Simple syscall in gVisor

sys_sum.go

// Copyright 2018 The gVisor Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package linux

import (
        "gvisor.googlesource.com/gvisor/pkg/sentry/arch"
        "gvisor.googlesource.com/gvisor/pkg/sentry/kernel"
)

// Sum returns the sum of the first two passed integer arguments
func Sum(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
        num1 := args[0].Int()
        num2 := args[1].Int()
        return uintptr(num1 + num2), nil, nil
}

test-sum.go

// Copyright 2018 The gVisor Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package main

import (
        "fmt"
        "os"
        "syscall"
)

const SUM = 400

func main() {
        r1, _, errNo := syscall.RawSyscall(SUM, 5, 6, 0)
        if errNo != 0 {
                fmt.Fprintf(os.Stderr, "ERROR: %d\n", errNo)
                os.Exit(1)
        }
        fmt.Printf("%d\n", r1)
}