Re: [Qemu-devel] [Qemu-arm] [PATCH 1/7] arm: Don't implement BXJ on M-profile CPUs

[Philippe Mathieu-Daudé]

On 04/10/2017 07:39 AM, Peter Maydell wrote:

For M-profile CPUs, the BXJ instruction does not exist at all, and
the encoding should always UNDEF. We were accidentally implementing
it to behave like A-profile BXJ; correct the error.

Signed-off-by: Peter Maydell <peter.mayd...@linaro.org>

Reviewed-by: Philippe Mathieu-Daudé <f4...@amsat.org>

---
 target/arm/translate.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/target/arm/translate.c b/target/arm/translate.c
index e32e38c..fe3f442 100644
--- a/target/arm/translate.c
+++ b/target/arm/translate.c
@@ -10485,7 +10485,12 @@ static int disas_thumb2_insn(CPUARMState *env, 
DisasContext *s, uint16_t insn_hw
                         }
                         break;
                     case 4: /* bxj */
-                        /* Trivial implementation equivalent to bx.  */
+                        /* Trivial implementation equivalent to bx.
+                         * This instruction doesn't exist at all for M-profile.
+                         */
+                        if (arm_dc_feature(s, ARM_FEATURE_M)) {
+                            goto illegal_op;
+                        }
                         tmp = load_reg(s, rn);
                         gen_bx(s, tmp);
                         break;