linux-kernel - Re: [PATCH v6 0/3] kbuild: allow symbol whitelisting with TRIM_UNUSED

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Message-ID: <CAK7LNAQniztgAbF8N_OK+BJmaVUTVzhYmnY0-u1R_VsfEdOkTA@mail.gmail.com>
Date:   Sat, 29 Feb 2020 13:16:29 +0900
From:   Masahiro Yamada <masahiroy@...nel.org>
To:     Quentin Perret <qperret@...gle.com>
Cc:     Nicolas Pitre <nico@...xnic.net>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Matthias Maennich <maennich@...gle.com>,
        "Cc: Android Kernel" <kernel-team@...roid.com>,
        Jessica Yu <jeyu@...nel.org>,
        Christoph Hellwig <hch@...radead.org>
Subject: Re: [PATCH v6 0/3] kbuild: allow symbol whitelisting with TRIM_UNUSED_KSYM

On Sat, Feb 29, 2020 at 2:20 AM Quentin Perret <qperret@...gle.com> wrote:
>
> The current norm on Android and many other systems is for vendors to
> introduce significant changes to their downstream kernels, and to
> contribute very little (if any) code back upstream. The Generic Kernel
> Image (GKI) project in Android attempts to improve the status-quo by
> having a unique kernel for all android devices of the same architecture,
> regardless of the SoC vendor. The key idea is to make all interested
> parties agree on a common solution, and contribute their code upstream
> to make it available to use by the wider community.
>
> The kernel-to-drivers ABI on Android devices varies significantly from
> one vendor kernel to another today because of changes to exported
> symbols, dependencies on vendor symbols, and surely other things. The
> first step for GKI is to try and put some order into this by agreeing on
> one version of the ABI that works for everybody.
>
> For practical reasons, we need to reduce the ABI surface to a subset of
> the exported symbols, simply to make the problem realistically solvable,
> but there is currently no upstream support for this use-case.
>
> As such, this series attempts to improve the situation by enabling users
> to specify a symbol 'whitelist' at compile time. Any symbol specified in
> this whitelist will be kept exported when CONFIG_TRIM_UNUSED_KSYMS is
> set, even if it has no in-tree user. The whitelist is defined as a
> simple text file, listing symbols, one per line.


Series, applied to linux-kbuild.

Thanks.


> v6:
>  - made permission checks on the whitelist file more robust (Masahiro)
>  - better style/identation in Makefile (Masahiro)
>
> v5:
>  - made sure to be POSIX-compliant (+ tested with dash and posh)
>  - added failure path if the whitelist path is incorrect (Matthias,
>    Nicolas)
>  - collected Acked-By (and other) tags from Nicolas and Matthias
>
> v4:
>  - removed [[]] bash-specific pattern from the scripts (Nicolas)
>  - use $CONFIG_SHELL consistently in all patches (Masahiro)
>  - added shortlog for initial generation of autoksyms.h (Masahiro)
>  - added comment on how 'eval' expands the whitelist path (Masahiro)
>
> v3:
>  - added a cover letter to explain why this is in fact an attempt to
>    help upstream in the long term (Christoph)
>  - made path relative to the kernel source tree (Matthias)
>  - made the Kconfig help text less confusing (Jessica)
>  - added patch 02 and 03 to optimize build time when a whitelist is
>    provided
>
> v2:
>  - make sure to quote the whitelist path properly (Nicolas)
>
> Quentin Perret (3):
>   kbuild: allow symbol whitelisting with TRIM_UNUSED_KSYMS
>   kbuild: split adjust_autoksyms.sh in two parts
>   kbuild: generate autoksyms.h early
>
>  Makefile                    |  7 +++--
>  init/Kconfig                | 13 ++++++++++
>  scripts/adjust_autoksyms.sh | 24 +++--------------
>  scripts/gen_autoksyms.sh    | 52 +++++++++++++++++++++++++++++++++++++
>  4 files changed, 74 insertions(+), 22 deletions(-)
>  create mode 100755 scripts/gen_autoksyms.sh
>
> --
> 2.25.1.481.gfbce0eb801-goog
>


-- 
Best Regards
Masahiro Yamada