The bounds check needs to be done after the increment, not before, or
else it needs to use a one lower immediate. Also use word operations
rather than byte ones for both the increment and the compare (allowing
E820_BIOS_MAX to be more easily bumped, should the need ever arise).
Signed-off-by: Jan Beulich <jbeul...@suse.com>
--- a/xen/arch/x86/boot/mem.S
+++ b/xen/arch/x86/boot/mem.S
@@ -22,11 +22,10 @@ get_memory_map:
cmpl $SMAP,%eax # check the return is `SMAP'
jne .Lmem88
- movb bootsym(e820nr),%al # up to 128 entries
- cmpb $E820_BIOS_MAX,%al
+ incw bootsym(e820nr)
+ cmpw $E820_BIOS_MAX,bootsym(e820nr) # up to this many entries
jae .Lmem88
- incb bootsym(e820nr)
movw %di,%ax
addw $20,%ax
movw %ax,%di
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