From: Jan Beulich Date: Wed, 3 Jan 2018 10:03:56 +0000 (+0100) Subject: x86/E820: don't overrun array X-Git-Tag: archive/raspbian/4.11.1-1+rpi1~1^2~66^2~871 X-Git-Url: https://dgit.raspbian.org/?a=commitdiff_plain;h=0036c9dbcd8b52316aeebb475929d3a36cf5e514;p=xen.git x86/E820: don't overrun array 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 Reviewed-by: Andrew Cooper --- diff --git a/xen/arch/x86/boot/mem.S b/xen/arch/x86/boot/mem.S index 4b1fa4dae9..ca90db0a5d 100644 --- 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