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The x/sys/windows package currently uses go:linkname for other facilities inside of runtime that are not suitable to be exposed as a public API due to their dangers but are still necessary for manipulating any low-level plumbing that the runtime controls. Logging, via the built-in println and panic handler, is one such low-level plumbing feature. In this case, x/sys/windows/svc needs to be able to redirect panics to the Windows event log. Because the event log is a complicated interface, this requires a bit more fiddling than the simple solution used on Android (baking it into runtime itself), and because Windows services are very diverse, the event log might not even always be a desirable destination. This commit accomplishes this by exposing a function pointer called "overrideWrite" that low-level runtime packages like x/sys/windows/svc can use to redirect output logs toward the event log or otherwise. It is not safe or acceptable to use as a generic mechanism, and for that reason, we wouldn't want to expose this as a real stable API, similar to the other instances of go:linkname in x/sys/windows. But for packages that must interoperate with low-level Go runtime fundamentals, this is a safety hatch for packages that are developed in tandem with the runtime. x/sys/windows is one such package. Updates #42888. Change-Id: I77a32ff7e1494324e8cc38e792e007f86d32672d Reviewed-on: https://go-review.googlesource.com/c/go/+/278792 Trust: Jason A. Donenfeld <Jason@zx2c4.com> Run-TryBot: Jason A. Donenfeld <Jason@zx2c4.com> TryBot-Result: Go Bot <gobot@golang.org> Reviewed-by: Russ Cox <rsc@golang.org>
33 lines
709 B
Go
33 lines
709 B
Go
// Copyright 2019 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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//go:build !faketime
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package runtime
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import "unsafe"
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// faketime is the simulated time in nanoseconds since 1970 for the
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// playground.
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//
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// Zero means not to use faketime.
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var faketime int64
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//go:nosplit
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func nanotime() int64 {
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return nanotime1()
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}
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var overrideWrite func(fd uintptr, p unsafe.Pointer, n int32) int32
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// write must be nosplit on Windows (see write1)
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//
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//go:nosplit
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func write(fd uintptr, p unsafe.Pointer, n int32) int32 {
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if overrideWrite != nil {
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return overrideWrite(fd, noescape(p), n)
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}
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return write1(fd, p, n)
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}
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