int 0x15, ah=0x88 question

int 0x15, ah=0x88 question

[S-n-e-a-k-e-r]

Hi all,

Following code comes from arch/i386/boot/setup.S (memory detection):

387         movb    $0x88, %ah
388         int     $0x15
389         movw    %ax, (2)

Why memory address 2 is used? Where else in the kernel is it used? We are in
real mode, so (2) should be the same as %ds:(2), or not?

Sorry that I'm bugging the mailing list with that question but I didn't
found the answer anywhere. So a web page, a book or something else would be also
nice as an answer.

Regards,

Andy

Ps: please cc me!

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Re: int 0x15, ah=0x88 question

[Dave Jones]

On Mon, May 19, 2003 at 12:22:07PM +0200, S-n-e-a-k-e-r@gmx.net wrote:
 > 
 > 387         movb    $0x88, %ah
 > 388         int     $0x15
 > 389         movw    %ax, (2)
 > 
 > Why memory address 2 is used? Where else in the kernel is it used? We are in
 > real mode, so (2) should be the same as %ds:(2), or not?

This code is building the entries in the zero page for use later.

 > Sorry that I'm bugging the mailing list with that question but I didn't
 > found the answer anywhere. So a web page, a book or something else would be also
 > nice as an answer.

See Documentation/i386/zero-page.txt

		Dave