On Thu, Feb 23, 2017 at 02:28:13PM +0100, Peter Zijlstra wrote:
> + * Since various instruction decoders disagree on the length of UD1,
> + * we cannot use it either. So use UD0 for WARN.
> + *
> + * (binutils knows about "ud1" but {en,de}codes it as 2 bytes, whereas
> + * our kernel decoder thinks it takes a ModRM byte, which seems consistent
> + * with various things like the Intel SDM instruction encoding rules)
> + */
> +
> +#define ASM_UD0 ".byte 0x0f, 0xff"
> +#define ASM_UD1 ".byte 0x0f, 0xb9" /* + ModRM */
> +#define ASM_UD2 ".byte 0x0f, 0x0b"
http://repo.or.cz/nasm.git/blob/HEAD:/x86/insns.dat
has:
1378 UD0 void [ 0f ff]
186,UNDOC
1379 UD1 void [ 0f b9]
186,UNDOC
1380 UD2B void [ 0f b9]
186,UNDOC,ND
1381 UD2 void [ 0f 0b]
186
1382 UD2A void [ 0f 0b]
186,ND
which seems to use the 2 byte version of UD1.
hpa, any input?
