81 lines
1.7 KiB
Diff
81 lines
1.7 KiB
Diff
From 664484dc8aa91fff6c8906ede14ce492b7904129 Mon Sep 17 00:00:00 2001
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From: Glauber Costa <glommer@redhat.com>
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Date: Wed, 24 Jun 2009 14:31:41 +0100
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Subject: [PATCH 13/18] compute checksum for roms bigger than a segment
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Some option roms (e1000 provided by gpxe project as an example)
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are bigger than a segment. The current algorithm to compute the
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checksum fails in such case. To proper compute the checksum, this
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patch deals with the possibility of the rom's size crossing a
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segment border.
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We don't need to worry about it crossing more than one segment
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border, since the option roms format only save one byte to store
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the image size (thus, maximum size = 0xff = 128k = 2 segments)
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[ including improvements suggested by malc ]
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Signed-off-by: Glauber Costa <glommer@redhat.com>
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Signed-off-by: Mark McLoughlin <markmc@redhat.com>
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---
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kvm/bios/rombios.c | 33 +++++++++++++++++++++++++++------
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1 files changed, 27 insertions(+), 6 deletions(-)
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diff --git a/kvm/bios/rombios.c b/kvm/bios/rombios.c
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index c4f6ccd..c4bfe60 100644
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--- a/kvm/bios/rombios.c
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+++ b/kvm/bios/rombios.c
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@@ -10196,22 +10196,43 @@ no_serial:
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ret
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rom_checksum:
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- push ax
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- push bx
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- push cx
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+ pusha
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+ push ds
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+
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xor ax, ax
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xor bx, bx
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xor cx, cx
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+ xor dx, dx
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+
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mov ch, [2]
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shl cx, #1
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+
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+ jnc checksum_loop
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+ xchg dx, cx
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+ dec cx
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+
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checksum_loop:
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add al, [bx]
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inc bx
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loop checksum_loop
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+
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+ test dx, dx
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+ je checksum_out
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+
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+ add al, [bx]
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+ mov cx, dx
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+ mov dx, ds
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+ add dh, #0x10
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+ mov ds, dx
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+ xor dx, dx
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+ xor bx, bx
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+
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+ jmp checksum_loop
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+
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+checksum_out:
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and al, #0xff
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- pop cx
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- pop bx
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- pop ax
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+ pop ds
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+ popa
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ret
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--
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1.6.2.2
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