Merge pull request #2704 from OffchainLabs/gligneul/fix-stylus-captur…

…e-hostio

[NIT-2814] Fix CaptureHostIO when slices are bigger than 2^16

arbitrator/arbutil/src/evm/req.rs

@@ -298,9 +298,10 @@ impl<D: DataReader, H: RequestHandler<D>> EvmApi<D> for EvmApiRequestor<D, H> {
  let mut request = Vec::with_capacity(2 * 8 + 3 * 2 + name.len() + args.len() + outs.len());
  request.extend(start_ink.to_be_bytes());
  request.extend(end_ink.to_be_bytes());
- request.extend((name.len() as u16).to_be_bytes());
- request.extend((args.len() as u16).to_be_bytes());
- request.extend((outs.len() as u16).to_be_bytes());
+ // u32 is enough to represent the slices lengths because the WASM environment runs in 32 bits.
+ request.extend((name.len() as u32).to_be_bytes());
+ request.extend((args.len() as u32).to_be_bytes());
+ request.extend((outs.len() as u32).to_be_bytes());
  request.extend(name.as_bytes());
  request.extend(args);
  request.extend(outs);

arbitrator/stylus/tests/write-result-len.wat

@@ -0,0 +1,24 @@
+;; Copyright 2024, Offchain Labs, Inc.
+;; For license information, see https://github.com/nitro/blob/master/LICENSE
+
+(module
+ (import "vm_hooks" "read_args" (func $read_args (param i32)))
+ (import "vm_hooks" "write_result" (func $write_result (param i32 i32)))
+ (memory (export "memory") 2 2)
+ (func $main (export "user_entrypoint") (param $args_len i32) (result i32)
+ (local $len i32)
+
+ ;; write args to 0x0
+ (call $read_args (i32.const 0))
+
+ ;; treat first 4 bytes as size to write
+ (i32.load (i32.const 0))
+ local.set $len
+
+ ;; call write
+ (call $write_result (i32.const 0) (local.get $len))
+
+ ;; return success
+ i32.const 0
+ )
+)

arbos/programs/api.go

@@ -400,9 +400,9 @@ func newApiClosures(
  }
  startInk := takeU64()
  endInk := takeU64()
- nameLen := takeU16()
- argsLen := takeU16()
- outsLen := takeU16()
+ nameLen := takeU32()
+ argsLen := takeU32()
+ outsLen := takeU32()
  name := string(takeFixed(int(nameLen)))
  args := takeFixed(int(argsLen))
  outs := takeFixed(int(outsLen))

system_tests/stylus_trace_test.go

@@ -6,6 +6,7 @@ package arbtest
 import (
  "bytes"
  "encoding/binary"
+ "math"
  "math/big"
  "testing"
 
@@ -478,3 +479,17 @@ func TestStylusOpcodeTraceEquivalence(t *testing.T) {
  checkOpcode(t, wasmResult, 12, vm.RETURN, offset, returnLen)
  checkOpcode(t, evmResult, 5078, vm.RETURN, offset, returnLen)
 }
+
+func TestStylusHugeWriteResultTrace(t *testing.T) {
+ const jit = false
+ builder, auth, cleanup := setupProgramTest(t, jit)
+ ctx := builder.ctx
+ l2client := builder.L2.Client
+ defer cleanup()
+
+ program := deployWasm(t, ctx, auth, l2client, watFile("write-result-len"))
+ const returnLen = math.MaxUint16 + 1
+ args := binary.LittleEndian.AppendUint32(nil, returnLen)
+ result := sendAndTraceTransaction(t, builder, program, nil, args)
+ checkOpcode(t, result, 3, vm.RETURN, nil, intToBe32(returnLen))
+}