From: Aleph One <amerei@gmail.com>
To: Ricardo Nabinger Sanchez <rnsanchez@terra.com.br>
Cc: linux-assembly@vger.kernel.org
Subject: Re: grub thing
Date: Thu, 2 Mar 2006 06:49:55 +0000 [thread overview]
Message-ID: <20060302064955.7de89dd0.amerei@gmail.com> (raw)
In-Reply-To: <20060301103411.10ac083e.rnsanchez@terra.com.br>
On Wed, 1 Mar 2006 10:34:11 -0300
Ricardo Nabinger Sanchez <rnsanchez@terra.com.br> wrote:
~Quoting Aleph One <amerei@gmail.com>
~Sent on Wed, 1 Mar 2006 07:10:33 +0000
~
~> i'm looking at a disassembly of grub's stage 1. and i wanna know why it
~> need's to CLI before setting up the environment?? i tried to interpret it
~> line by line and this is what i have so far
~
~I'm not an expert, but interruptions must be disabled. I believe grub
~doesn't install interrupt handlers, and thus a single interrupt would lock
~the machine (as the appropriate handler would likely point to garbage).
~
~would the BIOS (or similar in other architectures) give the processor to
~the bootloader with interrupts disabled already?
~
~> also, since the origin is at 0000:7c00h i figured that must imply that
~> "mov sp, 0x2000" means that the stack starts at 0x7c00+0x2000 = 9c000
~> right?
~
~I guess not. to get what you described, I would do:
~
~ mov sp, 0x2000
~ add sp, 0x7c00
~
~from your disassembly, I'd expect SP to be 0x2000, counting from 0x0000.
groovy! thanks for clarifying this to me. i kinda got messed up thinking about relating the stack with the 7c000 start address :(
~--
~Ricardo Nabinger Sanchez
~GNU/Linux #140696 [http://counter.li.org]
~Slackware Linux + FreeBSD
~
~ Left to themselves, things tend to go from bad to worse.
~-
~To unsubscribe from this list: send the line "unsubscribe linux-assembly" in
~the body of a message to majordomo@vger.kernel.org
~More majordomo info at http://vger.kernel.org/majordomo-info.html
next prev parent reply other threads:[~2006-03-02 6:49 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-02-22 21:26 nasm -f bin / Elf format Thiago Silva
2006-02-23 0:32 ` Brian Raiter
2006-03-01 7:10 ` grub thing Aleph One
2006-03-01 13:34 ` Ricardo Nabinger Sanchez
2006-03-02 6:49 ` Aleph One [this message]
2006-03-01 14:42 ` Marcin Kościelnicki
2006-03-01 18:08 ` Ricardo Nabinger Sanchez
2006-03-02 6:46 ` Aleph One
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