Consider activation frame for stack height metering (#2)

* Charge a base cost for calling a function

* Added regression test for empty functions

* Satisfy clippy

src/stack_limiter/max_height.rs

@@ -5,6 +5,12 @@ use parity_wasm::elements::{self, BlockType, Type};
 #[cfg(feature = "sign_ext")]
 use parity_wasm::elements::SignExtInstruction;
 
+// The cost in stack items that should be charged per call of a function. This is
+// is a static cost that is added to each function call. This makes sense because even
+// if a function does not use any parameters or locals some stack space on the host
+// machine might be consumed to hold some context.
+const ACTIVATION_FRAME_COST: u32 = 2;
+
 /// Control stack frame.
 #[derive(Debug)]
 struct Frame {
@@ -36,7 +42,7 @@ struct Stack {
 
 impl Stack {
 	fn new() -> Stack {
-		Stack { height: 0, control_stack: Vec::new() }
+		Stack { height: ACTIVATION_FRAME_COST, control_stack: Vec::new() }
 	}
 
 	/// Returns current height of the value stack.
@@ -431,7 +437,7 @@ mod tests {
 		);
 
 		let height = compute(0, &module).unwrap();
-		assert_eq!(height, 3);
+		assert_eq!(height, 3 + ACTIVATION_FRAME_COST);
 	}
 
 	#[test]
@@ -448,7 +454,7 @@ mod tests {
 		);
 
 		let height = compute(0, &module).unwrap();
-		assert_eq!(height, 1);
+		assert_eq!(height, 1 + ACTIVATION_FRAME_COST);
 	}
 
 	#[test]
@@ -466,7 +472,7 @@ mod tests {
 		);
 
 		let height = compute(0, &module).unwrap();
-		assert_eq!(height, 0);
+		assert_eq!(height, ACTIVATION_FRAME_COST);
 	}
 
 	#[test]
@@ -501,7 +507,7 @@ mod tests {
 		.expect("Failed to deserialize the module");
 
 		let height = compute(0, &module).unwrap();
-		assert_eq!(height, 2);
+		assert_eq!(height, 2 + ACTIVATION_FRAME_COST);
 	}
 
 	#[test]
@@ -525,7 +531,7 @@ mod tests {
 		);
 
 		let height = compute(0, &module).unwrap();
-		assert_eq!(height, 1);
+		assert_eq!(height, 1 + ACTIVATION_FRAME_COST);
 	}
 
 	#[test]
@@ -547,7 +553,7 @@ mod tests {
 		);
 
 		let height = compute(0, &module).unwrap();
-		assert_eq!(height, 1);
+		assert_eq!(height, 1 + ACTIVATION_FRAME_COST);
 	}
 
 	#[test]
@@ -573,6 +579,6 @@ mod tests {
 		);
 
 		let height = compute(0, &module).unwrap();
-		assert_eq!(height, 3);
+		assert_eq!(height, 3 + ACTIVATION_FRAME_COST);
 	}
 }

tests/diff.rs

@@ -92,6 +92,7 @@ mod stack_height {
 	def_stack_height_test!(global);
 	def_stack_height_test!(imports);
 	def_stack_height_test!(many_locals);
+	def_stack_height_test!(empty_functions);
 }
 
 mod gas {

tests/expectations/stack-height/empty_functions.wat

@@ -0,0 +1,52 @@
+(module
+  (type (;0;) (func))
+  (func (;0;) (type 0)
+    global.get 0
+    i32.const 2
+    i32.add
+    global.set 0
+    global.get 0
+    i32.const 1024
+    i32.gt_u
+    if  ;; label = @1
+      unreachable
+    end
+    call 0
+    global.get 0
+    i32.const 2
+    i32.sub
+    global.set 0)
+  (func (;1;) (type 0)
+    global.get 0
+    i32.const 2
+    i32.add
+    global.set 0
+    global.get 0
+    i32.const 1024
+    i32.gt_u
+    if  ;; label = @1
+      unreachable
+    end
+    call 0
+    global.get 0
+    i32.const 2
+    i32.sub
+    global.set 0)
+  (func (;2;) (type 0)
+    global.get 0
+    i32.const 2
+    i32.add
+    global.set 0
+    global.get 0
+    i32.const 1024
+    i32.gt_u
+    if  ;; label = @1
+      unreachable
+    end
+    call 1
+    global.get 0
+    i32.const 2
+    i32.sub
+    global.set 0)
+  (global (;0;) (mut i32) (i32.const 0))
+  (export "main" (func 2)))

tests/expectations/stack-height/global.wat

@@ -17,7 +17,7 @@
     local.get 1
     local.get 0
     global.get 1
-    i32.const 2
+    i32.const 4
     i32.add
     global.set 1
     global.get 1
@@ -28,7 +28,7 @@
     end
     call 1
     global.get 1
-    i32.const 2
+    i32.const 4
     i32.sub
     global.set 1
     drop)
@@ -36,7 +36,7 @@
     local.get 0
     local.get 1
     global.get 1
-    i32.const 2
+    i32.const 4
     i32.add
     global.set 1
     global.get 1
@@ -47,7 +47,7 @@
     end
     call 1
     global.get 1
-    i32.const 2
+    i32.const 4
     i32.sub
     global.set 1)
   (global (;0;) (mut i32) (i32.const 1))

