On Mon, Mar 11, 2019 at 6:28 PM Steven Rostedt rostedt@goodmis.org wrote:
On Mon, 11 Mar 2019 20:39:12 -0400 Joel Fernandes joel@joelfernandes.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