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Blame qemu-bios-bigger-roms.patch

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From 8b08062b369c913c9b9a66c20618f9bd82a6b676 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] 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 6186199..fc289c0 100644
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--- a/kvm/bios/rombios.c
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+++ b/kvm/bios/rombios.c
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@@ -10170,22 +10170,43 @@ 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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1.6.2.5
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