commit 1b463205dc9a0f87a8439d95225891d6242711b5
author Michael Anthony Knyszek <mknyszek@google.com> Thu Dec 19 17:38:58 2024 +0000
committer Gopher Robot <gobot@golang.org> Thu Dec 19 12:27:00 2024 -0800
tree c7dd51bd39121c1752a458ae31f8cbdef9ffe8f5
parent 453fb03fae2cddf2a8a275056f12c8290341734c

gocore: record global pointers not described in DWARF as roots

Currently globals are entirely defined by what we can find in DWARF, but
there are some globals (for example, runtime..interfaceSwitch.0) which
have no corresponding DWARF. This is problematic, because markObjects
uses the full set of global pointers *instead of* the roots we found to
mark objects. This is more precise, but creates a discrepancy, and
callers (such as the dominator functionality) can't actually find a path
to all listed objects.

Fix this by walking all these undescribed global pointers and recording
them explicitly as "unknown" roots. This makes viewcore much more robust
to future changes, at the expense of not being able to type the
undescribed things it finds.

This change also refactors ForEachRootPtr's internals into something
that could be executed from markObjects, and refactors markObjects to be
simpler and use the Process APIs.

Goroutine stack roots already do this, but globals do not, causing
certain intuitive invariants (like that each object in ForEachObject
should be reachable from ForEachRoot) to be violated.

Change-Id: Ie170098e5e5df929bbef5dee47b068de213a89a4
Reviewed-on: https://go-review.googlesource.com/c/debug/+/637876
Auto-Submit: Nicolas Hillegeer <aktau@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Nicolas Hillegeer <aktau@google.com>