cmd/compile/internal: asm hangs forever (12 hours) with pegged cpu in QEMU cross-compile

[xxxserxxx]

Go version

go version go1.25.7 linux/arm64

Output of go env in your module/workspace:

AR='ar'
CC='cc'
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_ENABLED='1'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-O2 -g'
CXX='c++'
GCCGO='gccgo'
GO111MODULE=''
GOARCH='arm64'
GOARM64='v8.0'
GOAUTH='netrc'
GOBIN=''
GOCACHE='/root/.cache/go-build'
GOCACHEPROG=''
GODEBUG=''
GOENV='/root/.config/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFIPS140='off'
GOFLAGS=''
GOGCCFLAGS='-fPIC -pthread -Wl,--no-gc-sections -fmessage-length=0 -ffile-prefix-map=/tmp/go-build4113777134=/tmp/go-build -gno-record-gcc-switches'
GOHOSTARCH='arm64'
GOHOSTOS='linux'
GOINSECURE=''
GOMOD='/workspace/go.mod'
GOMODCACHE='/root/go/pkg/mod'
GONOPROXY=''
GONOSUMDB=''
GOOS='linux'
GOPATH='/root/go'
GOPRIVATE=''
GOPROXY='https://proxy.golang.org,direct'
GOROOT='/usr/lib/go'
GOSUMDB='sum.golang.org'
GOTELEMETRY='local'
GOTELEMETRYDIR='/root/.config/go/telemetry'
GOTMPDIR=''
GOTOOLCHAIN='local'
GOTOOLDIR='/usr/lib/go/pkg/tool/linux_arm64'
GOVCS=''
GOVERSION='go1.25.7'
GOWORK=''
PKG_CONFIG='pkg-config'

What did you do?

I'm trying to compile a small program using gioui for arm64 on an amd64 Arch Linux machine. The program compiles natively without issue.

Because of the X and Wayland dependencies, cross-compiling directly fails -- apparently during finding resources like headers -- so I am trying to cross compile in an LXC container via podman and qemu.

$ pacman -S qemu-user-static qemu-user-static-binfmt
$ sudo podman run --rm --privileged docker.io/multiarch/qemu-user-static --reset -p yes

And then I compile this project using the Containerfile in the project with:

$ podman build --platform linux/arm64 -t armbuilder -v ${PWD}:/workspace .   # Once
$ podman run --platform linux/arm64/v8 -v ${PWD}:/workspace armbuilder

The second command I've run in various ways to try to identify the problem, the most recent failing variation was:

$ podman run -it --platform linux/arm64/v8 -v ${PWD}:/workspace armbuilder go build -v -o build/linux_arm64 ./cmd/dlg

If I add the -x flag, it almost(?) always compiles within a few minutes. I haven't seen it fail yet with -x, and I haven't yet seen it not hang without it.

This machine is an AMD Ryzen 7 5800H, which I think is technically a mobile CPU; it has 16 cores and the machine it's in has 32GB RAM. I don't think I've ever touched the swap space, or gotten to less than 10GB free in the past year I've owned it.

I've tried with both the official alpine image, and more recently (because I need glibc linkage for my target platform) with wolfi (cgr.dev/chainguard/wolfi-base:latest).

To reproduce (hopefully it's reproducable off my machine), pull the bookmark "go-build-hang-issue".

What did you see happen?

The first time I got it to compile without dependency errors, it ran for a couple of hours and I left it overnight. The next morning -- about 12 hours after starting the build -- I checked and it was still hung up on the package it was compilyng when I left it the night before. Every attempt since hangs at the same place, even when the image is deleted and re-created. It hangs on this step:

cd /usr/lib/go/src/math
/usr/lib/go/pkg/tool/linux_arm64/asm -p math -trimpath "$WORK/b038=>" -I $WORK/b038/ -I /usr/lib/go/pkg/include -D GOOS_linux -D GOARCH_arm64 -gensymabis -o $WORK/b038/symabis ./dim_arm64.s ./exp_arm64.s ./floor_arm64.s ./modf_arm64.s

A single core is pegged. As I said, if I build with -x it will make it through the entire build in minutes. If I use only -v, or no flags, it hangs.

What did you expect to see?

I expect the build to:

1. Fail with an error message.
2. or Succeed.

[mrkfrmn]

cc @golang/compiler

[egonelbre]

Which QEMU version are you running?

See golang/wiki@8691739 and #77572 for similar issues. Although, they were issues with Go 1.26.

[xxxserxxx]

$ qemu-aarch64-static --version
qemu-aarch64 version 10.2.0

which is well past the v7.0.0 in #77572, and past the 7.1.0 mentioned in commit #8691739. Although, #77572 was for qemu-x86_64, and I don't know if all QEMUs are versioned concurrently.

Was #77572 about a hung process, though? I'm not getting a crash or dump -- it just hangs forever. There is another ticket about a container-related hang, but it has to do with an NFS (or other invalid mount) and I'm not doing anything exotic like that. Furthermore, my hang goes away when I run Go with -x, at which point it not only doesn't hang, but completes and compiles a well-executing binary as well. I can copy it onto my Phosh phone and run it.

[DanielMorsing]

We've found qemu-static to cause memory corruption, so it could result in a number of ill-effects, like crashing or getting stuck in infinite loops. The diagnostic flags changing the behavior is weird though, not entirely sure why that would make a difference.

Could you try sending the process an abort signal? it should give us a stack trace to figure out just where it starts spinning and maybe show us where we should apply hardening.