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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.
package systrap
import (
"unsafe"
"golang.org/x/sys/unix"
"gvisor.dev/gvisor/pkg/abi/linux"
"gvisor.dev/gvisor/pkg/hostarch"
"gvisor.dev/gvisor/pkg/sentry/arch"
)
// getRegs gets the general purpose register set.
func (t *thread) getRegs(regs *arch.Registers) error {
iovec := unix.Iovec{
Base: (*byte)(unsafe.Pointer(regs)),
Len: uint64(unsafe.Sizeof(*regs)),
}
_, _, errno := unix.RawSyscall6(
unix.SYS_PTRACE,
unix.PTRACE_GETREGSET,
uintptr(t.tid),
linux.NT_PRSTATUS,
uintptr(unsafe.Pointer(&iovec)),
0, 0)
if errno != 0 {
return errno
}
return nil
}
// setRegs sets the general purpose register set.
func (t *thread) setRegs(regs *arch.Registers) error {
iovec := unix.Iovec{
Base: (*byte)(unsafe.Pointer(regs)),
Len: uint64(unsafe.Sizeof(*regs)),
}
_, _, errno := unix.RawSyscall6(
unix.SYS_PTRACE,
unix.PTRACE_SETREGSET,
uintptr(t.tid),
linux.NT_PRSTATUS,
uintptr(unsafe.Pointer(&iovec)),
0, 0)
if errno != 0 {
return errno
}
return nil
}
// getSignalInfo retrieves information about the signal that caused the stop.
func (t *thread) getSignalInfo(si *linux.SignalInfo) error {
_, _, errno := unix.RawSyscall6(
unix.SYS_PTRACE,
unix.PTRACE_GETSIGINFO,
uintptr(t.tid),
0,
uintptr(unsafe.Pointer(si)),
0, 0)
if errno != 0 {
return errno
}
return nil
}
// clone creates a new sysmsg thread from this one.
//
// The returned thread will be stopped and available for any system thread to
// call attach on it.
//
// Precondition: the OS thread must be locked and own t.
func (t *thread) clone() (*thread, error) {
r, ok := hostarch.Addr(stackPointer(&t.initRegs)).RoundUp()
if !ok {
return nil, unix.EINVAL
}
var flags uintptr
// Create a sysmsg thread.
//
// CLONE_THREAD isn't set, because a stub process has SIGSTOP
// in its queue. A sysmsg thread will not be traced by ptrace,
// so it will be stopped immediately if it will share signal
// queue with its stub process.
flags = uintptr(
unix.CLONE_FILES |
unix.CLONE_FS |
unix.CLONE_PTRACE |
unix.CLONE_VM |
linux.SIGKILL)
rval, err := t.syscallIgnoreInterrupt(
&t.initRegs,
unix.SYS_CLONE,
arch.SyscallArgument{Value: flags},
// The stack pointer is just made up, but we have it be
// something sensible so the kernel doesn't think we're
// up to no good. Which we are.
arch.SyscallArgument{Value: uintptr(r)},
arch.SyscallArgument{},
arch.SyscallArgument{},
// We use these registers initially, but really they
// could be anything. We're going to stop immediately.
arch.SyscallArgument{Value: uintptr(unsafe.Pointer(&t.initRegs))})
if err != nil {
return nil, err
}
return &thread{
tgid: int32(rval),
tid: int32(rval),
}, nil
}
// getEventMessage retrieves a message about the ptrace event that just happened.
func (t *thread) getEventMessage() (uintptr, error) {
var msg uintptr
_, _, errno := unix.RawSyscall6(
unix.SYS_PTRACE,
unix.PTRACE_GETEVENTMSG,
uintptr(t.tid),
0,
uintptr(unsafe.Pointer(&msg)),
0, 0)
if errno != 0 {
return msg, errno
}
return msg, nil
}
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