From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 99804623; Tue, 29 Oct 2024 00:05:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730160305; cv=none; b=t9vTkXaikAi4KTenorWG7sQrZtpDuIuvXQi4/1Ug86qK9T+PHBFdmquM2D2j44eZsad09JkMHzTnAVXAMJG1hhtGdXTPwmLhANPZ8ne78iO/ORjm4aXhczJj6EGHKHUPsVo3PKw8RN7wz8tUURJVJNHGv/KSIIqeFXN8kxHw6D8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730160305; c=relaxed/simple; bh=y3u3gDzVsi7CD55QSPo+YZ8Qt3ypcM7i00iDNxmFwwg=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=FLoZwyXs5oKrMru+qHz6hXHSE4Mez/a5XMxqSy4+g1t6nLY9NMlZsfm0ZBDC5xjk8f1i6b0zflrvzoIy1iMxqnDNH24GRNrjthDkgG3S+5pjbyX6W5Oonx1FdCxIYiLw0wCzkPOuV8uym1o+BgJum2FZjpDB6OQX3qpdQcDCvto= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=F3YQeoLX; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="F3YQeoLX" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5844DC4CECD; Tue, 29 Oct 2024 00:05:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1730160305; bh=y3u3gDzVsi7CD55QSPo+YZ8Qt3ypcM7i00iDNxmFwwg=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=F3YQeoLXBPPTkKCccJC/1Dr7T0eSRl7vPp8BLgbgcaGpkELBkc7aDyADnlj7trMMB GwpHbACJHKte8LijTCV9Ehmt4qR03rqCSEB7RHVmoZwZXQ9EjZeIbUMus7WZyZBzJN YgN0jtUtjHo7Sg1LHM7i1Vues/6L2V1vRBGHHYFuntKArYHRvyuKUlGev+Z9MlLzMg t4hWBDGiMBZ+dtgfuPonAmSY038DrM4piKF+pdTG8iHFy8bO9dlQDUxw6pPJSLP195 1ad12FSKWo10zz92+RSMnOgvzU6mgbwBBqooO2fGICupMlciUXOF+2QlrBLBgtxtH/ DCi5eLMNHjdRg== Date: Mon, 28 Oct 2024 17:05:02 -0700 From: Kees Cook To: Rong Xu Cc: Alice Ryhl , Andrew Morton , Arnd Bergmann , Bill Wendling , Borislav Petkov , Breno Leitao , Brian Gerst , Dave Hansen , David Li , Han Shen , Heiko Carstens , "H. Peter Anvin" , Ingo Molnar , Jann Horn , Jonathan Corbet , Josh Poimboeuf , Juergen Gross , Justin Stitt , Masahiro Yamada , "Mike Rapoport (IBM)" , Nathan Chancellor , Nick Desaulniers , Nicolas Schier , "Paul E. McKenney" , Peter Zijlstra , Sami Tolvanen , Thomas Gleixner , Wei Yang , workflows@vger.kernel.org, Miguel Ojeda , Maksim Panchenko , "David S. Miller" , Andreas Larsson , Yonghong Song , Yabin Cui , Krzysztof Pszeniczny , Sriraman Tallam , Stephane Eranian , x86@kernel.org, linux-arch@vger.kernel.org, sparclinux@vger.kernel.org, linux-doc@vger.kernel.org, linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, llvm@lists.linux.dev Subject: Re: [PATCH v6 3/7] Adjust symbol ordering in text output section Message-ID: <202410281700.6BE0413F@keescook> References: <20241026051410.2819338-1-xur@google.com> <20241026051410.2819338-4-xur@google.com> Precedence: bulk X-Mailing-List: workflows@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20241026051410.2819338-4-xur@google.com> On Fri, Oct 25, 2024 at 10:14:05PM -0700, Rong Xu wrote: > When the -ffunction-sections compiler option is enabled, each function > is placed in a separate section named .text.function_name rather than > putting all functions in a single .text section. > > However, using -function-sections can cause problems with the > linker script. The comments included in include/asm-generic/vmlinux.lds.h > note these issues.: > “TEXT_MAIN here will match .text.fixup and .text.unlikely if dead > code elimination is enabled, so these sections should be converted > to use ".." first.” > > It is unclear whether there is a straightforward method for