From: Nick Desaulniers <ndesaulniers@google.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Kees Cook <keescook@chromium.org>,
Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>,
Nathan Chancellor <natechancellor@gmail.com>,
Sedat Dilek <sedat.dilek@gmail.com>,
Marco Elver <elver@google.com>,
Andrey Konovalov <andreyknvl@google.com>,
Masahiro Yamada <masahiroy@kernel.org>,
clang-built-linux@googlegroups.com,
Daniel Borkmann <daniel@iogearbox.net>,
Alexei Starovoitov <ast@kernel.org>,
Will Deacon <will@kernel.org>,
Vincenzo Frascino <vincenzo.frascino@arm.com>,
linux-kernel@vger.kernel.org,
Nick Desaulniers <ndesaulniers@google.com>,
Fangrui Song <maskray@google.com>
Subject: [PATCH v3 2/7] Revert "kbuild: disable clang's default use of -fmerge-all-constants"
Date: Wed, 2 Sep 2020 15:59:06 -0700 [thread overview]
Message-ID: <20200902225911.209899-3-ndesaulniers@google.com> (raw)
In-Reply-To: <20200902225911.209899-1-ndesaulniers@google.com>
This reverts commit 87e0d4f0f37fb0c8c4aeeac46fff5e957738df79.
-fno-merge-all-constants has been the default since clang-6; the minimum
supported version of clang in the kernel is clang-10 (10.0.1).
Suggested-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Reviewed-by: Fangrui Song <maskray@google.com>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Reviewed-by: Sedat Dilek <sedat.dilek@gmail.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://reviews.llvm.org/rL329300.
Link: https://github.com/ClangBuiltLinux/linux/issues/9
---
Makefile | 9 ---------
1 file changed, 9 deletions(-)
diff --git a/Makefile b/Makefile
index 1cfa5029fd2f..e475650c9599 100644
--- a/Makefile
+++ b/Makefile
@@ -932,15 +932,6 @@ KBUILD_CFLAGS += $(call cc-disable-warning, maybe-uninitialized)
# disable invalid "can't wrap" optimizations for signed / pointers
KBUILD_CFLAGS += $(call cc-option,-fno-strict-overflow)
-# clang sets -fmerge-all-constants by default as optimization, but this
-# is non-conforming behavior for C and in fact breaks the kernel, so we
-# need to disable it here generally.
-KBUILD_CFLAGS += $(call cc-option,-fno-merge-all-constants)
-
-# for gcc -fno-merge-all-constants disables everything, but it is fine
-# to have actual conforming behavior enabled.
-KBUILD_CFLAGS += $(call cc-option,-fmerge-constants)
-
# Make sure -fstack-check isn't enabled (like gentoo apparently did)
KBUILD_CFLAGS += $(call cc-option,-fno-stack-check,)
--
2.28.0.402.g5ffc5be6b7-goog
next prev parent reply other threads:[~2020-09-02 23:00 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-02 22:59 [PATCH v3 0/7] set clang minimum version to 10.0.1 Nick Desaulniers
2020-09-02 22:59 ` [PATCH v3 1/7] compiler-clang: add build check for clang 10.0.1 Nick Desaulniers
2020-11-03 4:55 ` Jarkko Sakkinen
2020-11-03 6:38 ` Nathan Chancellor
2020-11-03 9:00 ` Jarkko Sakkinen
2020-11-03 18:48 ` Nick Desaulniers
2020-11-04 0:38 ` Jarkko Sakkinen
2020-11-04 1:18 ` Nick Desaulniers
2020-11-04 1:34 ` Jarkko Sakkinen
2020-11-04 1:36 ` Jarkko Sakkinen
2020-11-17 3:04 ` John Hubbard
2020-11-17 18:46 ` Nick Desaulniers
2020-11-18 2:31 ` Nathan Chancellor
2020-11-18 2:37 ` Andrew Morton
2020-09-02 22:59 ` Nick Desaulniers [this message]
2020-09-02 22:59 ` [PATCH v3 3/7] Revert "arm64: bti: Require clang >= 10.0.1 for in-kernel BTI support" Nick Desaulniers
2020-09-02 22:59 ` [PATCH v3 4/7] Revert "arm64: vdso: Fix compilation with clang older than 8" Nick Desaulniers
2020-09-02 22:59 ` [PATCH v3 5/7] Partially revert "ARM: 8905/1: Emit __gnu_mcount_nc when using Clang 10.0.0 or newer" Nick Desaulniers
2020-09-02 22:59 ` [PATCH v3 6/7] kasan: Remove mentions of unsupported Clang versions Nick Desaulniers
2020-09-02 22:59 ` [PATCH v3 7/7] compiler-gcc: improve version error Nick Desaulniers
2020-09-07 21:25 ` Will Deacon
2020-09-03 14:06 ` [PATCH v3 0/7] set clang minimum version to 10.0.1 Sedat Dilek
2020-09-03 17:28 ` Nathan Chancellor
2020-09-04 5:42 ` Miguel Ojeda
2020-09-07 16:12 ` Arvind Sankar
2020-09-08 4:42 ` Nathan Chancellor
2020-09-07 21:26 ` Will Deacon
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