Re: kernel loading question

[Willy Tarreau <willy@w.ods.org>]

On Fri, Dec 02, 2005 at 09:34:26PM -0800, Daniel Bonekeeper wrote:
> Well, this probably should not be posted here, but who knows ? =)
> 
> Well, on arch/i386/boot/compressed/head.S line 65 we call
> decompress_kernel that decompresses the kernel starting at $0x100000.
> If we were loaded high, we first move the code back to $0x1000 before
> ljmp'ing it.
> 
> My question is: why, when loaded high, we care to disable interrupts
> (cli  # make sure we don't get interrupted) while otherwise, we don't
> do that ? in both cases, aren't we supposed to disable cli (as they
> can happen in both situations) ?
> 
> Since currently, the kernel boots fine for everybody in the world, I
> know that this is not a bug... but why don't disable interruptions on
> both cases ?

Agreed it's strange. I believe that since very few people load the
kernel in low memory nowadays given its size, it's possible that the
missing CLI never gets noticed, and I suspect that the very first
instructions after the jump are a CLI anyway.

Regards,
Willy