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// Copyright 2018 Google LLC
//
// 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 boot
import (
"fmt"
"os"
"sync"
"syscall"
"github.com/golang/protobuf/proto"
"gvisor.googlesource.com/gvisor/pkg/abi"
"gvisor.googlesource.com/gvisor/pkg/eventchannel"
"gvisor.googlesource.com/gvisor/pkg/log"
"gvisor.googlesource.com/gvisor/pkg/sentry/arch"
rpb "gvisor.googlesource.com/gvisor/pkg/sentry/arch/registers_go_proto"
"gvisor.googlesource.com/gvisor/pkg/sentry/strace"
spb "gvisor.googlesource.com/gvisor/pkg/sentry/unimpl/unimplemented_syscall_go_proto"
)
func initCompatLogs(fd int) error {
ce, err := newCompatEmitter(fd)
if err != nil {
return err
}
eventchannel.AddEmitter(ce)
return nil
}
type compatEmitter struct {
sink *log.BasicLogger
nameMap strace.SyscallMap
// mu protects the fields below.
mu sync.Mutex
// trackers map syscall number to the respective tracker instance.
// Protected by 'mu'.
trackers map[uint64]syscallTracker
}
func newCompatEmitter(logFD int) (*compatEmitter, error) {
nameMap, ok := strace.Lookup(abi.Linux, arch.AMD64)
if !ok {
return nil, fmt.Errorf("amd64 Linux syscall table not found")
}
c := &compatEmitter{
// Always logs to default logger.
sink: log.Log(),
nameMap: nameMap,
trackers: make(map[uint64]syscallTracker),
}
if logFD > 0 {
f := os.NewFile(uintptr(logFD), "user log file")
target := log.MultiEmitter{c.sink, log.GoogleEmitter{&log.Writer{Next: f}}}
c.sink = &log.BasicLogger{Level: log.Info, Emitter: target}
}
return c, nil
}
// Emit implements eventchannel.Emitter.
func (c *compatEmitter) Emit(msg proto.Message) (hangup bool, err error) {
// Only interested in UnimplementedSyscall, skip the rest.
us, ok := msg.(*spb.UnimplementedSyscall)
if !ok {
return false, nil
}
regs := us.Registers.GetArch().(*rpb.Registers_Amd64).Amd64
c.mu.Lock()
defer c.mu.Unlock()
sysnr := regs.OrigRax
tr := c.trackers[sysnr]
if tr == nil {
switch sysnr {
case syscall.SYS_PRCTL, syscall.SYS_ARCH_PRCTL:
tr = newCmdTracker(0)
case syscall.SYS_IOCTL, syscall.SYS_EPOLL_CTL, syscall.SYS_SHMCTL:
tr = newCmdTracker(1)
default:
tr = &onceTracker{}
}
c.trackers[sysnr] = tr
}
if tr.shouldReport(regs) {
c.sink.Infof("Unsupported syscall: %s, regs: %+v", c.nameMap.Name(uintptr(sysnr)), regs)
tr.onReported(regs)
}
return false, nil
}
// Close implements eventchannel.Emitter.
func (c *compatEmitter) Close() error {
c.sink = nil
return nil
}
// syscallTracker interface allows filters to apply differently depending on
// the syscall and arguments.
type syscallTracker interface {
// shouldReport returns true is the syscall should be reported.
shouldReport(regs *rpb.AMD64Registers) bool
// onReported marks the syscall as reported.
onReported(regs *rpb.AMD64Registers)
}
// onceTracker reports only a single time, used for most syscalls.
type onceTracker struct {
reported bool
}
func (o *onceTracker) shouldReport(_ *rpb.AMD64Registers) bool {
return !o.reported
}
func (o *onceTracker) onReported(_ *rpb.AMD64Registers) {
o.reported = true
}
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