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-rw-r--r--src/runtime/cgo_sigaction.go94
1 files changed, 94 insertions, 0 deletions
diff --git a/src/runtime/cgo_sigaction.go b/src/runtime/cgo_sigaction.go
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+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Support for sanitizers. See runtime/cgo/sigaction.go.
+
+//go:build (linux && amd64) || (freebsd && amd64) || (linux && arm64) || (linux && ppc64le)
+
+package runtime
+
+import "unsafe"
+
+// _cgo_sigaction is filled in by runtime/cgo when it is linked into the
+// program, so it is only non-nil when using cgo.
+//
+//go:linkname _cgo_sigaction _cgo_sigaction
+var _cgo_sigaction unsafe.Pointer
+
+//go:nosplit
+//go:nowritebarrierrec
+func sigaction(sig uint32, new, old *sigactiont) {
+ // racewalk.go avoids adding sanitizing instrumentation to package runtime,
+ // but we might be calling into instrumented C functions here,
+ // so we need the pointer parameters to be properly marked.
+ //
+ // Mark the input as having been written before the call
+ // and the output as read after.
+ if msanenabled && new != nil {
+ msanwrite(unsafe.Pointer(new), unsafe.Sizeof(*new))
+ }
+ if asanenabled && new != nil {
+ asanwrite(unsafe.Pointer(new), unsafe.Sizeof(*new))
+ }
+ if _cgo_sigaction == nil || inForkedChild {
+ sysSigaction(sig, new, old)
+ } else {
+ // We need to call _cgo_sigaction, which means we need a big enough stack
+ // for C. To complicate matters, we may be in libpreinit (before the
+ // runtime has been initialized) or in an asynchronous signal handler (with
+ // the current thread in transition between goroutines, or with the g0
+ // system stack already in use).
+
+ var ret int32
+
+ var g *g
+ if mainStarted {
+ g = getg()
+ }
+ sp := uintptr(unsafe.Pointer(&sig))
+ switch {
+ case g == nil:
+ // No g: we're on a C stack or a signal stack.
+ ret = callCgoSigaction(uintptr(sig), new, old)
+ case sp < g.stack.lo || sp >= g.stack.hi:
+ // We're no longer on g's stack, so we must be handling a signal. It's
+ // possible that we interrupted the thread during a transition between g
+ // and g0, so we should stay on the current stack to avoid corrupting g0.
+ ret = callCgoSigaction(uintptr(sig), new, old)
+ default:
+ // We're running on g's stack, so either we're not in a signal handler or
+ // the signal handler has set the correct g. If we're on gsignal or g0,
+ // systemstack will make the call directly; otherwise, it will switch to
+ // g0 to ensure we have enough room to call a libc function.
+ //
+ // The function literal that we pass to systemstack is not nosplit, but
+ // that's ok: we'll be running on a fresh, clean system stack so the stack
+ // check will always succeed anyway.
+ systemstack(func() {
+ ret = callCgoSigaction(uintptr(sig), new, old)
+ })
+ }
+
+ const EINVAL = 22
+ if ret == EINVAL {
+ // libc reserves certain signals — normally 32-33 — for pthreads, and
+ // returns EINVAL for sigaction calls on those signals. If we get EINVAL,
+ // fall back to making the syscall directly.
+ sysSigaction(sig, new, old)
+ }
+ }
+
+ if msanenabled && old != nil {
+ msanread(unsafe.Pointer(old), unsafe.Sizeof(*old))
+ }
+ if asanenabled && old != nil {
+ asanread(unsafe.Pointer(old), unsafe.Sizeof(*old))
+ }
+}
+
+// callCgoSigaction calls the sigaction function in the runtime/cgo package
+// using the GCC calling convention. It is implemented in assembly.
+//
+//go:noescape
+func callCgoSigaction(sig uintptr, new, old *sigactiont) int32