linux-kernel - Re: [PATCH v2] srcu: avoid escaped section names

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Message-ID: <CA+icZUVgfnVQ1=zjUGhGKnJAs9g3Q06sWN3ffNdrfZMZLCEkbA@mail.gmail.com>
Date:   Wed, 30 Sep 2020 18:41:42 +0200
From:   Sedat Dilek <sedat.dilek@...il.com>
To:     Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     "Paul E . McKenney" <paulmck@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Josh Triplett <josh@...htriplett.org>,
        Kees Cook <keescook@...omium.org>,
        linux-kernel@...r.kernel.org, rcu@...r.kernel.org,
        Clang-Built-Linux ML <clang-built-linux@...glegroups.com>
Subject: Re: [PATCH v2] srcu: avoid escaped section names

On Tue, Sep 29, 2020 at 9:25 PM 'Nick Desaulniers' via Clang Built
Linux <clang-built-linux@...glegroups.com> wrote:
>
> The stringification operator, `#`, in the preprocessor escapes strings.
> For example, `# "foo"` becomes `"\"foo\""`.  GCC and Clang differ in how
> they treat section names that contain \".
>
> The portable solution is to not use a string literal with the
> preprocessor stringification operator.
>
> Link: https://bugs.llvm.org/show_bug.cgi?id=42950
> Fixes: commit fe15b50cdeee ("srcu: Allocate per-CPU data for DEFINE_SRCU() in modules")
> Signed-off-by: Nick Desaulniers <ndesaulniers@...gle.com>

Puh, remember one year ago an overnight bisecting to catch the root
cause for "escaped section names".

The two patches I see - this here and "export.h: fix section name for
CONFIG_TRIM_UNUSED_KSYMS for Clang" were new cases?

Do we have a check-script to catch/avoid such cases (Joe Perches?)?

Reviewed-by: Sedat Dilek <sedat.dilek@...il.com>

- Sedat -

> ---
> Changes V1->V2:
> * drop unrelated Kconfig changes accidentally committed in v1.
>
>  include/linux/srcutree.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h
> index 9cfcc8a756ae..9de652f4e1bd 100644
> --- a/include/linux/srcutree.h
> +++ b/include/linux/srcutree.h
> @@ -124,7 +124,7 @@ struct srcu_struct {
>  # define __DEFINE_SRCU(name, is_static)                                        \
>         is_static struct srcu_struct name;                              \
>         struct srcu_struct * const __srcu_struct_##name                 \
> -               __section("___srcu_struct_ptrs") = &name
> +               __section(___srcu_struct_ptrs) = &name
>  #else
>  # define __DEFINE_SRCU(name, is_static)                                        \
>         static DEFINE_PER_CPU(struct srcu_data, name##_srcu_data);      \
> --
> 2.28.0.709.gb0816b6eb0-goog
>
> --
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