fef5a15396
On Windows, when calling into needm in cgocallback on a new thread that is unknown to the Go runtime, we currently call through an ABI wrapper. The ABI wrapper tries to restore the G register from TLS. On other platforms, TLS is set up just enough that the wrapper will simply load a nil g from TLS, but on Windows TLS isn't set up at all, so there's nowhere for the wrapper to load from. So, bypass the wrapper in the call to needm. needm takes no arguments and returns no results so there are no special ABI considerations, except that we must clear X15 which is used as a zero register in Go code (a function normally performed by the ABI wrapper). needm is also otherwise already special and carefully crafted to avoid doing anything that would require a valid G or M, at least until it is able to create one. While we're here, this change simplifies setg so that it doesn't set up TLS on Windows and instead provides an OS-specific osSetupTLS to do that. The result of this is that setg(nil) no longer clears the TLS space pointer on Windows. There's exactly one place this is used (dropm) where it doesn't matter anymore, and an empty TLS means that setg's wrapper will crash on the return path. Another result is that the G slot in the TLS will be properly cleared, however, which isn't true today. For #40724. Change-Id: I65c3d924a3b16abe667b06fd91d467d6d5da31d7 Reviewed-on: https://go-review.googlesource.com/c/go/+/303070 Trust: Michael Knyszek <mknyszek@google.com> Run-TryBot: Michael Knyszek <mknyszek@google.com> Reviewed-by: Cherry Zhang <cherryyz@google.com> |
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