ddb503be96
Currently, if a sigpanic call is injected into C code, it's possible for preparePanic to leave the stack in a state where traceback can't unwind correctly past the sigpanic. Specifically, shouldPushPanic sniffs the stack to decide where to put the PC from the signal context. In the cgo case, it will find that !findfunc(pc).valid() because pc is in C code, and then it will check if the top of the stack looks like a Go PC. However, this stack slot is just in a C frame, so it could be uninitialized and contain anything, including what looks like a valid Go PC. For example, in https://build.golang.org/log/c601a18e2af24794e6c0899e05dddbb08caefc17, it sees 1c02c23a <runtime.newproc1+682>. When this condition is met, it skips putting the signal PC on the stack at all. As a result, when we later unwind from the sigpanic, we'll "successfully" but incorrectly unwind to whatever PC was in this uninitialized slot and go who knows where from there. Fix this by making shouldPushPanic assume that the signal PC is always usable if we're running C code, so we always make it appear like sigpanic's caller. This lets us be pickier again about unexpected return PCs in gentraceback. Updates #23640. Change-Id: I1e8ade24b031bd905d48e92d5e60c982e8edf160 Reviewed-on: https://go-review.googlesource.com/91137 Run-TryBot: Austin Clements <austin@google.com> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Ian Lance Taylor <iant@golang.org> |
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