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cmd/go: make go install -buildmode=pie cmd/compile reproducible #31320

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eliasnaur opened this issue Apr 7, 2019 · 2 comments
Closed

cmd/go: make go install -buildmode=pie cmd/compile reproducible #31320

eliasnaur opened this issue Apr 7, 2019 · 2 comments
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@eliasnaur
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eliasnaur commented Apr 7, 2019 •
edited

I'm trying to run Android builders directly from the device without a host. To do that, make.bash must successfully complete. However, the Android kernel will only execute PIE executables, which means that the toolchain must be built with the equivalent of -buildmode=pie enabled all the time.

After hacking buildmode=pie, ./make.bash will complain that the bootstrap process does not converge. The root cause is that the build ids of the toolchain never converge.

To demonstrate the problem, I'm building cmd/compile with buildmode=pie on my host linux machine and comparing the build ids.

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

$ go version
go version devel +cb6646234c Fri Apr 5 20:54:50 2019 +0000 linux/amd64

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
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/elias/.cache/go-build"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOOS="linux"
GOPATH="/home/elias/go"
GOPROXY=""
GORACE=""
GOROOT="/home/elias/dev/go-tip"
GOTMPDIR=""
GOTOOLDIR="/home/elias/dev/go-tip/pkg/tool/linux_amd64"
GCCGO="gccgo"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/home/elias/dev/go-tip/src/go.mod"
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-build246738344=/tmp/go-build -gno-record-gcc-switches"

What did you do?

$ go install -buildmode=pie cmd/compile && file ../pkg/tool/linux_amd64/compile
../pkg/tool/linux_amd64/compile: ELF 64-bit LSB pie executable, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, for GNU/Linux 3.2.0, Go BuildID=p1yMqYIYR70YO68fXa_U/2AOqrHjBazbV9Pmqp2sx/mXSClqAD4HkdJo6pdJuD/f1DbS9Mtz2lCJo8Le99p, BuildID[sha1]=4bf0f9af8307f82987827bc36d9df21b954621dc, not stripped
$ go install -buildmode=pie cmd/compile && file ../pkg/tool/linux_amd64/compile
../pkg/tool/linux_amd64/compile: ELF 64-bit LSB pie executable, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, for GNU/Linux 3.2.0, Go BuildID=3JjeFa844Dxo9khAB0VA/4Cl1BAWmnJOrPX_KfkEv/mXSClqAD4HkdJo6pdJuD/TdYbWSqMM26Lmo_Gf6WL, BuildID[sha1]=68be3330ad82371c8c3823114e337ef9a3a26e03, not stripped

What did you expect to see?

The same build ids in two consecutive builds of cmd/compile.

What did you see instead?

The build ids never converge.

buildmode=pie enables external linking (#18968), but the test for reproducible Cgo builds does pass for me with PIE enabled:

$ go test -buildmode=pie -run TestCgoConsistentResults cmd/go
ok  	cmd/go	2.318s
@eliasnaur
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eliasnaur commented Apr 7, 2019 •
edited

It seems the culprit the ELF build ids. Using --build-id=none makes the build ids match:

$ CGO_LDFLAGS="-Wl,--build-id=none" go install -buildmode=pie -a cmd/compile && file ../pkg/tool/linux_amd64/compile
../pkg/tool/linux_amd64/compile: ELF 64-bit LSB pie executable, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, for GNU/Linux 3.2.0, Go BuildID=VzdcHcFht3eH3P1KPRnn/ZK6he554u3xbpIEMBilo/mXSClqAD4HkdJo6pdJuD/aM9_XXpJYAYVBAex8sXW, not stripped
$ CGO_LDFLAGS="-Wl,--build-id=none" go install -buildmode=pie -a cmd/compile && file ../pkg/tool/linux_amd64/compile
../pkg/tool/linux_amd64/compile: ELF 64-bit LSB pie executable, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, for GNU/Linux 3.2.0, Go BuildID=VzdcHcFht3eH3P1KPRnn/ZK6he554u3xbpIEMBilo/mXSClqAD4HkdJo6pdJuD/aM9_XXpJYAYVBAex8sXW, not stripped

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Change https://golang.org/cl/170942 mentions this issue: cmd/go/internal/work: make toolchain builds reproducible when buildmode=pie

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