pkg/profile: CPU profiler crashes CGO application

[vitalyisaev2]

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

$ go version
go version go1.12.4 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/isaev/.cache/go-build"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOOS="linux"
GOPATH="/home/isaev/go"
GOPROXY=""
GORACE=""
GOROOT="/usr/local/go"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/linux_amd64"
GCCGO="gccgo"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/home/isaev/go/src/github.com/vitalyisaev2/pprof_cgo_issue/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-build766056182=/tmp/go-build -gno-record-gcc-switches"

Deps

* OS: Fedora 29
* GCC: 8.3.1
* OpenSSL: 1.1.1b

What did you do?

I have a little application that uses OpenSSL via CGO. It works good in default mode, but crashes with SIGSEGV when I enable CPU profiler (from https://github.com/pkg/profile).

$ ./pprof_cgo_issue -profiler
2019/04/30 12:14:40 profile: cpu profiling enabled, cpu.pprof
Segmentation fault (core dumped)

$ gdb ./pprof_cgo_issue /tmp/core.d685d2a145b4.pprof_cgo_issue.1556626480.20
(gdb) bt
#0  0x00007fb47640c246 in ?? () from /lib64/libgcc_s.so.1
#1  0x00007fb47640cefd in _Unwind_Backtrace () from /lib64/libgcc_s.so.1
#2  0x00000000007322bc in cgoTraceback (parg=0xc0002dd970, parg@entry=<error reading variable: value has been optimized out>) at traceback.c:82
#3  0x00000000007364e6 in x_cgo_callers (sig=27, info=0xc0002ddaf0, context=0xc0002dd9c0, cgoTraceback=<optimized out>, cgoCallers=<optimized out>, sigtramp=0x46a2f0 <runtime.sigtramp>) at gcc_traceback.c:22
#4  <signal handler called>
#5  0x00007fb476614232 in ?? () from /lib64/libcrypto.so.1.1

In order to reproduce, please follow the README from this repo with minimal working example: https://github.com/vitalyisaev2/pprof_cgo_issue

What did you expect to see?

Successful termination of application with cpu.pprof file as a result in the working dir.

What did you see instead?

Segmentation fault.

[lebovski]

The same problem:

go version
go version go1.12 linux/amd64

* OS: Fedora 29
* GCC: 8.3.1
* OpenSSL: 1.1.1b

[ianlancetaylor]

Thanks for the reproduction case. I can reproduce this on my system.

As far as I can tell the problem is that libcrypto.so.1.1 does not have correct backtrace information. Your program is importing github.com/ianlancetaylor/cgosymbolizer, which tries to do a backtrace through C code to get a better backtrace. It is that backtrace that crashes. If I comment out that import, the program succeeds.

I don't see anything that the Go project can do to fix this problem. The problem seems to lie entirely outside of the Go project, either in libcrypto.so.1.1 (as I suspect) or in the cgosymbolizer code (which I wrote but don't seriously support) or in the backtrace code (which is part of the GCC project). So I'm going to close this issue because there isn't anything we can do. Please comment if you disagree.

[vitalyisaev2]

@ianlancetaylor thank you!