On 08/23/2011 09:22 AM, Borislav Petkov wrote:
> On Tue, Aug 23, 2011 at 12:11:43PM -0400, Andrew Lutomirski wrote:
>> In any case, this seems insanely overcomplicated. I'd be less afraid
>> of something like my approach (which, I think, makes all of the
>> SYSCALL weirdness pretty much transparent to ptrace users) or of just
>> removing SYSCALL entirely from 32-bit code.
>
> I don't think that removing SYSCALL from 32-bit code just so that UML
> trapped syscalls work is something we'd like since SYSCALL is much
> cheaper than INT $0x80:
>
> "As a result, SYSCALL and SYSRET can take fewer than one-fourth the
> number of internal clock cycles to complete than the legacy CALL and RET
> instructions."
>
> http://support.amd.com/us/Processor_TechDocs/24593.pdf, p. 152.
>
> I know, it is 32-bit syscall on 64-bit kernel which should be pretty
> rare but still...
>
Right, but if you had said the difference had disappeared on current AMD
silicon it would be much less of an issue. That's why I wanted to find
that bit out from you.
-hpa
------------------------------------------------------------------------------
Get a FREE DOWNLOAD! and learn more about uberSVN rich system,
user administration capabilities and model configuration. Take
the hassle out of deploying and managing Subversion and the
tools developers use with it. http://p.sf.net/sfu/wandisco-d2d-2
_______________________________________________
User-mode-linux-devel mailing list
User-mode-linux-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel
