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=-12.0 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 69CA2C433FF for ; Wed, 31 Jul 2019 03:36:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 30DAB2067D for ; Wed, 31 Jul 2019 03:36:54 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=nifty.com header.i=@nifty.com header.b="FJ3tbwUl" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727318AbfGaDgx (ORCPT ); Tue, 30 Jul 2019 23:36:53 -0400 Received: from conssluserg-03.nifty.com ([210.131.2.82]:50617 "EHLO conssluserg-03.nifty.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726645AbfGaDgx (ORCPT ); Tue, 30 Jul 2019 23:36:53 -0400 Received: from mail-ua1-f42.google.com (mail-ua1-f42.google.com [209.85.222.42]) (authenticated) by conssluserg-03.nifty.com with ESMTP id x6V3agnq023839; Wed, 31 Jul 2019 12:36:45 +0900 DKIM-Filter: OpenDKIM Filter v2.10.3 conssluserg-03.nifty.com x6V3agnq023839 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nifty.com; s=dec2015msa; t=1564544205; bh=ZWUXlJ6vCyDfxDsdJIqtKViAIw2UA65PS88eID+Zq5s=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=FJ3tbwUl7HgSgYGVuOcJoaNhC8Sposhetgk7+SQRefX9gJUOi6alyn/NUSDT9YvEg 7YLfnIfWkY64gXlES2Qpsj8T05VpxIMdCU8rj9sR16fS81pg14UmqpkkyxSQjzMklK GkKyTNv2I7Rmgs7kINCt6DlUaRt5E4EMV0M61J1irriKgvHg/yJJ+BKuqDEwJGhfI/ 4JUUNhvgQsiYPLTPGN9kQLrXiWee3QBshV22B5ruUPSNww7hqPAi7v3ZEsqbB98NUe Nf48qAQpfzjWWaV/iRRNhWOVj7ZaRUJbxZOWdkSssMQqd2rOHM+HvEHXomyq39AkXz 6PPr7IhkmLRPQ== X-Nifty-SrcIP: [209.85.222.42] Received: by mail-ua1-f42.google.com with SMTP id a97so26368983uaa.9; Tue, 30 Jul 2019 20:36:45 -0700 (PDT) X-Gm-Message-State: APjAAAVUYgZ+ExF0l0g0H/G9diiiEDchVqg2QI3hVjxzUBg0tMVk81us sjkZzweio2rSApGthe0Pqf9w9vYZLrSff6r5gpI= X-Google-Smtp-Source: APXvYqz6s/L4vEIgOO2gnaVIIJ8dt0VbYEcQqKM0Wi8oUweR8OASjZl3ArznIJxx3/aQwf0xeNqQaVdKGtWMddWarxo= X-Received: by 2002:ab0:5ea6:: with SMTP id y38mr76076029uag.40.1564544202169; Tue, 30 Jul 2019 20:36:42 -0700 (PDT) MIME-Version: 1.0 References: <20190509143859.9050-1-joe.lawrence@redhat.com> <20190509143859.9050-4-joe.lawrence@redhat.com> In-Reply-To: From: Masahiro Yamada Date: Wed, 31 Jul 2019 12:36:05 +0900 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v4 03/10] livepatch: Add klp-convert tool To: Joe Lawrence Cc: Linux Kernel Mailing List , live-patching@vger.kernel.org, Linux Kbuild mailing list Content-Type: text/plain; charset="UTF-8" Sender: live-patching-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: live-patching@vger.kernel.org On Wed, Jul 31, 2019 at 11:50 AM Masahiro Yamada wrote: > > On Thu, May 9, 2019 at 11:39 PM Joe Lawrence wrote: > > > > From: Josh Poimboeuf > > > > Livepatches may use symbols which are not contained in its own scope, > > and, because of that, may end up compiled with relocations that will > > only be resolved during module load. Yet, when the referenced symbols > > are not exported, solving this relocation requires information on the > > object that holds the symbol (either vmlinux or modules) and its > > position inside the object, as an object may contain multiple symbols > > with the same name. Providing such information must be done > > accordingly to what is specified in > > Documentation/livepatch/module-elf-format.txt. > > > > Currently, there is no trivial way to embed the required information > > as requested in the final livepatch elf object. klp-convert solves > > this problem in two different forms: (i) by relying on Symbols.list, > > which is built during kernel compilation, to automatically infer the > > relocation targeted symbol, and, when such inference is not possible > > (ii) by using annotations in the elf object to convert the relocation > > accordingly to the specification, enabling it to be handled by the > > livepatch loader. > > > > Given the above, create scripts/livepatch to hold tools developed for > > livepatches and add source files for klp-convert there. > > > > The core file of klp-convert is scripts/livepatch/klp-convert.c, which > > implements the heuristics used to solve the relocations and the > > conversion of unresolved symbols into the expected format, as defined > > in [1]. > > > > klp-convert receives as arguments the Symbols.list file, an input > > livepatch module to be converted and the output name for the converted > > livepatch. When it starts running, klp-convert parses Symbols.list and > > builds two internal lists of symbols, one containing the exported and > > another containing the non-exported symbols. Then, by parsing the rela > > sections in the elf object, klp-convert identifies which symbols must > > be converted, which are those unresolved and that do not have a > > corresponding exported symbol, and attempts to convert them > > accordingly to the specification. > > > > By using Symbols.list, klp-convert identifies which symbols have names > > that only appear in a single kernel object, thus being capable of > > resolving these