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runtime: force segv for nil defer function to be in deferreturn()

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If the defer function pointer is nil, force the seg fault to happen in deferreturn
rather than in jmpdefer. jmpdefer is used fairly infrequently now because most
functions have open-coded defers.

The open-coded defer implementation calls gentraceback() with a callback when
looking for the first open-coded defer frame. gentraceback() throws an error if it
is called with a callback on an LR architecture and jmpdefer is on the stack,
because the stack trace can be incorrect in that case - see issue #8153. So, we
want to make sure that we don't have a seg fault in jmpdefer.

Fixes #36050

Change-Id: Ie25e6f015d8eb170b40248dedeb26a37b7f9b38d
Reviewed-on: https://go-review.googlesource.com/c/go/+/210978
Reviewed-by: Keith Randall <khr@golang.org>
Run-TryBot: Dan Scales <danscales@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This commit is contained in:
Dan Scales 2019-12-10 17:27:26 -08:00
parent 100bf440b9
commit 22d28a24c8
2 changed files with 37 additions and 3 deletions
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6
src/runtime/panic.go
View file

@ -561,6 +561,12 @@ func deferreturn(arg0 uintptr) {
d.fn = nil
gp._defer = d.link
freedefer(d)
// If the defer function pointer is nil, force the seg fault to happen
// here rather than in jmpdefer. gentraceback() throws an error if it is
// called with a callback on an LR architecture and jmpdefer is on the
// stack, because the stack trace can be incorrect in that case - see
// issue #8153).
_ = fn.fn
jmpdefer(fn, uintptr(unsafe.Pointer(&arg0)))
}