From: Sami Tolvanen <samitolvanen@google.com>
To: Masahiro Yamada <masahiroy@kernel.org>
Cc: linux-kbuild <linux-kbuild@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Nathan Chancellor <nathan@kernel.org>,
Nick Desaulniers <ndesaulniers@google.com>,
Nicolas Schier <nicolas@fjasle.eu>,
Peter Zijlstra <peterz@infradead.org>,
linux-modules@vger.kernel.org, linux-s390@vger.kernel.org,
linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
clang-built-linux <clang-built-linux@googlegroups.com>,
Ard Biesheuvel <ardb@kernel.org>
Subject: Re: [PATCH v4 05/14] modpost: extract symbol versions from *.cmd files
Date: Mon, 9 May 2022 14:52:21 -0700 [thread overview]
Message-ID: <CABCJKucG4dOLm9pPWrACc+YReBXG4GNM9V0djsy0YTp8pRGmaw@mail.gmail.com> (raw)
In-Reply-To: <20220508190631.2386038-6-masahiroy@kernel.org>
On Sun, May 8, 2022 at 12:09 PM Masahiro Yamada <masahiroy@kernel.org> wrote:
>
> Currently, CONFIG_MODVERSIONS needs extra link to embed the symbol
> versions into ELF objects. Then, modpost extracts the version CRCs
> from them.
>
> The following figures show how it currently works, and how I am trying
> to change it.
>
> Current implementation
> ======================
> |----------|
> embed CRC -------------------------->| final |
> $(CC) $(LD) / |---------| | link for |
> -----> *.o -------> *.o -->| modpost | | vmlinux |
> / / | |-- *.mod.c -->| or |
> / genksyms / |---------| | module |
> *.c ------> *.symversions |----------|
>
> Genksyms outputs the calculated CRCs in the form of linker script
> (*.symversions), which is used by $(LD) to update the object.
>
> If CONFIG_LTO_CLANG=y, the build process is much more complex. Embedding
> the CRCs is postponed until the LLVM bitcode is converted into ELF,
> creating another intermediate *.prelink.o.
>
> However, this complexity is unneeded. There is no reason why we must
> embed version CRCs in objects so early.
>
> There is final link stage for vmlinux (scripts/link-vmlinux.sh) and
> modules (scripts/Makefile.modfinal). We can link CRCs at the very last
> moment.
>
> New implementation
> ==================
> |----------|
> --------------------------------------->| final |
> $(CC) / |---------| | link for |
> -----> *.o ---->| | | vmlinux |
> / | modpost |--- .vmlinux.export.c -->| or |
> / genksyms | |--- *.mod.c ------------>| module |
> *.c ------> *.cmd -->|---------| |----------|
>
> Pass the symbol versions to modpost as separate text data, which are
> available in *.cmd files.
>
> This commit changes modpost to extract CRCs from *.cmd files instead of
> from ELF objects.
>
> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
> Tested-by: Nathan Chancellor <nathan@kernel.org>
This looks good to me, it's great to get rid of the .symversions files!
Reviewed-by: Sami Tolvanen <samitolvanen@google.com>
Sami
next prev parent reply other threads:[~2022-05-09 21:55 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-08 19:06 [PATCH v4 00/14] kbuild: yet another series of cleanups (modpost, LTO, MODULE_REL_CRCS, export.h) Masahiro Yamada
2022-05-08 19:06 ` [PATCH v4 01/14] modpost: remove left-over cross_compile declaration Masahiro Yamada
2022-05-09 17:08 ` Nick Desaulniers
2022-05-12 4:35 ` Masahiro Yamada
2022-05-08 19:06 ` [PATCH v4 02/14] modpost: change the license of EXPORT_SYMBOL to bool type Masahiro Yamada
2022-05-12 4:36 ` Masahiro Yamada
2022-05-08 19:06 ` [PATCH v4 03/14] modpost: split the section mismatch checks into section-check.c Masahiro Yamada
2022-05-09 17:19 ` Nick Desaulniers
2022-05-10 6:55 ` Masahiro Yamada
2022-05-11 18:47 ` Nick Desaulniers
2022-05-11 19:27 ` Masahiro Yamada
2022-05-11 19:51 ` Jeff Johnson
2022-05-11 20:01 ` Nick Desaulniers
2022-05-08 19:06 ` [PATCH v4 04/14] modpost: add sym_find_with_module() helper Masahiro Yamada
2022-05-08 19:06 ` [PATCH v4 05/14] modpost: extract symbol versions from *.cmd files Masahiro Yamada
2022-05-09 21:52 ` Sami Tolvanen [this message]
2022-05-08 19:06 ` [PATCH v4 06/14] kbuild: link symbol CRCs at final link, removing CONFIG_MODULE_REL_CRCS Masahiro Yamada
2022-05-09 17:50 ` Nick Desaulniers
2022-05-10 13:03 ` Masahiro Yamada
2022-05-08 19:06 ` [PATCH v4 07/14] kbuild: stop merging *.symversions Masahiro Yamada
2022-05-08 19:06 ` [PATCH v4 08/14] genksyms: adjust the output format to modpost Masahiro Yamada
2022-05-08 19:06 ` [PATCH v4 09/14] kbuild: do not create *.prelink.o for Clang LTO or IBT Masahiro Yamada
2022-05-09 23:13 ` Sami Tolvanen
2022-05-08 19:06 ` [PATCH v4 10/14] kbuild: check static EXPORT_SYMBOL* by script instead of modpost Masahiro Yamada
2022-05-09 18:05 ` Nick Desaulniers
2022-05-10 13:53 ` Masahiro Yamada
2022-05-08 19:06 ` [PATCH v4 11/14] kbuild: make built-in.a rule robust against too long argument error Masahiro Yamada
2022-05-08 19:06 ` [PATCH v4 12/14] kbuild: make *.mod " Masahiro Yamada
2022-05-08 19:06 ` [PATCH v4 13/14] kbuild: add cmd_and_savecmd macro Masahiro Yamada
2022-05-08 19:06 ` [PATCH v4 14/14] kbuild: rebuild multi-object modules when objtool is updated Masahiro Yamada
2022-05-09 4:24 ` [PATCH v4 00/14] kbuild: yet another series of cleanups (modpost, LTO, MODULE_REL_CRCS, export.h) Masahiro Yamada
2022-05-09 22:13 ` Nathan Chancellor
2022-05-10 6:55 ` Masahiro Yamada
2022-05-09 22:19 ` Nathan Chancellor
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