From: "Russ Cox" <rsc@plan9.bell-labs.com>
To: 9fans@cse.psu.edu
Subject: Re: [9fans] calculating the gdt pointer in 32 bit (protected) mode
Date: Wed, 23 Jan 2002 18:51:09 -0500 [thread overview]
Message-ID: <20020123235113.0F69B19A1C@mail.cse.psu.edu> (raw)
It's pretty much what it says.
$tgdtptr(SB) is a constant evaluated
for us by the loader as though it were
a function.
The byte sequence here:
BYTE $0x0f
BYTE $0x01
BYTE $0x16
WORD $tgdtptr(SB)
assembles to "LGDT $tgdtptr".
It's a word-sized instruction, though.
If you're already in 32-bit mode, you
need to use
BYTE $0x0f
BYTE $0x01
BYTE $0x16
LONG $tgdtptr(SB)
so that the immediate data is the right size.
Russ
next reply other threads:[~2002-01-23 23:51 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-01-23 23:51 Russ Cox [this message]
-- strict thread matches above, loose matches on Subject: below --
2002-01-24 3:32 jmk
2002-01-24 2:23 Russ Cox
2002-01-24 3:14 ` Ronald G Minnich
2002-01-24 1:16 andrey mirtchovski
2002-01-24 0:42 jmk
2002-01-24 0:21 andrey mirtchovski
2002-01-23 23:43 andrey mirtchovski
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