present CM3 Trace agenda

contrib/coresight-trace.txt

@@ -0,0 +1,68 @@
++OpenOCD and CoreSight Tracing
++
+Many recent ARM chips  (Using e..g. Cortex-M3 and
+Cortex-M4 cores) support CoreSight debug/trace.
+This note sketches an approach currently planned for those cores
+with OpenOCD.
+
+ This tracing data can help debug and tune ARM software, but not
+all cores support tracing.  Some support more extensive tracing
+other cores with trace support +should be able to use the same
+approach and maybe some of the same analysis code.
+
++the Cortex-M3 is assumed here to be the
++core in use, for simplicity and to reflect current OpenOCD users.
+
+
+This note summarizes a software model to generate, collect, and
+analyze such trace data .  That is not fully implemented as of early
+January 2011, +and thus is not *yet* usable.
++
++
++Some microcontroller cores support a low pin-count Single-wire trace,
+with a mode where +trace data is emitted (usually to a UART.  To use
+this mode, +SWD must be in use.
++At this writing, OpenOCD SWD support is not yet complete either.
+
+(There are also multi-wire trace ports requiring more complex debug
+adapters than OpenOCD currently supports, and offering richer data.
++
++
++* ENABLING involves activating  SWD and (single wire) trace.
++
++current expectations are that OpenOCD itself will handle enabling;
+activating single wire trace involves a debug adapter interaction, and
+collecting that trace data requires particular (re)wiring.
++
++* CONFIGURATION involves setting up ITM  and/or ETM modules to emit the
++desired data from the Cortex core.  (This might include dumping
++event counters printf-style messages; code profiling; and more.  Not all
++cores offer the same trace capabilities.
++
++current expectations are that Tcl scripts will be used to configure these
++modules for the desired tracing, by direct writes to registers.  In some
++cases (as with RTOS event tracking and similar messaging, this might
++be  augmented or replaced by user code running on the ARM core.
++
++COLLECTION involves reading that trace data, probably through UART, and
++saving it in a useful format to analyse  For now, deferred analysis modes
+are assumed, not than real-time or interactive ones.
++
++
++current expectations are to to dump data in text using contrib/itmdump.c
++or derived tools, and to post-process it into reports.  Such reports might
++include program messaging (such as application data streams via ITM, maybe
++using printf type messaging; code coverage analysis or so forth.  Recent
++versions of CMSIS software reserve some ITM codespace for RTOS  event
+tracing and include ITM messaging support.
+Clearly some of that data would be valuable for interactive debugging.
++
++Should someone get ambitious, GUI reports should be possible.  GNU tools
++for simpler reports like gprof may be simpler to support at first.
++In any case, OpenOCD is not currently GUI-oriented.  Accordingly, we now
++expect any such graphics to come from postprocessing.
+
+ measurments for RTOS event timings should also be easy to collect.
++Examples include context and message switch times, as well as times
+for application interactions.
++

contrib/itmdump.c

@@ -0,0 +1,441 @@
+/*
+ * Copyright (C) 2010 by David Brownell
+ *
+ * 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 3 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/>.
+ */
+
+/*
+ * Simple utility to parse and dump ARM Cortex-M3 SWO trace output.  Once the
+ * mechanisms work right, this information can be used for various purposes
+ * including profiling (particularly easy for flat PC-sample profiles) and
+ * for debugging.
+ *
+ * SWO is the Single Wire Output found on some ARM cores, most notably on the
+ * Cortex-M3.  It combines data from several sources:
+ *
+ *  - Software trace (ITM):  so-called "printf-style" application messaging
+ *    using "ITM stimulus ports"; and differential timestamps.
+ *  - Hardware trace (DWT):  for profiling counters and comparator matches.
+ *  - TPIU may issue sync packets.
+ *
+ * The trace data format is defined in Appendix E, "Debug ITM and DWT packet
+ * protocol", of the ARMv7-M Architecture Reference Manual (DDI 0403C).  It
+ * is a superset of the ITM data format from the Coresight TRM.
+ *
+ * The trace data has two encodings.  The working assumption is that data
+ * gets into this program using the UART encoding.
+ */
+
+#include <errno.h>
+#include <libgen.h>
+#include <stdio.h>
+#include <stdbool.h>
+#include <string.h>
+#include <unistd.h>
+
+
+/* Example ITM trace word (0xWWXXYYZZ) parsing for task events, sent
+ * on port 31 (Reserved for "the" RTOS in CMSIS v1.30)
+ *   WWXX: event code (0..3 pre-assigned, 4..15 reserved)
+ *   YY:   task priority
+ *   ZZ:   task number
+ *
+ * NOTE that this specific encoding could be space-optimized; and that
+ * trace data streams could also be history-sensitive.
