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cmd/dist: misc/cgo/test: incorrect pie options used for ppc64x #21954

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laboger opened this issue Sep 20, 2017 · 9 comments
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cmd/dist: misc/cgo/test: incorrect pie options used for ppc64x #21954

laboger opened this issue Sep 20, 2017 · 9 comments
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FrozenDueToAge NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one.
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Go1.10

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@laboger
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laboger commented Sep 20, 2017

What version of Go are you using (go version)?
go version go1.9 linux/ppc64le and go upstream

Does this issue reproduce with the latest release?
Yes, but the failures only happen on Unbuntu 16.04 and no other distro we've tried.

What operating system and processor architecture are you using (go env)?
Failures have only been seen on Ubuntu 16.04.
ppc64le

When building golang with ./all.bash, failures occur in some tests in misc/cgo/test with errors like this:
error while loading shared libraries: R_PPC64_ADDR16_HA re136cd776c for symbol `' out of range

After digging through cmd/dist/test.go I found that the failures occurred only when the tests were built with the external linker when passing -pie as a flag to the external linker. For example in misc/cgo/nocgo I can build the test by hand:
go test -ldflags '-linkmode=external "-extldflags=-pie"' -c
./nocgo.test
./nocgo.test: error while loading shared libraries: R_PPC64_ADDR16_HA re136cd776c for symbol `' out of range

According to the linker documentation -pie should only be used with position independent code, but for ppc64x, it is not PIC by default. Either these tests should not be built and run on ppc64x with these options, or different options should be used. It seems like -buildmode=pie is what should be used here because that will build PIC but I tried that and that resulted in different build errors which I haven't investigated yet.
@ianlancetaylor ianlancetaylor changed the title misc/cgo/test: incorrect pie options used for ppc64x cmd/dist: misc/cgo/test: incorrect pie options used for ppc64x Sep 20, 2017
@ianlancetaylor
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Why would the failures only occur on Ubuntu? Is there some difference in the default system linker?

@ianlancetaylor ianlancetaylor added this to the Go1.10 milestone Sep 20, 2017
@ianlancetaylor ianlancetaylor added the NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. label Sep 20, 2017
@ianlancetaylor
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In any case I agree that this test seems a bit dubious and that it should probably be using -buildmode=pie (which did not exist when the test was added).

@ianlancetaylor
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(The -pie tests were added in https://golang.org/cl/6280).

@laboger
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laboger commented Sep 21, 2017

If I try to build these tests with -buildmode=pie it does build the test and it says it passes but I get this warning. Not sure if it matters:

searching for runtime.a in $WORK/_/home/boger/golang/go1.9/go/misc/cgo/nocgo/test/runtime.a
searching for runtime.a in $WORK/runtime.a
searching for runtime/cgo.a in $WORK//home/boger/golang/go1.9/go/misc/cgo/nocgo/_test/runtime/cgo.a
searching for runtime/cgo.a in $WORK/runtime/cgo.a
searching for runtime/cgo.a in /home/boger/golang/go1.9/go/pkg/linux_ppc64le_shared/runtime/cgo.a
warning: unable to find runtime/cgo.a

My toolchain doesn't have a pkg/linux_ppc64le_shared directory and I'm not sure what causes it to get built. I went looking for that directory on various systems and golang builds I've done and see that it is there sometimes but not others and I'm not aware of what I might have done to cause it to be created and populated.

@laboger
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laboger commented Sep 21, 2017

I don't know why this failure only happens on Ubuntu 16.04. I built on a 17.04 as well as earlier Ubuntu versions, and some RHEL 7.x systems and they all worked. 16.04 has 2.26.1, 17.04 has 2.28. I believe the message comes from the dynamic linker at runtime so maybe the glibc version is a factor. Once I noticed that the testscase is not using valid linker options for ppc64le, I no longer thought it was important why it failed, especially since it did not seem easy for me to figure that out.

@gopherbot
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Change https://golang.org/cl/66870 mentions this issue: cmd/dist,misg/cgo/test: fix pie options for tests on ppc64x

@mkumatag
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mkumatag commented Oct 4, 2017

with latest code, following tests are passed:

##### ../misc/cgo/test
PASS
ok  	_/root/workspace/test-golang-upstream/go/misc/cgo/test	1.706s
PASS
ok  	_/root/workspace/test-golang-upstream/go/misc/cgo/test	1.731s
PASS
ok  	_/root/workspace/test-golang-upstream/go/misc/cgo/testtls	0.003s
PASS
ok  	_/root/workspace/test-golang-upstream/go/misc/cgo/testtls	0.003s
PASS
ok  	_/root/workspace/test-golang-upstream/go/misc/cgo/test	1.692s
PASS
ok  	_/root/workspace/test-golang-upstream/go/misc/cgo/testtls	0.004s
PASS
ok  	_/root/workspace/test-golang-upstream/go/misc/cgo/nocgo	0.006s

#####

But breaking later in the code:

##### ../misc/cgo/testcarchive
--- FAIL: TestCompileWithoutShared (1.26s)
	carchive_test.go:600: [go build -buildmode=c-archive -gcflags=-shared=false -o libgo2.a libgo2]
	carchive_test.go:602: 
	carchive_test.go:609: [gcc -fPIC -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build472192193=/tmp/go-build -gno-record-gcc-switches -I pkg/linux_ppc64le_shared -o ./testnoshared main5.c libgo2.a]
	carchive_test.go:611: 
	carchive_test.go:618: [./testnoshared 3]
	carchive_test.go:620: ./testnoshared: error while loading shared libraries: R_PPC64_ADDR16_HA re1028a6ca8 for symbol `' out of range
	carchive_test.go:361: got exit status 127; expected signal broken pipe
FAIL

@mkumatag
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mkumatag commented Oct 4, 2017

created #22126 to track above issue.

@laboger laboger mentioned this issue Oct 27, 2017
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@gopherbot
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Change https://golang.org/cl/73970 mentions this issue: runtime: use -buildmode=pie in testCgoPprofPIE instead of -extldflags=-pie

gopherbot pushed a commit that referenced this issue Oct 30, 2017
@laboger
runtime: use -buildmode=pie in testCgoPprofPIE instead of -extldflags…
58de9f3 
…=-pie

Errors occur in runtime test testCgoPprofPIE when the test
is built by passing -pie to the external linker with code
that was not built as PIC. This occurs on ppc64le because
non-PIC is the default, and fails only on newer distros
where the address range used for programs is high enough
to cause relocation overflow. This test should be built
with -buildmode=pie since that correctly generates PIC
with -pie.

Related issues are #21954 and #22126.

Updates #22459

Change-Id: Ib641440bc9f94ad2b97efcda14a4b482647be8f7
Reviewed-on: https://go-review.googlesource.com/73970
Run-TryBot: Lynn Boger <laboger@linux.vnet.ibm.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
@laboger laboger mentioned this issue Sep 5, 2018
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@golang golang locked and limited conversation to collaborators Oct 27, 2018
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