linux-kernel - Re: [PATCH v2] modpost: compile constant module information only once

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [day] [month] [year] [list]
Message-ID: <CAK7LNATrtMzf4UG_kKL7c0E2=q8_Yh6j61-2F-f4VH0y9+vjug@mail.gmail.com>
Date: Tue, 3 Sep 2024 23:04:28 +0900
From: Masahiro Yamada <masahiroy@...nel.org>
To: Thomas Weißschuh <linux@...ssschuh.net>
Cc: Nathan Chancellor <nathan@...nel.org>, Nicolas Schier <nicolas@...sle.eu>, 
	Luis Chamberlain <mcgrof@...nel.org>, linux-kernel@...r.kernel.org, 
	linux-kbuild@...r.kernel.org, linux-modules@...r.kernel.org
Subject: Re: [PATCH v2] modpost: compile constant module information only once

On Mon, Sep 2, 2024 at 2:56 AM Thomas Weißschuh <linux@...ssschuh.net> wrote:
>
> Various information about modules is compiled into the info sections.
> For that a dedicated .mod.c file is generated by modpost for each module
> and then linked into the module.
> However most of the information in the .mod.c is the same for all
> modules, internal and external.
> Split the shared information into a dedicated source file that is
> compiled once and then linked into all modules.
>
> This avoids frequent rebuilds for all .mod.c files when using
> CONFIG_LOCALVERSION_AUTO because the local version ends up in .mod.c
> through UTS_RELEASE and VERMAGIC_STRING.
> The modules are still relinked in this case.
>
> The code is also easier to maintain as it's now in a proper source file
> instead of an inline string literal.
>
> Signed-off-by: Thomas Weißschuh <linux@...ssschuh.net>


Applied to linux-kbuild. Thanks!


