Remove scratch buffer from ext_call

frame/contracts/fixtures/caller_contract.wat

@@ -2,7 +2,7 @@
 	(import "env" "ext_scratch_size" (func $ext_scratch_size (result i32)))
 	(import "env" "ext_scratch_read" (func $ext_scratch_read (param i32 i32 i32)))
 	(import "env" "ext_balance" (func $ext_balance (param i32 i32)))
-	(import "env" "ext_call" (func $ext_call (param i32 i32 i64 i32 i32 i32 i32) (result i32)))
+	(import "env" "ext_call" (func $ext_call (param i32 i32 i64 i32 i32 i32 i32 i32 i32) (result i32)))
 	(import "env" "ext_instantiate" (func $ext_instantiate (param i32 i32 i64 i32 i32 i32 i32) (result i32)))
 	(import "env" "ext_println" (func $ext_println (param i32 i32)))
 	(import "env" "memory" (memory 1 1))
@@ -17,12 +17,16 @@
 	)
 
 	(func $current_balance (param $sp i32) (result i64)
+		(i32.store
+			(i32.sub (get_local $sp) (i32.const 16))
+			(i32.const 8)
+		)
 		(call $ext_balance
 			(i32.sub (get_local $sp) (i32.const 8))
-			(i32.const 2048)
+			(i32.sub (get_local $sp) (i32.const 16))
 		)
 		(call $assert
-			(i32.eq (i32.load (i32.const 2048)) (i32.const 8))
+			(i32.eq (i32.load (i32.sub (get_local $sp) (i32.const 16))) (i32.const 8))
 		)
 		(i64.load (i32.sub (get_local $sp) (i32.const 8)))
 	)
@@ -149,6 +153,18 @@
 			(i64.eq (get_local $balance) (call $current_balance (get_local $sp)))
 		)
 
+		;; Zero out destination buffer of output
+		(i32.store
+			(i32.sub (get_local $sp) (i32.const 4))
+			(i32.const 0)
+		)
+
+		;; Length of the output buffer
+		(i32.store
+			(i32.sub (get_local $sp) (i32.const 8))
+			(i32.const 4)
+		)
+
 		;; Call the new contract and expect it to return failing exit code.
 		(set_local $exit_code
 			(call $ext_call
@@ -159,6 +175,8 @@
 				(i32.const 8)	;; Length of the buffer with value to transfer.
 				(i32.const 9)	;; Pointer to input data buffer address
 				(i32.const 7)	;; Length of input data buffer
+				(i32.sub (get_local $sp) (i32.const 4)) ;; Ptr to output buffer
+				(i32.sub (get_local $sp) (i32.const 8)) ;; Ptr to output buffer len
 			)
 		)
 
@@ -169,16 +187,7 @@
 
 		;; Check that scratch buffer contains the expected return data.
 		(call $assert
-			(i32.eq (call $ext_scratch_size) (i32.const 3))
-		)
-		(i32.store
-			(i32.sub (get_local $sp) (i32.const 4))
-			(i32.const 0)
-		)
-		(call $ext_scratch_read
-			(i32.sub (get_local $sp) (i32.const 4))
-			(i32.const 0)
-			(i32.const 3)
+			(i32.eq (i32.load (i32.sub (get_local $sp) (i32.const 8))) (i32.const 3))
 		)
 		(call $assert
 			(i32.eq
@@ -202,6 +211,8 @@
 				(i32.const 8)	;; Length of the buffer with value to transfer.
 				(i32.const 8)	;; Pointer to input data buffer address
 				(i32.const 8)	;; Length of input data buffer
+				(i32.const 4294967295) ;; u32 max sentinel value: do not copy output
+				(i32.const 0) ;; Length is ignored in this cas
 			)
 		)
 
@@ -210,16 +221,23 @@
 			(i32.eq (get_local $exit_code) (i32.const 0x0100))
 		)
 
