From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C1591C433E3 for ; Wed, 31 Mar 2021 09:04:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9EC5C619DC for ; Wed, 31 Mar 2021 09:04:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234498AbhCaJDi (ORCPT ); Wed, 31 Mar 2021 05:03:38 -0400 Received: from pegase1.c-s.fr ([93.17.236.30]:25665 "EHLO pegase1.c-s.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234424AbhCaJDT (ORCPT ); Wed, 31 Mar 2021 05:03:19 -0400 Received: from localhost (mailhub1-int [192.168.12.234]) by localhost (Postfix) with ESMTP id 4F9L2C0l3Fz9v07Q; Wed, 31 Mar 2021 11:03:15 +0200 (CEST) X-Virus-Scanned: Debian amavisd-new at c-s.fr Received: from pegase1.c-s.fr ([192.168.12.234]) by localhost (pegase1.c-s.fr [192.168.12.234]) (amavisd-new, port 10024) with ESMTP id oA7kk_XuadgY; Wed, 31 Mar 2021 11:03:14 +0200 (CEST) Received: from messagerie.si.c-s.fr (messagerie.si.c-s.fr [192.168.25.192]) by pegase1.c-s.fr (Postfix) with ESMTP id 4F9L2B5WKFz9v06x; Wed, 31 Mar 2021 11:03:14 +0200 (CEST) Received: from localhost (localhost [127.0.0.1]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 9A9AE8B7F8; Wed, 31 Mar 2021 11:03:15 +0200 (CEST) X-Virus-Scanned: amavisd-new at c-s.fr Received: from messagerie.si.c-s.fr ([127.0.0.1]) by localhost (messagerie.si.c-s.fr [127.0.0.1]) (amavisd-new, port 10023) with ESMTP id F0uHUOqvisPa; Wed, 31 Mar 2021 11:03:15 +0200 (CEST) Received: from [192.168.4.90] (unknown [192.168.4.90]) by messagerie.si.c-s.fr (Postfix) with ESMTP id BA3BD8B75B; Wed, 31 Mar 2021 11:03:14 +0200 (CEST) Subject: Re: [PATCH 1/2] powerpc/vdso: fix unnecessary rebuilds of vgettimeofday.o To: Masahiro Yamada , Michael Ellerman , Benjamin Herrenschmidt , Paul Mackerras , linuxppc-dev Cc: Ard Biesheuvel , Daniel Axtens , Greentime Hu , Michal Suchanek , Nicholas Piggin , Oliver O'Halloran , Ravi Bangoria , Linux Kernel Mailing List References: <20201223171142.707053-1-masahiroy@kernel.org> From: Christophe Leroy Message-ID: <07ee85bb-e6d6-d66e-1282-591716037625@csgroup.eu> Date: Wed, 31 Mar 2021 11:03:09 +0200 User-Agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.9.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: fr Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Le 28/01/2021 à 05:01, Masahiro Yamada a écrit : > On Thu, Dec 24, 2020 at 2:12 AM Masahiro Yamada wrote: >> >> vgettimeofday.o is unnecessarily rebuilt. Adding it to 'targets' is not >> enough to fix the issue. Kbuild is correctly rebuilding it because the >> command line is changed. >> >> PowerPC builds each vdso directory twice; first in vdso_prepare to >> generate vdso{32,64}-offsets.h, second as part of the ordinary build >> process to embed vdso{32,64}.so.dbg into the kernel. >> >> The problem shows up when CONFIG_PPC_WERROR=y due to the following line >> in arch/powerpc/Kbuild: >> >> subdir-ccflags-$(CONFIG_PPC_WERROR) := -Werror >> >> In the preparation stage, Kbuild directly visits the vdso directories, >> hence it does not inherit subdir-ccflags-y. In the second descend, >> Kbuild adds -Werror, which results in the command line flipping >> with/without -Werror. >> >> It implies a potential danger; if a more critical flag that would impact >> the resulted vdso, the offsets recorded in the headers might be different >> from real offsets in the embedded vdso images. >> >> Removing the unneeded second descend solves the problem. >> >> Link: https://lore.kernel.org/linuxppc-dev/87tuslxhry.fsf@mpe.ellerman.id.au/ >> Reported-by: Michael Ellerman >> Signed-off-by: Masahiro Yamada >> --- > > > Michael, please take a look at this. > > The unneeded rebuild problem is still remaining. Seems like with this patch, vdso32_wrapper.o is not rebuilt when vdso32.so.dbg is rebuilt. Leading to ... disasters. I'll send a patch > > >> >> arch/powerpc/kernel/Makefile | 4 ++-- >> arch/powerpc/kernel/vdso32/Makefile | 5 +---- >> arch/powerpc/kernel/{vdso32 => }/vdso32_wrapper.S | 0 >> arch/powerpc/kernel/vdso64/Makefile | 6 +----- >> arch/powerpc/kernel/{vdso64 => }/vdso64_wrapper.S | 0 >> 5 files changed, 4 insertions(+), 11 deletions(-) >> rename arch/powerpc/kernel/{vdso32 => }/vdso32_wrapper.S (100%) >> rename arch/powerpc/kernel/{vdso64 => }/vdso64_wrapper.S (100%) >> >> diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile >> index fe2ef598e2ea..79ee7750937d 100644 >> --- a/arch/powerpc/kernel/Makefile >> +++ b/arch/powerpc/kernel/Makefile >> @@ -51,7 +51,7 @@ obj-y += ptrace/ >> obj-$(CONFIG_PPC64) += setup_64.o \ >> paca.o nvram_64.o note.o syscall_64.o >> obj-$(CONFIG_COMPAT) += sys_ppc32.o signal_32.o >> -obj-$(CONFIG_VDSO32) += vdso32/ >> +obj-$(CONFIG_VDSO32) += vdso32_wrapper.o >> obj-$(CONFIG_PPC_WATCHDOG) += watchdog.o >> obj-$(CONFIG_HAVE_HW_BREAKPOINT) += hw_breakpoint.o >> obj-$(CONFIG_PPC_DAWR) += dawr.o >> @@ -60,7 +60,7 @@ obj-$(CONFIG_PPC_BOOK3S_64) += cpu_setup_power.o >> obj-$(CONFIG_PPC_BOOK3S_64) += mce.o mce_power.o >> obj-$(CONFIG_PPC_BOOK3E_64) += exceptions-64e.o idle_book3e.o >> obj-$(CONFIG_PPC_BARRIER_NOSPEC) += security.o >> -obj-$(CONFIG_PPC64) += vdso64/ >> +obj-$(CONFIG_PPC64) += vdso64_wrapper.o >> obj-$(CONFIG_ALTIVEC) += vecemu.o >> obj-$(CONFIG_PPC_BOOK3S_IDLE) += idle_book3s.o >> procfs-y := proc_powerpc.o >> diff --git a/arch/powerpc/kernel/vdso32/Makefile b/arch/powerpc/kernel/vdso32/Makefile >> index 59aa2944ecae..42fc3de89b39 100644 >> --- a/arch/powerpc/kernel/vdso32/Makefile >> +++ b/arch/powerpc/kernel/vdso32/Makefile >> @@ -30,7 +30,7 @@ CC32FLAGS += -m32 >> KBUILD_CFLAGS := $(filter-out -mcmodel=medium,$(KBUILD_CFLAGS)) >> endif >> >> -targets := $(obj-vdso32) vdso32.so.dbg >> +targets := $(obj-vdso32) vdso32.so.dbg vgettimeofday.o >> obj-vdso32 := $(addprefix $(obj)/, $(obj-vdso32)) >> >> GCOV_PROFILE := n >> @@ -46,9 +46,6 @@ obj-y += vdso32_wrapper.o >> targets += vdso32.lds >> CPPFLAGS_vdso32.lds += -P -C -Upowerpc >> >> -# Force dependency (incbin is bad) >> -$(obj)/vdso32_wrapper.o : $(obj)/vdso32.so.dbg >> - >> # link rule for the .so file, .lds has to be first >> $(obj)/vdso32.so.dbg: $(src)/vdso32.lds $(obj-vdso32) $(obj)/vgettimeofday.o FORCE >> $(call if_changed,vdso32ld_and_check) >> diff --git a/arch/powerpc/kernel/vdso32/vdso32_wrapper.S b/arch/powerpc/kernel/vdso32_wrapper.S >> similarity index 100% >> rename from arch/powerpc/kernel/vdso32/vdso32_wrapper.S >> rename to arch/powerpc/kernel/vdso32_wrapper.S >> diff --git a/arch/powerpc/kernel/vdso64/Makefile b/arch/powerpc/kernel/vdso64/Makefile >> index d365810a689a..b50b39fedf74 100644 >> --- a/arch/powerpc/kernel/vdso64/Makefile >> +++ b/arch/powerpc/kernel/vdso64/Makefile >> @@ -17,7 +17,7 @@ endif >> >> # Build rules >> >> -targets := $(obj-vdso64) vdso64.so.dbg >> +targets := $(obj-vdso64) vdso64.so.dbg vgettimeofday.o >> obj-vdso64 := $(addprefix $(obj)/, $(obj-vdso64)) >> >> GCOV_PROFILE := n >> @@ -29,15 +29,11 @@ ccflags-y := -shared -fno-common -fno-builtin -nostdlib \ >> -Wl,-soname=linux-vdso64.so.1 -Wl,--hash-style=both >> asflags-y := -D__VDSO64__ -s >> >> -obj-y += vdso64_wrapper.o >> targets += vdso64.lds >> CPPFLAGS_vdso64.lds += -P -C -U$(ARCH) >> >> $(obj)/vgettimeofday.o: %.o: %.c FORCE >> >> -# Force dependency (incbin is bad) >> -$(obj)/vdso64_wrapper.o : $(obj)/vdso64.so.dbg >> - >> # link rule for the .so file, .lds has to be first >> $(obj)/vdso64.so.dbg: $(src)/vdso64.lds $(obj-vdso64) $(obj)/vgettimeofday.o FORCE >> $(call if_changed,vdso64ld_and_check) >> diff --git a/arch/powerpc/kernel/vdso64/vdso64_wrapper.S b/arch/powerpc/kernel/vdso64_wrapper.S >> similarity index 100% >> rename from arch/powerpc/kernel/vdso64/vdso64_wrapper.S >> rename to arch/powerpc/kernel/vdso64_wrapper.S >> -- >> 2.27.0 >> > >