linux-kernel - Re: [PATCH 4/8] scripts/kallsyms: exclude symbols generated by itself dynamically

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Message-ID: <CAKwvOd=MLHjGPSyVtmtW=1P=n2OLCXEFG+L=wLPVr4Orwuu2Xg@mail.gmail.com>
Date:   Fri, 7 Apr 2023 13:12:41 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Masahiro Yamada <masahiroy@...nel.org>
Cc:     linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org,
        Zhen Lei <thunder.leizhen@...wei.com>,
        Arnd Bergmann <arnd@...db.de>,
        Nathan Chancellor <nathan@...nel.org>,
        Nicolas Schier <nicolas@...sle.eu>
Subject: Re: [PATCH 4/8] scripts/kallsyms: exclude symbols generated by itself dynamically

On Wed, Mar 8, 2023 at 3:53 AM Masahiro Yamada <masahiroy@...nel.org> wrote:
>
> Drop the symbols generated by scripts/kallsyms itself automatically
> instead of maintaining the symbol list manually.
>
> Pass the kallsyms object from the previous kallsyms step (if it exists)
> as the third parameter of scripts/mksysmap, which will weed out the
> generated symbols from the input to the next kallsyms step.
>
> Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
> ---
>
>  scripts/kallsyms.c      | 17 -----------------
>  scripts/link-vmlinux.sh |  6 +++---
>  scripts/mksysmap        | 11 ++++++++++-
>  3 files changed, 13 insertions(+), 21 deletions(-)
>
> diff --git a/scripts/kallsyms.c b/scripts/kallsyms.c
> index 8148e880f78e..e572fda6fe42 100644
> --- a/scripts/kallsyms.c
> +++ b/scripts/kallsyms.c
> @@ -104,23 +104,6 @@ static bool is_ignored_symbol(const char *name, char type)
>  {
>         /* Symbol names that exactly match to the following are ignored.*/
>         static const char * const ignored_symbols[] = {
> -               /*
> -                * Symbols which vary between passes. Passes 1 and 2 must have
> -                * identical symbol lists. The kallsyms_* symbols below are
> -                * only added after pass 1, they would be included in pass 2
> -                * when --all-symbols is specified so exclude them to get a
> -                * stable symbol list.
> -                */
> -               "kallsyms_addresses",
> -               "kallsyms_offsets",
> -               "kallsyms_relative_base",
> -               "kallsyms_num_syms",
> -               "kallsyms_names",
> -               "kallsyms_markers",
> -               "kallsyms_token_table",
> -               "kallsyms_token_index",
> -               "kallsyms_seqs_of_names",
> -               /* Exclude linker generated symbols which vary between passes */

^ Do we want to retain this comment for the below two symbols?

>                 "_SDA_BASE_",           /* ppc */
>                 "_SDA2_BASE_",          /* ppc */
>                 NULL
> diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
> index 32e573943cf0..679eb4653b16 100755
> --- a/scripts/link-vmlinux.sh
> +++ b/scripts/link-vmlinux.sh
> @@ -174,7 +174,7 @@ kallsyms_step()
>         kallsyms_S=${kallsyms_vmlinux}.S
>
>         vmlinux_link ${kallsyms_vmlinux} "${kallsymso_prev}" ${btf_vmlinux_bin_o}
> -       mksysmap ${kallsyms_vmlinux} ${kallsyms_vmlinux}.syms
> +       mksysmap ${kallsyms_vmlinux} ${kallsyms_vmlinux}.syms ${kallsymso_prev}
>         kallsyms ${kallsyms_vmlinux}.syms ${kallsyms_S}
>
>         info AS ${kallsyms_S}
> @@ -188,7 +188,7 @@ kallsyms_step()
>  mksysmap()
>  {
>         info NM ${2}
> -       ${CONFIG_SHELL} "${srctree}/scripts/mksysmap" ${1} ${2}
> +       ${CONFIG_SHELL} "${srctree}/scripts/mksysmap" ${1} ${2} ${3}
>  }
>
>  sorttable()
> @@ -277,7 +277,7 @@ if is_enabled CONFIG_DEBUG_INFO_BTF && is_enabled CONFIG_BPF; then
>         ${RESOLVE_BTFIDS} vmlinux
>  fi
>
> -mksysmap vmlinux System.map
> +mksysmap vmlinux System.map ${kallsymso}
>
>  if is_enabled CONFIG_BUILDTIME_TABLE_SORT; then
>         info SORTTAB vmlinux
> diff --git a/scripts/mksysmap b/scripts/mksysmap
> index 8ea1955e03c6..1efd61ee0bac 100755
> --- a/scripts/mksysmap
> +++ b/scripts/mksysmap
> @@ -4,7 +4,7 @@
>  # tools to retrieve the actual addresses of symbols in the kernel.
>  #
>  # Usage
> -# mksysmap vmlinux System.map
> +# mksysmap vmlinux System.map [exclude]
>
>
>  #####
> @@ -51,4 +51,13 @@ ${NM} -n ${1} | sed >${2} -e "
>
>  # for LoongArch?
>  / L0$/d
> +
> +# ---------------------------------------------------------------------------
> +# Ignored kallsyms symbols
> +#
> +# If the 3rd parameter exists, symbols from it will be omitted from the output.
> +# This makes kallsyms have the identical symbol lists in the step 1 and 2.
> +# Without this, the step2 would get new symbols generated by scripts/kallsyms.c
> +# when CONFIG_KALLSYMS_ALL is enabled. That might require one more pass.
> +$(if [ $# -ge 3 ]; then ${NM} ${3} | sed -n '/ U /!s:.* \([^ ]*\)$:/ \1$/d:p'; fi)
>  "
> --
> 2.34.1
>


-- 
Thanks,
~Nick Desaulniers