Re: [RESEND PATCH 0/5] perf core: Support overwrite ring buffer

Ingo Molnar
2016-03-08T16:44:53Z

* Dmitry Vyukov <dvyukov@google.com> wrote:

> On Tue, Mar 8, 2016 at 5:27 PM, Ingo Molnar <mingo@kernel.org> wrote:
> >
> > * Dmitry Vyukov <dvyukov@google.com> wrote:
> >
> >> On Tue, Mar 8, 2016 at 4:54 PM, Ingo Molnar <mingo@kernel.org> wrote:
> >> >
> >> > * Dmitry Vyukov <dvyukov@google.com> wrote:
> >> >
> >> >> > so, according to the error message it wants a writable directory. Lets try it that
> >> >> > way:
> >> >> >
> >> >> > triton:~> mkdir go
> >> >> > triton:~>
> >> >> > triton:~> export GOPATH=/home/mingo/go/
> >> >> > triton:~> go get github.com/google/syzkaller
> >> >> > can't load package: package github.com/google/syzkaller: no buildable Go source files in /home/mingo/go/src/github.com/google/syzkaller
> >> >>
> >> >> Yes, GOPATH needs to be set a writable dir.
> >> >> You can ignore "can't load package" error. The goal of that step is
> >> >> checkout syzkaller with all dependencies into correct dirs under
> >> >> GOPATH. That's already done by now.
> >> >> Or you can do (/... at the end):
> >> >> $ go get github.com/google/syzkaller/...
> >> >> That will checkout and build.
> >> >> Either way you can continue with the make step.
> >> >
> >> > Cool, the '/...' trick works.
> >> >
> >> >
> >> >> > looks like someone wants 'Go' to be used as little as possible! ;-)
> >> >>
> >> >> You probably did not observe recently a noobie trying to build a C
> >> >> project with sufficiently-complicate-build-system and a bunch of
> >> >> dependencies that needs to be on specific, unknown revisions, and that
> >> >> still does not compile with you compiler and does not link with your
> >> >> linker, and then of course target machine has a wrong glibc version :)
> >> >
> >> > Nah, old Linux tools very much suck, we know that and we suffer from it.
> >> >
> >> > But new tools should not suck! :-)
> >> >
> >> > So, going from the description at:
> >> >
> >> > http://lkml.kernel.org/r/CACT4Y+Ym0TZLkmRrM0ZGgLpu8kqS-YjoWTMrvaLz=tx2tnyO3w@mail.gmail.com
> >> >
> >> > I now have it built, and created $GOPATH/src/github.com/google/syzkaller/perf.cfg
> >> > with:
> >> >
> >> >
> >> > triton:~/go/src/github.com/google/syzkaller> cat perf.cfg
> >> > {
> >> > "http": "localhost:50000",
> >> > "workdir": "/home/mingo/go/src/github.com/google/syzkaller/workdir",
> >> > "syzkaller": "/home/mingo/go/src/github.com/google/syzkaller",
> >> > "vmlinux": "-",
> >> > "type": "local",
> >> > "count": 1,
> >> > "procs": 16,
> >> > "nocover": true,
> >> > "nodropprivs": true,
> >> > "enable_syscalls": [
> >> > "getpid",
> >> > "perf_event_open",
> >> > "ioctl$PERF*",
> >> > "prctl$void",
> >> > "bpf$*",
> >> > "sched_yield"
> >> > ]
> >> > }
> >> >
> >> > Then I tried to do:
> >> >
> >> > $ bin/syz-manager -config perf.cfg
> >> >
> >> > in ~/go/src/github.com/google/syzkaller, but that doesn't work because there's no
> >> > 'bin' directory:
> >> >
> >> > triton:~/go/src/github.com/google/syzkaller> bin/syz-manager -config perf.cfg
> >> > bash: bin/syz-manager: No such file or directory
> >> >
> >> > So that should really read something like:
> >> >
> >> > cd ~/go
> >> > bin/syz-manager -config src/github.com/google/syzkaller/perf.cfg
> >> >
> >> > next roadblock:
> >> >
> >> > fomalhaut:~/go> bin/syz-manager -config src/github.com/google/syzkaller/perf.cfg
