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a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:reply-to :from:date:message-id:subject:to:cc; bh=OZXwVNbXZV4lI1LIGmmW/Kxp49zjuh7sF9Qwivelrog=; b=fCCMb7Awf2SKXWoxZk7z/9hhgPgRIBSt9vMbvWcQW3kHLpgX/T1jwqHHi10siXkLPd 40CnYlDBPj1Ye84WuFY9EzjhtNbiNsqFR1fphEkH22Ud9bBv0oNLkkBasRXcMfVOa7G5 cpAmUMAN3FnIEoHrQuA31cAvTUnJ10N3kY57PvB5cPNFlRboBOeByRxTTkkq31Wn+hb8 gOGwYk9mDbNtf+W6bnH5AG/f34QdB7sb4OYnTqM8GeDF00wLARTMQ8momwkK8IF5vk24 mMpEbCaTLM1pB+AWXajZE59/NbHnQL4Tmt1BIMGKWVggHXNp2a/QEUMar2gsjLTH85GX wAvw== X-Gm-Message-State: AOAM530lzJCM58UNHpK9AgpsS8eTDWFHUcRfzVfwpA2ouxt91OF65Osx Ue16WVNAEef7cJnm/+AhxTtz+hUJ8VzlDh3Bqtk= X-Google-Smtp-Source: ABdhPJzAiTMpa8HnPMwu8kOSlaF1npXrnm+zwFs4ky75CzlildU3IircUIlwv58E+G3wHMSg02zdAzwjIhOHaGrstVM= X-Received: by 2002:a5d:9c4e:: with SMTP id 14mr2066351iof.57.1614333733229; Fri, 26 Feb 2021 02:02:13 -0800 (PST) MIME-Version: 1.0 References: <20210225112122.2198845-1-arnd@kernel.org> In-Reply-To: From: Sedat Dilek Date: Fri, 26 Feb 2021 11:02:01 +0100 Message-ID: Subject: Re: [PATCH] [RFC] arm64: enable HAVE_LD_DEAD_CODE_DATA_ELIMINATION To: Arnd Bergmann X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210226_050215_403881_108102E1 X-CRM114-Status: GOOD ( 23.21 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: sedat.dilek@gmail.com Cc: Mark Rutland , Ionela Voinescu , Kees Cook , Arnd Bergmann , Catalin Marinas , Nick Desaulniers , "linux-kernel@vger.kernel.org" , Kristina Martsenko , Ard Biesheuvel , Nathan Chancellor , Clang-Built-Linux ML , Mark Brown , Andrew Scull , Marc Zyngier , Geert Uytterhoeven , Vincenzo Frascino , Will Deacon , David Brazdil , Linux ARM Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, Feb 26, 2021 at 10:51 AM Arnd Bergmann wrote: > > On Fri, Feb 26, 2021 at 10:05 AM Sedat Dilek wrote: > > On Fri, Feb 26, 2021 at 9:14 AM Arnd Bergmann wrote: > > > > > > BTW, is CONFIG_LD_DEAD_CODE_DATA_ELIMINATION=y setable for x86 (64bit)? > > > > ( Did not look or check for it. ) > > > > > > No, in mainline, HAVE_LD_DEAD_CODE_DATA_ELIMINATION is currently > > > only selected on MIPS and PowerPC. I only sent experimental patches to > > > enable it on arm64 and m68k, but have not tried booting them. If you > > > select the symbol on x86, you should see similar results. > > > > > > > OK, i see: > > > > $ git grep HAVE_LD_DEAD_CODE_DATA_ELIMINATION arch/mips/ > > arch/mips/Kconfig: select HAVE_LD_DEAD_CODE_DATA_ELIMINATION > > > > $ git grep HAVE_LD_DEAD_CODE_DATA_ELIMINATION arch/powerpc/ > > arch/powerpc/Kconfig: select HAVE_LD_DEAD_CODE_DATA_ELIMINATION > > > > So, I need to add this to arch/x86/Kconfig. > > > > You happen to know if changes to arch/x86/kernel/vmlinux.lds.S > > (sections) are needed? > > No idea. I'm still debugging a possible regression on arm64, but both > issues I found for arm64 are specific to that architecture and won't > happen on x86. It's likely that something else breaks though. > My first experiences with gc were with the freetz project (mips embedded router) and don't ask me what GCC version. I will try with gc + trim + cfi later after my current build has finished. > > Last question: > > The last days I see a lot of fixes touching inlining with LLVM/Clang v13-git. > > What git tag are you using? > > What are your experiences? > > Pending patches (kernel-side)? > > > > I use: > > $ /opt/llvm-toolchain/bin/clang --version > > dileks clang version 13.0.0 (https://github.com/llvm/llvm-project.git > > c465429f286f50e52a8d2b3b39f38344f3381cce) > > This is what I have on the build box: > Ubuntu clang version > 13.0.0-++20210223104451+ebca13c66504-1~exp1~20210223095200.234 > Distro-clang takes much longer here. Selfmade stage1-only LLVM toolchain compiles here 10% faster. cfi takes approx. 20% longer. With trim + gc I suppose it will take much longer. Let me test. Will report later. - Sedat - _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel