From: Andrew Cooper <andrew.cooper3@citrix.com>
To: Jan Beulich <jbeulich@suse.com>,
"Daniel P. Smith" <dpsmith@apertussolutions.com>
Cc: "Stefano Stabellini" <sstabellini@kernel.org>,
"Julien Grall" <julien@xen.org>,
"Volodymyr Babchuk" <Volodymyr_Babchuk@epam.com>,
"George Dunlap" <george.dunlap@citrix.com>,
"Ian Jackson" <iwj@xenproject.org>, "Wei Liu" <wl@xen.org>,
"Roger Pau Monné" <roger.pau@citrix.com>,
"Tamas K Lengyel" <tamas@tklengyel.com>,
"Tim Deegan" <tim@xen.org>, "Juergen Gross" <jgross@suse.com>,
"Alexandru Isaila" <aisaila@bitdefender.com>,
"Petre Pircalabu" <ppircalabu@bitdefender.com>,
"Dario Faggioli" <dfaggioli@suse.com>,
"Paul Durrant" <paul@xen.org>,
"Daniel De Graaf" <dgdegra@tycho.nsa.gov>,
persaur@gmail.com, christopher.w.clark@gmail.com,
adam.schwalm@starlab.io, scott.davis@starlab.io,
xen-devel@lists.xenproject.org
Subject: Re: [PATCH 3/6] xsm: enabling xsm to always be included
Date: Mon, 21 Jun 2021 11:41:21 +0100 [thread overview]
Message-ID: <8a909d6b-e69c-05ce-35dd-0f6be719b5ae@citrix.com> (raw)
In-Reply-To: <6d50efc1-6c13-1481-b70c-0abfa99aa610@suse.com>
On 21/06/2021 07:58, Jan Beulich wrote:
> On 18.06.2021 22:27, Daniel P. Smith wrote:
>> On 6/18/21 8:26 AM, Jan Beulich wrote:
>>> On 18.06.2021 01:39, Daniel P. Smith wrote:
>>>> The only difference between !CONFIG_XSM and CONFIG_XSM with !CONFIG_XSM_SILO and !CONFIG_XSM_FLASK
>>>> is whether the XSM hooks in dummy.h are called as static inline functions or as function
>>>> pointers to static functions. As such this commit,
>>>> * eliminates CONFIG_XSM
>>> Following from what Andrew has said (including him mentioning your
>>> changing of certain Kconfig option defaults), I'm not convinced this is
>>> a good move. This still ought to serve as the overall XSM-yes-or-no
>>> setting. If internally you make said two variants match in behavior,
>>> that's a different thing.
>> Apologies that I did not express this clearly. What I was attempting to
>> say is the fact of the matter is that there is no logical behavior
>> difference between "XSM no" and "XSM yes with dummy policy". The only
>> difference is the mechanics of how the dummy functions get called.
>> Specifically via macro magic the dummy functions are either flipped into
>> static inline declarations that are then included into the code where
>> they are invoked or the macro magic has them ending up in the dummy.c
>> XSM module where they are wrapped in macro generated functions that are
>> set as the functions in the dummy xsm_ops structure. Thus it is always
>> the same logic being invoked, it is just mechanics of how you get to the
>> logic.
> That's what I understood, really. What I dislike is the inline functions
> going away in what we currently call !XSM.
I'm sorry, but this is an unreasonable objection.
The mess used to create the status quo *is* the majority reason why
fixing/developing XSM is so hard, and why the code is so obfuscated. To
prove this point, how many people on this email thread realise that
calls using XSM_HOOK offer 0 security under xsm_default_action()?
Having xsm_default_action() forced inline isn't obviously the right move
in the first place, and I doubt that you could even measure a
performance difference for using real function calls.
Even if there is a marginal performance difference, and I doubt that
there is, performance is far less important than de-obfuscating the code
and fixing our various security mechanisms to be first-class supported
citizens.
~Andrew
next prev parent reply other threads:[~2021-06-21 10:41 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-17 23:39 [PATCH 0/6] xsm: refactoring xsm hooks Daniel P. Smith
2021-06-17 23:39 ` [PATCH 1/6] xsm: refactor xsm_ops handling Daniel P. Smith
2021-06-18 11:34 ` Andrew Cooper
2021-06-18 11:44 ` Jan Beulich
2021-06-18 11:45 ` Andrew Cooper
2021-06-18 16:26 ` Daniel P. Smith
2021-06-18 16:17 ` Daniel P. Smith
2021-07-12 12:36 ` [PATCH 0.5/6] xen: Implement xen/alternative-call.h for use in common code Andrew Cooper
2021-06-17 23:39 ` [PATCH 2/6] xsm: decouple xsm header inclusion selection Daniel P. Smith
2021-06-17 23:39 ` [PATCH 3/6] xsm: enabling xsm to always be included Daniel P. Smith
2021-06-18 11:53 ` Andrew Cooper
2021-06-18 16:35 ` Daniel P. Smith
2021-06-21 6:53 ` Jan Beulich
2021-06-24 17:18 ` Daniel P. Smith
2021-06-25 6:39 ` Jan Beulich
2021-06-18 12:26 ` Jan Beulich
2021-06-18 20:27 ` Daniel P. Smith
2021-06-21 6:58 ` Jan Beulich
2021-06-21 10:41 ` Andrew Cooper [this message]
2021-06-21 11:39 ` Jan Beulich
2021-06-18 21:20 ` Andrew Cooper
2021-06-21 7:03 ` Jan Beulich
2021-06-17 23:39 ` [PATCH 4/6] xsm: remove xen_defualt_t from hook definitions Daniel P. Smith
2021-06-18 11:56 ` Andrew Cooper
2021-06-18 16:35 ` Daniel P. Smith
2021-06-18 12:32 ` Jan Beulich
2021-06-17 23:39 ` [PATCH 5/6] xsm: expanding function related macros in dummy.h Daniel P. Smith
2021-06-18 12:03 ` Andrew Cooper
2021-06-18 12:40 ` Jan Beulich
2021-06-18 12:44 ` Jan Beulich
2021-06-18 16:38 ` Daniel P. Smith
2021-06-18 16:36 ` Daniel P. Smith
2021-06-17 23:39 ` [PATCH 6/6] xsm: removing the XSM_ASSERT_ACTION macro Daniel P. Smith
2021-06-18 10:14 ` [PATCH 0/6] xsm: refactoring xsm hooks Andrew Cooper
2021-06-18 11:48 ` Jan Beulich
2021-06-18 21:21 ` Andrew Cooper
2021-06-21 6:45 ` Jan Beulich
2021-06-18 15:53 ` Daniel P. Smith
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