Re: [PATCH 5.18 000/231] 5.18.13-rc1 review

Jiri Slaby
2022-07-21T05:31:23Z

On 21. 07. 22, 0:00, Peter Zijlstra wrote:
> On Wed, Jul 20, 2022 at 11:47:02PM +0200, Peter Zijlstra wrote:
>> On Wed, Jul 20, 2022 at 12:57:26PM -0500, Justin Forbes wrote:
>>> On Wed, Jul 20, 2022 at 10:28:33AM -0700, Linus Torvalds wrote:
>>>> [ Adding PeterZ and Jiri to the participants. ]
>>>>
>>>> Looks like 5.18.13 added that commit 9bb2ec608a20 ("objtool: Update
>>>> Retpoline validation") but I don't see 3131ef39fb03 ("x86/asm/32: Fix
>>>> ANNOTATE_UNRET_SAFE use on 32-bit") in that list.
>>>
>>> It should be noted that the build doesn't fail, it just warns.
>>> I am guessing the 32bit failure is what promoted someone to look at
>>> the logs to begin with and notice the warn initially. I just verified
>>> that it exists in our builds of 5.18.13-rc1, but not on mainline builds.
>>> I am gueesing it is because commit 9bb2ec608a20 ("objtool: Update Retpoline
>>> validation") should be followed up with at least commit f43b9876e857c
>>> ("x86/retbleed: Add fine grained Kconfig knobs")
>>
>> Still updateing the stable repro to see what the actual code looks like,
>> but that warning seems to suggest the -mfunction-return=thunk-extern
>> compiler argument went missing.
>>
>> For all the files objtool complains about, does the V=1 build output
>> show that option?
>
> Ok, I'm now looking at stable-rc/linux-5.18.y which reports itself as:
>
> VERSION = 5
> PATCHLEVEL = 18
> SUBLEVEL = 13
> EXTRAVERSION = -rc1
>
> and I'm most terribly confused... it has the objtool patch to validate
> return thunks, *however*, I'm not seeing any actual retbleed mitigations
> *anywhere*.
>
> How, what, why!?

They were all put aside until all this gets resolved. You can find them
in the stable-queue tree:
git://git.kernel.org/pub/scm/linux/kernel/git/stable/stable-queue.git

in retbleed-5.18/.

regards,
--
js
suse labs