From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Wed, 30 Mar 2022 21:57:43 -0700 From: Kees Cook Subject: Re: [PATCH 1/2] kbuild: Remove '-mno-global-merge' Message-ID: <202203302156.87918948B8@keescook> References: <20220330234528.1426991-1-nathan@kernel.org> <20220330234528.1426991-2-nathan@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220330234528.1426991-2-nathan@kernel.org> To: Nathan Chancellor Cc: Masahiro Yamada , Nick Desaulniers , Richard Weinberger , Anton Ivanov , Johannes Berg , linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, linux-um@lists.infradead.org, llvm@lists.linux.dev, patches@lists.linux.dev List-ID: On Wed, Mar 30, 2022 at 04:45:27PM -0700, Nathan Chancellor wrote: > This flag is specific to clang, where it is only used by the 32-bit and > 64-bit ARM backends. In certain situations, the presence of this flag > will cause a warning, as shown by commit 6580c5c18fb3 ("um: clang: Strip > out -mno-global-merge from USER_CFLAGS"). > > Since commit 61163efae020 ("kbuild: LLVMLinux: Add Kbuild support for > building kernel with Clang") that added this flag back in 2014, there > have been quite a few changes to the GlobalMerge pass in LLVM. Building > several different ARCH=arm and ARCH=arm64 configurations with LLVM 11 > (minimum) and 15 (current main version) with this flag removed (i.e., > with the default of '-mglobal-merge') reveals no modpost warnings, so it > is likely that the issue noted in the comment is no longer relevant due > to changes in LLVM or modpost, meaning this flag can be removed. > > If any new warnings show up that are a result of the removal of this > flag, it can be added back under arch/arm{,64}/Makefile to avoid > warnings on other architectures. > > Signed-off-by: Nathan Chancellor Yeah, this looks right -- the history of this option seems to show it is no longer needed. Reviewed-by: Kees Cook -- Kees Cook