Re: [Qemu-devel] [PATCH 6/7] target/arm/translate-a64: Don't underdecode FP insns

[Laurent Desnogues <laurent.desnogues@gmail.com>]

On Fri, Jan 25, 2019 at 7:26 PM Peter Maydell <peter.maydell@linaro.org> wrote:
>
> In the encoding groups
>  * floating-point data-processing (1 source)
>  * floating-point data-processing (2 source)
>  * floating-point data-processing (3 source)
>  * floating-point immediate
>  * floating-point compare
>  * floating-ponit conditional compare
>  * floating-point conditional select
>
>
> bit 31 is M and bit 29 is S (and bit 30 is 0, already checked at
> this point in the decode). None of these groups allocate any
> encoding for M=1 or S=1. We checked this in disas_fp_compare(),
> disas_fp_ccomp() and disas_fp_csel(), but missed it in disas_fp_1src(),
> disas_fp_2src(), disas_fp_3src() and disas_fp_imm().
>
> We also missed that in the fp immediate encoding the imm5 field
> must be all zeroes.
>
> Correctly UNDEF the unallocated encodings here.
>
> Reported-by: Laurent Desnogues <laurent.desnogues@gmail.com>
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

Reviewed-by: Laurent Desnogues <laurent.desnogues@gmail.com>

Thanks,

Laurent

> ---
>  target/arm/translate-a64.c | 22 +++++++++++++++++++++-
>  1 file changed, 21 insertions(+), 1 deletion(-)
>
> diff --git a/target/arm/translate-a64.c b/target/arm/translate-a64.c
> index efd2f6490b5..474d9bfb5f0 100644
> --- a/target/arm/translate-a64.c
> +++ b/target/arm/translate-a64.c
> @@ -5636,11 +5636,17 @@ static void handle_fp_fcvt(DisasContext *s, int opcode,
>   */
>  static void disas_fp_1src(DisasContext *s, uint32_t insn)
>  {
> +    int mos = extract32(insn, 29, 3);
>      int type = extract32(insn, 22, 2);
>      int opcode = extract32(insn, 15, 6);
>      int rn = extract32(insn, 5, 5);
>      int rd = extract32(insn, 0, 5);
>
> +    if (mos) {
> +        unallocated_encoding(s);
> +        return;
> +    }
> +
>      switch (opcode) {
>      case 0x4: case 0x5: case 0x7:
>      {
> @@ -5867,13 +5873,14 @@ static void handle_fp_2src_half(DisasContext *s, int opcode,
>   */
>  static void disas_fp_2src(DisasContext *s, uint32_t insn)
>  {
> +    int mos = extract32(insn, 29, 3);
>      int type = extract32(insn, 22, 2);
>      int rd = extract32(insn, 0, 5);
>      int rn = extract32(insn, 5, 5);
>      int rm = extract32(insn, 16, 5);
>      int opcode = extract32(insn, 12, 4);
>
> -    if (opcode > 8) {
> +    if (opcode > 8 || mos) {
>          unallocated_encoding(s);
>          return;
>      }
> @@ -6028,6 +6035,7 @@ static void handle_fp_3src_half(DisasContext *s, bool o0, bool o1,
>   */
>  static void disas_fp_3src(DisasContext *s, uint32_t insn)
>  {
> +    int mos = extract32(insn, 29, 3);
>      int type = extract32(insn, 22, 2);
>      int rd = extract32(insn, 0, 5);
>      int rn = extract32(insn, 5, 5);
> @@ -6036,6 +6044,11 @@ static void disas_fp_3src(DisasContext *s, uint32_t insn)
>      bool o0 = extract32(insn, 15, 1);
>      bool o1 = extract32(insn, 21, 1);
>
> +    if (mos) {
> +        unallocated_encoding(s);
> +        return;
> +    }
> +
>      switch (type) {
>      case 0:
>          if (!fp_access_check(s)) {
> @@ -6105,12 +6118,19 @@ uint64_t vfp_expand_imm(int size, uint8_t imm8)
>  static void disas_fp_imm(DisasContext *s, uint32_t insn)
>  {
>      int rd = extract32(insn, 0, 5);
> +    int imm5 = extract32(insn, 5, 5);
>      int imm8 = extract32(insn, 13, 8);
>      int type = extract32(insn, 22, 2);
> +    int mos = extract32(insn, 29, 3);
>      uint64_t imm;
>      TCGv_i64 tcg_res;
>      TCGMemOp sz;
>
> +    if (mos || imm5) {
> +        unallocated_encoding(s);
> +        return;
> +    }
> +
>      switch (type) {
>      case 0:
>          sz = MO_32;
> --
> 2.20.1
>