Nadav Amit <namit@xxxxxxxxxxxxxxxxx> writes:
> Relative jumps and calls do the masking according to the operand size, and not
> according to the address size as the KVM emulator does today. In 64-bit mode,
> the resulting RIP is always 64-bit. Otherwise it is masked according to the
> instruction operand-size. Note that when 16-bit address size is used, bits
> 63:32 are unmodified.
>
> Signed-off-by: Nadav Amit <namit@xxxxxxxxxxxxxxxxx>
> ---
> arch/x86/kvm/emulate.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
> index 6833b41..e406705 100644
> --- a/arch/x86/kvm/emulate.c
> +++ b/arch/x86/kvm/emulate.c
> @@ -506,7 +506,9 @@ static void rsp_increment(struct x86_emulate_ctxt *ctxt, int inc)
>
> static inline void jmp_rel(struct x86_emulate_ctxt *ctxt, int rel)
> {
> - register_address_increment(ctxt, &ctxt->_eip, rel);
> + /* 64-bit mode relative jumps are always 64-bit; otherwise mask */
> + int op_bytes = ctxt->mode == X86EMUL_MODE_PROT64 ? 8 : ctxt->op_bytes;
Just a nit, probably break this up for readability ?
> + masked_increment(&ctxt->eip, op_bytes, rel);
> }
>
> static u32 desc_limit_scaled(struct desc_struct *desc)
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