Date: Wed, 9 Apr 2014 11:45:58 -0400 From: John Baldwin <jhb@freebsd.org> To: freebsd-arch@freebsd.org Subject: Re: Time for turning off gdb by default? Or worse... Message-ID: <201404091145.58792.jhb@freebsd.org> In-Reply-To: <DD38131E-9A43-4EFA-A27D-ED6B64F6A35A@bsdimp.com> References: <DD38131E-9A43-4EFA-A27D-ED6B64F6A35A@bsdimp.com>
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On Tuesday, April 08, 2014 4:34:35 pm Warner Losh wrote:
> Greetings,
>
> The gdb in the tree seems to be of very limited usefulness these days. It
> doesn’t seem to work on clang-enabled architectures w/o building -gdwarf-2,
> it doesn’t seem to work with threaded applications, and on some
> architectures it doesn’t seem to work at all (mips comes to mind, but it may
> have been the two binaries I tried).
>
> It seems like we’d be doing our users a favor by applying:
>
> diff -r 8bfca9de870e share/mk/bsd.own.mk
> --- a/share/mk/bsd.own.mk
> +++ b/share/mk/bsd.own.mk
> @@ -266,7 +266,6 @@ WITH_HESIOD=
> FREEBSD_UPDATE \
> GAMES \
> GCOV \
> - GDB \
> GNU \
> GNU_GREP_COMPAT \
> GPIB \
> @@ -355,6 +354,7 @@ WITH_HESIOD=
> CLANG_EXTRAS \
> CTF \
> DEBUG_FILES \
> + GDB \
> HESIOD \
> INSTALL_AS_USER \
> LLDB \
>
> to the tree, which will turn gdb off by default. It may make more sense to
> just remove it entirely, but I’m not sure I want to go there just yet in
> case there are things that I’m missing. I believe that the port will be
> adequate for all architectures we support, but haven’t tested this directly
> yet. I do know that on amd64, the port just worked, where the in-tree gdb
> was an epic fail.
kgdb is a must. I think it would be less work to forward port kgdb support
into gdb7 from ports than to keep our ancient gdb alive. Some things I can
think of for gdb7:
1) The threads patch could be greatly simplified if we fixed the ptrace
backend to properly handle inferiors with tids. This would remove a
lot of the threads patch where the thread inferior tries to invoke
ptrace directly and convert registers, etc. The way it does this now
is a total hack and requires much larger patches. This would also
make it a lot easier to get thread debugging working on more
architectures as the thread-db bits would become mostly MI (if not
entirely)
2) Porting the kgdb frontend to work with gdb7. It would be nicer to
have a more modern base for kgdb and the ability to use python
scripting with kgdb, custom printers for in-kernel structures, etc.
I think if we have a useful devel/kgdb that builds against devel/gdb we
can probably think about retiring gdb<ancient>, but it's premature right
now.
--
John Baldwin
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