-		;; Check that scratch buffer is empty since call trapped.
-		(call $assert
-			(i32.eq (call $ext_scratch_size) (i32.const 0))
-		)
-
 		;; Check that balance has not changed.
 		(call $assert
 			(i64.eq (get_local $balance) (call $current_balance (get_local $sp)))
 		)
 
+		;; Zero out destination buffer of output
+		(i32.store
+			(i32.sub (get_local $sp) (i32.const 4))
+			(i32.const 0)
+		)
+
+		;; Length of the output buffer
+		(i32.store
+			(i32.sub (get_local $sp) (i32.const 8))
+			(i32.const 4)
+		)
+
 		;; Call the contract successfully.
 		(set_local $exit_code
 			(call $ext_call
@@ -230,6 +248,8 @@
 				(i32.const 8)	;; Length of the buffer with value to transfer.
 				(i32.const 8)	;; Pointer to input data buffer address
 				(i32.const 8)	;; Length of input data buffer
+				(i32.sub (get_local $sp) (i32.const 4)) ;; Ptr to output buffer
+				(i32.sub (get_local $sp) (i32.const 8)) ;; Ptr to output buffer len
 			)
 		)
 
@@ -240,16 +260,7 @@
 
 		;; Check that scratch buffer contains the expected return data.
 		(call $assert
-			(i32.eq (call $ext_scratch_size) (i32.const 4))
-		)
-		(i32.store
-			(i32.sub (get_local $sp) (i32.const 4))
-			(i32.const 0)
-		)
-		(call $ext_scratch_read
-			(i32.sub (get_local $sp) (i32.const 4))
-			(i32.const 0)
-			(i32.const 4)
+			(i32.eq (i32.load (i32.sub (get_local $sp) (i32.const 8))) (i32.const 4))
 		)
 		(call $assert
 			(i32.eq
@@ -270,6 +281,4 @@
 	(data (i32.const 0) "\00\80")		;; The value to transfer on instantiation and calls.
 										;; Chosen to be greater than existential deposit.
 	(data (i32.const 8) "\00\11\22\33\44\55\66\77")		;; The input data to instantiations and calls.
-
-	(data (i32.const 2048) "\08") ;; size of our $ext_balance output buffer
 )

frame/contracts/fixtures/destroy_and_transfer.wat

@@ -3,7 +3,7 @@
 	(import "env" "ext_scratch_read" (func $ext_scratch_read (param i32 i32 i32)))
 	(import "env" "ext_get_storage" (func $ext_get_storage (param i32 i32 i32) (result i32)))
 	(import "env" "ext_set_storage" (func $ext_set_storage (param i32 i32 i32)))
-	(import "env" "ext_call" (func $ext_call (param i32 i32 i64 i32 i32 i32 i32) (result i32)))
+	(import "env" "ext_call" (func $ext_call (param i32 i32 i64 i32 i32 i32 i32 i32 i32) (result i32)))
 	(import "env" "ext_instantiate" (func $ext_instantiate (param i32 i32 i64 i32 i32 i32 i32) (result i32)))
 	(import "env" "memory" (memory 1 1))
 
@@ -113,6 +113,9 @@
 					(i32.const 8)	;; Length of the buffer with value to transfer
 					(i32.const 0)	;; Pointer to input data buffer address
 					(i32.const 1)	;; Length of input data buffer
+					(i32.const 4294967295) ;; u32 max sentinel value: do not copy output
+					(i32.const 0) ;; Length is ignored in this case
+
 				)
 				(i32.const 0x0100)
 			)
@@ -129,6 +132,8 @@
 					(i32.const 8)	;; Length of the buffer with value to transfer
 					(i32.const 0)	;; Pointer to input data buffer address
 					(i32.const 0)	;; Length of input data buffer
+					(i32.const 4294967295) ;; u32 max sentinel value: do not copy output
+					(i32.const 0) ;; Length is ignored in this case
 				)
 				(i32.const 0)
 			)
@@ -147,6 +152,8 @@
 					(i32.const 8)	;; Length of the buffer with value to transfer
 					(i32.const 0)	;; Pointer to input data buffer address
 					(i32.const 1)	;; Length of input data buffer
+					(i32.const 4294967295) ;; u32 max sentinel value: do not copy output
+					(i32.const 0) ;; Length is ignored in this case
 				)
 				(i32.const 0)
 			)

