runtime/race: externally link, PIE, race-enabled executable crashes on startup

[mwhudson]

Please answer these questions before submitting your issue. Thanks!

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

go version devel +91824fb Fri Apr 22 10:21:03 2016 +1200 linux/amd64

or

go version go1.6.1 linux/amd64

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

linux/amd64, 16.04 or 16.10

1. What did you do?

go run -ldflags='-linkmode=external -extldflags=-pie' -race /opt/opensource/go-test-cases/trivial.go

1. What did you expect to see?

No output.

1. What did you see instead?

==12590==ERROR: ThreadSanitizer failed to allocate 0x2698000 (40468480) bytes at address 1765924f4c680 (errno: 12)
signal: segmentation fault (core dumped)

This came to my attention because the development release of Ubuntu has enabled PIE by default on amd64 and ./all.bash fails in the "Testing race detector" step. This could be patched around by passing -no-pie to the external linker when -race is passed to the linker but that seems like a short term hack only.

[mwhudson]

cc @dvyukov @ianlancetaylor

[dvyukov]

It's a miracle that it works at all with external linking! :)

I can reproduce the issue with -pie. ThreadSanitizer shadow memory mapping is tricky. Let's do -no-pie for now.

[dvyukov]

Btw, tsan tries to map shadow at 0x1765924f4c680. Tsan shadow mapping for Go/linux is:

uptr MemToShadow(uptr x) {
  return (x * 4) | 0x200000000000ull;
}

It means that the binary is mapped at 0x555555555555. That used to be 0x7f0000000000. Whoever did that broke C++ ThreadSanitizer on Ubuntu.

[gopherbot]

CL https://golang.org/cl/22453 mentions this issue.