bzImage loading directly from floppy

From: Pavel Machek (pavel@suse.cz)
Date: Fri May 25 2001 - 15:25:43 EST

Hi!

...is broken. If imagesize is 0xf123, bootsect_second only returns
0xf000 in ax, which is < 0xf123, so it continues loading. Then,
bootsect_second returns 0x10000, but it is 16 bit register, so it is
0x0000, and that's also < 0xf123. So it is looping forever.

It can be fixed like this: (Another possible workaround is to set max
size in tools/misc.c to 0xefff instead of 0xffff. OTOH it would be
nice to be able to boot images up to 2.88MB directly from floppy).
                                                                Pavel
(Okay to commit into x86-64 tree?)

--- linux/arch/i386/boot/setup.S Tue May 8 12:11:01 2001
+++ linux/arch/x86_64/boot/setup.S Fri May 25 22:18:57 2001
@@ -771,6 +774,8 @@
         incb %cs:bootsect_dst_base+2 # to 0x10000
 bootsect_ex:
         movb %cs:bootsect_dst_base+2, %ah
+ cmpb $0x20, %ah
+ je realbig
         shlb $4, %ah # we now have the number of
                                                 # moved frames in %ax
         xorb %al, %al
@@ -779,6 +784,13 @@
         popw %cx
         lret
 
+realbig:
+ movw $0xffff,%ax
+ popw %bx
+ popw %si
+ popw %cx
+ lret
+
 bootsect_gdt:
         .word 0, 0, 0, 0
         .word 0, 0, 0, 0 

-- 
I'm pavel@ucw.cz. "In my country we have almost anarchy and I don't care."
Panos Katsaloulis describing me w.r.t. patents at discuss@linmodems.org
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This archive was generated by hypermail 2b29 : Thu May 31 2001 - 21:00:28 EST