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// 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.
//go:build go1.18
// +build go1.18
// //go:linkname directives type-checked by checklinkname. Any other
// non-linkname assumptions outside the Go 1 compatibility guarantee should
// have an accompanied vet check or version guard build tag.
package systrap
import (
"fmt"
"unsafe"
"golang.org/x/sys/unix"
"gvisor.dev/gvisor/pkg/abi/linux"
"gvisor.dev/gvisor/pkg/log"
"gvisor.dev/gvisor/pkg/sentry/arch"
"gvisor.dev/gvisor/pkg/sentry/memmap"
"gvisor.dev/gvisor/pkg/sentry/pgalloc"
"gvisor.dev/gvisor/pkg/sentry/platform/systrap/sysmsg"
)
//go:linkname beforeFork syscall.runtime_BeforeFork
func beforeFork()
//go:linkname afterFork syscall.runtime_AfterFork
func afterFork()
//go:linkname afterForkInChild syscall.runtime_AfterForkInChild
func afterForkInChild()
// cputicks is implemented in assembly.
func cputicks() int64
// spinloop is implemented in assembly.
func spinloop()
// getThreadContextFromID returns a ThreadContext struct that corresponds to the
// given ID.
//
// Precondition: cid must be a valid thread context ID that has a mapping for it
// that exists in s.contexts.
func (s *subprocess) getThreadContextFromID(cid uint64) *sysmsg.ThreadContext {
tcSlot := s.threadContextRegion + uintptr(cid)*sysmsg.AllocatedSizeofThreadContextStruct
return (*sysmsg.ThreadContext)(unsafe.Pointer(tcSlot))
}
func mmapContextQueueForSentry(memoryFile *pgalloc.MemoryFile, opts pgalloc.AllocOpts) (memmap.FileRange, *contextQueue) {
fr, err := memoryFile.Allocate(uint64(stubContextQueueRegionLen), opts)
if err != nil {
panic(fmt.Sprintf("failed to allocate a new subprocess context memory region"))
}
addr, _, errno := unix.RawSyscall6(
unix.SYS_MMAP,
0,
uintptr(fr.Length()),
unix.PROT_WRITE|unix.PROT_READ,
unix.MAP_SHARED|unix.MAP_FILE,
uintptr(memoryFile.FD()), uintptr(fr.Start))
if errno != 0 {
panic(fmt.Sprintf("mmap failed for subprocess context memory region: %v", errno))
}
return fr, (*contextQueue)(unsafe.Pointer(addr))
}
func saveFPState(ctx *sharedContext, ac *arch.Context64) {
fpState := ac.FloatingPointData().BytePointer()
dst := unsafeSlice(uintptr(unsafe.Pointer(fpState)), archState.FpLen())
src := ctx.shared.FPState[:]
copy(dst, src)
}
// restoreFPStateDecoupledContext writes FPState from c to the thread context
// shared memory region if there is any need to do so.
func restoreFPState(ctx *sharedContext, c *platformContext, ac *arch.Context64) {
if !c.needRestoreFPState {
return
}
c.needRestoreFPState = false
ctx.setFPStateChanged()
fpState := ac.FloatingPointData().BytePointer()
src := unsafeSlice(uintptr(unsafe.Pointer(fpState)), archState.FpLen())
dst := ctx.shared.FPState[:]
copy(dst, src)
}
// alive returns true if the subprocess is alive.
func (s *subprocess) alive() bool {
if s.dead.Load() {
return false
}
// Wait4 doesn't support WNOWAIT, but here is no other way to find out
// whether a process exited or was stopped by ptrace.
siginfo := linux.SignalInfo{}
_, _, errno := unix.Syscall6(
unix.SYS_WAITID,
unix.P_PID,
uintptr(s.syscallThread.thread.tid),
uintptr(unsafe.Pointer(&siginfo)),
uintptr(unix.WEXITED|unix.WNOHANG|unix.WNOWAIT),
0, 0)
if errno == 0 && siginfo.PID() == 0 {
return true
}
if errno == 0 && siginfo.Code != linux.CLD_EXITED && siginfo.Code != linux.CLD_KILLED {
return true
}
// The process is dead, let's collect its zombie.
wstatus := unix.WaitStatus(0)
pid, err := unix.Wait4(int(s.syscallThread.thread.tid), &wstatus, unix.WNOHANG, nil)
log.Warningf("the subprocess %d exited (status: %s, err %s)", pid, wstatus, err)
s.dead.Store(true)
return false
}
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