From 772f1b3721ac138b69c525cb2186b6d72ed200e1 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Daniel=20P=2E=20Berrang=C3=A9?= Date: Wed, 23 Jan 2019 12:00:15 +0000 Subject: trace: forbid use of %m in trace event format strings MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The '%m' format instructs glibc's printf()/syslog() implementation to insert the contents of strerror(errno). Since this is a glibc extension it should generally be avoided in QEMU due to need for portability to a variety of platforms. Even though vfio is Linux-only code that could otherwise use "%m", it must still be avoided in trace-events files because several of the backends do not use the format string and so this error information is invisible to them. The errno string value should be given as an explicit trace argument instead, making it accessible to all backends. This also allows it to work correctly with future patches that use the format string with systemtap's simple printf code. Reviewed-by: Eric Blake Signed-off-by: Daniel P. Berrangé Message-id: 20190123120016.4538-4-berrange@redhat.com Signed-off-by: Stefan Hajnoczi --- scripts/tracetool/__init__.py | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'scripts') diff --git a/scripts/tracetool/__init__.py b/scripts/tracetool/__init__.py index 3478ac9..6fca674 100644 --- a/scripts/tracetool/__init__.py +++ b/scripts/tracetool/__init__.py @@ -274,6 +274,10 @@ class Event(object): props = groups["props"].split() fmt = groups["fmt"] fmt_trans = groups["fmt_trans"] + if fmt.find("%m") != -1 or fmt_trans.find("%m") != -1: + raise ValueError("Event format '%m' is forbidden, pass the error " + "as an explicit trace argument") + if len(fmt_trans) > 0: fmt = [fmt_trans, fmt] args = Arguments.build(groups["args"]) -- cgit v1.1