core_debug: Add an address trigger to stop logging at a given address

This compares the address being fetched with the contents of a
register that can be set via DMI, and if they match, stops the
logging.  Since this works on the address being fetched rather than
executed, it is subject to false positives.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

core_debug.vhdl

@@ -91,6 +91,7 @@ architecture behave of core_debug is
     -- Log buffer address and data registers
     constant DBG_CORE_LOG_ADDR       : std_ulogic_vector(3 downto 0) := "0110";
     constant DBG_CORE_LOG_DATA       : std_ulogic_vector(3 downto 0) := "0111";
+    constant DBG_CORE_LOG_TRIGGER    : std_ulogic_vector(3 downto 0) := "1000";
 
     constant LOG_INDEX_BITS : natural := log2(LOG_LENGTH);
 
@@ -108,6 +109,8 @@ architecture behave of core_debug is
 
     signal log_dmi_addr : std_ulogic_vector(31 downto 0) := (others => '0');
     signal log_dmi_data : std_ulogic_vector(63 downto 0) := (others => '0');
+    signal log_dmi_trigger : std_ulogic_vector(63 downto 0) := (others => '0');
+    signal do_log_trigger : std_ulogic := '0';
     signal do_dmi_log_rd : std_ulogic;
     signal dmi_read_log_data : std_ulogic;
     signal dmi_read_log_data_1 : std_ulogic;
@@ -133,6 +136,7 @@ begin
         dbg_gpr_data    when DBG_CORE_GSPR_DATA,
         log_write_addr & log_dmi_addr when DBG_CORE_LOG_ADDR,
         log_dmi_data    when DBG_CORE_LOG_DATA,
+        log_dmi_trigger when DBG_CORE_LOG_TRIGGER,
 	(others => '0') when others;
 
     -- DMI writes
@@ -149,6 +153,9 @@ begin
 		stopping <= '0';
 		terminated <= '0';
 	    else
+                if do_log_trigger = '1' then
+                    log_dmi_trigger(1) <= '1';
+                end if;
 		-- Edge detect on dmi_req for 1-shot pulses
 		dmi_req_1 <= dmi_req;
 		if dmi_req = '1' and dmi_req_1 = '0' then
@@ -180,6 +187,8 @@ begin
                         elsif dmi_addr = DBG_CORE_LOG_ADDR then
                             log_dmi_addr <= dmi_din(31 downto 0);
                             do_dmi_log_rd <= '1';
+                        elsif dmi_addr = DBG_CORE_LOG_TRIGGER then
+                            log_dmi_trigger <= dmi_din;
 			end if;
 		    else
 			report("DMI read from " & to_string(dmi_addr));
@@ -246,7 +255,7 @@ begin
 
     begin
         -- Use MSB of read addresses to stop the logging
-        log_wr_enable <= not (log_read_addr(31) or log_dmi_addr(31));
+        log_wr_enable <= not (log_read_addr(31) or log_dmi_addr(31) or log_dmi_trigger(1));
 
         log_ram: process(clk)
         begin
@@ -285,6 +294,12 @@ begin
                 end if;
                 log_dmi_read_done <= log_dmi_reading;
                 log_dmi_reading <= do_dmi_log_rd;
+                do_log_trigger <= '0';
+                if log_data(42) = log_dmi_trigger(63) and
+                    log_data(41 downto 0) = log_dmi_trigger(43 downto 2) and
+                    log_dmi_trigger(0) = '1' then
+                    do_log_trigger <= '1';
+                end if;
             end if;
         end process;
         log_write_addr(LOG_INDEX_BITS - 1 downto 0) <= std_ulogic_vector(log_wr_ptr);

scripts/mw_debug/mw_debug.c

@@ -44,6 +44,7 @@
 
 #define DBG_LOG_ADDR		0x16
 #define DBG_LOG_DATA		0x17
+#define DBG_LOG_TRIGGER		0x18
 
 static bool debug;
 
@@ -466,8 +467,11 @@ static void gpr_read(uint64_t reg, uint64_t count)
 
 static void mem_read(uint64_t addr, uint64_t count)
 {
-	uint64_t data;
-	int i, rc;
+	union {
+		uint64_t data;
+		unsigned char c[8];
+	} u;
+	int i, j, rc;
 
 	rc = dmi_write(DBG_WB_CTRL, 0x7ff);
 	if (rc < 0)
@@ -476,12 +480,15 @@ static void mem_read(uint64_t addr, uint64_t count)
 	if (rc < 0)
 		return;
 	for (i = 0; i < count; i++) {
-		rc = dmi_read(DBG_WB_DATA, &data);
+		rc = dmi_read(DBG_WB_DATA, &u.data);
 		if (rc < 0)
 			return;
-		printf("%016llx: %016llx\n",
+		printf("%016llx: %016llx  ",
 		       (unsigned long long)addr,
-		       (unsigned long long)data);
+		       (unsigned long long)u.data);
+		for (j = 0; j < 8; ++j)
+			putchar(u.c[j] >= 0x20 && u.c[j] < 0x7f? u.c[j]: '.');
+		putchar('\n');
 		addr += 8;
 	}
 }
@@ -622,6 +629,28 @@ static void log_dump(const char *filename)
 	check(dmi_write(DBG_LOG_ADDR, orig_laddr), "writing LOG_ADDR");
 }
 
+static void ltrig_show(void)
+{
+	uint64_t trig;
+
+	check(dmi_read(DBG_LOG_TRIGGER, &trig), "reading LOG_TRIGGER");
+	if (trig & 1)
+		printf("log stop trigger at %" PRIx64, trig & ~3);
+	else
+		printf("log stop trigger disabled");
+	printf(", %striggered\n", (trig & 2? "": "not "));
+}
+
+static void ltrig_off(void)
+{
+	check(dmi_write(DBG_LOG_TRIGGER, 0), "writing LOG_TRIGGER");
+}
+
+static void ltrig_set(uint64_t addr)
+{
+	check(dmi_write(DBG_LOG_TRIGGER, (addr & ~(uint64_t)2) | 1), "writing LOG_TRIGGER");
+}
+
 static void usage(const char *cmd)
 {
 	fprintf(stderr, "Usage: %s -b <jtag|sim> <command> <args>\n", cmd);
@@ -651,6 +680,9 @@ static void usage(const char *cmd)
 	fprintf(stderr, "  lstart			start logging\n");
 	fprintf(stderr, "  lstop			stop logging\n");
 	fprintf(stderr, "  ldump <file>			dump log to file\n");
+	fprintf(stderr, "  ltrig 			show logging stop trigger status\n");
+	fprintf(stderr, "  ltrig off 			clear logging stop trigger address\n");
+	fprintf(stderr, "  ltrig <addr>			set logging stop trigger address\n");
 
 	fprintf(stderr, "\n");
 	fprintf(stderr, " JTAG:\n");
@@ -801,9 +833,20 @@ int main(int argc, char *argv[])
 				usage(argv[0]);
 			filename = argv[++i];
 			log_dump(filename);
+		} else if (strcmp(argv[i], "ltrig") == 0) {
+			uint64_t addr;
+
+			if ((i+1) >= argc)
+				ltrig_show();
+			else if (strcmp(argv[++i], "off") == 0)
+				ltrig_off();
+			else {
+				addr = strtoul(argv[i], NULL, 16);
+				ltrig_set(addr);
+			}
 		} else {
 			fprintf(stderr, "Unknown command %s\n", argv[i]);
-			exit(1);
+			usage(argv[0]);
 		}
 	}
 	core_status();