linux-user/aarch64: Add SM bit to SVE signal context

Make sure to zero the currently reserved fields.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20220708151540.18136-36-richard.henderson@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

linux-user/aarch64/signal.c

@@ -78,7 +78,8 @@ struct target_extra_context {
 struct target_sve_context {
     struct target_aarch64_ctx head;
     uint16_t vl;
-    uint16_t reserved[3];
+    uint16_t flags;
+    uint16_t reserved[2];
     /* The actual SVE data immediately follows.  It is laid out
      * according to TARGET_SVE_SIG_{Z,P}REG_OFFSET, based off of
      * the original struct pointer.
@@ -101,6 +102,8 @@ struct target_sve_context {
 #define TARGET_SVE_SIG_CONTEXT_SIZE(VQ) \
     (TARGET_SVE_SIG_PREG_OFFSET(VQ, 17))
 
+#define TARGET_SVE_SIG_FLAG_SM  1
+
 struct target_rt_sigframe {
     struct target_siginfo info;
     struct target_ucontext uc;
@@ -177,9 +180,13 @@ static void target_setup_sve_record(struct target_sve_context *sve,
 {
     int i, j;
 
+    memset(sve, 0, sizeof(*sve));
     __put_user(TARGET_SVE_MAGIC, &sve->head.magic);
     __put_user(size, &sve->head.size);
     __put_user(vq * TARGET_SVE_VQ_BYTES, &sve->vl);
+    if (FIELD_EX64(env->svcr, SVCR, SM)) {
+        __put_user(TARGET_SVE_SIG_FLAG_SM, &sve->flags);
+    }
 
     /* Note that SVE regs are stored as a byte stream, with each byte element
      * at a subsequent address.  This corresponds to a little-endian store