Messages in this thread | | | Date | Tue, 24 Feb 2015 14:51:10 -0800 | From | "H. Peter Anvin" <> | Subject | Re: [PATCH 1/4] x86: entry.S: tidy up several suboptimal insns |
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On 02/24/2015 12:36 PM, Borislav Petkov wrote: > On Tue, Feb 24, 2015 at 09:13:03PM +0100, Denys Vlasenko wrote: >> They aren't equal. $1 and $2 in two lowest bits will also >> be interpreted as "userspace" here. "Equal to $3" sends >> a wrong message here to a human reading the code, >> the code doesn't test for CPL=3, it tests for any nonzero CPL. > > Doh, of course. > > I was going to propose to make it even more explicit: > > andb $3, CS(%rsp)... > > but that's destructive. > > So yours makes it less misleading, actually. To me at least and > obviously. >
Yes, please use JZ/JNZ with TEST.
-hpa
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