From: Eric Blake <eblake@redhat.com>
To: "Philippe Mathieu-Daudé" <philmd@redhat.com>, qemu-devel@nongnu.org
Cc: Kevin Wolf <kwolf@redhat.com>,
Aleksandar Markovic <amarkovic@wavecomp.com>,
qemu-block@nongnu.org, qemu-trivial@nongnu.org,
Max Reitz <mreitz@redhat.com>,
Stefan Hajnoczi <stefanha@redhat.com>,
Aleksandar Rikalo <aleksandar.rikalo@rt-rk.com>,
Aurelien Jarno <aurelien@aurel32.net>
Subject: Re: [PATCH v2 3/3] trace: Forbid dynamic field width in event format
Date: Mon, 18 Nov 2019 12:42:25 -0600 [thread overview]
Message-ID: <da2f1c61-1f99-8124-4485-c1ed4358d1e2@redhat.com> (raw)
In-Reply-To: <191fbe18-73b2-4d22-5540-8775688166a8@redhat.com>
On 11/8/19 10:07 AM, Eric Blake wrote:
> On 11/8/19 8:40 AM, Philippe Mathieu-Daudé wrote:
>> Since not all trace backends support dynamic field width in
>> format (dtrace via stap does not), forbid them.
>>
>> Add a check to refuse field width in new formats:
>>
>
>> +++ b/scripts/tracetool/__init__.py
>> @@ -206,6 +206,7 @@ class Event(object):
>> "\s*"
>> "(?:(?:(?P<fmt_trans>\".+),)?\s*(?P<fmt>\".+))?"
>> "\s*")
>> + _DFWRE = re.compile(".*(%0?\*).*")
>
> The use of leading and trailing .* is pointless if the RE itself is used
> unanchored and where you only care if the () matched.
Following up on this (based on an IRC conversation):
re.match _is_ anchored by default, while re.search is unanchored
>
> This doesn't catch all valid uses of * in a printf format. Better might
> be something like:
>
> _DFWRE = re.compile("%[\d\.\- +#']*\*")
>
> which matches only if there is a %, any number of characters that can
> form a printf flag, as well as a numeric field width but dynamic precision.
>
>
>> + if Event._DFWRE.match(fmt):
Or put differently, if you want to drop the .* from the compiled regex,
then you need to use .search(fmt) here rather than .match(fmt).
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3226
Virtualization: qemu.org | libvirt.org
prev parent reply other threads:[~2019-11-18 18:44 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-08 14:40 [PATCH v2 0/3] hw: Remove dynamic field width from trace events Philippe Mathieu-Daudé
2019-11-08 14:40 ` [PATCH v2 1/3] hw/block/pflash: " Philippe Mathieu-Daudé
2019-11-08 15:56 ` Eric Blake
2019-11-14 21:26 ` Philippe Mathieu-Daudé
2019-11-18 19:21 ` Eric Blake
2019-11-18 20:39 ` Philippe Mathieu-Daudé
2019-11-08 14:40 ` [PATCH v2 2/3] hw/mips/gt64xxx: " Philippe Mathieu-Daudé
2019-11-08 15:58 ` Eric Blake
2019-11-14 21:24 ` Philippe Mathieu-Daudé
2019-11-18 19:10 ` Philippe Mathieu-Daudé
2019-11-18 19:15 ` Eric Blake
2019-11-08 14:40 ` [PATCH v2 3/3] trace: Forbid dynamic field width in event format Philippe Mathieu-Daudé
2019-11-08 16:07 ` Eric Blake
2019-11-18 18:42 ` Eric Blake [this message]
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