> >> > 2016/03/08 16:53:44 bad config syzkaller param: can't find bin/syz-fuzzer
> >> >
> >> > so how do I proceed from here?
> >>
> >>
> >> You need to call make in syzkaller dir, it will create
> >> syzkaller/bin/syz-manager. I.e.
> >>
> >> $ cd /home/mingo/go/src/github.com/google/syzkaller
> >> $ make
> >
> > Ok, cool, this got me further.
> >
> >> $ bin/syz-manager -config perf.cfg
> >
> > I now get periodic output of:
> >
> > fomalhaut:~/go/src/github.com/google/syzkaller> bin/syz-manager -config src/github.com/google/syzkaller/perf.cfg
> > 2016/03/08 17:24:07 failed to read config file: open src/github.com/google/syzkaller/perf.cfg: no such file or directory
> > fomalhaut:~/go/src/github.com/google/syzkaller> bin/syz-manager -config perf.cfg
> > 2016/03/08 17:24:19 loading corpus...
> > 2016/03/08 17:24:19 loaded 0 programs
> > 2016/03/08 17:24:19 serving http on http://localhost:50000
> > 2016/03/08 17:24:19 serving rpc on tcp://127.0.0.1:37006
> > 2016/03/08 17:24:34 local-0: saving crash 'BUG: /sys/kernel/debug/kcov is missing (permission denied). Enable CONFIG_KCOV and mount debugfs.' to crash-local-0-1457454274467286949
> > 2016/03/08 17:24:34 local-0: lost connection: exit status 1
> > 2016/03/08 17:24:34 local-0: saving crash 'lost connection' to crash-local-0-1457454274467603509
> > 2016/03/08 17:24:49 local-0: saving crash 'BUG: /sys/kernel/debug/kcov is missing (permission denied). Enable CONFIG_KCOV and mount debugfs.' to crash-local-0-1457454289719432704
> > 2016/03/08 17:24:49 local-0: lost connection: exit status 1
> > 2016/03/08 17:24:49 local-0: saving crash 'lost connection' to crash-local-0-1457454289719774031
> > 2016/03/08 17:25:04 local-0: saving crash 'BUG: /sys/kernel/debug/kcov is missing (permission denied). Enable CONFIG_KCOV and mount debugfs.' to crash-local-0-1457454304992856310
> > 2016/03/08 17:25:04 local-0: lost connection: exit status 1
> > 2016/03/08 17:25:04 local-0: saving crash 'lost connection' to crash-local-0-1457454304993224299
> > 2016/03/08 17:25:20 local-0: saving crash 'BUG: /sys/kernel/debug/kcov is missing (permission denied). Enable CONFIG_KCOV and mount debugfs.' to crash-local-0-1457454320280216980
> > 2016/03/08 17:25:20 local-0: lost connection: exit status 1
> > 2016/03/08 17:25:20 local-0: saving crash 'lost connection' to crash-local-0-1457454320280581459
> > 2016/03/08 17:25:35 local-0: saving crash 'BUG: /sys/kernel/debug/kcov is missing (permission denied). Enable CONFIG_KCOV and mount debugfs.' to crash-local-0-1457454335572633035
> > 2016/03/08 17:25:35 local-0: lost connection: exit status 1
> > 2016/03/08 17:25:35 local-0: saving crash 'lost connection' to crash-local-0-1457454335572967343
> > 2016/03/08 17:25:50 local-0: saving crash 'BUG: /sys/kernel/debug/kcov is missing (permission denied). Enable CONFIG_KCOV and mount debugfs.' to crash-local-0-1457454350865099485
> > 2016/03/08 17:25:50 local-0: lost connection: exit status 1
> > 2016/03/08 17:25:50 local-0: saving crash 'lost connection' to crash-local-0-1457454350865429049
> >
> > is CONFIG_KCOV=y a must-have feature? There's no KCOV support upstream that I can
> > see.
>
> Change:
> "nocover": true,
> to:
> "cover": false,
> in the config file.
>
> KCOV will increase efficiency of the fuzzer, but it is not necessary.
> As far as I understand Peter tested without KCOV.

