gdbstub: Switch to the thread receiving a signal

Respond with Txxthread:yyyy; instead of a plain Sxx to indicate which
thread received the signal. Otherwise, the debugger will associate it
with the main one. Also automatically select this thread, as that is
what gdb expects.

Signed-off-by: Pavel Labath <pavel@labath.sk>
Message-Id: <20211019174953.36560-1-pavel@labath.sk>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20211026102234.3961636-29-alex.bennee@linaro.org>

gdbstub.c

@@ -3138,8 +3138,12 @@ gdb_handlesig(CPUState *cpu, int sig)
     tb_flush(cpu);
 
     if (sig != 0) {
-        snprintf(buf, sizeof(buf), "S%02x", target_signal_to_gdb(sig));
-        put_packet(buf);
+        gdb_set_stop_cpu(cpu);
+        g_string_printf(gdbserver_state.str_buf,
+                        "T%02xthread:", target_signal_to_gdb(sig));
+        gdb_append_thread_id(cpu, gdbserver_state.str_buf);
+        g_string_append_c(gdbserver_state.str_buf, ';');
+        put_strbuf();
     }
     /* put_packet() might have detected that the peer terminated the
        connection.  */

tests/tcg/multiarch/Makefile.target

@@ -68,11 +68,19 @@ run-gdbstub-qxfer-auxv-read: sha1
 		--bin $< --test $(MULTIARCH_SRC)/gdbstub/test-qxfer-auxv-read.py, \
 	"basic gdbstub qXfer:auxv:read support")
 
+run-gdbstub-thread-breakpoint: testthread
+	$(call run-test, $@, $(GDB_SCRIPT) \
+		--gdb $(HAVE_GDB_BIN) \
+		--qemu $(QEMU) --qargs "$(QEMU_OPTS)" \
+		--bin $< --test $(MULTIARCH_SRC)/gdbstub/test-thread-breakpoint.py, \
+	"hitting a breakpoint on non-main thread")
+
 else
 run-gdbstub-%:
 	$(call skip-test, "gdbstub test $*", "need working gdb")
 endif
-EXTRA_RUNS += run-gdbstub-sha1 run-gdbstub-qxfer-auxv-read
+EXTRA_RUNS += run-gdbstub-sha1 run-gdbstub-qxfer-auxv-read \
+	      run-gdbstub-thread-breakpoint
 
 # ARM Compatible Semi Hosting Tests
 #

tests/tcg/multiarch/gdbstub/test-thread-breakpoint.py

@@ -0,0 +1,60 @@
+from __future__ import print_function
+#
+# Test auxiliary vector is loaded via gdbstub
+#
+# This is launched via tests/guest-debug/run-test.py
+#
+
+import gdb
+import sys
+
+failcount = 0
+
+def report(cond, msg):
+    "Report success/fail of test"
+    if cond:
+        print ("PASS: %s" % (msg))
+    else:
+        print ("FAIL: %s" % (msg))
+        global failcount
+        failcount += 1
+
+def run_test():
+    "Run through the tests one by one"
+
+    sym, ok = gdb.lookup_symbol("thread1_func")
+    gdb.execute("b thread1_func")
+    gdb.execute("c")
+
+    frame = gdb.selected_frame()
+    report(str(frame.function()) == "thread1_func", "break @ %s"%frame)
+
+#
+# This runs as the script it sourced (via -x, via run-test.py)
+#
+try:
+    inferior = gdb.selected_inferior()
+    arch = inferior.architecture()
+    print("ATTACHED: %s" % arch.name())
+except (gdb.error, AttributeError):
+    print("SKIPPING (not connected)", file=sys.stderr)
+    exit(0)
+
+if gdb.parse_and_eval('$pc') == 0:
+    print("SKIP: PC not set")
+    exit(0)
+
+try:
+    # These are not very useful in scripts
+    gdb.execute("set pagination off")
+    gdb.execute("set confirm off")
+
+    # Run the actual tests
+    run_test()
+except (gdb.error):
+    print ("GDB Exception: %s" % (sys.exc_info()[0]))
+    failcount += 1
+    pass
+
+print("All tests complete: %d failures" % failcount)
+exit(failcount)