+ */
+static void show_task(int port, unsigned data)
+{
+	unsigned code = data >> 16;
+	char buf[16];
+
+	switch (code) {
+	case 0:
+		strcpy(buf, "run");
+		break;
+	case 1:
+		strcpy(buf, "block");
+		break;
+	case 2:
+		strcpy(buf, "create");
+		break;
+	case 3:
+		strcpy(buf, "destroy");
+		break;
+	/* 4..15 reserved for other infrastructure ops */
+	default:
+		sprintf(buf, "code %d", code);
+		break;
+	}
+	printf("TASK %d, pri %d: %s",
+		(data >> 0) & 0xff,
+		(data >> 8) & 0xff,
+		buf);
+}
+
+static void show_reserved(FILE *f, char *label, int c)
+{
+	unsigned i;
+
+	printf("%s - %#02x", label, c);
+
+	for (i = 0; (c & 0x80) && i < 4; i++) {
+		c = fgetc(f);
+		if (c == EOF) {
+			printf("(ERROR %d - %s) ", errno, strerror(errno));
+			break;
+		}
+		printf(" %#02x", c);
+	}
+
+	printf("\n");
+}
+
+static bool read_varlen(FILE *f, int c, unsigned *value)
+{
+	unsigned size;
+	unsigned char buf[4];
+	unsigned i;
+
+	*value = 0;
+
+	switch (c & 3) {
+	case 3:
+		size = 4;
+		break;
+	case 2:
+		size = 2;
+		break;
+	case 1:
+		size = 1;
+		break;
+	default:
+		printf("INVALID SIZE\n");
+		return false;
+	}
+
+	memset(buf, 0, sizeof buf);
+	if (fread(buf, 1, size, f) != size)
+		goto err;
+
+	*value =  (buf[3] << 24)
+		+ (buf[2] << 16)
+		+ (buf[2] << 8)
+		+ (buf[0] << 0);
+	return true;
+
+err:
+	printf("(ERROR %d - %s)\n", errno, strerror(errno));
+	return;
+}
+
+static void show_hard(FILE *f, int c)
+{
+	unsigned type = c >> 3;
+	unsigned value;
+	unsigned size;
+	char *label;
+
+	printf("DWT - ", type);
+
+	if (!read_varlen(f, c, &value))
+		return;
+	printf("%#x", value);
+
+	switch (type) {
+	case 0:				/* event counter wrapping */
+		printf("overflow %s%s%s%s%s%s",
+			(value & (1 << 5)) ? "cyc " : "",
+			(value & (1 << 4)) ? "fold " : "",
+			(value & (1 << 3)) ? "lsu " : "",
+			(value & (1 << 2)) ? "slp " : "",
+			(value & (1 << 1)) ? "exc " : "",
+			(value & (1 << 0)) ? "cpi " : "");
+		break;
+	case 1:				/* exception tracing */
+		switch (value >> 12) {
+		case 1:
+			label = "entry to";
+			break;
+		case 2:
+			label = "exit from";
+			break;
+		case 3:
+			label = "return to";
+			break;
+		default:
+			label = "?";
+			break;
+		}
+		printf("%s exception %d", label, value & 0x1ff);
+		break;
+	case 2:				/* PC sampling */
+		if (c == 0x15)
+			printf("PC - sleep");
+		else
+			printf("PC - %#08x", value);
+		break;
+	case 8:				/* data tracing, pc value */
+	case 10:
+	case 12:
+	case 14:
+		printf("Data trace %d, PC %#08x", (c >> 4) & 3, value);
+		/* optionally followed by data value */
+		break;
+	case 9:				/* data tracing, address offset */
+	case 11:
+	case 13:
+	case 15:
+		printf("Data trace %d, address offset %#04x",
+				(c >> 4) & 3, value);
+		/* always followed by data value */
+		break;
+	case 16 ... 23:			/* data tracing, data value */
+		printf("Data trace %d, ", (c >> 4) & 3);
+		label = (c & 0x8) ? "write" : "read";
+		switch (c & 3) {
+		case 3:
+			printf("word %s, value %#08x", label, value);
+			break;
+		case 2:
+			printf("halfword %s, value %#04x", label, value);
+			break;
+		case 1:
+			printf("byte %s, value %#02x", label, value);
+			break;
+		}
+		break;
+	default:
+		printf("UNDEFINED");
+		break;
+	}
+
+	printf("\n");
+	return;
+}
+
+/*
+ * Table of SWIT (SoftWare InstrumentTation) message dump formats, for
+ * ITM port 0..31 application data.
+ *
+ * Eventually this should be customizable; all usage is application defined.
