Metal Backend: added workaround to prevent 'Infinite Loop' bug when build kernels

docs/changes.txt

@@ -77,6 +77,7 @@
 - Unicode: Update UTF-8 to UTF-16 conversion to match RFC 3629
 - User Options: Added error message when mixing --username and --show to warn users of exponential delay
 - MetaMask: update extraction tool to support MetaMask Mobile wallets
+- Metal Backend: added workaround to prevent 'Infinite Loop' bug when build kernels
 
 * changes v6.2.5 -> v6.2.6
 

src/ext_metal.m

@@ -681,7 +681,8 @@ int hc_mtlCreateCommandQueue (void *hashcat_ctx, mtl_device_id metal_device, mtl
 
 int hc_mtlCreateKernel (void *hashcat_ctx, mtl_device_id metal_device, mtl_library metal_library, const char *func_name, mtl_function *metal_function, mtl_pipeline *metal_pipeline)
 {
-  backend_ctx_t *backend_ctx = ((hashcat_ctx_t *) hashcat_ctx)->backend_ctx;
+  backend_ctx_t  *backend_ctx  = ((hashcat_ctx_t *) hashcat_ctx)->backend_ctx;
+  user_options_t *user_options = ((hashcat_ctx_t *) hashcat_ctx)->user_options;
 
   MTL_PTR *mtl = (MTL_PTR *) backend_ctx->mtl;
 
@@ -708,7 +709,7 @@ int hc_mtlCreateKernel (void *hashcat_ctx, mtl_device_id metal_device, mtl_libra
     return -1;
   }
 
-  NSError *error = nil;
+  __block NSError *error = nil;
 
   NSString *f_name = [NSString stringWithCString: func_name encoding: NSUTF8StringEncoding];
 
@@ -721,6 +722,9 @@ int hc_mtlCreateKernel (void *hashcat_ctx, mtl_device_id metal_device, mtl_libra
     return -1;
   }
 
+  // workaround for MTLCompilerService 'Infinite Loop' bug
+
+  /*
   mtl_pipeline mtl_pipe = [metal_device newComputePipelineStateWithFunction: mtl_func error: &error];
 
   if (error != nil)
@@ -729,6 +733,46 @@ int hc_mtlCreateKernel (void *hashcat_ctx, mtl_device_id metal_device, mtl_libra
 
     return -1;
   }
+  */
+
+  error = nil;
+
+  __block mtl_pipeline mtl_pipe;
+
+  dispatch_group_t group = dispatch_group_create ();
+  dispatch_queue_t queue = dispatch_get_global_queue (DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
+
+  // wait for 60 secs by default or using user-defined runtime if is set
+  long timeout = (user_options->runtime > 0) ? user_options->runtime : 60;
+
+  dispatch_time_t when = dispatch_time (DISPATCH_TIME_NOW,NSEC_PER_SEC * timeout);
+
+  __block int rc_async_err = 0;
+
+  dispatch_group_async (group, queue, ^(void)
+  {
+    mtl_pipe = [metal_device newComputePipelineStateWithFunction: mtl_func error: &error];
+
+    if (error != nil)
+    {
+      event_log_error (hashcat_ctx, "%s(): failed to create '%s' pipeline, %s", __func__, func_name, [[error localizedDescription] UTF8String]);
+
+      rc_async_err = -1;
+    }
+  });
+
+  long rc_queue = dispatch_group_wait (group, when);
+
+  dispatch_release (group);
+
+  if (rc_async_err != 0) return -1;
+
+  if (rc_queue != 0)
+  {
+    event_log_error (hashcat_ctx, "%s(): failed to create '%s' pipeline, timeout reached (status %ld)", __func__, func_name, rc_queue);
+
+    return -1;
+  }
 
   if (mtl_pipe == nil)
   {