Re: [PATCH 7/7] DWARF: add the config option

From	Jiri Kosina <jikos@kernel.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH 7/7] DWARF: add the config option
Date	2017-05-09 20:50 +0200
Message-ID	<tFimS-5AC-13@gated-at.bofh.it> (permalink)
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On Sun, 7 May 2017, Josh Poimboeuf wrote:

> DWARF is great for debuggers.  It helps you find all the registers on 
> the stack, so you can see function arguments and local variables.  All 
> expressed in a nice compact format.
> 
> But that's overkill for unwinders.  We don't need all those registers,
> and the state machine is too complicated.  

OTOH if we make the failures in processing of those "auxiliary" 
information non-fatal (in a sense that it neither causes kernel bug nor 
does it actually corrupt the unwinding process, but the only effect is 
losing "optional" information), having this data available doesn't hurt. 

It's there anyway for builds containing debuginfo, and the information is 
all there so that it can be used by things like gdb or crash, so it seems 
natural to re-use as much as possible of it.

> Unwinders basically only need to know one thing: given an instruction 
> address and a stack pointer, where is the caller's stack frame?

Again, DWARF should be able to give us all of this (including the 
FP-fallback etc). It feels a bit silly to purposedly ignore it and 
reinvent parts of it again, instead of fixing (read: "asking toolchain 
guys to fix") the cases where we actually are not getting the proper data 
in DWARF. That's a win-win at the end of the day.

Thanks,

-- 
Jiri Kosina
SUSE Labs

Thread

[PATCH 7/7] DWARF: add the config option Jiri Slaby <jslaby@suse.cz> - 2017-05-05 14:30 +0200
  Re: [PATCH 7/7] DWARF: add the config option Linus Torvalds <torvalds@linux-foundation.org> - 2017-05-05 22:00 +0200
    Re: [PATCH 7/7] DWARF: add the config option Ingo Molnar <mingo@kernel.org> - 2017-05-06 09:30 +0200
      Re: [PATCH 7/7] DWARF: add the config option Jiri Slaby <jslaby@suse.cz> - 2017-05-10 09:50 +0200
    Re: [PATCH 7/7] DWARF: add the config option Jiri Kosina <jikos@kernel.org> - 2017-05-06 16:30 +0200
    Re: [PATCH 7/7] DWARF: add the config option Ingo Molnar <mingo@kernel.org> - 2017-05-07 23:50 +0200
      Re: [PATCH 7/7] DWARF: add the config option Josh Poimboeuf <jpoimboe@redhat.com> - 2017-05-07 23:50 +0200
        Re: [PATCH 7/7] DWARF: add the config option Vojtech Pavlik <vojtech@suse.com> - 2017-05-08 10:20 +0200
          Re: [PATCH 7/7] DWARF: add the config option Josh Poimboeuf <jpoimboe@redhat.com> - 2017-05-08 15:20 +0200
      Re: [PATCH 7/7] DWARF: add the config option hpa@zytor.com - 2017-05-08 00:10 +0200
    Re: [PATCH 7/7] DWARF: add the config option Josh Poimboeuf <jpoimboe@redhat.com> - 2017-05-07 23:50 +0200
      Re: [PATCH 7/7] DWARF: add the config option Andy Lutomirski <luto@amacapital.net> - 2017-05-08 07:40 +0200
        Re: [PATCH 7/7] DWARF: add the config option Ingo Molnar <mingo@kernel.org> - 2017-05-08 08:20 +0200
        Re: [PATCH 7/7] DWARF: add the config option Josh Poimboeuf <jpoimboe@redhat.com> - 2017-05-08 16:50 +0200
          Re: [PATCH 7/7] DWARF: add the config option hpa@zytor.com - 2017-05-08 21:10 +0200
      Re: [PATCH 7/7] DWARF: add the config option Andy Lutomirski <luto@kernel.org> - 2017-05-09 02:30 +0200
        Re: [PATCH 7/7] DWARF: add the config option Josh Poimboeuf <jpoimboe@redhat.com> - 2017-05-09 03:40 +0200
          Re: [PATCH 7/7] DWARF: add the config option Andy Lutomirski <luto@kernel.org> - 2017-05-09 04:40 +0200
            Re: [PATCH 7/7] DWARF: add the config option Josh Poimboeuf <jpoimboe@redhat.com> - 2017-05-09 05:40 +0200
              Re: [PATCH 7/7] DWARF: add the config option hpa@zytor.com - 2017-05-09 12:10 +0200
                Re: [PATCH 7/7] DWARF: add the config option Josh Poimboeuf <jpoimboe@redhat.com> - 2017-05-09 17:00 +0200
                Re: [PATCH 7/7] DWARF: add the config option "H.J. Lu" <hjl.tools@gmail.com> - 2017-05-09 18:50 +0200
                Re: [PATCH 7/7] DWARF: add the config option Jiri Slaby <jslaby@suse.cz> - 2017-05-10 10:20 +0200
                Re: [PATCH 7/7] DWARF: add the config option Josh Poimboeuf <jpoimboe@redhat.com> - 2017-05-10 15:10 +0200
                Re: [PATCH 7/7] DWARF: add the config option "H.J. Lu" <hjl.tools@gmail.com> - 2017-05-10 18:30 +0200
      Re: [PATCH 7/7] DWARF: add the config option Jiri Kosina <jikos@kernel.org> - 2017-05-09 20:50 +0200
        Re: [PATCH 7/7] DWARF: add the config option Josh Poimboeuf <jpoimboe@redhat.com> - 2017-05-09 21:30 +0200
          Re: [PATCH 7/7] DWARF: add the config option Jiri Slaby <jslaby@suse.cz> - 2017-05-10 10:40 +0200
            Re: [PATCH 7/7] DWARF: add the config option Josh Poimboeuf <jpoimboe@redhat.com> - 2017-05-10 15:20 +0200
    Re: [PATCH 7/7] DWARF: add the config option Jiri Slaby <jslaby@suse.cz> - 2017-05-10 09:50 +0200
      Re: [PATCH 7/7] DWARF: add the config option Josh Poimboeuf <jpoimboe@redhat.com> - 2017-05-10 14:50 +0200
        Re: [PATCH 7/7] DWARF: add the config option Jiri Slaby <jslaby@suse.cz> - 2017-05-10 14:50 +0200
      Re: [PATCH 7/7] DWARF: add the config option Linus Torvalds <torvalds@linux-foundation.org> - 2017-05-10 20:20 +0200

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