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authorMichael Roth <mdroth@linux.vnet.ibm.com>2014-05-20 12:20:39 -0500
committerLuiz Capitulino <lcapitulino@redhat.com>2014-05-21 09:25:31 -0400
commitfc13d937269c1cd01a4b7720c1dcce01722727a2 (patch)
tree394f5db89292f081978466db6efbb8748b1216e1
parent347888113020e874027cb200bb38aa0852e42839 (diff)
downloadqemu-arm-fc13d937269c1cd01a4b7720c1dcce01722727a2.tar.gz
qapi: zero-initialize all QMP command parameters
In general QMP command parameter values are specified by consumers of the QMP/HMP interface, but in the case of optional parameters these values may be left uninitialized. It is considered a bug for code to make use of optional parameters that have not been flagged as being present by the marshalling code (via corresponding has_<parameter> parameter), however our marshalling code will still pass these uninitialized values on to the corresponding QMP function (to then be ignored). Some compilers (clang in particular) consider this unsafe however, and generate warnings as a result. As reported by Peter Maydell: This is something clang's -fsanitize=undefined spotted. The code generated by qapi-commands.py in qmp-marshal.c for qmp_marshal_* functions where there are some optional arguments looks like this: bool has_force = false; bool force; mi = qmp_input_visitor_new_strict(QOBJECT(args)); v = qmp_input_get_visitor(mi); visit_type_str(v, &device, "device", errp); visit_start_optional(v, &has_force, "force", errp); if (has_force) { visit_type_bool(v, &force, "force", errp); } visit_end_optional(v, errp); qmp_input_visitor_cleanup(mi); if (error_is_set(errp)) { goto out; } qmp_eject(device, has_force, force, errp); In the case where has_force is false, we never initialize force, but then we use it by passing it to qmp_eject. I imagine we don't then actually use the value, but clang complains in particular for 'bool' variables because the value that ends up being loaded from memory for 'force' is not either 0 or 1 (being uninitialized stack contents). Fix this by initializing all QMP command parameters to {0} in the marshalling code prior to passing them on to the QMP functions. Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com> Reported-by: Peter Maydell <peter.maydell@linaro.org> Tested-by: Peter Maydell <peter.maydell@linaro.org> Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Markus Armbruster <armbru@redhat.com> Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
-rw-r--r--scripts/qapi-commands.py2
1 files changed, 1 insertions, 1 deletions
diff --git a/scripts/qapi-commands.py b/scripts/qapi-commands.py
index 386f17ef44..7d93d01ed2 100644
--- a/scripts/qapi-commands.py
+++ b/scripts/qapi-commands.py
@@ -111,7 +111,7 @@ bool has_%(argname)s = false;
argname=c_var(argname), argtype=c_type(argtype))
else:
ret += mcgen('''
-%(argtype)s %(argname)s;
+%(argtype)s %(argname)s = {0};
''',
argname=c_var(argname), argtype=c_type(argtype))