Ok, so now I get:

fomalhaut:~/go/src/github.com/google/syzkaller> bin/syz-manager -config perf.cfg
2016/03/08 17:39:25 loading corpus...
2016/03/08 17:39:25 loaded 0 programs
2016/03/08 17:39:25 serving http on http://localhost:50000
2016/03/08 17:39:25 serving rpc on tcp://127.0.0.1:33809

| |-sshd(49552)---sshd(49555)---bash(49562)---syz-manager(49652)-+-syz-fuzzer(49661)-+-syz-executor(49935)
| | | |-syz-executor(49936)
| | | |-syz-executor(49937)
| | | |-syz-executor(49938)
| | | |-syz-executor(49939)
| | | |-syz-executor(49940)
| | | |-syz-executor(49941)
| | | |-syz-executor(49942)
| | | |-syz-executor(49943)
| | | |-syz-executor(49944)
| | | |-syz-executor(49945)
| | | |-syz-executor(49946)
| | | |-syz-executor(49947)
| | | |-syz-executor(49948)
| | | |-syz-executor(49949)
| | | |-syz-executor(49950)
| | | |-{syz-fuzzer}(49662)
| | | |-{syz-fuzzer}(49663)
| | | |-{syz-fuzzer}(49664)
| | | |-{syz-fuzzer}(49665)
| | | |-{syz-fuzzer}(49666)
| | | |-{syz-fuzzer}(49688)
| | | |-{syz-fuzzer}(49689)
| | | |-{syz-fuzzer}(49690)
| | | |-{syz-fuzzer}(49691)
| | | |-{syz-fuzzer}(49692)
| | | |-{syz-fuzzer}(49693)
| | | |-{syz-fuzzer}(49694)
| | | |-{syz-fuzzer}(49695)
| | | |-{syz-fuzzer}(49696)
| | | |-{syz-fuzzer}(49697)
| | | |-{syz-fuzzer}(49698)
| | | |-{syz-fuzzer}(49699)
| | | |-{syz-fuzzer}(49700)
| | | |-{syz-fuzzer}(49701)
| | | |-{syz-fuzzer}(49704)
| | | |-{syz-fuzzer}(49705)
| | | |-{syz-fuzzer}(49706)
| | | |-{syz-fuzzer}(49710)
| | | |-{syz-fuzzer}(49711)
| | | |-{syz-fuzzer}(49737)
| | | |-{syz-fuzzer}(49739)
| | | |-{syz-fuzzer}(49762)
| | | |-{syz-fuzzer}(49764)
| | | |-{syz-fuzzer}(49787)
| | | |-{syz-fuzzer}(49789)
| | | |-{syz-fuzzer}(49802)
| | | |-{syz-fuzzer}(49803)
| | | |-{syz-fuzzer}(49804)
| | | |-{syz-fuzzer}(49818)
| | | |-{syz-fuzzer}(49822)
| | | |-{syz-fuzzer}(49846)
| | | |-{syz-fuzzer}(49847)
| | | |-{syz-fuzzer}(49848)
| | | |-{syz-fuzzer}(49849)
| | | |-{syz-fuzzer}(49850)
| | | |-{syz-fuzzer}(49851)
| | | |-{syz-fuzzer}(49852)
| | | |-{syz-fuzzer}(49893)
| | | |-{syz-fuzzer}(49894)
| | | |-{syz-fuzzer}(49895)
| | | |-{syz-fuzzer}(49896)
| | | |-{syz-fuzzer}(49933)
| | | `-{syz-fuzzer}(49934)
| | |-{syz-manager}(49653)
| | |-{syz-manager}(49654)
| | |-{syz-manager}(49655)
| | |-{syz-manager}(49656)
| | |-{syz-manager}(49657)
| | |-{syz-manager}(49658)
| | |-{syz-manager}(49659)
| | |-{syz-manager}(49667)
| | |-{syz-manager}(49668)
| | |-{syz-manager}(49669)
| | |-{syz-manager}(49670)
| | |-{syz-manager}(49671)
| | |-{syz-manager}(49672)
| | |-{syz-manager}(49673)
| | |-{syz-manager}(49674)
| | |-{syz-manager}(49675)
| | |-{syz-manager}(49676)
| | |-{syz-manager}(49677)
| | |-{syz-manager}(49678)
| | |-{syz-manager}(49679)
| | |-{syz-manager}(49680)
| | |-{syz-manager}(49681)
| | |-{syz-manager}(49682)
| | |-{syz-manager}(49683)
| | |-{syz-manager}(49684)
| | |-{syz-manager}(49685)
| | |-{syz-manager}(49686)
| | |-{syz-manager}(49687)
| | |-{syz-manager}(49913)
| | `-{syz-manager}(49914)

I'm seeing some zombies:

49935 pts/2 Z+ 0:00 [syz-executor] <defunct>
49936 pts/2 Z+ 0:00 [syz-executor] <defunct>
49937 pts/2 Z+ 0:00 [syz-executor] <defunct>
49938 pts/2 Z+ 0:00 [syz-executor] <defunct>
49939 pts/2 Z+ 0:00 [syz-executor] <defunct>
49940 pts/2 Z+ 0:00 [syz-executor] <defunct>
49941 pts/2 Z+ 0:00 [syz-executor] <defunct>
49942 pts/2 Z+ 0:00 [syz-executor] <defunct>
49943 pts/2 Z+ 0:00 [syz-executor] <defunct>
49944 pts/2 Z+ 0:00 [syz-executor] <defunct>
49945 pts/2 Z+ 0:00 [syz-executor] <defunct>
49946 pts/2 Z+ 0:00 [syz-executor] <defunct>
49947 pts/2 Z+ 0:00 [syz-executor] <defunct>
49948 pts/2 Z+ 0:00 [syz-executor] <defunct>
49949 pts/2 Z+ 0:00 [syz-executor] <defunct>
49950 pts/2 Z+ 0:00 [syz-executor] <defun

does it mean it found a kernel bug already?

It only had a couple of seconds of runtime:

49652 mingo 20 0 1434276 52144 11344 S 0.0 0.0 0:00.54 syz-manager
49661 mingo 20 0 2196672 43948 10448 S 0.0 0.0 0:05.59 syz-fuzzer

Thanks,

Ingo