-channel %u description",
+			channel_index);
+		return ret;
+	}
+
+	if (!channel_is_active(&channel)) {
+		LOG_WARNING("rtt: Down-channel %u is not active", channel_index);
+		return ERROR_OK;
+	}
+
+	if (channel.size < RTT_CHANNEL_BUFFER_MIN_SIZE) {
+		LOG_WARNING("rtt: Down-channel %u is not large enough",
+			channel_index);
+		return ERROR_OK;
+	}
+
+	ret = write_to_channel(target, &channel, buffer, length);
+
+	if (ret != ERROR_OK)
+		return ret;
+
+	LOG_DEBUG("rtt: Wrote %zu bytes into down-channel %u", *length,
+		channel_index);
+
+	return ERROR_OK;
+}
+
+int target_rtt_read_control_block(struct target *target,
+		target_addr_t address, struct rtt_control *ctrl, void *user_data)
+{
+	int ret;
+	uint8_t buf[RTT_CB_SIZE];
+
+	ret = target_read_buffer(target, address, RTT_CB_SIZE, buf);
+
+	if (ret != ERROR_OK)
+		return ret;
+
+	memcpy(ctrl->id, buf, RTT_CB_MAX_ID_LENGTH);
+	ctrl->id[RTT_CB_MAX_ID_LENGTH - 1] = '\0';
+	ctrl->num_up_channels = buf_get_u32(buf + RTT_CB_MAX_ID_LENGTH + 0,
+		0, 32);
+	ctrl->num_down_channels = buf_get_u32(buf + RTT_CB_MAX_ID_LENGTH + 4,
+		0, 32);
+
+	return ERROR_OK;
+}
+
+int target_rtt_find_control_block(struct target *target,
+		target_addr_t *address, size_t size, const char *id, bool *found,
+		void *user_data)
+{
+	uint8_t buf[1024];
+
+	*found = false;
+
+	size_t j = 0;
+	size_t cb_offset = 0;
+	const size_t id_length = strlen(id);
+
+	LOG_INFO("rtt: Searching for control block '%s'", id);
+
+	for (target_addr_t addr = 0; addr < size; addr = addr + sizeof(buf)) {
+		int ret;
+
+		const size_t buf_size = MIN(sizeof(buf), size - addr);
+		ret = target_read_buffer(target, *address + addr, buf_size, buf);
+
+		if (ret != ERROR_OK)
+			return ret;
+
+		size_t start = 0;
+		size_t i = 0;
+
+		while (i < buf_size) {
+			if (buf[i] != id[j]) {
+				start++;
+				cb_offset++;
+				i = start;
+				j = 0;
+
+				continue;
+			}
+
+			i++;
+			j++;
+
+			if (j == id_length) {
+				*address = *address + cb_offset;
+				*found = true;
+				return ERROR_OK;
+			}
+		}
+	}
+
+	return ERROR_OK;
+}
+
+int target_rtt_read_channel_info(struct target *target,
+		const struct rtt_control *ctrl, unsigned int channel_index,
+		enum rtt_channel_type type, struct rtt_channel_info *info,
+		void *user_data)
+{
+	int ret;
+	struct rtt_channel channel;
+
+	ret = read_rtt_channel(target, ctrl, channel_index, type, &channel);
+
+	if (ret != ERROR_OK) {
+		LOG_ERROR("rtt: Failed to read channel %u description",
+			channel_index);
+		return ret;
+	}
+
+	ret = read_channel_name(target, channel.name_addr, info->name,
+		info->name_length);
+
+	if (ret != ERROR_OK)
+		return ret;
+
+	info->size = channel.size;
+	info->flags = channel.flags;
+
+	return ERROR_OK;
+}
+
+static int read_from_channel(struct target *target,
+		const struct rtt_channel *channel, uint8_t *buffer,
+		size_t *length)
+{
+	int ret;
+	uint32_t len;
+
+	if (!*length)
+		return ERROR_OK;
+
+	if (channel->read_pos == channel->write_pos) {
+		len = 0;
+	} else if (channel->read_pos < channel->write_pos) {
+		len = MIN(*length, channel->write_pos - channel->read_pos);
+
+		ret = target_read_buffer(target,
+			channel->buffer_addr + channel->read_pos, len, buffer);
+
+		if (ret != ERROR_OK)
+			return ret;
+	} else {
+		uint32_t first_length;
+
+		len = MIN(*length,
+			channel->size - channel->read_pos + channel->write_pos);
+		first_length = MIN(len, channel->size - channel->read_pos);
+
+		ret = target_read_buffer(target,
+			channel->buffer_addr + channel->read_pos, first_length, buffer);
+
+		if (ret != ERROR_OK)
+			return ret;
+
+		ret = target_read_buffer(target, channel->buffer_addr,
+			len - first_length, buffer + first_length);
+
+		if (ret != ERROR_OK)
+			return ret;
+	}
+
+	if (len > 0) {
+		ret = target_write_u32(target, channel->address + 16,
+			(channel->read_pos + len) % channel->size);
+
+		if (ret != ERROR_OK)
+			return ret;
+	}
+
+	*length = len;
+
+	return ERROR_OK;
+}
+
+int target_rtt_read_callback(struct target *target,
+		const struct rtt_control *ctrl, struct rtt_sink_list **sinks,
+		size_t num_channels, void *user_data)
+{
+	num_channels = MIN(num_channels, ctrl->num_up_channels);
+
+	for (size_t i = 0; i < num_channels; i++) {
+		int ret;
+		struct rtt_channel channel;
+		uint8_t buffer[1024];
+		size_t length;
+
+		if (!sinks[i])
+			continue;
+
+		ret = read_rtt_channel(target, ctrl, i, RTT_CHANNEL_TYPE_UP,
+			&channel);
+
+		if (ret != ERROR_OK) {
+			LOG_ERROR("rtt: Failed to read up-channel %zu description", i);
+			return ret;
+		}
+
+		if (!channel_is_active(&channel)) {
+			LOG_WARNING("rtt: Up-channel %zu is not active", i);
+			continue;
+		}
+
+		if (channel.size < RTT_CHANNEL_BUFFER_MIN_SIZE) {
+			LOG_WARNING("rtt: Up-channel %zu is not large enough", i);
+			continue;
+		}
+
+		length = sizeof(buffer);
+		ret = read_from_channel(target, &channel, buffer, &length);
+
+		if (ret != ERROR_OK) {
+			LOG_ERROR("rtt: Failed to read from up-channel %zu", i);
+			return ret;
+		}
+
+		for (struct rtt_sink_list *sink = sinks[i]; sink; sink = sink->next)
+			sink->read(i, buffer, length, sink->user_data);
+	}
+
+	return ERROR_OK;
+}