From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751943AbeCEOsv (ORCPT ); Mon, 5 Mar 2018 09:48:51 -0500 Received: from mx2.suse.de ([195.135.220.15]:57050 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752003AbeCEOst (ORCPT ); Mon, 5 Mar 2018 09:48:49 -0500 Date: Mon, 5 Mar 2018 15:48:46 +0100 From: Petr Mladek To: Sergey Senozhatsky Cc: Tejun Heo , Steven Rostedt , Dave Young , Andi Kleen , Greentime Hu , Vincent Chen , Arnd Bergmann , Peter Zijlstra , Andrew Morton , Stephen Rothwell , adi-buildroot-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org, Sergey Senozhatsky Subject: Re: [PATCH] dump_stack: convert generic dump_stack into a weak symbol Message-ID: <20180305144846.3jommv372c73dltt@pathway.suse.cz> References: <20180305053742.9149-1-sergey.senozhatsky@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180305053742.9149-1-sergey.senozhatsky@gmail.com> User-Agent: NeoMutt/20170421 (1.8.2) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon 2018-03-05 14:37:42, Sergey Senozhatsky wrote: > We want to move dump_stack related functions out of printk C > code and consolidate them in lib/dump_stack file. The reason why > dump_stack_print_info()/etc ended up in printk.c was a "generic" > (dummy) lib dump_stack() function, which archs can override. > For example, blackfin and nds32, define their own EXPORT_SYMBOL > dump_stack() functions. > > In case of blackfin that arch-specific dump_stack() symbol invokes > a global dump_stack_print_info() function. So we can't easily move > dump_stack_print_info() to lib/dump_stack, because this way we will > link with lib/dump_stack.o file, which will bring in a generic > dump_stack() symbol with it, causing a multiple definitions error: > - one dump_stack() from arch/blackfin/dumpstack > - the other one from lib/dump_stack > > Convert generic dump_stack() into a weak symbol. So we will be > able link with lib/dump_stack and at the same time archs will > be able to override dump_stack(). It also opens up a way for us > to move dump_stack_set_arch_desc(), dump_stack_print_info() and > show_regs_print_info() to lib/dump_stack. > > Signed-off-by: Sergey Senozhatsky > --- > arch/blackfin/kernel/dumpstack.c | 1 - > arch/nds32/kernel/traps.c | 2 -- > lib/dump_stack.c | 4 ++-- > 3 files changed, 2 insertions(+), 5 deletions(-) > > diff --git a/arch/blackfin/kernel/dumpstack.c b/arch/blackfin/kernel/dumpstack.c > index 3c992c1f8ef2..61af017130cd 100644 > --- a/arch/blackfin/kernel/dumpstack.c > +++ b/arch/blackfin/kernel/dumpstack.c > @@ -174,4 +174,3 @@ void dump_stack(void) > show_stack(current, &stack); > trace_buffer_restore(tflags); > } > -EXPORT_SYMBOL(dump_stack); I was afraid that blackfin modules would not longer be able to use arch-specific dump_stack symbol. But it seems that only the symbol name is important. Alos the list of symbols look promissing: before: $> objdump -x vmlinux | less | grep dump_stack 00248530 l O __ksymtab 00000008 ___ksymtab_dump_stack 002500d4 l O __ksymtab_strings 0000000c ___kstrtab_dump_stack 00272bb6 l O .bss 00000080 _dump_stack_arch_desc_str 000051a8 g F .text 00000042 _dump_stack 002ab05c g F .init.text 0000002a _dump_stack_set_arch_desc 0003051c g F .text 000000a4 _dump_stack_print_info after: $> objdump -x vmlinux.patched | less | grep dump_stack 00000000 l df *ABS* 00000000 lib/dump_stack.c 0027c3e8 l O .bss 00000080 _dump_stack_arch_desc_str 00248580 l O __ksymtab 00000008 ___ksymtab_dump_stack 002653d4 l O __ksymtab_strings 0000000c ___kstrtab_dump_stack 000051a8 g F .text 00000042 _dump_stack 002b69dc g F .init.text 0000002a _dump_stack_set_arch_desc 001c2a90 g F .text 000000a4 _dump_stack_print_info I hope that I did not miss anything. I could not try this at runtime. I could just cross-compile. Anyway, from my side: Reviewed-by: Petr Mladek I'll wait a bit and push it into printk.git for-4.17. Greentime Hu, you tested this on nds32. Could I use your Tested-by, please? Best Regards, Petr