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28f650a2f7
If we are using vfork, and if something (such as TSAN) is intercepting the sigaction function, then we must call the system call, not the libc function. Otherwise the intercepted sigaction call in the child may trash the data structures in the parent. Change-Id: Id9588bfeaa934f32c920bf829c5839be5cacf243 Reviewed-on: https://go-review.googlesource.com/50251 Reviewed-by: Joe Tsai <thebrokentoaster@gmail.com> Reviewed-by: Austin Clements <austin@google.com>
90 lines
3.2 KiB
Go
90 lines
3.2 KiB
Go
// Copyright 2016 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Support for memory sanitizer. See runtime/cgo/sigaction.go.
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// +build linux,amd64
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package runtime
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import "unsafe"
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// _cgo_sigaction is filled in by runtime/cgo when it is linked into the
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// program, so it is only non-nil when using cgo.
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//go:linkname _cgo_sigaction _cgo_sigaction
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var _cgo_sigaction unsafe.Pointer
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//go:nosplit
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//go:nowritebarrierrec
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func rt_sigaction(sig uintptr, new, old *sigactiont, size uintptr) int32 {
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// The runtime package is explicitly blacklisted from sanitizer
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// instrumentation in racewalk.go, but we might be calling into instrumented C
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// functions here — so we need the pointer parameters to be properly marked.
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//
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// Mark the input as having been written before the call and the output as
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// read after.
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if msanenabled && new != nil {
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msanwrite(unsafe.Pointer(new), unsafe.Sizeof(*new))
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}
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var ret int32
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if _cgo_sigaction == nil || inForkedChild {
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ret = sysSigaction(sig, new, old, size)
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} else {
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// We need to call _cgo_sigaction, which means we need a big enough stack
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// for C. To complicate matters, we may be in libpreinit (before the
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// runtime has been initialized) or in an asynchronous signal handler (with
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// the current thread in transition between goroutines, or with the g0
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// system stack already in use).
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g := getg()
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sp := uintptr(unsafe.Pointer(&sig))
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switch {
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case g == nil:
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// No g: we're on a C stack or a signal stack.
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ret = callCgoSigaction(sig, new, old)
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case sp < g.stack.lo || sp >= g.stack.hi:
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// We're no longer on g's stack, so we must be handling a signal. It's
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// possible that we interrupted the thread during a transition between g
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// and g0, so we should stay on the current stack to avoid corrupting g0.
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ret = callCgoSigaction(sig, new, old)
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default:
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// We're running on g's stack, so either we're not in a signal handler or
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// the signal handler has set the correct g. If we're on gsignal or g0,
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// systemstack will make the call directly; otherwise, it will switch to
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// g0 to ensure we have enough room to call a libc function.
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//
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// The function literal that we pass to systemstack is not nosplit, but
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// that's ok: we'll be running on a fresh, clean system stack so the stack
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// check will always succeed anyway.
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systemstack(func() {
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ret = callCgoSigaction(sig, new, old)
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})
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}
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const EINVAL = 22
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if ret == EINVAL {
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// libc reserves certain signals — normally 32-33 — for pthreads, and
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// returns EINVAL for sigaction calls on those signals. If we get EINVAL,
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// fall back to making the syscall directly.
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ret = sysSigaction(sig, new, old, size)
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}
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}
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if msanenabled && old != nil && ret == 0 {
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msanread(unsafe.Pointer(old), unsafe.Sizeof(*old))
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}
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return ret
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}
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// sysSigaction calls the rt_sigaction system call. It is implemented in assembly.
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//go:noescape
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func sysSigaction(sig uintptr, new, old *sigactiont, size uintptr) int32
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// callCgoSigaction calls the sigaction function in the runtime/cgo package
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// using the GCC calling convention. It is implemented in assembly.
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//go:noescape
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func callCgoSigaction(sig uintptr, new, old *sigactiont) int32
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