linux-kernel - Re: [PATCH v10 05/27] kallsyms: increase maximum kernel symbol length to 512

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Message-ID: <YzMPCfjEu6c5bbCv@kroah.com>
Date:   Tue, 27 Sep 2022 16:56:09 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Miguel Ojeda <ojeda@...nel.org>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, patches@...ts.linux.dev,
        Jarkko Sakkinen <jarkko@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Petr Mladek <pmladek@...e.com>,
        Alex Gaynor <alex.gaynor@...il.com>,
        Wedson Almeida Filho <wedsonaf@...gle.com>,
        Gary Guo <gary@...yguo.net>, Boqun Feng <boqun.feng@...il.com>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        Jiri Kosina <jikos@...nel.org>,
        Miroslav Benes <mbenes@...e.cz>,
        Joe Lawrence <joe.lawrence@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        live-patching@...r.kernel.org, linux-perf-users@...r.kernel.org
Subject: Re: [PATCH v10 05/27] kallsyms: increase maximum kernel symbol
 length to 512

On Tue, Sep 27, 2022 at 03:14:36PM +0200, Miguel Ojeda wrote:
> Rust symbols can become quite long due to namespacing introduced
> by modules, types, traits, generics, etc. For instance,
> the following code:
> 
>     pub mod my_module {
>         pub struct MyType;
>         pub struct MyGenericType<T>(T);
> 
>         pub trait MyTrait {
>             fn my_method() -> u32;
>         }
> 
>         impl MyTrait for MyGenericType<MyType> {
>             fn my_method() -> u32 {
>                 42
>             }
>         }
>     }
> 
> generates a symbol of length 96 when using the upcoming v0 mangling scheme:
> 
>     _RNvXNtCshGpAVYOtgW1_7example9my_moduleINtB2_13MyGenericTypeNtB2_6MyTypeENtB2_7MyTrait9my_method
> 
> At the moment, Rust symbols may reach up to 300 in length.
> Setting 512 as the maximum seems like a reasonable choice to
> keep some headroom.
> 
> Reviewed-by: Kees Cook <keescook@...omium.org>
> Reviewed-by: Petr Mladek <pmladek@...e.com>
> Co-developed-by: Alex Gaynor <alex.gaynor@...il.com>
> Signed-off-by: Alex Gaynor <alex.gaynor@...il.com>
> Co-developed-by: Wedson Almeida Filho <wedsonaf@...gle.com>
> Signed-off-by: Wedson Almeida Filho <wedsonaf@...gle.com>
> Co-developed-by: Gary Guo <gary@...yguo.net>
> Signed-off-by: Gary Guo <gary@...yguo.net>
> Co-developed-by: Boqun Feng <boqun.feng@...il.com>
> Signed-off-by: Boqun Feng <boqun.feng@...il.com>
> Signed-off-by: Miguel Ojeda <ojeda@...nel.org>
> ---
>  include/linux/kallsyms.h            | 2 +-
>  kernel/livepatch/core.c             | 4 ++--
>  scripts/kallsyms.c                  | 4 ++--
>  tools/include/linux/kallsyms.h      | 2 +-
>  tools/lib/perf/include/perf/event.h | 2 +-
>  tools/lib/symbol/kallsyms.h         | 2 +-
>  6 files changed, 8 insertions(+), 8 deletions(-)

Reviewed-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>