debug_stream: text_msg: Set exception dump hooks if available

Set exception dump hooks if CONFIG_EXCEPTION_DUMP_HOOK=y. This enables
sending a simple text report of fatal exceptions. To get this working
one needs these config options:

CONFIG_EXCEPTION_DUMP_HOOK=y
CONFIG_SOF_DEBUG_STREAM_SLOT=y
CONFIG_SOF_DEBUG_STREAM_TEXT_MSG=y
CONFIG_SOF_DEBUG_STREAM_SLOT_NUMBER=2
CONFIG_SOF_TELEMETRY=n
CONFIG_SOF_TELEMETRY_PERFORMANCE_MEASUREMENTS=n
CONFIG_SOF_TELEMETRY_IO_PERFORMANCE_MEASUREMENTS=n

If system hangs and an the exception is reported successfully the
report can be seen with debug_stream.py (which should be installed in
the same directory with cavstool.py). It does matter if the too was
not running at the time. The report should be available there in the
debug slot window for debug_stream.py to decode as long as system
remains up. The report should looks something like this:

CPU 2:  ** FATAL EXCEPTION
 ** CPU 2 EXCCAUSE 63 (zephyr exception)
 **  PC 0xa00315db VADDR (nil)
 **  PS 0x60d20
 **    (INTLEVEL:0 EXCM: 0 UM:1 RING:0 WOE:1 OWB:13 CALLINC:2)
 **  A0 0xa0074680  SP 0xa00e7b60  A2 0x4  A3 0xa00e7b70
 **  A4 0xa00e7b50  A5 0x4  A6 0x1  A7 0x4
 **  A8 0xa007459a  A9 0xa00e7af0 A10 0xa00afe61 A11 0xa00e7b70
 ** A12 0xa00e7b50 A13 0x4 A14 0xffffff3c A15 0xa00fb740
 ** LBEG 0xa003ae05 LEND 0xa003ae14 LCOUNT 0xa0077bf3
 ** SAR 0x14
 **  THREADPTR (nil)

Signed-off-by: Jyri Sarha <jyri.sarha@linux.intel.com>

Author: Jyri Sarha

src/debug/debug_stream/debug_stream_text_msg.c

@@ -8,9 +8,13 @@
 #include <soc.h>
 #include <adsp_debug_window.h>
 #include <sof/common.h>
+#include <zephyr/logging/log.h>
+#include <zephyr/arch/exception.h>
 
 #include <user/debug_stream_text_msg.h>
 
+LOG_MODULE_REGISTER(debug_stream_text_msg);
+
 void ds_msg(const char *format, ...)
 {
 	va_list args;
@@ -33,3 +37,57 @@ void ds_msg(const char *format, ...)
 						  sizeof(buf.msg.hdr.data[0]));
 	debug_stream_slot_send_record(&buf.msg.hdr);
 }
+
+static struct {
+	struct debug_stream_text_msg msg;
+	char text[768];
+} __packed buf = { 0 };
+static int reports_sent_cpu[CONFIG_MP_MAX_NUM_CPUS] = { 0 };
+static size_t pos;
+
+static void ds_exception_drain(bool flush)
+{
+	if (flush) {
+		pos = 0;
+		return;
+	}
+
+	if (reports_sent_cpu[arch_proc_id()]++ > 0)
+		return;
+
+	buf.msg.hdr.id = DEBUG_STREAM_RECORD_ID_TEXT_MSG;
+	buf.msg.hdr.size_words = SOF_DIV_ROUND_UP(sizeof(buf.msg) + pos,
+						  sizeof(buf.msg.hdr.data[0]));
+	memset(buf.text + pos, 0, buf.msg.hdr.size_words * sizeof(uint32_t) - pos);
+	debug_stream_slot_send_record(&buf.msg.hdr);
+	pos = 0;
+}
+
+static void ds_exception_dump(const char *format, va_list args)
+{
+	ssize_t len;
+
+	if (reports_sent_cpu[arch_proc_id()] > 0)
+		return;
+
+	len = vsnprintf(buf.text + pos, sizeof(buf.text) - pos, format, args);
+	if (len < 0) {
+		pos = 0;
+		return;
+	}
+	pos += MIN(len, sizeof(buf.text));
+
+	if (pos >= sizeof(buf.text))
+		ds_exception_drain(false);
+}
+
+#if defined(CONFIG_EXCEPTION_DUMP_HOOK)
+static int init_exception_dump_hook(void)
+{
+	set_exception_dump_hook(ds_exception_dump, ds_exception_drain);
+	LOG_INF("exception_dump_hook set");
+	return 0;
+}
+
+SYS_INIT(init_exception_dump_hook, APPLICATION, CONFIG_KERNEL_INIT_PRIORITY_DEFAULT);
+#endif

src/include/user/debug_stream_text_msg.h

@@ -7,6 +7,7 @@
 #define __SOC_DEBUG_STREAM_TEXT_MSG_H__
 
 #include <user/debug_stream_slot.h>
+#include <stdarg.h>
 
 /*
  * Debug Stream text message.