linux-hardening - Re: [RFC PATCH v3 16/20] kallsyms: Drop CONFIG_CFI

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Message-ID: <CAKwvOdm1Abmu+NQ82ZLgX3O5g4vYPni23A9c4FJ+xeSYVwPtJw@mail.gmail.com>
Date:   Fri, 10 Jun 2022 16:40:16 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Sami Tolvanen <samitolvanen@...gle.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Kees Cook <keescook@...omium.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Nathan Chancellor <nathan@...nel.org>,
        Joao Moreira <joao@...rdrivepizza.com>,
        Sedat Dilek <sedat.dilek@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        linux-hardening@...r.kernel.org,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        clang-built-linux <llvm@...ts.linux.dev>
Subject: Re: [RFC PATCH v3 16/20] kallsyms: Drop CONFIG_CFI_CLANG workarounds

On Fri, Jun 10, 2022 at 4:35 PM Sami Tolvanen <samitolvanen@...gle.com> wrote:
>
> With -fsanitize=kcfi, the compiler no longer renames static
> functions with CONFIG_CFI_CLANG + ThinLTO. Drop the code that cleans
> up the ThinLTO hash from the function names.

Good riddance!
Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>

>
> Signed-off-by: Sami Tolvanen <samitolvanen@...gle.com>
> ---
>  kernel/kallsyms.c | 17 -----------------
>  1 file changed, 17 deletions(-)
>
> diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
> index fbdf8d3279ac..2fbb94817e02 100644
> --- a/kernel/kallsyms.c
> +++ b/kernel/kallsyms.c
> @@ -179,7 +179,6 @@ static bool cleanup_symbol_name(char *s)
>          * character in an identifier in C. Suffixes observed:
>          * - foo.llvm.[0-9a-f]+
>          * - foo.[0-9a-f]+
> -        * - foo.[0-9a-f]+.cfi_jt
>          */
>         res = strchr(s, '.');
>         if (res) {
> @@ -187,22 +186,6 @@ static bool cleanup_symbol_name(char *s)
>                 return true;
>         }
>
> -       if (!IS_ENABLED(CONFIG_CFI_CLANG) ||
> -           !IS_ENABLED(CONFIG_LTO_CLANG_THIN) ||
> -           CONFIG_CLANG_VERSION >= 130000)
> -               return false;
> -
> -       /*
> -        * Prior to LLVM 13, the following suffixes were observed when thinLTO
> -        * and CFI are both enabled:
> -        * - foo$[0-9]+
> -        */
> -       res = strrchr(s, '$');
> -       if (res) {
> -               *res = '\0';
> -               return true;
> -       }
> -
>         return false;
>  }
>
> --
> 2.36.1.476.g0c4daa206d-goog
>


-- 
Thanks,
~Nick Desaulniers