From: Nathan Chancellor <natechancellor@gmail.com>
To: Nick Desaulniers <ndesaulniers@google.com>
Cc: "Masahiro Yamada" <masahiroy@kernel.org>,
"Andrew Morton" <akpm@linux-foundation.org>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Ingo Molnar" <mingo@redhat.com>,
"Borislav Petkov" <bp@alien8.de>,
"Michal Marek" <michal.lkml@markovi.net>,
linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org,
"Kees Cook" <keescook@chromium.org>,
"Tony Luck" <tony.luck@intel.com>,
"Dmitry Vyukov" <dvyukov@google.com>,
"Michael Ellerman" <mpe@ellerman.id.au>,
"Joe Perches" <joe@perches.com>,
"Joel Fernandes" <joel@joelfernandes.org>,
"Daniel Axtens" <dja@axtens.net>,
"Arvind Sankar" <nivedita@alum.mit.edu>,
"Andy Shevchenko" <andriy.shevchenko@linux.intel.com>,
"Alexandru Ardelean" <alexandru.ardelean@analog.com>,
"Yury Norov" <yury.norov@gmail.com>,
x86@kernel.org, "H . Peter Anvin" <hpa@zytor.com>,
"Ard Biesheuvel" <ardb@kernel.org>,
"Paul E . McKenney" <paulmck@kernel.org>,
"Daniel Kiper" <daniel.kiper@oracle.com>,
"Bruce Ashfield" <bruce.ashfield@gmail.com>,
"Marco Elver" <elver@google.com>,
"Vamshi K Sthambamkadi" <vamshi.k.sthambamkadi@gmail.com>,
"Andi Kleen" <ak@suse.de>,
"Linus Torvalds" <torvalds@linux-foundation.org>,
"Dávid Bolvanský" <david.bolvansky@gmail.com>,
"Eli Friedman" <efriedma@quicinc.com>
Subject: Re: [PATCH v2 2/5] Makefile: add -fno-builtin-bcmp
Date: Wed, 19 Aug 2020 20:33:36 -0700 [thread overview]
Message-ID: <20200820033336.GB2167124@ubuntu-n2-xlarge-x86> (raw)
In-Reply-To: <20200819191654.1130563-3-ndesaulniers@google.com>
On Wed, Aug 19, 2020 at 12:16:51PM -0700, Nick Desaulniers wrote:
> The issue with using `-fno-builtin-*` flags was that they were not
> retained during an LTO link with LLVM. This was fixed in clang-11 by
> https://reviews.llvm.org/D71193
> (0508c994f0b14144041f2cfd3ba9f9a80f03de08), which is also the minimum
> supported version of clang for LTO. Use `-fno-builtin-bcmp` instead.
>
> With this applid, we can cleanly revert
> commit 5f074f3e192f ("lib/string.c: implement a basic bcmp")
>
> Reviewed-by: Kees Cook <keescook@chromium.org>
> Suggested-by: Nathan Chancellor <natechancellor@gmail.com>
> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
> ---
> Makefile | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/Makefile b/Makefile
> index e523dc8d30e0..def590b743a9 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -579,6 +579,7 @@ CLANG_FLAGS += -no-integrated-as
> endif
> CLANG_FLAGS += -Werror=unknown-warning-option
> CLANG_FLAGS += -fno-builtin-stpcpy
> +CLANG_FLAGS += -fno-builtin-bcmp
> KBUILD_CFLAGS += $(CLANG_FLAGS)
> KBUILD_AFLAGS += $(CLANG_FLAGS)
> export CLANG_FLAGS
> --
> 2.28.0.297.g1956fa8f8d-goog
>
next prev parent reply other threads:[~2020-08-20 3:33 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-19 19:16 [PATCH v2 0/5] -ffreestanding/-fno-builtin-* patches Nick Desaulniers
2020-08-19 19:16 ` [PATCH v2 1/5] Makefile: add -fno-builtin-stpcpy Nick Desaulniers
2020-08-20 3:33 ` Nathan Chancellor
2020-08-19 19:16 ` [PATCH v2 2/5] Makefile: add -fno-builtin-bcmp Nick Desaulniers
2020-08-20 3:33 ` Nathan Chancellor [this message]
2020-08-19 19:16 ` [PATCH v2 3/5] Revert "lib/string.c: implement a basic bcmp" Nick Desaulniers
2020-08-20 3:34 ` Nathan Chancellor
2020-08-19 19:16 ` [PATCH v2 4/5] x86/boot: use -fno-builtin-bcmp Nick Desaulniers
2020-08-19 19:29 ` Arvind Sankar
2020-08-19 20:11 ` Nick Desaulniers
2020-08-19 19:16 ` [PATCH v2 5/5] x86: don't build CONFIG_X86_32 as -ffreestanding Nick Desaulniers
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