From mboxrd@z Thu Jan 1 00:00:00 1970 From: Masami Hiramatsu Date: Fri, 20 Jun 2014 02:13:15 +0000 Subject: Re: [RFT PATCH -next v3] [BUGFIX] kprobes: Fix "Failed to find blacklist" error on ia64 and ppc64 Message-Id: <53A398BB.2010909@hitachi.com> List-Id: References: <5387F150.5000307@hitachi.com> <20140530031838.17427.75896.stgit@ltc230.yrl.intra.hitachi.co.jp> <539161D6.7020508@hitachi.com> <1403078179.32307.7.camel@concordia> <53A15201.7060404@hitachi.com> <1403141433.4768.1.camel@concordia> <53A26C99.6060000@hitachi.com> <53A285D0.1030106@in.ibm.com> <53A2908E.2000806@hitachi.com> <53A2B136.108@in.ibm.com> <53A2C315.9030006@hitachi.com> <53A2C78D.9060708@hitachi.com> <1403224646.18509.1.camel@concordia> In-Reply-To: <1403224646.18509.1.camel@concordia> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Michael Ellerman Cc: "Suzuki K. Poulose" , Benjamin Herrenschmidt , Tony Luck , Paul Mackerras , Jeremy Fitzhardinge , linux-ia64@vger.kernel.org, sparse@chrisli.org, "H. Peter Anvin" , Thomas Gleixner , linux-tip-commits@vger.kernel.org, anil.s.keshavamurthy@intel.com, Ingo Molnar , Fenghua Yu , Arnd Bergmann , Rusty Russell , Chris Wright , yrl.pp-manager.tt@hitachi.com, akataria@vmware.com, Tony Luck , Kevin Hao , Linus Torvalds , rdunlap@infradead.org, Linux Kernel Mailing List , dl9pf@gmx.de, Andrew Morton , linuxppc-dev@lists.ozlabs.org, "David S. Miller" (2014/06/20 9:37), Michael Ellerman wrote: > On Thu, 2014-06-19 at 20:20 +0900, Masami Hiramatsu wrote: >> (2014/06/19 20:01), Masami Hiramatsu wrote: >> >>>>>>> Ah, those messages should be shown in dmesg when booting if it doesn't work, >>>>>>> because the messages are printed by initialization process of kprobe blacklist. >>>>>>> So, reproducing it is just enabling CONFIG_KPROBES and boot it. >>>>>> Well, we don't get those messages on Power, since the kallsyms has the >>>>>> entries for ".function_name". The correct way to verify is, either : >>>>> >>>>> Hmm, that seems another issue on powerpc. Is that expected(and designed) >>>>> behavior? >>>> AFAIK, yes, it is. >>>> To be more precise : >>>> >>>> we have 'foo' and '.foo' for a function foo(), where 'foo' points to the >>>> function_entry and '.foo' points to the actual function. >>> >>> Ah, I see. So if we run >>> >>> func_ptr p = foo; >>> return p = kallsyms_lookup_name(".foo"); >>> >>> it returns true. >> >> One more thing I should know, is the address of ".function_name" within the >> kernel text? In other words, does kernel_text_address() return true for that >> address? If not, it's easy to verify the address. > > Yes. That is the text address, kernel_text_address() should definitely return > true. > > On 64-bit, ABIv1, "foo" points to the function descriptor, in the ".opd" > section. > > ".foo" points to the actual text of the function, in ".text". Hmm, I misunderstood that. Anyway, we can verify it by kernel_text_address(). > > On 64-bit, ABIv2, "foo" points to the text in ".text". There are no dot > symbols. OK, in that case, kernel_text_address() check is still available. :) Thank you, -- Masami HIRAMATSU Software Platform Research Dept. Linux Technology Research Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: masami.hiramatsu.pt@hitachi.com