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

[Peter Maydell <peter.maydell@linaro.org>]

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>
---
 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