target/arm: Implement M profile floating point

[Qemu-devel] [PATCH 13/26] target/arm: Clean excReturn bits when tail chaining

Posted by Peter Maydell 6 years, 9 months ago

The TailChain() pseudocode specifies that a tail chaining
exception should sanitize the excReturn all-ones bits and
(if there is no FPU) the excReturn FType bits; we weren't
doing this.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 target/arm/helper.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/target/arm/helper.c b/target/arm/helper.c
index 8e72e1097ce..fe8e78fe36d 100644
--- a/target/arm/helper.c
+++ b/target/arm/helper.c
@@ -8081,6 +8081,14 @@ static void v7m_exception_taken(ARMCPU *cpu, uint32_t lr, bool dotailchain,
     qemu_log_mask(CPU_LOG_INT, "...taking pending %s exception %d\n",
                   targets_secure ? "secure" : "nonsecure", exc);
 
+    if (dotailchain) {
+        /* Sanitize LR FType and PREFIX bits */
+        if (!arm_feature(env, ARM_FEATURE_VFP)) {
+            lr |= R_V7M_EXCRET_FTYPE_MASK;
+        }
+        lr = deposit32(lr, 24, 8, 0xff);
+    }
+
     if (arm_feature(env, ARM_FEATURE_V8)) {
         if (arm_feature(env, ARM_FEATURE_M_SECURITY) &&
             (lr & R_V7M_EXCRET_S_MASK)) {
-- 
2.20.1

Re: [Qemu-devel] [PATCH 13/26] target/arm: Clean excReturn bits when tail chaining

Posted by Richard Henderson 6 years, 9 months ago

On 4/16/19 5:57 AM, Peter Maydell wrote:
> The TailChain() pseudocode specifies that a tail chaining
> exception should sanitize the excReturn all-ones bits and
> (if there is no FPU) the excReturn FType bits; we weren't
> doing this.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>  target/arm/helper.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>


r~