[PATCH 2/2] scripts/gdb: implement 'qemu bt'

[Maxim Levitsky]

This script first runs the regular gdb's 'bt' command, and then if we are in a
coroutine it prints the coroutines backtraces in the order in which they
were called.

Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
---
 scripts/qemu-gdb.py          |  1 +
 scripts/qemugdb/coroutine.py | 32 +++++++++++++++++++++++++++++++-
 2 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/scripts/qemu-gdb.py b/scripts/qemu-gdb.py
index e0bfa7b5a4..4d2a9f6c43 100644
--- a/scripts/qemu-gdb.py
+++ b/scripts/qemu-gdb.py
@@ -40,6 +40,7 @@ timers.TimersCommand()
 
 coroutine.CoroutineSPFunction()
 coroutine.CoroutinePCFunction()
+coroutine.CoroutineBt()
 
 # Default to silently passing through SIGUSR1, because QEMU sends it
 # to itself a lot.
diff --git a/scripts/qemugdb/coroutine.py b/scripts/qemugdb/coroutine.py
index e1399211e6..39d53a102e 100644
--- a/scripts/qemugdb/coroutine.py
+++ b/scripts/qemugdb/coroutine.py
@@ -88,8 +88,11 @@ def bt_jmpbuf(jmpbuf):
 
     selected_frame.select()
 
+def co_cast(co):
+    return co.cast(gdb.lookup_type('CoroutineUContext').pointer())
+
 def coroutine_to_jmpbuf(co):
-    coroutine_pointer = co.cast(gdb.lookup_type('CoroutineUContext').pointer())
+    coroutine_pointer = co_cast(co)
     return coroutine_pointer['env']['__jmpbuf']
 
 
@@ -107,6 +110,33 @@ class CoroutineCommand(gdb.Command):
 
         bt_jmpbuf(coroutine_to_jmpbuf(gdb.parse_and_eval(argv[0])))
 
+class CoroutineBt(gdb.Command):
+    '''Display backtrace including coroutine switches'''
+    def __init__(self):
+        gdb.Command.__init__(self, 'qemu bt', gdb.COMMAND_STACK,
+                             gdb.COMPLETE_NONE)
+
+    def invoke(self, arg, from_tty):
+
+        gdb.execute("bt")
+
+        thread = gdb.selected_thread()
+        if thread == None or not thread.is_stopped():
+            raise gdb.GdbError("No currrent thread")
+
+        if gdb.parse_and_eval("qemu_in_coroutine()") == False:
+            return
+
+        co_ptr = gdb.parse_and_eval("qemu_coroutine_self()")
+        gdb.write("Coroutine at " + str(co_ptr) + ":\n")
+
+        while True:
+            co = co_cast(co_ptr)
+            co_ptr = co["base"]["caller"]
+            if co_ptr == 0:
+                break
+            bt_jmpbuf(coroutine_to_jmpbuf(co_ptr))
+
 class CoroutineSPFunction(gdb.Function):
     def __init__(self):
         gdb.Function.__init__(self, 'qemu_coroutine_sp')
-- 
2.26.2