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From:   Fangrui Song <maskray@google.com>
Date:   Wed, 12 Apr 2023 11:13:53 -0700
Message-ID: <CAFP8O3K2c-7wCeDrxPaFpNe-yV9M1g0BPQw7qA6JdpUD74dC1w@mail.gmail.com>
Subject: Re: [PATCH] ubsan: remove cc-option test for UBSAN_TRAP
To:     Kees Cook <keescook@chromium.org>
Cc:     Nick Desaulniers <ndesaulniers@google.com>,
        Nathan Chancellor <nathan@kernel.org>,
        Masahiro Yamada <masahiroy@kernel.org>,
        linux-hardening@vger.kernel.org, Tom Rix <trix@redhat.com>,
        Josh Poimboeuf <jpoimboe@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Miroslav Benes <mbenes@suse.cz>, linux-kernel@vger.kernel.org,
        llvm@lists.linux.dev, linux-kbuild@vger.kernel.org
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On Wed, Apr 12, 2023 at 8:12=E2=80=AFAM Kees Cook <keescook@chromium.org> w=
rote:
>
> On Tue, Apr 11, 2023 at 05:12:24PM -0700, Fangrui Song wrote:
> > On Fri, Apr 7, 2023 at 2:58=E2=80=AFPM Nathan Chancellor <nathan@kernel=
.org> wrote:
> > >
> > > On Fri, Apr 07, 2023 at 02:54:06PM -0700, Nick Desaulniers wrote:
> > > > -fsanitize-undefined-trap-on-error has been supported since GCC 5.1=
 and
> > > > Clang 3.2.  The minimum supported version of these according to
> > > > Documentation/process/changes.rst is 5.1 and 11.0.0 respectively. D=
rop
> > > > this cc-option check.
> > > >
> > > > Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
> > >
> > > Reviewed-by: Nathan Chancellor <nathan@kernel.org>
> > >
> > > As an aside, we should really consider having some standard format of
> > > comment around cc-option checks so that we can easily remove them whe=
n
> > > they become stale...
> > >
> > > > ---
> > > > Masahiro, Kees: get_maintainer.pl leaves much to be desired for thi=
s
> > > > file. Can one of you please pick this up?
> > > >
> > > >  lib/Kconfig.ubsan | 1 -
> > > >  1 file changed, 1 deletion(-)
> > > >
> > > > diff --git a/lib/Kconfig.ubsan b/lib/Kconfig.ubsan
> > > > index fd15230a703b..0e7ad0782399 100644
> > > > --- a/lib/Kconfig.ubsan
> > > > +++ b/lib/Kconfig.ubsan
> > > > @@ -15,7 +15,6 @@ if UBSAN
> > > >  config UBSAN_TRAP
> > > >       bool "On Sanitizer warnings, abort the running kernel code"
> > > >       depends on !COMPILE_TEST
> > > > -     depends on $(cc-option, -fsanitize-undefined-trap-on-error)
> > > >       help
> > > >         Building kernels with Sanitizer features enabled tends to g=
row
> > > >         the kernel size by around 5%, due to adding all the debuggi=
ng
> > > > --
> > > > 2.40.0.577.gac1e443424-goog
> > > >
> > >
> >
> > -fsanitize-undefined-trap-on-error is a legacy option from 2013 when
> > -fcatch-undefined-behavior instead of -fsanitize=3Dundefined enabled
> > UBSan.
> > On the Clang side, http://reviews.llvm.org/D10464 added
> > -fsanitize-trap=3D in June 2015.
> > It's best to use -fsanitize-trap=3Dundefined and avoid uses of
> > -fsanitize-undefined-trap-on-error.
>
> But that's Clang-only. -fsanitize-undefined-trap-on-error works for both
> GCC and Clang.
>
> --
> Kees Cook

Just filed a -fsanitize-trap=3D feature request for GCC:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D109489 :)

https://reviews.llvm.org/D10464 (2015) does mention the state of the
legacy option:

  // https://clang.llvm.org/docs/UsersManual.html#cmdoption-fsanitize-undef=
ined-trap-on-error
  -fsanitize-undefined-trap-on-error
  Deprecated alias for -fsanitize-trap=3Dundefined.


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