github.com/MerlinKodo/gvisor@v0.0.0-20231110090155-957f62ecf90e/pkg/sentry/platform/systrap/syscall_thread_unsafe.go (about)

     1  // Copyright 2021 The gVisor Authors.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package systrap
    16  
    17  import (
    18  	"fmt"
    19  	"sync/atomic"
    20  	"unsafe"
    21  
    22  	"github.com/MerlinKodo/gvisor/pkg/abi/linux"
    23  	"golang.org/x/sys/unix"
    24  )
    25  
    26  func (t *syscallThread) initRequestReplyAddresses(sentryStackAddr uintptr) {
    27  	// These are safe as these addresses are mmapped and never moved/gced.
    28  	sentryMessage := (*syscallSentryMessage)(unsafe.Pointer(sentryStackAddr))
    29  	stubMessage := (*syscallStubMessage)(unsafe.Pointer(sentryStackAddr + syscallStubMessageOffset))
    30  	atomic.StoreUint32(&sentryMessage.state, 0)
    31  
    32  	t.sentryMessage = sentryMessage
    33  	t.stubMessage = stubMessage
    34  }
    35  
    36  // maskAllSignals blocks all signals.
    37  func (t *syscallThread) maskAllSignalsAttached() {
    38  	p := t.thread
    39  
    40  	mask := ^uint64(0)
    41  	if _, _, errno := unix.RawSyscall6(unix.SYS_PTRACE, linux.PTRACE_SETSIGMASK, uintptr(p.tid), 8, uintptr(unsafe.Pointer(&mask)), 0, 0); errno != 0 {
    42  		panic(fmt.Sprintf("unable to setmask: %v", errno))
    43  	}
    44  }
    45  
    46  // unmaskAllSignals unblocks all signals.
    47  func (t *syscallThread) unmaskAllSignalsAttached() {
    48  	p := t.thread
    49  	mask := uint64(0)
    50  	if _, _, errno := unix.RawSyscall6(unix.SYS_PTRACE, linux.PTRACE_SETSIGMASK, uintptr(p.tid), 8, uintptr(unsafe.Pointer(&mask)), 0, 0); errno != 0 {
    51  		panic(fmt.Sprintf("unable to setmask: %v", errno))
    52  	}
    53  }
    54  
    55  func futexWakeUint32(addr *uint32) error {
    56  	if _, _, e := unix.RawSyscall6(unix.SYS_FUTEX, uintptr(unsafe.Pointer(addr)), linux.FUTEX_WAKE, 1, 0, 0, 0); e != 0 {
    57  		return fmt.Errorf("failed to FUTEX_WAKE: %v", e)
    58  	}
    59  	return nil
    60  }
    61  
    62  func futexWaitForUint32(addr *uint32, targetValue uint32) error {
    63  	for {
    64  		val := atomic.LoadUint32(addr)
    65  		if val == targetValue {
    66  			break
    67  		}
    68  
    69  		_, _, e := unix.Syscall6(unix.SYS_FUTEX, uintptr(unsafe.Pointer(addr)), linux.FUTEX_WAIT, uintptr(val), 0, 0, 0)
    70  		if e != 0 && e != unix.EAGAIN && e != unix.EINTR {
    71  			return fmt.Errorf("failed to FUTEX_WAIT: %v", e)
    72  		}
    73  	}
    74  	return nil
    75  }
    76  
    77  // futexWaitWake waits when other side will call FUTEX_WAKE. A value of the
    78  // futex word has to be equal to futexValue and it must not be changed.
    79  func futexWaitWake(futexAddr *uint32, futexValue uint32) error {
    80  	for {
    81  		_, _, e := unix.Syscall6(unix.SYS_FUTEX, uintptr(unsafe.Pointer(futexAddr)), linux.FUTEX_WAIT, uintptr(futexValue), 0, 0, 0)
    82  		if e == 0 {
    83  			break
    84  		}
    85  		if e != unix.EAGAIN && e != unix.EINTR {
    86  			return fmt.Errorf("failed to FUTEX_WAIT: %v", e)
    87  		}
    88  	}
    89  
    90  	return nil
    91  }