On 08/05/2013 09:14 PM, Mathieu Desnoyers wrote: >> >> For unconditional jmp that should be pretty safe barring any fundamental >> changes to the instruction set, in which case we can enable it as >> needed, but for extra robustness it probably should skip prefix bytes. > > On x86-32, some prefixes are actually meaningful. AFAIK, the 0x66 prefix > is used for: > > E9 cw jmp rel16 relative jump, only in 32-bit > > Other prefixes can probably be safely skipped. >
Yes. Some of them are used as hints or for MPX. > Another question is whether anything prevents the assembler from > generating a jump near (absolute indirect), or far jump. The code above > seems to assume that we have either a short or near relative jump. Absolutely something prevents! It would be a very serious error for the assembler to generate such instructions. -hpa