cmd/link: signal SIGBUS: bus error during linking with sufficient disk space

[sauravhaloi]

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

$ go version
go version go1.15.2 linux/amd64

Does this issue reproduce with the latest release?

Yes. I am observing this issue on latest go release in Ubuntu 20.04.1 LTS (Linux, amd64)

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

go env Output

$ go env
GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/shaloi/.cache/go-build"
GOENV="/home/shaloi/.config/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE=""
GOMODCACHE="/home/shaloi/workspace/golang/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/home/shaloi/workspace/golang"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/opt/golang/latest"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/opt/golang/latest/pkg/tool/linux_amd64"
GCCGO="gccgo"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD=""
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 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build714599985=/tmp/go-build -gno-record-gcc-switches"

What did you do?

$ go run main.go

What did you expect to see?

my application to be successfully built and executed.

What did you see instead?

$ go run main.go 
# command-line-arguments
unexpected fault address 0x7f06bc66f24f
fatal error: fault
[signal SIGBUS: bus error code=0x2 addr=0x7f06bc66f24f pc=0x517262]

goroutine 1 [running]:
runtime.throw(0x6cf03c, 0x5)
	/usr/local/go/src/runtime/panic.go:1116 +0x72 fp=0xc000106ce0 sp=0xc000106cb0 pc=0x436392
runtime.sigpanic()
	/usr/local/go/src/runtime/signal_unix.go:717 +0x485 fp=0xc000106d10 sp=0xc000106ce0 pc=0x44cae5
cmd/internal/goobj2.(*Reloc).Sym(...)
	/usr/local/go/src/cmd/internal/goobj2/objfile.go:317
cmd/link/internal/loader.Reloc2.Sym(0x7f06bc66f241, 0xc000da2900, 0xc000073c00, 0x0, 0x4)
	/usr/local/go/src/cmd/link/internal/loader/loader.go:83 +0x22 fp=0xc000106d40 sp=0xc000106d10 pc=0x517262
cmd/link/internal/loader.(*Loader).UndefinedRelocTargets(0xc000073c00, 0x1, 0x6cf60b, 0x6, 0x8b2b20)
	/usr/local/go/src/cmd/link/internal/loader/loader.go:2918 +0xf6 fp=0xc000106e08 sp=0xc000106d40 pc=0x524a96
cmd/link/internal/ld.(*Link).loadlib(0xc000073880)
	/usr/local/go/src/cmd/link/internal/ld/lib.go:594 +0x5a5 fp=0xc000106eb8 sp=0xc000106e08 pc=0x5c2445
cmd/link/internal/ld.Main(0x870840, 0x20, 0x20, 0x1, 0x7, 0x10, 0x0, 0x0, 0x6da8ff, 0x1b, ...)
	/usr/local/go/src/cmd/link/internal/ld/main.go:232 +0xd05 fp=0xc000107118 sp=0xc000106eb8 pc=0x5e1e05
main.main()
	/usr/local/go/src/cmd/link/main.go:68 +0x1dc fp=0xc000107f88 sp=0xc000107118 pc=0x65dd1c
runtime.main()
	/usr/local/go/src/runtime/proc.go:204 +0x209 fp=0xc000107fe0 sp=0xc000107f88 pc=0x438b89
runtime.goexit()
	/usr/local/go/src/runtime/asm_amd64.s:1374 +0x1 fp=0xc000107fe8 sp=0xc000107fe0 pc=0x46af01

Additional observations

• this error is only observed with go 1.15.2
• as mentioned in Issue: cmd/link: SIGBUS error when linking (because disk space consumed) #41466, in my case, there was no disk space issue

$ df -h
Filesystem      Size  Used Avail Use% Mounted on
udev            5.8G     0  5.8G   0% /dev
tmpfs           1.2G  2.2M  1.2G   1% /run
/dev/sda8       202G   59G  133G  31% /
tmpfs           5.9G  383M  5.5G   7% /dev/shm
tmpfs           5.0M  4.0K  5.0M   1% /run/lock
tmpfs           5.9G     0  5.9G   0% /sys/fs/cgroup
/dev/sda1       496M   60M  437M  12% /boot/efi
tmpfs           1.2G   20K  1.2G   1% /run/user/125
tmpfs           1.2G   80K  1.2G   1% /run/user/1000

[sauravhaloi]

I am not encountering this issue with go 1.15 or go 1.15.1

[davecheney]

Are you able to provide the source of the program you were compiling.

[sauravhaloi]

Are you able to provide the source of the program you were compiling.

Hi.. I wont be able to provide the source of the program.

[ianlancetaylor]

CC @cherrymui @thanm @jeremyfaller

[cherrymui]

I don't think the linker is changed between Go 1.15.1 and 1.15.2. Weird...

[thanm]

Especially surprising given the failure mode. Looking at

cmd/link/internal/loader.Reloc2.Sym(0x7f06bc66f241, 0xc000da2900, 0xc000073c00, 0x0, 0x4)
	/usr/local/go/src/cmd/link/internal/loader/loader.go:83 +0x22 fp=0xc000106d40 sp=0xc000106d10 pc=0x517262

that implies that Relocs.At2() returned a Reloc2 value with '*goobj2.Reloc' field set to a garbage value, which looking at the code seems impossible. Very strange.

[jeremyfaller]

@cherrymui suggested in chat that it might be corrupted object files. With full credit to her idea, if you do a clean build, does the problem persist?

[sauravhaloi]

@jeremyfaller As suggested, I did a build of my application after doing a clean up with go clean -i -r -x -cache, and the issue is resolved. I usually upgrade my Go versions without doing a cleanup of the object files, cache etc. Do you think that must have caused this? Thank you so much for your help!

[jeremyfaller]

between 1.15.1, and 1.15.2, the object files shouldn't have changed, but I'd imagine the tooling would have triggered the rebuilds that were required. That it didn't might mean you got a lucky hash collision (unlikely), there's a bug (possible) or there's something weird about your setup. Without serious investigation (likely requiring the code), I doubt we'll ever know.

I'm glad it's working now.