> ---
> Changes in v2:
> - Remove RFC status
> - Incorporate Masahiro's proposals
>   - Rename modinfo.o to .module-common.o
>   - Build a dedicated .module-common.o for external modules
> - Link to v1: https://lore.kernel.org/r/20240824-modinfo-const-v1-1-485f9c64b868@weissschuh.net
> ---
> Masahiro, feel free to add some attribution for yourself when applying.
> The new appraoch is pleasantly simpler.
> ---
>  scripts/Makefile.modfinal |  7 +++++--
>  scripts/mod/modpost.c     | 23 -----------------------
>  scripts/module-common.c   | 25 +++++++++++++++++++++++++
>  3 files changed, 30 insertions(+), 25 deletions(-)
>
> diff --git a/scripts/Makefile.modfinal b/scripts/Makefile.modfinal
> index 306a6bb86e4d..6b1b72257b29 100644
> --- a/scripts/Makefile.modfinal
> +++ b/scripts/Makefile.modfinal
> @@ -30,6 +30,9 @@ quiet_cmd_cc_o_c = CC [M]  $@
>  %.mod.o: %.mod.c FORCE
>         $(call if_changed_dep,cc_o_c)
>
> +$(extmod_prefix).module-common.o: $(srctree)/scripts/module-common.c FORCE
> +       $(call if_changed_dep,cc_o_c)
> +
>  quiet_cmd_ld_ko_o = LD [M]  $@
>        cmd_ld_ko_o +=                                                   \
>         $(LD) -r $(KBUILD_LDFLAGS)                                      \
> @@ -54,13 +57,13 @@ if_changed_except = $(if $(call newer_prereqs_except,$(2))$(cmd-check),      \
>         printf '%s\n' 'savedcmd_$@ := $(make-cmd)' > $(dot-target).cmd, @:)
>
>  # Re-generate module BTFs if either module's .ko or vmlinux changed
> -%.ko: %.o %.mod.o scripts/module.lds $(and $(CONFIG_DEBUG_INFO_BTF_MODULES),$(KBUILD_BUILTIN),vmlinux) FORCE
> +%.ko: %.o %.mod.o $(extmod_prefix).module-common.o scripts/module.lds $(and $(CONFIG_DEBUG_INFO_BTF_MODULES),$(KBUILD_BUILTIN),vmlinux) FORCE
>         +$(call if_changed_except,ld_ko_o,vmlinux)
>  ifdef CONFIG_DEBUG_INFO_BTF_MODULES
>         +$(if $(newer-prereqs),$(call cmd,btf_ko))
>  endif
>
> -targets += $(modules:%.o=%.ko) $(modules:%.o=%.mod.o)
> +targets += $(modules:%.o=%.ko) $(modules:%.o=%.mod.o) $(extmod_prefix).module-common.o
>
>  # Add FORCE to the prerequisites of a target to force it to be always rebuilt.
>  # ---------------------------------------------------------------------------
> diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
> index c8cd5d822bb6..107393a8c48a 100644
> --- a/scripts/mod/modpost.c
> +++ b/scripts/mod/modpost.c
> @@ -1755,26 +1755,9 @@ static void check_modname_len(struct module *mod)
>  static void add_header(struct buffer *b, struct module *mod)
>  {
>         buf_printf(b, "#include <linux/module.h>\n");
> -       /*
> -        * Include build-salt.h after module.h in order to
> -        * inherit the definitions.
> -        */
> -       buf_printf(b, "#define INCLUDE_VERMAGIC\n");
> -       buf_printf(b, "#include <linux/build-salt.h>\n");
> -       buf_printf(b, "#include <linux/elfnote-lto.h>\n");
>         buf_printf(b, "#include <linux/export-internal.h>\n");
> -       buf_printf(b, "#include <linux/vermagic.h>\n");
>         buf_printf(b, "#include <linux/compiler.h>\n");
>         buf_printf(b, "\n");
> -       buf_printf(b, "#ifdef CONFIG_UNWINDER_ORC\n");
> -       buf_printf(b, "#include <asm/orc_header.h>\n");
> -       buf_printf(b, "ORC_HEADER;\n");
> -       buf_printf(b, "#endif\n");
> -       buf_printf(b, "\n");
> -       buf_printf(b, "BUILD_SALT;\n");
> -       buf_printf(b, "BUILD_LTO_INFO;\n");
> -       buf_printf(b, "\n");
> -       buf_printf(b, "MODULE_INFO(vermagic, VERMAGIC_STRING);\n");
>         buf_printf(b, "MODULE_INFO(name, KBUILD_MODNAME);\n");
>         buf_printf(b, "\n");
>         buf_printf(b, "__visible struct module __this_module\n");
> @@ -1792,12 +1775,6 @@ static void add_header(struct buffer *b, struct module *mod)
>         if (!external_module)
>                 buf_printf(b, "\nMODULE_INFO(intree, \"Y\");\n");
>
> -       buf_printf(b,
> -                  "\n"
> -                  "#ifdef CONFIG_MITIGATION_RETPOLINE\n"
> -                  "MODULE_INFO(retpoline, \"Y\");\n"
> -                  "#endif\n");
> -
>         if (strstarts(mod->name, "drivers/staging"))
>                 buf_printf(b, "\nMODULE_INFO(staging, \"Y\");\n");
>
> diff --git a/scripts/module-common.c b/scripts/module-common.c
> new file mode 100644
> index 000000000000..12fbc6d3aae8
> --- /dev/null
> +++ b/scripts/module-common.c
> @@ -0,0 +1,25 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#include <linux/module.h>
> +/*
> + * Include build-salt.h after module.h in order to
> + * inherit the definitions.
> + */
> +#define INCLUDE_VERMAGIC
> +#include <linux/build-salt.h>
> +#include <linux/elfnote-lto.h>
> +#include <linux/vermagic.h>
> +
> +#ifdef CONFIG_UNWINDER_ORC
> +#include <asm/orc_header.h>
> +ORC_HEADER;
> +#endif
> +
> +BUILD_SALT;
> +BUILD_LTO_INFO;
> +
> +MODULE_INFO(vermagic, VERMAGIC_STRING);
> +
> +#ifdef CONFIG_MITIGATION_RETPOLINE
> +MODULE_INFO(retpoline, "Y");
> +#endif
>
> ---
> base-commit: 9f18baf3dd656e7ca166038d51e0b54a892d87db
> change-id: 20240824-modinfo-const-6f0d67e2b301
>
> Best regards,
> --
> Thomas Weißschuh <linux@...ssschuh.net>
>


-- 
Best Regards
Masahiro Yamada