+ *
+ * REVISIT there can be up to 256 trace ports, via "ITM Extension" packets
+ */
+struct {
+	int port;
+	void (*show)(int port, unsigned data);
+} format[] = {
+	{ .port = 31,  .show = show_task, },
+};
+
+static void show_swit(FILE *f, int c)
+{
+	unsigned size;
+	unsigned port = c >> 3;
+	unsigned char buf[4];
+	unsigned value = 0;
+	unsigned i;
+
+	printf("SWIT %u - ", port);
+
+	if (!read_varlen(f, c, &value))
+		return;
+	printf("%#08x", value);
+
+	for (i = 0; i <= sizeof(format) / sizeof(format[0]); i++) {
+		if (format[i].port == port) {
+			printf(", ");
+			format[i].show(port, value);
+			break;
+		}
+	}
+
+	printf("\n");
+	return;
+
+err:
+	printf("(ERROR %d - %s)\n", errno, strerror(errno));
+	return;
+}
+
+static void show_timestamp(FILE *f, int c)
+{
+	unsigned counter = 0;
+	char *label = "";
+	bool delayed = false;
+
+	printf("TIMESTAMP - ");
+
+	/* Format 2: header only */
+	if (!(c & 0x80)) {
+		switch (c) {
+		case 0:		/* sync packet -- coding error! */
+		case 0x70:	/* overflow -- ditto! */
+			printf("ERROR - %#02x\n", c);
+			break;
+		default:
+			/* synchronous to ITM */
+			counter = c >> 4;
+			goto done;
+		}
+		return;
+	}
+
+	/* Format 1:  one to four bytes of data too */
+	switch (c) {
+	default:
+		label = ", reserved control\n";
+		break;
+	case 0xc:
+		/* synchronous to ITM */
+		break;
+	case 0xd:
+		label = ", timestamp delayed";
+		delayed = true;
+		break;
+	case 0xe:
+		label = ", packet delayed";
+		delayed = true;
+		break;
+	case 0xf:
+		label = ", packet and timetamp delayed";
+		delayed = true;
+		break;
+	}
+
+	c = fgetc(f);
+	if (c == EOF)
+		goto err;
+	counter = c & 0x7f;
+	if (!(c & 0x80))
+		goto done;
+
+	c = fgetc(f);
+	if (c == EOF)
+		goto err;
+	counter |= (c & 0x7f) << 7;
+	if (!(c & 0x80))
+		goto done;
+
+	c = fgetc(f);
+	if (c == EOF)
+		goto err;
+	counter |= (c & 0x7f) << 14;
+	if (!(c & 0x80))
+		goto done;
+
+	c = fgetc(f);
+	if (c == EOF)
+		goto err;
+	counter |= (c & 0x7f) << 21;
+
+done:
+	/* REVISIT should we try to convert from delta values?  */
+	printf("+%u%s\n", counter, label);
+	return;
+
+err:
+	printf("(ERROR %d - %s) ", errno, strerror(errno));
+	goto done;
+}
+
+int main(int argc, char **argv)
+{
+	FILE *f = stdin;
+	int c;
+
+	/* parse arguments */
+	while ((c = getopt(argc, argv, "f:")) != EOF) {
+		switch (c) {
+		case 'f':
+			/* e.g. from UART connected to /dev/ttyUSB0 */
+			f = fopen(optarg, "r");
+			if (!f) {
+				perror(optarg);
+				return 1;
+			}
+			break;
+		default:
+usage:
+			fprintf(stderr, "usage: %s [-f input]",
+				basename(argv[0]));
+			return 1;
+		}
+	}
+
+	/* Parse data ... records have a header then data bytes.
+	 * NOTE: we assume getc() deals in 8-bit bytes.
+	 */
+	bool overflow = false;
+
+	while ((c = getc(f)) != EOF) {
+
+		/* Sync packet ... 7 zeroes, 0x80 */
+		if (c == 0) {
+			int i;
+
+			for (i = 0; i < 6; i++) {
+				c = fgetc(f);
+				if (c == EOF)
+					break;
+				if (c != 0)
+					goto bad_sync;
+			}
+			c = fgetc(f);
+			if (c == 0x80) {
+				printf("SYNC\n");
+				continue;
+			}
+bad_sync:
+			printf("BAD SYNC\n");
+			continue;
+		}
+
+		/* Overflow packet */
+		if (c == 0x70) {
+			/* REVISIT later, report just what overflowed!
+			 * Timestamp and SWIT can happen.  Non-ITM too?
+			 */
+			overflow = true;
+			printf("OVERFLOW ...\n");
+			continue;
+		}
+		overflow = false;
+
+		switch (c & 0x0f) {
+		case 0x00:		/* Timestamp */
+			show_timestamp(f, c);
+			break;
+		case 0x04:		/* "Reserved" */
+			show_reserved(f, "RESERVED", c);
+			break;
+		case 0x08:		/* ITM Extension */
+			/* FIXME someday, handle these ...  */
+			show_reserved(f, "ITM EXT", c);
+			break;
+		case 0x0c:		/* DWT Extension */
+			show_reserved(f, "DWT EXT", c);
+			break;
+		default:
+			if (c & 4)
+				show_hard(f, c);
+			else
+				show_swit(f, c);
+			break;
+		}
+
+	}
+
+	return 0;
+}