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On arm64, systemstack restores the frame pointer from g0.sched to R29 prior to calling the callback. That doesn't really make any sense. The frame pointer value in g0.sched is some arbitrary BP from a prior context save, but that is not the caller of systemstack. amd64 does not do this. In fact, it leaves BP completely unmodified so frame pointer unwinders like gdb can walk through the systemstack frame and continue traceback on the caller's stack. Unlike mcall, systemstack always returns to the original goroutine, so that is safe. We should do the same on arm64. For #63630. Cq-Include-Trybots: luci.golang.try:gotip-linux-arm64-longtest Change-Id: I6a6a636c35d321dd5d7dc1c4d09e29b55b1ab621 Reviewed-on: https://go-review.googlesource.com/c/go/+/669236 Reviewed-by: Michael Knyszek <mknyszek@google.com> Reviewed-by: Cherry Mui <cherryyz@google.com> Auto-Submit: Michael Pratt <mpratt@google.com> Reviewed-by: Nick Ripley <nick.ripley@datadoghq.com> LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Vendoring in std and cmd
========================
The Go command maintains copies of external packages needed by the
standard library in the src/vendor and src/cmd/vendor directories.
There are two modules, std and cmd, defined in src/go.mod and
src/cmd/go.mod. When a package outside std or cmd is imported
by a package inside std or cmd, the import path is interpreted
as if it had a "vendor/" prefix. For example, within "crypto/tls",
an import of "golang.org/x/crypto/cryptobyte" resolves to
"vendor/golang.org/x/crypto/cryptobyte". When a package with the
same path is imported from a package outside std or cmd, it will
be resolved normally. Consequently, a binary may be built with two
copies of a package at different versions if the package is
imported normally and vendored by the standard library.
Vendored packages are internally renamed with a "vendor/" prefix
to preserve the invariant that all packages have distinct paths.
This is necessary to avoid compiler and linker conflicts. Adding
a "vendor/" prefix also maintains the invariant that standard
library packages begin with a dotless path element.
The module requirements of std and cmd do not influence version
selection in other modules. They are only considered when running
module commands like 'go get' and 'go mod vendor' from a directory
in GOROOT/src.
Maintaining vendor directories
==============================
Before updating vendor directories, ensure that module mode is enabled.
Make sure that GO111MODULE is not set in the environment, or that it is
set to 'on' or 'auto', and if you use a go.work file, set GOWORK=off.
Also, ensure that 'go env GOROOT' shows the root of this Go source
tree. Otherwise, the results are undefined. It's recommended to build
Go from source and use that 'go' binary to update its source tree.
Requirements may be added, updated, and removed with 'go get'.
The vendor directory may be updated with 'go mod vendor'.
A typical sequence might be:
cd src # or src/cmd
go get golang.org/x/net@master
go mod tidy
go mod vendor
Use caution when passing '-u' to 'go get'. The '-u' flag updates
modules providing all transitively imported packages, not only
the module providing the target package.
Note that 'go mod vendor' only copies packages that are transitively
imported by packages in the current module. If a new package is needed,
it should be imported before running 'go mod vendor'.