cases without the intervention of the developer. When > > various homonymous symbols exist through kernel objects, it is not > > possible to infer the right one, thus klp-convert falls back into > > using developer annotations. If these were not provided, then the tool > > will print a list with all acceptable targets for the symbol being > > processed. > > > > Annotations in the context of klp-convert are accessible as struct > > klp_module_reloc entries in sections named > > .klp.module_relocs.. These entries are pairs of symbol > > references and positions which are to be resolved against definitions > > in . > > > > Define the structure klp_module_reloc in > > include/linux/uapi/livepatch.h allowing developers to annotate the > > livepatch source code with it. > > > > klp-convert relies on libelf and on a list implementation. Add files > > scripts/livepatch/elf.c and scripts/livepatch/elf.h, which are a > > libelf interfacing layer and scripts/livepatch/list.h, which is a > > list implementation. > > > > Update Makefiles to correctly support the compilation of the new tool, > > update MAINTAINERS file and add a .gitignore file. > > > > [1] - Documentation/livepatch/module-elf-format.txt > > > > Signed-off-by: Josh Poimboeuf > > Signed-off-by: Konstantin Khlebnikov > > Signed-off-by: Joao Moreira > > Signed-off-by: Joe Lawrence > > --- > > MAINTAINERS | 1 + > > include/uapi/linux/livepatch.h | 5 + > > scripts/Makefile | 1 + > > scripts/livepatch/.gitignore | 1 + > > scripts/livepatch/Makefile | 7 + > > scripts/livepatch/elf.c | 753 ++++++++++++++++++++++++++++++++ > > scripts/livepatch/elf.h | 73 ++++ > > scripts/livepatch/klp-convert.c | 713 ++++++++++++++++++++++++++++++ > > scripts/livepatch/klp-convert.h | 39 ++ > > scripts/livepatch/list.h | 391 +++++++++++++++++ > > 10 files changed, 1984 insertions(+) > > create mode 100644 scripts/livepatch/.gitignore > > create mode 100644 scripts/livepatch/Makefile > > create mode 100644 scripts/livepatch/elf.c > > create mode 100644 scripts/livepatch/elf.h > > create mode 100644 scripts/livepatch/klp-convert.c > > create mode 100644 scripts/livepatch/klp-convert.h > > create mode 100644 scripts/livepatch/list.h > > > > diff --git a/MAINTAINERS b/MAINTAINERS > > index 52842fa37261..c1587e1cc385 100644 > > --- a/MAINTAINERS > > +++ b/MAINTAINERS > > @@ -9022,6 +9022,7 @@ F: arch/x86/kernel/livepatch.c > > F: Documentation/livepatch/ > > F: Documentation/ABI/testing/sysfs-kernel-livepatch > > F: samples/livepatch/ > > +F: scripts/livepatch/ > > F: tools/testing/selftests/livepatch/ > > L: live-patching@vger.kernel.org > > T: git git://git.kernel.org/pub/scm/linux/kernel/git/livepatching/livepatching.git > > diff --git a/include/uapi/linux/livepatch.h b/include/uapi/linux/livepatch.h > > index e19430918a07..1c364d42d38e 100644 > > --- a/include/uapi/linux/livepatch.h > > +++ b/include/uapi/linux/livepatch.h > > @@ -12,4 +12,9 @@ > > #define KLP_RELA_PREFIX ".klp.rela." > > #define KLP_SYM_PREFIX ".klp.sym." > > > > +struct klp_module_reloc { > > + void *sym; > > + unsigned int sympos; > > +} __attribute__((packed)); > > + > > #endif /* _UAPI_LIVEPATCH_H */ > > diff --git a/scripts/Makefile b/scripts/Makefile > > index 9d442ee050bd..bf9ce74b70b0 100644 > > --- a/scripts/Makefile > > +++ b/scripts/Makefile > > @@ -39,6 +39,7 @@ build_unifdef: $(obj)/unifdef > > subdir-$(CONFIG_GCC_PLUGINS) += gcc-plugins > > subdir-$(CONFIG_MODVERSIONS) += genksyms > > subdir-$(CONFIG_SECURITY_SELINUX) += selinux > > +subdir-$(CONFIG_LIVEPATCH) += livepatch > > > > # Let clean descend into subdirs > > subdir- += basic dtc gdb kconfig mod package > > diff --git a/scripts/livepatch/.gitignore b/scripts/livepatch/.gitignore > > new file mode 100644 > > index 000000000000..dc22fe4b6a5b > > --- /dev/null > > +++ b/scripts/livepatch/.gitignore > > @@ -0,0 +1 @@ > > +klp-convert > > diff --git a/scripts/livepatch/Makefile b/scripts/livepatch/Makefile > > new file mode 100644 > > index 000000000000..2842ecdba3fd > > --- /dev/null > > +++ b/scripts/livepatch/Makefile > > @@ -0,0 +1,7 @@ > > +hostprogs-y := klp-convert > > +always := $(hostprogs-y) > > + > > +klp-convert-objs := klp-convert.o elf.o > > + > > +HOST_EXTRACFLAGS := -g -I$(INSTALL_HDR_PATH)/include -Wall > > This looks strange. > > Theoretically, you cannot include headers in $(INSTALL_HDR_PATH)/include > from host programs. > > headers_install works for the target architecture, not host architecture. > This may cause a strange result when you are cross-compiling the kernel. > > BTW, which header in $(INSTALL_HDR_PATH)/include do you need to include ? > > > Also, -Wall is redundant because it is set by the top-level Makefile. I deleted HOST_EXTRACFLAGS entirely, and I was still able to build klp-convert. What is the purpose of '-g' ? If it is only needed for local debugging, it should be removed from the upstream code, in my opinion. -- Best Regards Masahiro Yamada