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Re: [Xen-devel] [PATCH v3 2/2] xen/vm-events: Move parts of monitor_domctl code to common-side.
- To: Jan Beulich <JBeulich@xxxxxxxx>
- From: Corneliu ZUZU <czuzu@xxxxxxxxxxxxxxx>
- Date: Mon, 15 Feb 2016 18:28:43 +0200
- Cc: Tamas K Lengyel <tamas@xxxxxxxxxxxxx>, Keir Fraser <keir@xxxxxxx>, Ian Campbell <ian.campbell@xxxxxxxxxx>, Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxx, Stefano Stabellini <stefano.stabellini@xxxxxxxxxx>
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- Delivery-date: Mon, 15 Feb 2016 16:28:53 +0000
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On 2/15/2016 4:08 PM, Jan Beulich wrote:
After changing 1 to 1U though, I don't understand why we should also
range-check mop->event.
I'm imagining when (mop->event > 31):
* (1U << mop->event) = 0 or >= (0x1 + 0xFFFFFFFF) (?)
No, it's plain undefined.
Weirdo C, didn't know that!
I've just read http://www.danielvik.com/2010/05/c-language-quirks.html .
That's crazy, I can't believe such 'quirks' exist and that I never knew
of them.
So then, would this do:
/* sanity check - avoid '<<' operator undefined behavior */
if ( unlikely(mop->event > 31) )
return -EINVAL;
if ( unlikely(!(arch_monitor_get_capabilities(d) & (1U << mop->event))) )
return -EOPNOTSUPP;
?
Thanks,
Corneliu.
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