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Message-ID: <CAJWu+oqsD_wHGWfzj6POFowiY2qcu04auVzkA6Lu9R+LR4gkrQ@mail.gmail.com>
Date: Mon, 11 Mar 2019 18:38:49 -0700
From: Joel Fernandes <joelaf@...gle.com>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: Joel Fernandes <joel@...lfernandes.org>,
Daniel Colascione <dancol@...gle.com>,
Karim Yaghmour <karim.yaghmour@...rsys.com>,
Geert Uytterhoeven <geert@...ux-m68k.org>,
Greg KH <gregkh@...uxfoundation.org>,
LKML <linux-kernel@...r.kernel.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Alexei Starovoitov <ast@...nel.org>,
atish patra <atishp04@...il.com>,
Dan Williams <dan.j.williams@...el.com>,
Dietmar Eggemann <dietmar.eggemann@....com>,
Guenter Roeck <groeck@...omium.org>,
Jonathan Corbet <corbet@....net>,
Kees Cook <keescook@...omium.org>,
Android Kernel Team <kernel-team@...roid.com>,
"open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
"open list:KERNEL SELFTEST FRAMEWORK"
<linux-kselftest@...r.kernel.org>,
linux-trace-devel@...r.kernel.org,
Manoj Rao <linux@...ojrajarao.com>,
Masahiro Yamada <yamada.masahiro@...ionext.com>,
Masami Hiramatsu <mhiramat@...nel.org>,
Qais Yousef <qais.yousef@....com>,
Randy Dunlap <rdunlap@...radead.org>,
Shuah Khan <shuah@...nel.org>, Yonghong Song <yhs@...com>
Subject: Re: [PATCH v4 1/2] Provide in-kernel headers for making it easy to
extend the kernel
On Mon, Mar 11, 2019 at 6:28 PM Steven Rostedt <rostedt@...dmis.org> wrote:
>
> On Mon, 11 Mar 2019 20:39:12 -0400
> Joel Fernandes <joel@...lfernandes.org> wrote:
>
> > I think even though the kernel-headers can't have information about all data
> > structures, they do already contain a lot of data structure definitions we
> > need already. And anything needed can/should arguably be moved to include/ if
> > they are really needed for kernel extension by something "external" to the
> > kernel such as kernel modules or eBPF, right?
>
> That's not my worry. I would like to be able to easily walk data
> structures from within the kernel, without having to do a lot of work
> in userspace to get that information. The kprobe_events could then be
> passed type casts or such to access data fields of arguments to
> functions and such.
Ok.
> > In any case, such a solution such as what Steve suggested, still cannot do
> > what we can with headers - such as build kernel modules on the fly using the
> > C-compiler without any auto-generation of C code from any debug artifiacts.
> > Think systemtap working with the module-backend without any need for
> > linux-headers package on the file system. So such a solution would still be a
> > bit orthogonal in scope to what this proposed solution can solve IMO.
> >
>
> With the information I would like to have, it would be trivial to read
> the data to create the header files needed for modules.
But there are macros and other #define things too. We lose all of them
and can't recreate them from just DWARF (AFAIK). Including
include/generated/autoconf.h which #defines the CONFIG options. For
that we either need headers, or full kernel's sources with build
artifacts.
I do see a use case for the debug info you are talking about as you
mentioned for the kprobe_events argument list types, and I already
thought about it. But it does not seem to work for all the use cases I
am referring to here.
thanks,
- Joel
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