From: "Petr Vandrovec" <VANDROVE@vc.cvut.cz>
To: Andi Kleen <ak@suse.de>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>,
linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: 32-bit syscalls from 64-bit process on x86-64?
Date: Tue, 14 Dec 2004 23:01:12 +0100 [thread overview]
Message-ID: <380350F3EC1@vcnet.vc.cvut.cz> (raw)
On 14 Dec 04 at 8:45, Andi Kleen wrote:
> > #define TOLM \
> > "pushl %%cs\n" \
> > "pushl $91f\n" \
> > "ljmpl $0x33,$90f\n" \
>
> It's useless, there is nothing in the kernel code that checks the
> 32bit segment.
??? Processor checks for 32bit/64bit segment. It is impossible to load
upper 32bit of all registers with non-zero value or call 64bit
syscall entry point from 32bit mode. As x86-64 kernel offers 64bit
interface through syscall only, only way how to issue 64bit system call
is using syscall instruction in 64bit code.
Or are you trying to say that these samples do not work and you cannot
call 64bit entry point from 32bit app, or vice versa? Then I'm afraid
that you are not completely right, as these samples do work...
Petr Vandrovec
next reply other threads:[~2004-12-14 21:57 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-12-14 22:01 Petr Vandrovec [this message]
2004-12-15 4:27 ` 32-bit syscalls from 64-bit process on x86-64? Andi Kleen
2004-12-15 10:50 ` Jeremy Fitzhardinge
2004-12-15 10:55 ` Andi Kleen
2004-12-15 20:58 ` Jeremy Fitzhardinge
2004-12-16 4:35 ` Andi Kleen
-- strict thread matches above, loose matches on Subject: below --
2004-12-02 16:22 Jeremy Fitzhardinge
2004-12-02 18:52 ` Jeremy Fitzhardinge
2004-12-03 6:15 ` Andi Kleen
2004-12-03 23:16 ` Jeremy Fitzhardinge
2004-12-04 14:40 ` Petr Vandrovec
2004-12-04 21:33 ` Jeremy Fitzhardinge
2004-12-08 2:30 ` Jeremy Fitzhardinge
2004-12-14 7:45 ` Andi Kleen
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