linux-kernel - Re: [PATCH] x86/xen: Delay get_cpu_cap until stack canary is established

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Message-ID: <6d73d847-9f33-7dce-2f60-33481bb4776e@suse.com>
Date:   Tue, 20 Mar 2018 07:28:08 +0100
From:   Juergen Gross <jgross@...e.com>
To:     Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Jason Andryuk <jandryuk@...il.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86/xen: Delay get_cpu_cap until stack canary is
 established

On 19/03/18 23:22, Boris Ostrovsky wrote:
> On 03/19/2018 12:58 PM, Jason Andryuk wrote:
>> Commit 2cc42bac1c79 ("x86-64/Xen: eliminate W+X mappings") introduced a
>> call to get_cpu_cap, which is fstack-protected.  This is works on x86-64
> 
> s/This is works/This works/
> 
> Reviewed-by: Boris Ostrovsky <boris.ostrovsky@...cle.com>
> 
> Do we still need 4f277295e54?

I'd rather keep it in order to avoid nasty problems in case something
changes. After all we are trying to do an initialization in C code
which should be done in assembly before entering the C part. Doing this
properly for 32-bit pv-kernels would be rather difficult, but this is no
reason to drop the correct solution for the 64-bit case.


Juergen