tests/guest-debug: introduce basic gdbstub tests

The aim of these tests is to combine with an appropriate kernel
image (with symbol-file vmlinux) and check it behaves as it should.
Given a kernel it checks:

  - single step
  - software breakpoint
  - hardware breakpoint
  - access, read and write watchpoints

On success it returns 0 to the calling process.

I've not plumbed this into the "make check" logic though as we need a
solution for providing non-host binaries to the tests. However the test
is structured to work with pretty much any Linux kernel image as it
uses the basic kernel_init code which is common across architectures.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-id: 1449599553-24713-7-git-send-email-alex.bennee@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

tests/guest-debug/test-gdbstub.py

@@ -0,0 +1,176 @@
+#
+# This script needs to be run on startup
+# qemu -kernel ${KERNEL} -s -S
+# and then:
+# gdb ${KERNEL}.vmlinux -x ${QEMU_SRC}/tests/guest-debug/test-gdbstub.py
+
+import gdb
+
+failcount = 0
+
+
+def report(cond, msg):
+    "Report success/fail of test"
+    if cond:
+        print ("PASS: %s" % (msg))
+    else:
+        print ("FAIL: %s" % (msg))
+        failcount += 1
+
+
+def check_step():
+    "Step an instruction, check it moved."
+    start_pc = gdb.parse_and_eval('$pc')
+    gdb.execute("si")
+    end_pc = gdb.parse_and_eval('$pc')
+
+    return not (start_pc == end_pc)
+
+
+def check_break(sym_name):
+    "Setup breakpoint, continue and check we stopped."
+    sym, ok = gdb.lookup_symbol(sym_name)
+    bp = gdb.Breakpoint(sym_name)
+
+    gdb.execute("c")
+
+    # hopefully we came back
+    end_pc = gdb.parse_and_eval('$pc')
+    print ("%s == %s %d" % (end_pc, sym.value(), bp.hit_count))
+    bp.delete()
+
+    # can we test we hit bp?
+    return end_pc == sym.value()
+
+
+# We need to do hbreak manually as the python interface doesn't export it
+def check_hbreak(sym_name):
+    "Setup hardware breakpoint, continue and check we stopped."
+    sym, ok = gdb.lookup_symbol(sym_name)
+    gdb.execute("hbreak %s" % (sym_name))
+    gdb.execute("c")
+
+    # hopefully we came back
+    end_pc = gdb.parse_and_eval('$pc')
+    print ("%s == %s" % (end_pc, sym.value()))
+
+    if end_pc == sym.value():
+        gdb.execute("d 1")
+        return True
+    else:
+        return False
+
+
+class WatchPoint(gdb.Breakpoint):
+
+    def get_wpstr(self, sym_name):
+        "Setup sym and wp_str for given symbol."
+        self.sym, ok = gdb.lookup_symbol(sym_name)
+        wp_addr = gdb.parse_and_eval(sym_name).address
+        self.wp_str = '*(%(type)s)(&%(address)s)' % dict(
+            type = wp_addr.type, address = sym_name)
+
+        return(self.wp_str)
+
+    def __init__(self, sym_name, type):
+        wp_str = self.get_wpstr(sym_name)
+        super(WatchPoint, self).__init__(wp_str, gdb.BP_WATCHPOINT, type)
+
+    def stop(self):
+        end_pc = gdb.parse_and_eval('$pc')
+        print ("HIT WP @ %s" % (end_pc))
+        return True
+
+
+def do_one_watch(sym, wtype, text):
+
+    wp = WatchPoint(sym, wtype)
+    gdb.execute("c")
+    report_str = "%s for %s (%s)" % (text, sym, wp.sym.value())
+
+    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")
+
+
+class CatchBreakpoint(gdb.Breakpoint):
+    def __init__(self, sym_name):
+        super(CatchBreakpoint, self).__init__(sym_name)
+        self.sym, ok = gdb.lookup_symbol(sym_name)
+
+    def stop(self):
+        end_pc = gdb.parse_and_eval('$pc')
+        print ("CB: %s == %s" % (end_pc, self.sym.value()))
+        if end_pc == self.sym.value():
+            report(False, "Hit final catchpoint")
+
+
+def run_test():
+    "Run throught 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")
+
+    print ("Checking HW breakpoint works")
+    break_ok = check_hbreak("kernel_init")
+    report(break_ok, "hbreak @ kernel_init")
+
+    # Can't set this up until we are in the kernel proper
+    # if we make it to run_init_process we've over-run and
+    # one of the tests failed
+    print ("Setup catch-all for run_init_process")
+    cbp = CatchBreakpoint("run_init_process")
+    cpb2 = CatchBreakpoint("try_to_run_init_process")
+
+    print ("Checking Normal breakpoint works")
+    break_ok = check_break("wait_for_completion")
+    report(break_ok, "break @ wait_for_completion")
+
+    print ("Checking watchpoint works")
+    check_watches("system_state")
+
+#
+# This runs as the script it sourced (via -x)
+#
+
+try:
+    print ("Connecting to remote")
+    gdb.execute("target remote localhost:1234")
+
+    # These are not very useful in scripts
+    gdb.execute("set pagination off")
+    gdb.execute("set confirm off")
+
+    # Run the actual tests
+    run_test()
+
+except:
+    print ("GDB Exception: %s" % (sys.exc_info()[0]))
+    failcount += 1
+    import code
+    code.InteractiveConsole(locals=globals()).interact()
+    raise
+
+# Finally kill the inferior and exit gdb with a count of failures
+gdb.execute("kill")
+exit(failcount)