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Message-ID: <CAK7LNAQUkMtRmyiovCebrXhrdz2GnUo+0SQMHaCc0evZatohfw@mail.gmail.com>
Date: Wed, 27 Nov 2024 02:07:17 +0900
From: Masahiro Yamada <masahiroy@...nel.org>
To: Sami Tolvanen <samitolvanen@...gle.com>
Cc: Luis Chamberlain <mcgrof@...nel.org>, Miguel Ojeda <ojeda@...nel.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Matthew Maurer <mmaurer@...gle.com>,
Alex Gaynor <alex.gaynor@...il.com>, Gary Guo <gary@...yguo.net>,
Petr Pavlu <petr.pavlu@...e.com>, Daniel Gomez <da.gomez@...sung.com>, Neal Gompa <neal@...pa.dev>,
Hector Martin <marcan@...can.st>, Janne Grunau <j@...nau.net>, Miroslav Benes <mbenes@...e.cz>,
Asahi Linux <asahi@...ts.linux.dev>, Sedat Dilek <sedat.dilek@...il.com>,
linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-modules@...r.kernel.org, rust-for-linux@...r.kernel.org
Subject: Re: [PATCH v6 17/18] kbuild: Add gendwarfksyms as an alternative to genksyms
On Fri, Nov 22, 2024 at 5:43 AM Sami Tolvanen <samitolvanen@...gle.com> wrote:
>
> When MODVERSIONS is enabled, allow selecting gendwarfksyms as the
> implementation, but default to genksyms.
>
> Signed-off-by: Sami Tolvanen <samitolvanen@...gle.com>
> ---
> kernel/module/Kconfig | 25 ++++++++++++++++++++++++-
> scripts/Makefile | 2 +-
> scripts/Makefile.build | 35 +++++++++++++++++++++++++++++------
> 3 files changed, 54 insertions(+), 8 deletions(-)
>
> diff --git a/kernel/module/Kconfig b/kernel/module/Kconfig
> index f9e5f82fa88b..e6b2427e5c19 100644
> --- a/kernel/module/Kconfig
> +++ b/kernel/module/Kconfig
> @@ -169,13 +169,36 @@ config MODVERSIONS
> make them incompatible with the kernel you are running. If
> unsure, say N.
>
> +choice
> + prompt "Module versioning implementation"
> + depends on MODVERSIONS
> + default GENKSYMS
This is redundant because the first entry is the default.
> + help
> + Select the tool used to calculate symbol versions for modules.
> +
> + If unsure, select GENKSYMS.
> +
> +config GENKSYMS
> + bool "genksyms (from source code)"
> + help
> + Calculate symbol versions from pre-processed source code using
> + genksyms.
> +
> + If unsure, say Y.
> +
> config GENDWARFKSYMS
> - bool
> + bool "gendwarfksyms (from debugging information)"
> depends on DEBUG_INFO
> # Requires full debugging information, split DWARF not supported.
> depends on !DEBUG_INFO_REDUCED && !DEBUG_INFO_SPLIT
> # Requires ELF object files.
> depends on !LTO
> + help
> + Calculate symbol versions from DWARF debugging information using
> + gendwarfksyms. Requires DEBUG_INFO to be enabled.
> +
> + If unsure, say N.
