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

From Josh Poimboeuf <jpoimboe@redhat.com>
Newsgroups linux.kernel
Subject Re: [PATCH 7/7] DWARF: add the config option
Date 2017-05-08 16:50 +0200
Message-ID <tES93-59R-7@gated-at.bofh.it> (permalink)
References <tDKwV-1FQ-13@gated-at.bofh.it> <tDKwV-1FQ-15@gated-at.bofh.it> <tDRyp-6eu-7@gated-at.bofh.it> <tECdY-30b-3@gated-at.bofh.it> <tEJyN-80c-5@gated-at.bofh.it>
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On Sun, May 07, 2017 at 10:35:28PM -0700, Andy Lutomirski wrote:
> I think that, if the code were sufficiently robust, it would be handy
> if the unwinder displayed function arguments.  DWARF can do that to a
> limited extent.

Honestly I get the feeling that displaying function arguments wouldn't
be realistic (DWARF or no DWARF).  On x86-64, arguments are passed in
registers, so tracking down their values is a lot more involved than
just looking at the stack.

The DWARF CFI only shows you the callee-saved registers.  To figure out
the other registers you'd have to dive into the other DWARF sections and
examine previous stack frames for clues.  I think it's not a
deterministic process, based on how often I see gdb complain with
'<value optimized out>'.  I'd bet it's a lot harder than a basic stack
dump.

Also, most kernel functions rely on pointer arguments, which are pretty
much useless without dumping the contents of the structs they point to.
But then doing that properly would be a whole new level of difficulty.

-- 
Josh

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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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