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Date: Fri, 20 Jan 2012 14:41:51 -0800
From: "H. Peter Anvin" <hpa@zytor.com>
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To: Roland McGrath <mcgrathr@google.com>
CC: Denys Vlasenko <vda.linux@googlemail.com>,
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Subject: Re: Compat 32-bit syscall entry from 64-bit task!?
References: <20120116183730.GB21112@redhat.com> <20120118020453.GL7180@jl-vm1.vm.bytemark.co.uk> <20120118022217.GS11715@one.firstfloor.org> <fc8f165e541482d136ff8fc115fe6875.squirrel@webmail.greenhost.nl> <CA+55aFysH3h8sLHwNcaLnYMsgA28vmHgd3DSLPVw-=TzgfBrbg@mail.gmail.com> <CA+55aFzk6OOHoQ_e3pPQNUGN80tjXT7vYTNaRjXbWiQUnNRiTA@mail.gmail.com> <fd4ccb42a25876131e411299d24d9151.squirrel@webmail.greenhost.nl> <CA+55aFzcSVmdDj9Lh_gdbz1OzHyEm6ZrGPBDAJnywm2LF_eVyg@mail.gmail.com> <CA+55aFwMd8MMrcfG5f0zg=qjrBzUhgY1HgJx6QFcnpMQsW1PNg@mail.gmail.com> <4F1731C1.4050007@zytor.com> <4F1733DF.7040905@zytor.com> <4F1737C9.3070905@zytor.com> <CAB=4xhqW8RK2UpU5PPjSQo3nZYt8oZkaBf1VEhX37tbMVrAigg@mail.gmail.com> <4F173F48.2070604@zytor.com> <CA+55aFw3kv_JRsSCQEf6fQd0gX939MuoevDxFtcXkPY+bmyjtA@mail.gmail.com> <4F176605.5020101@zytor.com> <CAK1hOcManWsEvjS2xxtfGTKx=JLPvO2sBkWU-xQP+medV=rbAA@mail.gmail.com> <CAB=4xhqFYdU3s_NQkgdzVVG1r3vGDb=qPewPRFTrJ1B_eiEVDA@mail.gmail.com>
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On 01/20/2012 02:40 PM, Roland McGrath wrote:
> If you change the size of a regset, then the new full size will be the size
> of the core file notes.  Existing userland tools will not be expecting
> this, they expect a known exact size.  If you need to add new stuff, it
> really is easier all around to add a new regset flavor.  When adding a new
> one, you can make it variable-sized from the start so as to be extensible
> in the future.  We did this for NT_X86_XSTATE, for example.
>

Yes, that definitely seems cleaner.

	-hpa