From: "Kip Walker" <kwalker@broadcom.com>
To: "Finney, Steve" <Steve.Finney@spirentcom.com>
Cc: "Michael Uhler" <uhler@mips.com>, linux-mips@linux-mips.org
Subject: Re: 64 bit operations w/32 bit kernel
Date: Tue, 30 Sep 2003 07:49:31 -0700 [thread overview]
Message-ID: <3F7997FB.7159F7A@broadcom.com> (raw)
In-Reply-To: 1064862114.11818.21.camel@uhler-linux.mips.com
Michael Uhler wrote:
>
> On Mon, 2003-09-29 at 10:31, Finney, Steve wrote:
> > What would be the downside to enabling 64 bit operations in user space on a 32 bit kernel (setting the PX bit in the status register?). The particular issue is that I want to access 64 bit-memory mapped registers, and I really need to do it as an atomic operation. I tried borrowing sibyte/64bit.h from the kernel, but I get an illegal instruction on the double ops.
> >
> The most glaring problem is you violate the rule that the 64-bit GPRs
> are sign-extended when running a 32-bit binary. There are all kinds
> of assumptions in the hardware and software that depend on the
> GPRs being sign-extended, and to violate this will risk some
> serious instability of the software.
Not to mention that the kernel won't preserve the upper 32 bits across
interrupts and system calls, if you even manage to get 64-bit values in
the registers in the first place.
Kip
next prev parent reply other threads:[~2003-09-30 14:49 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-09-29 17:31 64 bit operations w/32 bit kernel Finney, Steve
2003-09-29 17:31 ` Finney, Steve
2003-09-29 19:01 ` Michael Uhler
2003-09-30 14:49 ` Kip Walker [this message]
2003-09-30 16:00 ` Ralf Baechle
2003-09-30 18:04 ` Maciej W. Rozycki
2003-09-30 18:47 ` Ralf Baechle
2003-10-01 3:58 ` Maciej W. Rozycki
2003-09-30 18:29 ` Michael Uhler
2003-09-30 19:10 ` Maciej W. Rozycki
2003-09-30 19:27 ` Michael Uhler
2003-10-01 4:26 ` Maciej W. Rozycki
2003-10-01 16:24 ` Ralf Baechle
2003-09-30 19:48 ` Ralf Baechle
-- strict thread matches above, loose matches on Subject: below --
2003-09-30 19:23 Finney, Steve
2003-09-30 19:23 ` Finney, Steve
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