linux-user/aarch64: Allocate new gcs stack on clone

Allocate the new stack early, so that error reporting need
not clean up other objects.

Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20251008215613.300150-65-richard.henderson@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

linux-user/syscall.c

@@ -6686,6 +6686,21 @@ static int do_fork(CPUArchState *env, unsigned int flags, abi_ulong newsp,
         ts = g_new0(TaskState, 1);
         init_task_state(ts);
 
+#ifdef TARGET_AARCH64
+        /*
+         * If GCS is enabled in the parent thread, it is also enabled
+         * in the child thread, but with a newly allocated stack.
+         */
+        abi_long new_gcspr = 0;
+        if (env->cp15.gcscr_el[0] & GCSCR_PCRSEL) {
+            new_gcspr = gcs_new_stack(ts);
+            if (new_gcspr == -1) {
+                g_free(ts);
+                return -TARGET_ENOMEM;
+            }
+        }
+#endif
+
         /* Grab a mutex so that thread setup appears atomic.  */
         pthread_mutex_lock(&clone_lock);
 
@@ -6707,6 +6722,11 @@ static int do_fork(CPUArchState *env, unsigned int flags, abi_ulong newsp,
         ts->info = parent_ts->info;
         ts->signal_mask = parent_ts->signal_mask;
 
+#ifdef TARGET_AARCH64
+        ts->gcs_el0_locked = parent_ts->gcs_el0_locked;
+        new_env->cp15.gcspr_el[0] = new_gcspr;
+#endif
+
         if (flags & CLONE_CHILD_CLEARTID) {
             ts->child_tidptr = child_tidptr;
         }