Re: [Qemu-devel] [PATCH] target/i386: Generate #UD when applying LOCK to a register destination

[Philippe Mathieu-Daudé]

On Tue, Nov 13, 2018 at 8:36 PM Richard Henderson
<address@hidden> wrote:
>
> Fixes a TCG crash due to attempting the atomic operation without
> having set up the address first.  This does not attempt to fix
> all of the other missing checks for LOCK.
>
> Fixes: a7cee522f35
> Fixes: https://bugs.launchpad.net/qemu/+bug/1803160
> Signed-off-by: Richard Henderson <address@hidden>

Reviewed-by: Philippe Mathieu-Daudé <address@hidden>
Tested-by: Philippe Mathieu-Daudé <address@hidden>

> ---
>  target/i386/translate.c | 35 ++++++++++++++++++++---------------
>  1 file changed, 20 insertions(+), 15 deletions(-)
>
> diff --git a/target/i386/translate.c b/target/i386/translate.c
> index f8bc7680af..0dd5fbe45c 100644
> --- a/target/i386/translate.c
> +++ b/target/i386/translate.c
> @@ -1268,10 +1268,30 @@ static void gen_helper_fp_arith_STN_ST0(int op, int 
> opreg)
>      }
>  }
>
> +static void gen_exception(DisasContext *s, int trapno, target_ulong cur_eip)
> +{
> +    gen_update_cc_op(s);
> +    gen_jmp_im(s, cur_eip);
> +    gen_helper_raise_exception(cpu_env, tcg_const_i32(trapno));
> +    s->base.is_jmp = DISAS_NORETURN;
> +}
> +
> +/* Generate #UD for the current instruction.  The assumption here is that
> +   the instruction is known, but it isn't allowed in the current cpu mode.  
> */
> +static void gen_illegal_opcode(DisasContext *s)
> +{
> +    gen_exception(s, EXCP06_ILLOP, s->pc_start - s->cs_base);
> +}
> +
>  /* if d == OR_TMP0, it means memory operand (address in A0) */
>  static void gen_op(DisasContext *s1, int op, TCGMemOp ot, int d)
>  {
>      if (d != OR_TMP0) {
> +        if (s1->prefix & PREFIX_LOCK) {
> +            /* Lock prefix when destination is not memory.  */
> +            gen_illegal_opcode(s1);
> +            return;
> +        }
>          gen_op_mov_v_reg(s1, ot, s1->T0, d);
>      } else if (!(s1->prefix & PREFIX_LOCK)) {
>          gen_op_ld_v(s1, ot, s1->T0, s1->A0);
> @@ -2469,21 +2489,6 @@ static void gen_leave(DisasContext *s)
>      gen_op_mov_reg_v(s, a_ot, R_ESP, s->T1);
>  }
>
> -static void gen_exception(DisasContext *s, int trapno, target_ulong cur_eip)
> -{
> -    gen_update_cc_op(s);
> -    gen_jmp_im(s, cur_eip);
> -    gen_helper_raise_exception(cpu_env, tcg_const_i32(trapno));
> -    s->base.is_jmp = DISAS_NORETURN;
> -}
> -
> -/* Generate #UD for the current instruction.  The assumption here is that
> -   the instruction is known, but it isn't allowed in the current cpu mode.  
> */
> -static void gen_illegal_opcode(DisasContext *s)
> -{
> -    gen_exception(s, EXCP06_ILLOP, s->pc_start - s->cs_base);
> -}
> -
>  /* Similarly, except that the assumption here is that we don't decode
>     the instruction at all -- either a missing opcode, an unimplemented
>     feature, or just a bogus instruction stream.  */
> --
> 2.17.2
>