lightningd: --dev-debugger=<subdaemon>

Or for blackbox tests --gdb1=<subdaemon> / --gdb2=<subdaemon>.

This makes the subdaemon wait as soon as it's execed, so we can attach
the debugger.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

daemon/test/scripts/helpers.sh

@@ -46,6 +46,12 @@ parse_cmdline()
 		    exit 1
 		fi
 		;;
+	    x"--gdb1="*)
+		DAEMON1_EXTRA=--dev-debugger=${1#--gdb1=}
+		;;
+	    x"--gdb2="*)
+		DAEMON2_EXTRA=--dev-debugger=${1#--gdb2=}
+		;;
 	    x"--reconnect")
 		RECONNECT=reconnect
 		;;
@@ -122,21 +128,21 @@ EOF
     [ $NUM_LIGHTNINGD = 2 ] || echo port=`findport 4010 $VARIANT` >> $DIR3/config
 }
 
-# Use DIR REDIR REDIRERR GDBFLAG BINARY
+# Use DIR REDIR REDIRERR GDBFLAG BINARY EXTRAARGS
 start_one_lightningd()
 {
     # Need absolute path for re-exec testing.
     local CMD
     CMD="$(readlink -f `pwd`/../../$5) --lightning-dir=$1"
     if [ -n "$4" ]; then
-	echo Press return once you run: gdb --args $CMD >&2
+	echo Press return once you run: gdb --args $CMD $6 >&2
 
 	read REPLY
     else
 	CMD="$PREFIX $CMD"
-	$CMD > $2 2> $3 &
+	$CMD $6 > $2 2> $3 &
     fi
-    echo $CMD
+    echo $CMD $6
 }
 
 start_lightningd()
@@ -153,8 +159,8 @@ start_lightningd()
 	SHUTDOWN_BITCOIN=/bin/true
     fi
 
-    LIGHTNINGD1=`start_one_lightningd $DIR1 $REDIR1 $REDIRERR1 "$GDB1" $BINARY`
-    LIGHTNINGD2=`start_one_lightningd $DIR2 $REDIR2 $REDIRERR2 "$GDB2" $BINARY`
+    LIGHTNINGD1=`start_one_lightningd $DIR1 $REDIR1 $REDIRERR1 "$GDB1" $BINARY $DAEMON1_EXTRA`
+    LIGHTNINGD2=`start_one_lightningd $DIR2 $REDIR2 $REDIRERR2 "$GDB2" $BINARY $DAEMON2_EXTRA`
     [ $NUM_LIGHTNINGD = 2 ] || LIGHTNINGD3=`start_one_lightningd $DIR3 $REDIR3 $REDIRERR3 "$GDB3" $BINARY`
 
     if ! check "$LCLI1 getlog 2>/dev/null | $FGREP Hello"; then

lightningd/Makefile

@@ -39,6 +39,7 @@ LIGHTNINGD_LIB_SRC :=				\
 	lightningd/commit_tx.c			\
 	lightningd/cryptomsg.c			\
 	lightningd/crypto_sync.c		\
+	lightningd/debug.c			\
 	lightningd/funding_tx.c			\
 	lightningd/htlc_tx.c			\
 	lightningd/key_derive.c			\

lightningd/debug.c

@@ -0,0 +1,21 @@
+#include <ccan/str/str.h>
+#include <lightningd/debug.h>
+#include <stdio.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+void subdaemon_debug(int argc, char *argv[])
+{
+	int i;
+	bool printed = false;
+
+	/* From debugger, tell gdb "return". */
+	for (i = 1; i < argc; i++) {
+		while (streq(argv[i], "--debugger")) {
+			if (!printed)
+				fprintf(stderr, "gdb -ex 'attach %u' %s\n",
+					getpid(), argv[0]);
+			printed = true;
+		}
+	}
+}

lightningd/debug.h

@@ -0,0 +1,7 @@
+#ifndef LIGHTNING_LIGHTNINGD_DEBUG_H
+#define LIGHTNING_LIGHTNINGD_DEBUG_H
+#include "config.h"
+
+void subdaemon_debug(int argc, char *argv[]);
+
+#endif /* LIGHTNING_LIGHTNINGD_DEBUG_H */

lightningd/gossip/gossip.c

@@ -16,6 +16,7 @@
 #include <fcntl.h>
 #include <inttypes.h>
 #include <lightningd/cryptomsg.h>
+#include <lightningd/debug.h>
 #include <lightningd/gossip/gen_gossip_control_wire.h>
 #include <lightningd/gossip/gen_gossip_status_wire.h>
 #include <secp256k1_ecdh.h>
@@ -381,7 +382,7 @@ int main(int argc, char *argv[])
 {
 	struct daemon *daemon;
 
-	breakpoint();
+	subdaemon_debug(argc, argv);
 
 	if (argc == 2 && streq(argv[1], "--version")) {
 		printf("%s\n", version());

lightningd/handshake/handshake.c

@@ -2,7 +2,6 @@
 #include "type_to_string.h"
 #include <assert.h>
 #include <bitcoin/privkey.h>
-#include <ccan/breakpoint/breakpoint.h>
 #include <ccan/build_assert/build_assert.h>
 #include <ccan/crypto/hkdf_sha256/hkdf_sha256.h>
 #include <ccan/endian/endian.h>
@@ -11,6 +10,7 @@
 #include <ccan/read_write_all/read_write_all.h>
 #include <ccan/short_types/short_types.h>
 #include <errno.h>
+#include <lightningd/debug.h>
 #include <lightningd/handshake/gen_handshake_control_wire.h>
 #include <lightningd/handshake/gen_handshake_status_wire.h>
 #include <lightningd/hsm/client.h>
@@ -979,7 +979,7 @@ int main(int argc, char *argv[])
 		exit(0);
 	}
 
