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Re: ljmp syntax question

From: "H. J. Lu" <hjl at lucon dot org>
To: "Smith, Stephen (SWCOE)" <Stephen dot Smith at honeywell dot com>
Cc: binutils at sources dot redhat dot com
Date: Wed, 21 Mar 2007 13:34:14 -0700
Subject: Re: ljmp syntax question
References: <D54AC102-676C-46C4-A2E6-82FA54BC8B75@monami-software.com> <45D2D66A.8090605@redhat.com> <22E7A5AF-8D62-427A-9CBE-8E1E406FA9B3@monami-software.com> <45D33D6A.70808@redhat.com> <DD1844E2-79FB-4D10-930C-8E9A244CB084@monami-software.com> <45D47C48.1040404@redhat.com> <EF244E26469B2C42B2B72AC465843D6B048130A4@AZ18EV808.global.ds.honeywell.com> <EF244E26469B2C42B2B72AC465843D6B048136FA@AZ18EV808.global.ds.honeywell.com>

On Wed, Mar 21, 2007 at 01:18:09PM -0700, Smith, Stephen (SWCOE) wrote:
> I am writing a BIOS and my code is at $0xF000:$0000 (real mode x86) .
> 
> I set up my GDT and switch into protected mode and now do the following:
> 
>     /* PROT_MODE_CSEG = 0x8, protcseg=0xFFFF0028 */
>     ljmp     $PROT_MODE_CSEG, $protcseg  
>     .code32
> protcseg:
>      movw     $PROT_MODE_DSEG, %ax
> 
> When I reach protcseg, CS=0x8, and eip=0x28 which is off by about
> 0xFFFF0000.   How should I have coded the long jump?

Are you running into this

http://sources.redhat.com/bugzilla/show_bug.cgi?id=3958


H.J.

Follow-Ups:
- RE: ljmp syntax question
  - From: Smith, Stephen \(SWCOE\)

References:
- objcopy doesn't generate srecords for all the memory regions
  - From: Smith, Stephen \(SWCOE\)
- ljmp syntax question
  - From: Smith, Stephen \(SWCOE\)

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