gdbstub: implement a softmmu based test

This adds a new tests that allows us to test softmmu only features
including watchpoints. To do achieve this we need to:

  - add _exit: labels to the boot codes
  - write a memory.py test case
  - plumb the test case into the build system
  - tweak the run_test script to:
    - re-direct output when asked
    - use socket based connection for all tests
    - add a small pause before connection

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20210108224256.2321-6-alex.bennee@linaro.org>

2 files changed, 148 insertions, 1 deletions

diff --git a/tests/tcg/multiarch/gdbstub/memory.py b/tests/tcg/multiarch/gdbstub/memory.py
new file mode 100644
index 0000000..67864ad
--- /dev/null
+++ b/tests/tcg/multiarch/gdbstub/memory.py
@@ -0,0 +1,130 @@
+from __future__ import print_function
+#
+# Test some of the softmmu debug features with the multiarch memory
+# test. It is a port of the original vmlinux focused test case but
+# using the "memory" test instead.
+#
+# 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 check_step():
+    "Step an instruction, check it moved."
+    start_pc = gdb.parse_and_eval('$pc')
+    gdb.execute("si")
+    end_pc = gdb.parse_and_eval('$pc')
+
+    return not (start_pc == end_pc)
+
+
+#
+# Currently it's hard to create a hbreak with the pure python API and
+# manually matching PC to symbol address is a bit flaky thanks to
+# function prologues. However internally QEMU's gdbstub treats them
+# the same as normal breakpoints so it will do for now.
+#
+def check_break(sym_name):
+    "Setup breakpoint, continue and check we stopped."
+    sym, ok = gdb.lookup_symbol(sym_name)
+    bp = gdb.Breakpoint(sym_name, gdb.BP_BREAKPOINT)
+
+    gdb.execute("c")
+
+    # hopefully we came back
+    end_pc = gdb.parse_and_eval('$pc')
+    report(bp.hit_count == 1,
+           "break @ %s (%s %d hits)" % (end_pc, sym.value(), bp.hit_count))
+
+    bp.delete()
+
+
+def do_one_watch(sym, wtype, text):
+
+    wp = gdb.Breakpoint(sym, gdb.BP_WATCHPOINT, wtype)
+    gdb.execute("c")
+    report_str = "%s for %s" % (text, sym)
+
+    if wp.hit_count > 0:
+        report(True, report_str)
+        wp.delete()
+    else:
+        report(False, report_str)
+
+
+def check_watches(sym_name):
+    "Watch a symbol for any access."
+
+    # Should hit for any read
+    do_one_watch(sym_name, gdb.WP_ACCESS, "awatch")
+
+    # Again should hit for reads
+    do_one_watch(sym_name, gdb.WP_READ, "rwatch")
+
+    # Finally when it is written
+    do_one_watch(sym_name, gdb.WP_WRITE, "watch")
+
+
+def run_test():
+    "Run through the tests one by one"
+
+    print("Checking we can step the first few instructions")
+    step_ok = 0
+    for i in range(3):
+        if check_step():
+            step_ok += 1
+
+    report(step_ok == 3, "single step in boot code")
+
+    # If we get here we have missed some of the other breakpoints.
+    print("Setup catch-all for _exit")
+    cbp = gdb.Breakpoint("_exit", gdb.BP_BREAKPOINT)
+
+    check_break("main")
+    check_watches("test_data[128]")
+
+    report(cbp.hit_count == 0, "didn't reach backstop")
+
+#
+# This runs as the script it sourced (via -x, via run-test.py)
+#
+try:
+    inferior = gdb.selected_inferior()
+    arch = inferior.architecture()
+    print("ATTACHED: %s" % arch.name())
+except (gdb.error, AttributeError):
+    print("SKIPPING (not connected)", file=sys.stderr)
+    exit(0)
+
+if gdb.parse_and_eval('$pc') == 0:
+    print("SKIP: PC not set")
+    exit(0)
+
+try:
+    # These are not very useful in scripts
+    gdb.execute("set pagination off")
+
+    # Run the actual tests
+    run_test()
+except (gdb.error):
+    print("GDB Exception: %s" % (sys.exc_info()[0]))
+    failcount += 1
+    pass
+
+# Finally kill the inferior and exit gdb with a count of failures
+gdb.execute("kill")
+exit(failcount)
diff --git a/tests/tcg/multiarch/system/Makefile.softmmu-target b/tests/tcg/multiarch/system/Makefile.softmmu-target
index db4bbed..4657f6e 100644
--- a/tests/tcg/multiarch/system/Makefile.softmmu-target
+++ b/tests/tcg/multiarch/system/Makefile.softmmu-target
@@ -7,8 +7,25 @@
 # complications of building.
 #
 
-MULTIARCH_SYSTEM_SRC=$(SRC_PATH)/tests/tcg/multiarch/system
+MULTIARCH_SRC=$(SRC_PATH)/tests/tcg/multiarch
+MULTIARCH_SYSTEM_SRC=$(MULTIARCH_SRC)/system
 VPATH+=$(MULTIARCH_SYSTEM_SRC)
 
 MULTIARCH_TEST_SRCS=$(wildcard $(MULTIARCH_SYSTEM_SRC)/*.c)
 MULTIARCH_TESTS = $(patsubst $(MULTIARCH_SYSTEM_SRC)/%.c, %, $(MULTIARCH_TEST_SRCS))
+
+ifneq ($(HAVE_GDB_BIN),)
+GDB_SCRIPT=$(SRC_PATH)/tests/guest-debug/run-test.py
+
+run-gdbstub-memory: memory
+	$(call run-test, $@, $(GDB_SCRIPT) \
+		--gdb $(HAVE_GDB_BIN) \
+		--qemu $(QEMU) \
+		--output $<.gdb.out \
+		--qargs \
+		"-monitor none -display none -chardev file$(COMMA)path=$<.out$(COMMA)id=output $(QEMU_OPTS)" \
+		--bin $< --test $(MULTIARCH_SRC)/gdbstub/memory.py, \
+	"softmmu gdbstub support")
+
+MULTIARCH_RUNS += run-gdbstub-memory
+endif