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// Copyright 2020 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 (
"fmt"
"unsafe"
"golang.org/x/sys/unix"
"gvisor.dev/gvisor/pkg/abi/linux"
"gvisor.dev/gvisor/pkg/sentry/arch"
"gvisor.dev/gvisor/pkg/sentry/platform/systrap/sysmsg"
)
func (p *sysmsgThread) unmapStackFromSentry() {
_, _, errno := unix.RawSyscall(unix.SYS_MUNMAP, sysmsg.MsgToStackAddr(uintptr(unsafe.Pointer(p.msg))), sysmsg.PerThreadSharedStackSize, 0)
if errno != 0 {
panic("failed to unmap: " + errno.Error())
}
}
func (p *sysmsgThread) setMsg(addr uintptr) {
// add is always from the stub mapping which is mapped once and never
// moved, so it is safe to use unsafe.Pointer here.
p.msg = (*sysmsg.Msg)(unsafe.Pointer(addr))
}
func (p *sysmsgThread) init(sentryAddr, guestAddr uintptr) {
t := p.thread
// Set the sysmsg signal stack.
//
// sentryAddr is from the stub mapping which is mapped once and never
// moved, so it is safe to use unsafe.Pointer here.
alt := (*linux.SignalStack)(unsafe.Pointer(sentryAddr))
*alt = linux.SignalStack{}
alt.Addr = uint64(guestAddr)
alt.Size = uint64(sysmsg.MsgOffsetFromSharedStack)
_, err := t.syscallIgnoreInterrupt(&t.initRegs, unix.SYS_SIGALTSTACK,
arch.SyscallArgument{Value: guestAddr},
arch.SyscallArgument{Value: 0},
arch.SyscallArgument{Value: 0},
arch.SyscallArgument{Value: 0},
arch.SyscallArgument{Value: 0},
arch.SyscallArgument{Value: 0},
)
if err != nil {
panic(fmt.Sprintf("sigaltstack: %v", err))
}
}
// sysmsgSigactions installs signal handles for signals which can be triggered
// by stubProcess and have to be handled by Sentry.
//
// It is called in a child process after fork(), so the race instrumentation
// has to be disabled.
//
//go:nosplit
//go:norace
func sysmsgSigactions(stubSysmsgStart uintptr) unix.Errno {
act := linux.SigAction{
Handler: uint64(stubSysmsgStart) + uint64(sysmsg.Sighandler_blob_offset____export_sighandler),
Flags: linux.SA_ONSTACK | linux.SA_RESTORER | linux.SA_SIGINFO,
Restorer: uint64(stubSysmsgStart) + uint64(sysmsg.Sighandler_blob_offset____export_restore_rt),
Mask: 1<<(linux.SIGCHLD-1) | 1<<(linux.SIGSYS-1),
}
for _, s := range []unix.Signal{
unix.SIGSYS,
unix.SIGBUS,
unix.SIGFPE,
unix.SIGILL,
unix.SIGCHLD,
unix.SIGTRAP,
unix.SIGSEGV,
} {
_, _, errno := unix.RawSyscall6(unix.SYS_RT_SIGACTION, uintptr(s), uintptr(unsafe.Pointer(&act)), 0, 8, 0, 0)
if errno != 0 {
return errno
}
}
return 0
}
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