-	breakpoint();
+	subdaemon_debug(argc, argv);
 	secp256k1_ctx = secp256k1_context_create(SECP256K1_CONTEXT_VERIFY
 						 | SECP256K1_CONTEXT_SIGN);
 	status_setup(STATUS_FD);

lightningd/lightningd.c

@@ -74,6 +74,7 @@ static struct lightningd *new_lightningd(const tal_t *ctx)
 	list_head_init(&ld->peers);
 	ld->peer_counter = 0;
 	ld->bip32_max_index = 0;
+	ld->dev_debug_subdaemon = NULL;
 	list_head_init(&ld->utxos);
 	ld->dstate.log_book = new_log_book(&ld->dstate, 20*1024*1024,LOG_INFORM);
 	ld->log = ld->dstate.base_log = new_log(&ld->dstate,
@@ -175,8 +176,11 @@ int main(int argc, char *argv[])
 	/* Figure out where we are first. */
 	ld->daemon_dir = find_my_path(ld, argv[0]);
 
-	/* Handle options and config; move to .lightningd */
 	register_opts(&ld->dstate);
+	opt_register_arg("--dev-debugger=<subdaemon>", opt_subdaemon_debug, NULL,
+			 ld, "Wait for gdb attach at start of <subdaemon>");
+
+	/* Handle options and config; move to .lightningd */
 	newdir = handle_opts(&ld->dstate, argc, argv);
 
 	/* Activate crash log now we're in the right place. */

lightningd/lightningd.h

@@ -40,6 +40,9 @@ struct lightningd {
 	struct ext_key *bip32_base;
 	u32 bip32_max_index;
 
+	/* If we want to debug a subdaemon. */
+	const char *dev_debug_subdaemon;
+
 	/* UTXOs we have available to spend. */
 	struct list_head utxos;
 };

lightningd/opening/opening.c

@@ -11,6 +11,7 @@
 #include <lightningd/channel.h>
 #include <lightningd/commit_tx.h>
 #include <lightningd/crypto_sync.h>
+#include <lightningd/debug.h>
 #include <lightningd/key_derive.h>
 #include <lightningd/opening/gen_opening_control_wire.h>
 #include <lightningd/opening/gen_opening_status_wire.h>
@@ -683,7 +684,7 @@ int main(int argc, char *argv[])
 		exit(0);
 	}
 
-	breakpoint();
+	subdaemon_debug(argc, argv);
 
 	/* We handle write returning errors! */
 	signal(SIGCHLD, SIG_IGN);

lightningd/subdaemon.c

@@ -46,7 +46,7 @@ static bool move_fd(int from, int to)
 }
 
 /* We use sockets, not pipes, because fds are bidir. */
-static int subdaemon(const char *dir, const char *name,
+static int subdaemon(const char *dir, const char *name, bool debug,
 		     int *statusfd, int *reqfd, va_list ap)
 {
 	int childreq[2], childstatus[2], execfail[2];
@@ -79,6 +79,7 @@ static int subdaemon(const char *dir, const char *name,
 	if (childpid == 0) {
 		int fdnum = 3;
 		long max;
+		const char *debug_arg = NULL;
 
 		if (reqfd)
 			close(childreq[0]);
@@ -109,7 +110,10 @@ static int subdaemon(const char *dir, const char *name,
 		max = sysconf(_SC_OPEN_MAX);
 		for (fd = fdnum; fd < max; fd++)
 			close(fd);
-		execl(path_join(NULL, dir, name), name, NULL);
+
+		if (debug)
+			debug_arg = "--debugger";
+		execl(path_join(NULL, dir, name), name, debug_arg, NULL);
 
 	child_errno_fail:
 		err = errno;
@@ -259,9 +263,11 @@ struct subdaemon *new_subdaemon(const tal_t *ctx,
 	va_list ap;
 	struct subdaemon *sd = tal(ctx, struct subdaemon);
 	int req_fd, status_fd;
+	bool debug;
 
+	debug = ld->dev_debug_subdaemon && strends(name,ld->dev_debug_subdaemon);
 	va_start(ap, finished);
-	sd->pid = subdaemon(ld->daemon_dir, name, &status_fd,
+	sd->pid = subdaemon(ld->daemon_dir, name, debug, &status_fd,
 			    reqname ? &req_fd : NULL, ap);
 	va_end(ap);
 	if (sd->pid == (pid_t)-1) {
@@ -383,3 +389,9 @@ void subdaemon_req_(struct subdaemon *sd,
 	list_add_tail(&sd->reqs, &sr->list);
 	io_wake(sd);
 }
+
+char *opt_subdaemon_debug(const char *optarg, struct lightningd *ld)
+{
+	ld->dev_debug_subdaemon = optarg;
+	return NULL;
+}

lightningd/subdaemon.h

@@ -90,4 +90,7 @@ void subdaemon_req_(struct subdaemon *sd,
 		    int fd_out, int *fd_in,
 		    void (*reqcb)(struct subdaemon *, const u8 *, void *),
 		    void *reqcb_data);
+
+char *opt_subdaemon_debug(const char *optarg, struct lightningd *ld);
+
 #endif /* LIGHTNING_LIGHTNINGD_SUBDAEMON_H */