tests/expectations/stack-height/imports.wat

@@ -13,7 +13,7 @@
     local.get 0
     local.get 1
     global.get 0
-    i32.const 2
+    i32.const 4
     i32.add
     global.set 0
     global.get 0
@@ -24,7 +24,7 @@
     end
     call 2
     global.get 0
-    i32.const 2
+    i32.const 4
     i32.sub
     global.set 0)
   (global (;0;) (mut i32) (i32.const 0))

tests/expectations/stack-height/many_locals.wat

@@ -4,7 +4,7 @@
     (local i64 i64 i32))
   (func (;1;) (type 0)
     global.get 0
-    i32.const 3
+    i32.const 5
     i32.add
     global.set 0
     global.get 0
@@ -15,7 +15,7 @@
     end
     call 0
     global.get 0
-    i32.const 3
+    i32.const 5
     i32.sub
     global.set 0)
   (global (;0;) (mut i32) (i32.const 0)))

tests/expectations/stack-height/simple.wat

@@ -5,7 +5,7 @@
     drop)
   (func (;1;) (type 0)
     global.get 0
-    i32.const 1
+    i32.const 3
     i32.add
     global.set 0
     global.get 0
@@ -16,7 +16,7 @@
     end
     call 0
     global.get 0
-    i32.const 1
+    i32.const 3
     i32.sub
     global.set 0)
   (global (;0;) (mut i32) (i32.const 0))

tests/expectations/stack-height/start.wat

@@ -8,7 +8,7 @@
   (func (;2;) (type 1))
   (func (;3;) (type 1)
     global.get 0
-    i32.const 1
+    i32.const 3
     i32.add
     global.set 0
     global.get 0
@@ -19,10 +19,25 @@
     end
     call 1
     global.get 0
-    i32.const 1
+    i32.const 3
+    i32.sub
+    global.set 0)
+  (func (;4;) (type 1)
+    global.get 0
+    i32.const 2
+    i32.add
+    global.set 0
+    global.get 0
+    i32.const 1024
+    i32.gt_u
+    if  ;; label = @1
+      unreachable
+    end
+    call 2
+    global.get 0
+    i32.const 2
     i32.sub
     global.set 0)
   (global (;0;) (mut i32) (i32.const 0))
-  (export "exported_start" (func 3))
+  (export "call" (func 4))
-  (export "call" (func 2))
   (start 3))

tests/expectations/stack-height/table.wat

@@ -7,7 +7,7 @@
     local.get 0
     i32.const 0
     global.get 0
-    i32.const 2
+    i32.const 4
     i32.add
     global.set 0
     global.get 0
@@ -18,7 +18,7 @@
     end
     call 2
     global.get 0
-    i32.const 2
+    i32.const 4
     i32.sub
     global.set 0
     drop)
@@ -29,7 +29,7 @@
   (func (;3;) (type 1) (param i32)
     local.get 0
     global.get 0
-    i32.const 2
+    i32.const 4
     i32.add
     global.set 0
     global.get 0
@@ -40,14 +40,14 @@
     end
     call 1
     global.get 0
-    i32.const 2
+    i32.const 4
     i32.sub
     global.set 0)
   (func (;4;) (type 2) (param i32 i32) (result i32)
     local.get 0
     local.get 1
     global.get 0
-    i32.const 2
+    i32.const 4
     i32.add
     global.set 0
     global.get 0
@@ -58,7 +58,7 @@
     end
     call 2
     global.get 0
-    i32.const 2
+    i32.const 4
     i32.sub
     global.set 0)
   (table (;0;) 10 funcref)

tests/fixtures/stack-height/empty_functions.wat

@@ -0,0 +1,8 @@
+(module
+  (func (;0;)
+    call 0
+  )
+  (func (;1;) (export "main")
+    call 0
+  )
+)

tests/fixtures/stack-height/global.wat

@@ -6,8 +6,8 @@
 
   (func $i32.add (export "i32.add") (param i32 i32) (result i32)
     get_local 0
-	get_local 1
+	  get_local 1
-	i32.add
+	  i32.add
   )
   (func (param $arg i32)
      (local $tmp i32)
@@ -15,7 +15,7 @@
      global.get 0
      i32.const 1
      i32.add
-	 tee_local $tmp
+	   tee_local $tmp
      global.set $counter
 
      get_local $tmp

tests/fixtures/stack-height/start.wat

@@ -3,7 +3,7 @@
 	(import "env" "memory" (memory 1 1))
 
 	(start $start)
-	(func $start (export "exported_start")
+	(func $start
 		(local i32)
 	)
 	(func (export "call")

tests/fixtures/stack-height/table.wat

@@ -1,15 +1,15 @@
 (module
   (import "env" "foo" (func $foo))
   (func (param i32)
-     get_local 0
+    get_local 0
-     i32.const 0
+    i32.const 0
-     call $i32.add
+    call $i32.add
-     drop
+    drop
   )
   (func $i32.add (export "i32.add") (param i32 i32) (result i32)
     get_local 0
-	get_local 1
+	  get_local 1
-	i32.add
+	  i32.add
   )
   (table 10 anyfunc)