> +endchoice
>
> config ASM_MODVERSIONS
> bool
> diff --git a/scripts/Makefile b/scripts/Makefile
> index d7fec46d38c0..8533f4498885 100644
> --- a/scripts/Makefile
> +++ b/scripts/Makefile
> @@ -53,7 +53,7 @@ hostprogs += unifdef
> targets += module.lds
>
> subdir-$(CONFIG_GCC_PLUGINS) += gcc-plugins
> -subdir-$(CONFIG_MODVERSIONS) += genksyms
> +subdir-$(CONFIG_GENKSYMS) += genksyms
> subdir-$(CONFIG_GENDWARFKSYMS) += gendwarfksyms
> subdir-$(CONFIG_SECURITY_SELINUX) += selinux
> subdir-$(CONFIG_SECURITY_IPE) += ipe
> diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> index f41ce2131979..d6b211a7b261 100644
> --- a/scripts/Makefile.build
> +++ b/scripts/Makefile.build
> @@ -107,13 +107,24 @@ cmd_cpp_i_c = $(CPP) $(c_flags) -o $@ $<
> $(obj)/%.i: $(obj)/%.c FORCE
> $(call if_changed_dep,cpp_i_c)
>
> +getexportsymbols = $(NM) $@ | sed -n 's/.* __export_symbol_\(.*\)/$(1)/p'
> +
> +gendwarfksyms = $(objtree)/scripts/gendwarfksyms/gendwarfksyms \
> + $(if $(KBUILD_SYMTYPES), --symtypes $(@:.o=.symtypes)) \
> + $(if $(KBUILD_GENDWARFKSYMS_STABLE), --stable)
> +
> genksyms = $(objtree)/scripts/genksyms/genksyms \
> $(if $(KBUILD_SYMTYPES), -T $(@:.o=.symtypes)) \
> $(if $(KBUILD_PRESERVE), -p) \
> $(addprefix -r , $(wildcard $(@:.o=.symref)))
>
> # These mirror gensymtypes_S and co below, keep them in synch.
> +ifdef CONFIG_GENDWARFKSYMS
> +cmd_gensymtypes_c = $(if $(skip_gendwarfksyms),, \
> + $(call getexportsymbols,\1) | $(gendwarfksyms) $@)
> +else
> cmd_gensymtypes_c = $(CPP) -D__GENKSYMS__ $(c_flags) $< | $(genksyms)
> +endif # CONFIG_GENDWARFKSYMS
>
> # LLVM assembly
> # Generate .ll files from .c
> @@ -279,14 +290,26 @@ $(obj)/%.ll: $(obj)/%.rs FORCE
> # This is convoluted. The .S file must first be preprocessed to run guards and
> # expand names, then the resulting exports must be constructed into plain
> # EXPORT_SYMBOL(symbol); to build our dummy C file, and that gets preprocessed
> -# to make the genksyms input.
> +# to make the genksyms input or compiled into an object for gendwarfksyms.
> #
> # These mirror gensymtypes_c and co above, keep them in synch.
> -cmd_gensymtypes_S = \
> - { echo "\#include <linux/kernel.h>" ; \
> - echo "\#include <asm/asm-prototypes.h>" ; \
> - $(NM) $@ | sed -n 's/.* __export_symbol_\(.*\)/EXPORT_SYMBOL(\1);/p' ; } | \
> - $(CPP) -D__GENKSYMS__ $(c_flags) -xc - | $(genksyms)
> +getasmexports = \
> + { echo "\#include <linux/kernel.h>" ; \
> + echo "\#include <linux/string.h>" ; \
> + echo "\#include <asm/asm-prototypes.h>" ; \
> + $(call getexportsymbols,EXPORT_SYMBOL(\1);) ; }
> +
> +ifdef CONFIG_GENDWARFKSYMS
> +cmd_gensymtypes_S = \
> + $(getasmexports) | \
> + $(CC) $(c_flags) -c -o $(@:.o=.gendwarfksyms.o) -xc -; \
> + $(call getexportsymbols,\1) | \
> + $(gendwarfksyms) $(@:.o=.gendwarfksyms.o)
> +else
> +cmd_gensymtypes_S = \
> + $(getasmexports) | \
> + $(CPP) -D__GENKSYMS__ $(c_flags) -xc - | $(genksyms)
> +endif # CONFIG_GENDWARFKSYMS
>
> quiet_cmd_cpp_s_S = CPP $(quiet_modtag) $@
> cmd_cpp_s_S = $(CPP) $(a_flags) -o $@ $<
> --
> 2.47.0.371.ga323438b13-goog
>
--
Best Regards
Masahiro Yamada
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