From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wy0-f177.google.com ([74.125.82.177]) by canuck.infradead.org with esmtps (Exim 4.72 #1 (Red Hat Linux)) id 1Q5fZ0-0002MO-4H for linux-mtd@lists.infradead.org; Fri, 01 Apr 2011 14:43:03 +0000 Received: by wyb28 with SMTP id 28so3669935wyb.36 for ; Fri, 01 Apr 2011 07:43:00 -0700 (PDT) Subject: Re: [PATCH 0/2] do not select KALLSYMS_ALL From: Artem Bityutskiy To: Paulo Marques In-Reply-To: <4D948D52.4040708@grupopie.com> References: <1301474416-8202-1-git-send-email-dedekind1@gmail.com> <4D948D52.4040708@grupopie.com> Content-Type: text/plain; charset="UTF-8" Date: Fri, 01 Apr 2011 17:40:33 +0300 Message-ID: <1301668833.2789.90.camel@localhost> Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Cc: Randy Dunlap , MTD list , lkml Reply-To: dedekind1@gmail.com List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Thu, 2011-03-31 at 15:18 +0100, Paulo Marques wrote: > Artem Bityutskiy wrote: > > [...] > > I personally think KALLSYMS_ALL should be just merged with KALLSYMS and > > disappear - we should have only one option. CONFIG_KALLSYMS_EXTRA_PASS should > > die as well. > > That sounds a little too extreme... > > KALLSYMS is useful for most kernels, since it provides nice readable > stack dumps for panics and BUG's. > > KALLSYMS_ALL adds a lot of extra symbols that can be useful mostly to > development kernels and shouldn't be used to add unnecessary bloat to > user kernels. OK, thanks. > Now as for CONFIG_KALLSYMS_EXTRA_PASS: to build the kallsyms table, the > build process first links a kernel image with an empty kallsyms table > and use that to fetch information for all the symbols. > > It then uses that information to build the table with the right size, > and links it again. If everything goes ok, this new version as all the > symbols in the correct places and the final table can be built with the > correct addresses. > > The final linking should produce the same result as only the data on the > kallsyms table changed, but not its size. > > However, there have been bugs in the past with section alignments and > symbol reordering for symbols with the same address, etc., etc. that > make this final table not have the exact same size, and the build fails > with an inconsistent kallsyms data message. At this point, the user can > turn on the CONFIG_KALLSYMS_EXTRA_PASS and temporarily solve the problem > while the developers find the correct fix. Without this option, in this > situation the kernel would simply fail the compilation. > > All this has been stable for a while and this option hasn't been needed > recently (AFAIK), but if there is some bug in some new binutils or > something, the option might be needed again. Thanks for explanation! But... why on earth this option is in Kconfig then, if this is only about extra pass during the kernel _compilation_ ? This and the vague help message in Kconfig help section are very misleading. This should not be in Kconfig at all then, it should be purely a Makefile thing! -- Best Regards, Artem Bityutskiy (Артём Битюцкий)