frame/contracts/fixtures/drain.wat

@@ -1,8 +1,6 @@
 (module
-	(import "env" "ext_scratch_size" (func $ext_scratch_size (result i32)))
-	(import "env" "ext_scratch_read" (func $ext_scratch_read (param i32 i32 i32)))
 	(import "env" "ext_balance" (func $ext_balance (param i32 i32)))
-	(import "env" "ext_call" (func $ext_call (param i32 i32 i64 i32 i32 i32 i32) (result i32)))
+	(import "env" "ext_call" (func $ext_call (param i32 i32 i64 i32 i32 i32 i32 i32 i32) (result i32)))
 	(import "env" "memory" (memory 1 1))
 
 	;; [0, 8) reserved for $ext_balance output
@@ -46,6 +44,8 @@
 					(i32.const 8)	;; Length of the buffer with value to transfer
 					(i32.const 0)	;; Pointer to input data buffer address
 					(i32.const 0)	;; Length of input data buffer
+					(i32.const 4294967295) ;; u32 max sentinel value: do not copy output
+					(i32.const 0) ;; Length is ignored in this case
 				)
 				(i32.const 0)
 			)

frame/contracts/fixtures/self_destruct.wat

@@ -1,8 +1,7 @@
 (module
 	(import "env" "ext_scratch_size" (func $ext_scratch_size (result i32)))
-	(import "env" "ext_scratch_read" (func $ext_scratch_read (param i32 i32 i32)))
 	(import "env" "ext_address" (func $ext_address (param i32 i32)))
-	(import "env" "ext_call" (func $ext_call (param i32 i32 i64 i32 i32 i32 i32) (result i32)))
+	(import "env" "ext_call" (func $ext_call (param i32 i32 i64 i32 i32 i32 i32 i32 i32) (result i32)))
 	(import "env" "ext_terminate" (func $ext_terminate (param i32 i32)))
 	(import "env" "memory" (memory 1 1))
 
@@ -55,6 +54,8 @@
 							(i32.const 8)	;; Length of the buffer with value to transfer
 							(i32.const 0)	;; Pointer to input data buffer address
 							(i32.const 0)	;; Length of input data buffer
+							(i32.const 4294967295) ;; u32 max sentinel value: do not copy output
+							(i32.const 0) ;; Length is ignored in this case
 						)
 						(i32.const 0)
 					)

frame/contracts/fixtures/self_destructing_constructor.wat

@@ -1,8 +1,6 @@
 (module
-	(import "env" "ext_scratch_size" (func $ext_scratch_size (result i32)))
-	(import "env" "ext_scratch_read" (func $ext_scratch_read (param i32 i32 i32)))
 	(import "env" "ext_balance" (func $ext_balance (param i32 i32)))
-	(import "env" "ext_call" (func $ext_call (param i32 i32 i64 i32 i32 i32 i32) (result i32)))
+	(import "env" "ext_call" (func $ext_call (param i32 i32 i64 i32 i32 i32 i32 i32 i32) (result i32)))
 	(import "env" "memory" (memory 1 1))
 
 	;; [0, 8) reserved for $ext_balance output
@@ -44,6 +42,8 @@
 					(i32.const 8)	;; Length of the buffer with value to transfer
 					(i32.const 0)	;; Pointer to input data buffer address
 					(i32.const 0)	;; Length of input data buffer
+					(i32.const 4294967295) ;; u32 max sentinel value: do not copy output
+					(i32.const 0) ;; Length is ignored in this case
 				)
 				(i32.const 0)
 			)

