Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755392Ab3JaWue (ORCPT ); Thu, 31 Oct 2013 18:50:34 -0400 Received: from caramon.arm.linux.org.uk ([78.32.30.218]:42232 "EHLO caramon.arm.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753812Ab3JaWud (ORCPT ); Thu, 31 Oct 2013 18:50:33 -0400 Date: Thu, 31 Oct 2013 22:50:22 +0000 From: Russell King - ARM Linux To: Andrew Morton Cc: Ming Lei , linux-kernel@vger.kernel.org, Rusty Russell , linux-arm-kernel@lists.infradead.org, Michal Marek Subject: Re: [PATCH] scripts/kallsyms: filter symbols not in kernel address space Message-ID: <20131031225022.GJ16735@n2100.arm.linux.org.uk> References: <1382975339-25831-1-git-send-email-tom.leiming@gmail.com> <20131031154311.e65d16d79ba540ced736413b@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20131031154311.e65d16d79ba540ced736413b@linux-foundation.org> User-Agent: Mutt/1.5.19 (2009-01-05) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2327 Lines: 52 On Thu, Oct 31, 2013 at 03:43:11PM -0700, Andrew Morton wrote: > On Mon, 28 Oct 2013 23:48:59 +0800 Ming Lei wrote: > > > This patch uses CONFIG_PAGE_OFFSET to filter symbols which > > are not in kernel address space because these symbols are > > generally for generating code purpose and can't be run at > > kernel mode, so we needn't keep them in /proc/kallsyms. > > > > For example, on ARM there are some symbols which are > > linked in relocatable code section, then perf can't parse > > symbols any more from /proc/kallsyms, and this patch fixes > > the problem. > > This is a non-back-compatible change and I'd like to see a much > stronger assurance that it is safe to merge and will not break any > existing application on the planet, please. > > For a start, please describe with great precision what these excluded > symbols are (examples would help) and explain why no application will > conceivably have had any use for them. These symbols are used to build what is relocatable code; the code which ends up being placed in the machine vectors and the following page. Rather than have to manually calculate them, I merged a patch which used the tools we have, namely the assembler and linker, to do the job for us. Unfortunately, these symbols have ended up in kallsyms, which various programs read, and having symbols down at the lower 8k is not what they expect. What it means is we don't have to play these kinds of games in the assembler: - .equ stubs_offset, __vectors_start + 0x1000 - __stubs_start __vectors_start: - W(b) vector_rst + stubs_offset - W(b) vector_und + stubs_offset - W(ldr) pc, .LCvswi + stubs_offset - W(b) vector_pabt + stubs_offset - W(b) vector_dabt + stubs_offset - W(b) vector_addrexcptn + stubs_offset - W(b) vector_irq + stubs_offset - W(b) vector_fiq + stubs_offset where each vector_* symbol is located at an address greater than __stubs_start. Here's the obvious question: can you understand what's going on with all that? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/