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flat assembler > OS Construction > What arguments are provided when leaving MBR and entering

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l4m2



Joined: 15 Jan 2015
Posts: 648
What arguments are provided when leaving MBR and entering PBR?
Post 01 Apr 2019, 12:46
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revolution
When all else fails, read the source


Joined: 24 Aug 2004
Posts: 16792
Location: In your JS exploiting you and your system
The MBR, and any subsequent code that is loaded, can be anything of your choosing, so you can make the arguments anything you wish to. Or did I misunderstand the question?
Post 01 Apr 2019, 13:16
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DimonSoft



Joined: 03 Mar 2010
Posts: 572
Location: Belarus
AFAIR, the PBR code should be loaded to the physical address 7C000 and DL should contain the BIOS drive number for int 13h services, real mode is also expected. Everything else may be different since even BIOS’s themselves don’t give any guarantees except those I’ve just mentioned.
Post 03 Apr 2019, 10:59
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revolution
When all else fails, read the source


Joined: 24 Aug 2004
Posts: 16792
Location: In your JS exploiting you and your system
DimonSoft: Do you mean the MBR (not the PBR)? Since the BIOS will load the MBR and run it. After that everything is up to the user.

Actually I'm not sure what a PBR even is, I just assumed it was some code loaded by a custom MBR.
Post 03 Apr 2019, 11:16
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guignol



Joined: 06 Dec 2008
Posts: 621
Location: I mean good, I know better, only us will do best
Partition Boot Record

(but at first I thought about pokemon too)
Post 03 Apr 2019, 12:52
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DimonSoft



Joined: 03 Mar 2010
Posts: 572
Location: Belarus
revolution wrote:
DimonSoft: Do you mean the MBR (not the PBR)? Since the BIOS will load the MBR and run it. After that everything is up to the user.

Actually I'm not sure what a PBR even is, I just assumed it was some code loaded by a custom MBR.

I consider PBR acronym to mean Partition Boot Record (aka VBR, Volume Boot Record). And, again AFAIR, PBR is usually written with the same expectations as MBR since the whole idea is the same, with the single difference that MBR contains partition table somewhere near the end of the boot sector. It makes sense to reuse the conditions for both instead of inventing something new.

---

More info can be found here, it seems my memory served me quite well: https://wiki.osdev.org/MBR_(x86)
Post 03 Apr 2019, 21:55
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