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

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Date:   Mon, 13 Jun 2022 12:19:52 -0700
From:   Bill Wendling <morbo@...gle.com>
To:     Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     Sami Tolvanen <samitolvanen@...gle.com>,
        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 4:40 PM Nick Desaulniers
<ndesaulniers@...gle.com> wrote:
>
> 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>
>
Much clapping!

-bw

> >
> > 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