runtime.Breakpoint SIGSEGV in s390x

[alexsaezm]

What version of Go are you using (go version)?

$ go version
go version go1.17.7 linux/s390x

Does this issue reproduce with the latest release?

Yes.

What operating system and processor architecture are you using (go env)?

go env Output

$ go env
GO111MODULE=""
GOARCH="s390x"
GOBIN=""
GOCACHE="/root/.cache/go-build"
GOENV="/root/.config/go/env"
GOEXE=""
GOEXPERIMENT=""
GOFLAGS=""
GOHOSTARCH="s390x"
GOHOSTOS="linux"
GOINSECURE=""
GOMODCACHE="/root/go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/root/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/lib/golang"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/lib/golang/pkg/tool/linux_s390x"
GOVCS=""
GOVERSION="go1.17.7"
GCCGO="gccgo"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/dev/null"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -march=z196 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build1381326963=/tmp/go-build -gno-record-gcc-switches"

What did you do?

In s390x, if you run the following code:

package main

import "runtime"

func main() {
	runtime.Breakpoint()
}

You get a SIGSEGV:

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x6de30]

goroutine 1 [running]:
runtime.Breakpoint(...)
	/usr/lib/golang/src/runtime/proc.go:4537
main.main()
	/root/test/main.go:6 +0x20

What did you expect to see?

A trap like in amd64.

What did you see instead?

A SIGSEGV. It is similar at what happens in this other issue.

[cherrymui]

I'll note that Breakpoint is mainly for getting into the debugger. A faulting instruction is probably fine. It would be nice if it is an actual trap instruction. You're welcome to send a CL. Thanks.

[alexsaezm]

I'll note that Breakpoint is mainly for getting into the debugger. A faulting instruction is probably fine. It would be nice if it is an actual trap instruction. You're welcome to send a CL. Thanks.

Yeah, that's how I found this while working on Delve. Delve uses Breakpoint in some parts and that breaks tests for example.
I'm planning n work on this as soon as I can. I just opened the issue for awareness.

[gopherbot]

Change https://go.dev/cl/457456 mentions this issue: cmd/internal/obj/s390x, runtime: fix breakpoint in s390x