converting > a suffix to "..". While I'm not a fan of the potential loss of a page, I'm not aware of a way to do this renaming. If we want to keep these as "cold", then this is probably the best way to do it. > This patch modifies the order of subsections within the text output > section. Specifically, it repositions sections with certain fixed patterns > (for example .text.unlikely) before TEXT_MAIN, ensuring that they are > grouped and matched together. It also places .text.hot section at the > beginning of a page to help the TLB performance. > > Note that the limitation arises because the linker script employs glob > patterns instead of regular expressions for string matching. While there > is a method to maintain the current order using complex patterns, this > significantly complicates the pattern and increases the likelihood of > errors. > > This patch also changes vmlinux.lds.S for the sparc64 architecture to > accommodate specific symbol placement requirements. > > Co-developed-by: Han Shen > Signed-off-by: Han Shen > Signed-off-by: Rong Xu > Suggested-by: Sriraman Tallam > Suggested-by: Krzysztof Pszeniczny > Tested-by: Yonghong Song > Tested-by: Yabin Cui > Change-Id: I5202d40bc7e24f93c2bfb2f0d987e9dc57dec1b1 Reviewed-by: Kees Cook -Kees > --- > arch/sparc/kernel/vmlinux.lds.S | 5 +++++ > include/asm-generic/vmlinux.lds.h | 19 ++++++++++++------- > 2 files changed, 17 insertions(+), 7 deletions(-) > > diff --git a/arch/sparc/kernel/vmlinux.lds.S b/arch/sparc/kernel/vmlinux.lds.S > index d317a843f7ea9..f1b86eb303404 100644 > --- a/arch/sparc/kernel/vmlinux.lds.S > +++ b/arch/sparc/kernel/vmlinux.lds.S > @@ -48,6 +48,11 @@ SECTIONS > { > _text = .; > HEAD_TEXT > + ALIGN_FUNCTION(); > +#ifdef CONFIG_SPARC64 > + /* Match text section symbols in head_64.S first */ > + *head_64.o(.text) > +#endif > TEXT_TEXT > SCHED_TEXT > LOCK_TEXT > diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h > index eeadbaeccf88b..fd901951549c0 100644 > --- a/include/asm-generic/vmlinux.lds.h > +++ b/include/asm-generic/vmlinux.lds.h > @@ -553,19 +553,24 @@ > * .text section. Map to function alignment to avoid address changes > * during second ld run in second ld pass when generating System.map > * > - * TEXT_MAIN here will match .text.fixup and .text.unlikely if dead > - * code elimination is enabled, so these sections should be converted > - * to use ".." first. > + * TEXT_MAIN here will match symbols with a fixed pattern (for example, > + * .text.hot or .text.unlikely) if dead code elimination or > + * function-section is enabled. Match these symbols first before > + * TEXT_MAIN to ensure they are grouped together. > + * > + * Also placing .text.hot section at the beginning of a page, this > + * would help the TLB performance. > */ > #define TEXT_TEXT \ > ALIGN_FUNCTION(); \ > + *(.text.asan.* .text.tsan.*) \ > + *(.text.unknown .text.unknown.*) \ > + *(.text.unlikely .text.unlikely.*) \ > + . = ALIGN(PAGE_SIZE); \ > *(.text.hot .text.hot.*) \ > *(TEXT_MAIN .text.fixup) \ > - *(.text.unlikely .text.unlikely.*) \ > - *(.text.unknown .text.unknown.*) \ > NOINSTR_TEXT \ > - *(.ref.text) \ > - *(.text.asan.* .text.tsan.*) > + *(.ref.text) > > > /* sched.text is aling to function alignment to secure we have same > -- > 2.47.0.163.g1226f6d8fa-goog > -- Kees Cook