vsyscall mapping with remote gperftools profile causes error

[toddlipcon]

Please answer these questions before submitting your issue. Thanks!

What version of pprof are you using?

latest github (a74ae6f)

What operating system and processor architecture are you using?

Ubuntu 16 x64

What did you do?

Tried to fetch a profile from a gperftools-based profile handler:
pprof http://my-host/pprof/profile?seconds=10

This produced the following:
pprof: unexpected negative adjusted address, mapping &{7 18446744073699065856 18446744073699069952 0 [vsyscall] false false false false 0 0} source 18446744073699066188, offset 0

This seems to be an issue handling the following vsyscall mapping from /proc/self/maps:

ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0 [vsyscall]

If possible, provide a recipe for reproducing the error.
Attaching a profile you are trying to analyze is good.

Attached the profile. It works without symbolization or if I download the binary and pass it on the command line. When I try to use the remote symbolz endpoint, though, it fails as above.
broken-profile.bin.gz

[aalexand]

Tried to fetch a profile from a gperftools-based profile handler.

How can I get a simple server with such handler up and running?

[toddlipcon]

Unfortunately that's a bit easier said than done, since gperftools doesn't itself provide an HTTP server. I hit this while running against an Apache Kudu server (http://github.com/apache/kudu) but the build takes a while so may not be convenient for you.

In order to repro I wrote a quick little Python HTTP server that responds with the bad profile on any GET requests, and with some junk on any POST request (for symbols). Here's a tarball with a little Python HTTP server:
test-server.tar.gz

You can run it with 'python server.py 12345' and then reproduce the bug:

todd@todd-laptop:~/gopath/src/github.com/google/pprof$ ./pprof http://localhost:12345/
Fetching profile over HTTP from http://localhost:12345/
Local symbolization failed for kudu-tserver: stat /opt/cloudera/parcels/CDH-5.15.0-1.cdh5.15.0.p0.205/lib/kudu/sbin-release/kudu-tserver: no such file or directory
Local symbolization failed for libpthread-2.12.so: stat /lib64/libpthread-2.12.so: no such file or directory
Local symbolization failed for libc-2.12.so: stat /lib64/libc-2.12.so: no such file or directory
Local symbolization failed for libstdc++.so.6.0.13: stat /usr/lib64/libstdc++.so.6.0.13: no such file or directory
Local symbolization failed for libssl.so.1.0.1e: stat /usr/lib64/libssl.so.1.0.1e: no such file or directory
Local symbolization failed for libcrypto.so.1.0.1e: stat /usr/lib64/libcrypto.so.1.0.1e: no such file or directory
Local symbolization failed for librt-2.12.so: stat /lib64/librt-2.12.so: no such file or directory
Some binary filenames not available. Symbolization may be incomplete.
Try setting PPROF_BINARY_PATH to the search path for local binaries.
pprof: unexpected negative adjusted address, mapping &{7 18446744073699065856 18446744073699069952 0 [vsyscall]  false false false false 0 0} source 18446744073699066176, offset 0

[aalexand]

This was fixed by #368.