From: Kees Cook <keescook@chromium.org>
To: Nick Desaulniers <ndesaulniers@google.com>
Cc: Miguel Ojeda <ojeda@kernel.org>,
Nathan Chancellor <nathan@kernel.org>,
George Burgess IV <gbiv@google.com>,
llvm@lists.linux.dev, linux-kernel@vger.kernel.org,
linux-hardening@vger.kernel.org
Subject: Re: [PATCH v6 4/4] fortify: Add Clang support
Date: Thu, 3 Feb 2022 13:26:24 -0800 [thread overview]
Message-ID: <202202031313.4A68EA9DB3@keescook> (raw)
In-Reply-To: <CAKwvOdk0UMAaw2j9OmjXN0Jc6FBOhfMP3JmSqMps2_MQFQLq-g@mail.gmail.com>
On Thu, Feb 03, 2022 at 12:37:41PM -0800, Nick Desaulniers wrote:
> On Thu, Feb 3, 2022 at 9:33 AM Kees Cook <keescook@chromium.org> wrote:
> >
> > Enable FORTIFY_SOURCE support for Clang:
> >
> > Use the new __pass_object_size and __overloadable attributes so
> > that Clang will have appropriate visibility into argument sizes such
> > that __builtin_object_size(p, 1) will behave correctly. Additional
> > details here:
> > https://github.com/llvm/llvm-project/issues/53516
> > https://github.com/ClangBuiltLinux/linux/issues/1401
> >
> > When available, use the new __diagnose_as attribute to make sure no
> > compile-time diagnostic warnings are lost due to the effectively renamed
> > string functions.
>
> Consider adding something along the lines of the following to the
> above paragraph:
> Without diagnose_as, compile time error messages won't be as precise
> as they could be, but at least users of older toolchains will have
> fortified routines. That is more valuable, but certainly a tradeoff.
Sure, I've changed it to:
When available, use the new __diagnose_as attribute to make sure no
compile-time diagnostic warnings are lost due to the effectively renamed
string functions. Without __diagnose_as, Clang's compile time diagnostic
messages won't be as precise as they could be, but at least users of
older toolchains will have fortified routines.
how's that read for you?
> > Redefine strlen() as a macro that tests for being a constant expression
> > so that strlen() can still be used in static initializers, which was
> > lost when adding __pass_object_size and __overloadable.
>
> I'd like to see `const` changes explicit in 4/4; I suspect that's
> _why_ __overloadable is even needed? If so, then a comment here about
> that wouldn't hurt.
>
> Having const be more explicit in the signature will make it more
> obvious why the definition cannot modify the parameter.
Mostly I wanted to minimize further changes to this area when building
with GCC because of all the corner cases that keep popping up, and avoid
tweaking the prototypes any harder. :)
--
Kees Cook
next prev parent reply other threads:[~2022-02-03 21:26 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-03 17:33 [PATCH v6 0/4] fortify: Add Clang support Kees Cook
2022-02-03 17:33 ` [PATCH v6 1/4] Compiler Attributes: Add __pass_object_size for Clang Kees Cook
2022-02-03 20:18 ` Nick Desaulniers
2022-02-03 20:58 ` Kees Cook
2022-02-03 22:01 ` Nick Desaulniers
2022-02-04 0:29 ` Kees Cook
2022-02-03 17:33 ` [PATCH v6 2/4] Compiler Attributes: Add __overloadable " Kees Cook
2022-02-03 20:26 ` Nick Desaulniers
2022-02-03 21:04 ` Kees Cook
2022-02-03 22:11 ` Nick Desaulniers
2022-02-04 0:26 ` Kees Cook
2022-02-04 0:58 ` Nick Desaulniers
2022-02-04 1:07 ` Miguel Ojeda
2022-02-03 17:33 ` [PATCH v6 3/4] Compiler Attributes: Add __diagnose_as " Kees Cook
2022-02-03 20:28 ` Nick Desaulniers
2022-02-03 17:33 ` [PATCH v6 4/4] fortify: Add Clang support Kees Cook
2022-02-03 20:37 ` Nick Desaulniers
2022-02-03 21:26 ` Kees Cook [this message]
2022-02-03 17:47 ` [PATCH v6 0/4] " Miguel Ojeda
2022-02-03 19:57 ` Kees Cook
2022-02-03 21:12 ` Miguel Ojeda
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