frame/contracts/src/wasm/mod.rs

@@ -565,9 +565,11 @@ mod tests {
 	;;    value_ptr: u32,
 	;;    value_len: u32,
 	;;    input_data_ptr: u32,
-	;;    input_data_len: u32
+	;;    input_data_len: u32,
+	;;    result_ptr: u32,
+	;;	  result_len_ptr: u32
 	;;) -> u32
-	(import "env" "ext_call" (func $ext_call (param i32 i32 i64 i32 i32 i32 i32) (result i32)))
+	(import "env" "ext_call" (func $ext_call (param i32 i32 i64 i32 i32 i32 i32 i32 i32) (result i32)))
 	(import "env" "memory" (memory 1 1))
 	(func (export "call")
 		(drop
@@ -579,6 +581,8 @@ mod tests {
 				(i32.const 8)  ;; Length of the buffer with value to transfer.
 				(i32.const 20) ;; Pointer to input data buffer address
 				(i32.const 4)  ;; Length of input data buffer
+				(i32.const 4294967295) ;; u32 max value is the sentinel value: do not copy output
+				(i32.const 0) ;; Length is ignored in this case
 			)
 		)
 	)
@@ -611,7 +615,7 @@ mod tests {
 				to: 9,
 				value: 6,
 				data: vec![1, 2, 3, 4],
-				gas_left: 9985500000,
+				gas_left: 9984500000,
 			}]
 		);
 	}
@@ -728,9 +732,11 @@ mod tests {
 	;;    value_ptr: u32,
 	;;    value_len: u32,
 	;;    input_data_ptr: u32,
-	;;    input_data_len: u32
+	;;    input_data_len: u32,
+	;;    result_ptr: u32,
+	;;	  result_len_ptr: u32
 	;;) -> u32
-	(import "env" "ext_call" (func $ext_call (param i32 i32 i64 i32 i32 i32 i32) (result i32)))
+	(import "env" "ext_call" (func $ext_call (param i32 i32 i64 i32 i32 i32 i32 i32 i32) (result i32)))
 	(import "env" "memory" (memory 1 1))
 	(func (export "call")
 		(drop
@@ -742,6 +748,8 @@ mod tests {
 				(i32.const 8)   ;; Length of the buffer with value to transfer.
 				(i32.const 20)   ;; Pointer to input data buffer address
 				(i32.const 4)   ;; Length of input data buffer
+				(i32.const 4294967295) ;; u32 max value is the sentinel value: do not copy output
+				(i32.const 0) ;; Length is ignored in this cas
 			)
 		)
 	)

frame/contracts/src/wasm/runtime.rs

@@ -525,16 +525,14 @@ define_env!(Env, <E: Ext>,
 		value_ptr: u32,
 		value_len: u32,
 		input_data_ptr: u32,
-		input_data_len: u32
+		input_data_len: u32,
+		result_ptr: u32,
+		result_len_ptr: u32
 	) -> u32 => {
 		let callee: <<E as Ext>::T as frame_system::Trait>::AccountId =
 			read_sandbox_memory_as(ctx, callee_ptr, callee_len)?;
-		let value: BalanceOf<<E as Ext>::T> =
-			read_sandbox_memory_as(ctx, value_ptr, value_len)?;
-
-		// Read input data into the scratch buffer, then take ownership of it.
-		read_sandbox_memory_into_scratch(ctx, input_data_ptr, input_data_len)?;
-		let input_data = mem::replace(&mut ctx.scratch_buf, Vec::new());
+		let value: BalanceOf<<E as Ext>::T> = read_sandbox_memory_as(ctx, value_ptr, value_len)?;
+		let input_data = read_sandbox_memory(ctx, input_data_ptr, input_data_len)?;
 
 		let nested_gas_limit = if gas == 0 {
 			ctx.gas_meter.gas_left()
@@ -560,12 +558,10 @@ define_env!(Env, <E: Ext>,
 
 		match call_outcome {
 			Ok(output) => {
-				ctx.scratch_buf = output.data;
+				write_sandbox_output(ctx, result_ptr, result_len_ptr, &output.data)?;
 				Ok(output.status.into())
 			},
-			Err(buffer) => {
-				ctx.scratch_buf = buffer;
-				ctx.scratch_buf.clear();
+			Err(_) => {
 				Ok(TRAP_RETURN_CODE)
 			},
 		}