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[209.132.180.67]) by mx.google.com with ESMTP id n2si17100004plp.341.2019.03.26.10.25.42; Tue, 26 Mar 2019 10:25:57 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732251AbfCZRYW (ORCPT + 99 others); Tue, 26 Mar 2019 13:24:22 -0400 Received: from monster.unsafe.ru ([5.9.28.80]:45694 "EHLO mail.unsafe.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731873AbfCZRYW (ORCPT ); Tue, 26 Mar 2019 13:24:22 -0400 Received: from Legion-PC.fortress (ip-89-102-33-211.net.upcbroadband.cz [89.102.33.211]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.unsafe.ru (Postfix) with ESMTPSA id B7E7CC61AAA; Tue, 26 Mar 2019 17:24:14 +0000 (UTC) Date: Tue, 26 Mar 2019 18:24:12 +0100 From: Alexey Gladkov To: Masahiro Yamada Cc: Michal Marek , Linux Kernel Mailing List , Linux Kbuild mailing list , linux-api@vger.kernel.org, "Kirill A . Shutemov" , Gleb Fotengauer-Malinovskiy , "Dmitry V. Levin" , Dmitry Torokhov , Rusty Russell , Jessica Yu Subject: Re: [RESEND PATCH v1] moduleparam: Save information about built-in modules in separate file Message-ID: <20190326172411.GA15936@Legion-PC.fortress> References: <20190315101013.GN8455@Legion-PC.fortress> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Mar 22, 2019 at 02:34:12PM +0900, Masahiro Yamada wrote: > Hi. > > (added some people to CC) > > > On Fri, Mar 15, 2019 at 7:10 PM Alexey Gladkov wrote: > > > > Problem: > > > > When a kernel module is compiled as a separate module, some important > > information about the kernel module is available via .modinfo section of > > the module. In contrast, when the kernel module is compiled into the > > kernel, that information is not available. > > > I might be missing something, but > vmlinux provides info of builtin modules > in /sys/module/. No. There are definitely not all modules. I have a builtin sha256_generic, but I can't find him in the /sys/module. > (Looks like currently only module_param and MODULE_VERSION) > > This patch is not exactly the same, but I see a kind of overwrap. > I'd like to be sure if we want this new scheme. The /sys/module is only for running kernel. One of my use cases is to create an initrd for a new kernel. > > > Information about built-in modules is necessary in the following cases: > > > > 1. When it is necessary to find out what additional parameters can be > > passed to the kernel at boot time. > > > Actually, /sys/module//parameters/ > exposes this information. > > Doesn't it work for your purpose? No, since creating an initrd needs to know all the modalias before I get the sysfs for new kernel. Also there are no modalias at all. > > 2. When you need to know which module names and their aliases are in > > the kernel. This is very useful for creating an initrd image. > > > > Proposal: > > > > The proposed patch does not remove .modinfo section with module > > information from the vmlinux at the build time and saves it into a > > separate file after kernel linking. So, the kernel does not increase in > > size and no additional information remains in it. Information is stored > > in the same format as in the separate modules (null-terminated string > > array). Because the .modinfo section is already exported with a separate > > modules, we are not creating a new API. > > > > It can be easily read in the userspace: > > > > $ tr '\0' '\n' < kernel.builtin.modinfo > > ext4.softdep=pre: crc32c > > ext4.license=GPL > > ext4.description=Fourth Extended Filesystem > > ext4.author=Remy Card, Stephen Tweedie, Andrew Morton, Andreas Dilger, Theodore Ts'o and others > > ext4.alias=fs-ext4 > > ext4.alias=ext3 > > ext4.alias=fs-ext3 > > ext4.alias=ext2 > > ext4.alias=fs-ext2 > > md_mod.alias=block-major-9-* > > md_mod.alias=md > > md_mod.description=MD RAID framework > > md_mod.license=GPL > > md_mod.parmtype=create_on_open:bool > > md_mod.parmtype=start_dirty_degraded:int > > ... > > > > Co-Developed-by: Gleb Fotengauer-Malinovskiy > > Signed-off-by: Gleb Fotengauer-Malinovskiy > > Signed-off-by: Alexey Gladkov > > --- > > Makefile | 1 + > > include/linux/moduleparam.h | 12 +++++------- > > scripts/link-vmlinux.sh | 8 ++++++++ > > 3 files changed, 14 insertions(+), 7 deletions(-) > > > > diff --git a/Makefile b/Makefile > > index d5713e7b1e50..971102194c92 100644 > > --- a/Makefile > > +++ b/Makefile > > @@ -1288,6 +1288,7 @@ _modinst_: > > fi > > @cp -f $(objtree)/modules.order $(MODLIB)/ > > @cp -f $(objtree)/modules.builtin $(MODLIB)/ > > + @cp -f $(objtree)/kernel.builtin.modinfo $(MODLIB)/ > > $(Q)$(MAKE) -f $(srctree)/scripts/Makefile.modinst > > > > # This depmod is only for convenience to give the initial > > diff --git a/include/linux/moduleparam.h b/include/linux/moduleparam.h > > index ba36506db4fb..5ba250d9172a 100644 > > --- a/include/linux/moduleparam.h > > +++ b/include/linux/moduleparam.h > > @@ -10,23 +10,21 @@ > > module name. */ > > #ifdef MODULE > > #define MODULE_PARAM_PREFIX /* empty */ > > +#define __MODULE_INFO_PREFIX /* empty */ > > #else > > #define MODULE_PARAM_PREFIX KBUILD_MODNAME "." > > +/* We cannot use MODULE_PARAM_PREFIX because some modules override it. */ > > +#define __MODULE_INFO_PREFIX KBUILD_MODNAME "." > > #endif > > > > /* Chosen so that structs with an unsigned long line up. */ > > #define MAX_PARAM_PREFIX_LEN (64 - sizeof(unsigned long)) > > > > -#ifdef MODULE > > #define __MODULE_INFO(tag, name, info) \ > > static const char __UNIQUE_ID(name)[] \ > > __used __attribute__((section(".modinfo"), unused, aligned(1))) \ > > - = __stringify(tag) "=" info > > -#else /* !MODULE */ > > -/* This struct is here for syntactic coherency, it is not used */ > > -#define __MODULE_INFO(tag, name, info) \ > > - struct __UNIQUE_ID(name) {} > > -#endif > > + = __MODULE_INFO_PREFIX __stringify(tag) "=" info > > + > > #define __MODULE_PARM_TYPE(name, _type) \ > > __MODULE_INFO(parmtype, name##type, #name ":" _type) > > > > diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh > > index c8cf45362bd6..399d7e4d11ec 100755 > > --- a/scripts/link-vmlinux.sh > > +++ b/scripts/link-vmlinux.sh > > @@ -258,10 +258,12 @@ if [ -n "${CONFIG_KALLSYMS}" ]; then > > > > # step 1 > > vmlinux_link "" .tmp_vmlinux1 > > + "${OBJCOPY}" -R .modinfo .tmp_vmlinux1 > > kallsyms .tmp_vmlinux1 .tmp_kallsyms1.o > > > > # step 2 > > vmlinux_link .tmp_kallsyms1.o .tmp_vmlinux2 > > + "${OBJCOPY}" -R .modinfo .tmp_vmlinux2 > > kallsyms .tmp_vmlinux2 .tmp_kallsyms2.o > > > > # step 3 > > @@ -273,6 +275,7 @@ if [ -n "${CONFIG_KALLSYMS}" ]; then > > kallsyms_vmlinux=.tmp_vmlinux3 > > > > vmlinux_link .tmp_kallsyms2.o .tmp_vmlinux3 > > + "${OBJCOPY}" -R .modinfo .tmp_vmlinux3 > > > > kallsyms .tmp_vmlinux3 .tmp_kallsyms3.o > > fi > > @@ -281,6 +284,11 @@ fi > > info LD vmlinux > > vmlinux_link "${kallsymso}" vmlinux > > > > +info MODINFO kernel.builtin.modinfo > > +"${OBJCOPY}" -j .modinfo -O binary vmlinux kernel.builtin.modinfo > > +chmod 444 kernel.builtin.modinfo > > +"${OBJCOPY}" -R .modinfo vmlinux > > + > > if [ -n "${CONFIG_BUILDTIME_EXTABLE_SORT}" ]; then > > info SORTEX vmlinux > > sortextable vmlinux > > -- > > 2.19.2 > > > > > -- > Best Regards > Masahiro Yamada > -- Rgrds, legion