netdev - Re: [RFC PATCH bpf-next v2 0/4] Separate error injection table from kprobes

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Date:   Tue, 9 Jan 2018 10:17:31 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Josef Bacik <josef@...icpanda.com>
Cc:     mhiramat@...nel.org, Alexei Starovoitov <ast@...com>,
        Josef Bacik <jbacik@...com>, rostedt@...dmis.org,
        mingo@...hat.com, davem@...emloft.net, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, ast@...nel.org, kernel-team@...com,
        daniel@...earbox.net, linux-btrfs@...r.kernel.org,
        darrick.wong@...cle.com, Akinobu Mita <akinobu.mita@...il.com>
Subject: Re: [RFC PATCH bpf-next v2 0/4] Separate error injection table from
 kprobes

On Thu, 4 Jan 2018 11:07:16 -0500
Josef Bacik <josef@...icpanda.com> wrote:

> On Tue, Dec 26, 2017 at 04:46:28PM +0900, Masami Hiramatsu wrote:
> > Hi Josef and Alexei,
> > 
> > Here are the 2nd version of patches to moving error injection
> > table from kprobes. In this series I did a small fixes and
> > add function-based fault injection.
> > 
> > Here is the previous version:
> > 
> > https://lkml.org/lkml/2017/12/22/554
> > 
> > There are 2 main reasons why I separate it from kprobes.
> > 
> >  - kprobes users can modify execution path not only at 
> >    error-injection whitelist functions but also other
> >    functions. I don't like to suggest user that such
> >    limitation is from kprobes itself.
> > 
> >  - This error injection information is also useful for
> >    ftrace (function-hook) and livepatch. It should not
> >    be limited by CONFIG_KPROBES.
> > 
> > So I introduced CONFIG_FUNCTION_ERROR_INJECTION for this feature.
> > Also CONFIG_FAIL_FUNCTION is added, which provides function-based
> > error injection interface via debugfs following fault-injection
> > framework. See [4/4].
> > 
> > Any thoughts?
> 
> Sorry Masami, I've been on vacation for the last two weeks.  This approach is
> fine by me, if we want to allow other mechanisms other than bpf to use this
> functionality then hooray.  I'll do a proper review when you post v3, just
> wanted to let you know I wasn't ignoring you.  Thanks,

Yeah, thank you for the kindful notice ;)

BTW, could you tell me how I can run your test case?

When I tried to build the tests (samples/bpf) I got below error and stopped.

[mhiramat@...box bpf]$ LANG=C make 
make -C ../../ /home/mhiramat/ksrc/linux/samples/bpf/
make[1]: Entering directory '/home/mhiramat/ksrc/linux'
  CHK     include/config/kernel.release
  CHK     include/generated/uapi/linux/version.h
  CHK     include/generated/utsrelease.h
  CHK     include/generated/bounds.h
  CHK     include/generated/timeconst.h
  CHK     include/generated/asm-offsets.h
  CALL    scripts/checksyscalls.sh
  DESCEND  objtool
  CHK     scripts/mod/devicetable-offsets.h
  HOSTCC  /home/mhiramat/ksrc/linux/samples/bpf/test_lru_dist.o
/home/mhiramat/ksrc/linux/samples/bpf/test_lru_dist.c:39:8: error: redefinition of 'struct list_head'
 struct list_head {
        ^~~~~~~~~
In file included from /home/mhiramat/ksrc/linux/samples/bpf/test_lru_dist.c:9:0:
./tools/include/linux/types.h:69:8: note: originally defined here
 struct list_head {
        ^~~~~~~~~
make[2]: *** [scripts/Makefile.host:107: /home/mhiramat/ksrc/linux/samples/bpf/test_lru_dist.o] Error 1
make[1]: *** [Makefile:1675: /home/mhiramat/ksrc/linux/samples/bpf/] Error 2
make[1]: Leaving directory '/home/mhiramat/ksrc/linux'
make: *** [Makefile:204: all] Error 2


Thank you,

-- 
Masami Hiramatsu <mhiramat@...nel.org>