265d19ed52
The current mp.incgocallback() logic allows for trace events to be recorded using frame pointer unwinding during cgocallbackg when they shouldn't be. Specifically, mp.incgo will be false during the reentersyscall call at the end. It's possible to crash with tracing enabled because of this, if C code which uses the frame pointer register for other purposes calls into Go. This can be seen, for example, by forcing testprogcgo/trace_unix.c to write a garbage value to RBP prior to calling into Go. We can drop the mp.incgo check, and instead conservatively avoid doing frame pointer unwinding if there is any C on the stack. This is the case if mp.ncgo > 0, or if mp.isextra is true (meaning we're coming from a thread created by C). Rename incgocallback to reflect that we're checking if there's any C on the stack. We can also move the ncgo increment in cgocall closer to where the transition to C happens, which lets us use frame pointer unwinding for the entersyscall event during the first Go-to-C call on a stack, when there isn't yet any C on the stack. Fixes #59830. Change-Id: If178a705a9d38d0d2fb19589a9e669cd982d32cd Reviewed-on: https://go-review.googlesource.com/c/go/+/488755 Reviewed-by: Michael Knyszek <mknyszek@google.com> Reviewed-by: Dmitri Shuralyov <dmitshur@google.com> Reviewed-by: Felix Geisendörfer <felix.geisendoerfer@datadoghq.com> Auto-Submit: Michael Knyszek <mknyszek@google.com> Run-TryBot: Nick Ripley <nick.ripley@datadoghq.com> TryBot-Result: Gopher Robot <gobot@golang.org> |
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