linux-kernel - Re: X32 psABI status

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Message-ID: <20110213233926.1b3ca15a@lxorguk.ukuu.org.uk>
Date:	Sun, 13 Feb 2011 23:39:26 +0000
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Arnd Bergmann <arnd@...db.de>, x32-abi@...glegroups.com,
	"H.J. Lu" <hjl.tools@...il.com>, GCC Development <gcc@....gnu.org>,
	GNU C Library <libc-alpha@...rceware.org>,
	LKML <linux-kernel@...r.kernel.org>,
	"H. Peter Anvin" <hpa@...ux.intel.com>
Subject: Re: X32 psABI status

> a. the int $0x80 instruction is much slower than syscall.  An actual
>    i386 process can use the syscall instruction which is disambiguated
>    by the CPU based on mode, but an x32 process is in the same CPU mode
>    as a normal 64-bit process.

So set a flag, whoopee

> b. 64-bit arguments have to be split between two registers for the
>    i386 entry points, requiring user-space stubs.

Diddums. Given you've yet to explain why everyone desperately needs this
extra interface why do we care ?

> All in all, the cost of an extra system call table is quite modest.

And the cost of not doing it is a gloriously wonderful zero. Yo've still
not explained the justification or what large number of apps are going to
use it.

It's a simple question - why do we care, why do we want the overhead and
the hassle, what do users get in return ?

Alan
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