[haiku-bugs] Re: [Haiku] #4028: Hybrid GPT/MBR Initial Program Loader
- From: "meianoite" <trac@xxxxxxxxxxxx>
- Date: Thu, 02 Jun 2011 19:20:05 -0000
#4028: Hybrid GPT/MBR Initial Program Loader
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Reporter: meianoite | Owner: axeld
Type: enhancement | Status: new
Priority: normal | Milestone: R1
Component: File Systems | Version: R1/pre-alpha1
Resolution: | Keywords:
Blocked By: | Blocking:
Has a Patch: 1 | Platform: All
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Comment (by meianoite):
Changelog:
LBA pointer buffer is moved from 8 bytes on the MBR itself to a 64-bit
buffer right after the stack. Makes more room for code and is more
robust;[[BR]]
Deals with interrupts before and after relocation;[[BR]]
Work memory (0x600 to 0x7bff) is zero cleaned before relocation;[[BR]]
Deals with probable segment tainting by the BIOS. Nothing is assumed to be
zeroed by default anymore;[[BR]]
Jumps to relocated code and loaded boot code made absolute (far);[[BR]]
Boot drive range check is disabled by default (turned into a compile-time
option). Now assumes the BIOS is reasonable in this regard;[[BR]]
Test for BIOS extended disk read before attempting GPT read;[[BR]]
Reading arbitrary quantities of sectors bloated the code for no real gain.
Now the amount of sectors to load depend on the partitioning scheme;[[BR]]
Restored some code from the FreeBSD loaders used as the basis for this
one. Made the above item possible (slightly modified so GPT boot loader
reading goes up to circa 545KiB now and stops there instead of erroring
out);[[BR]]
In the process, noticed that error check after LBA disk read was removed.
Duh! Restored it;[[BR]]
Changed some sections to make code more compact despite doing more
work;[[BR]]
Comments are now more extensive. Magic numbers explained. Offsets
explained. Exploited side effects are explicitly mentioned.
--
Ticket URL: <http://dev.haiku-os.org/ticket/4028#comment:8>
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