From patchwork Thu Oct 10 19:23:53 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Rong Xu X-Patchwork-Id: 13830915 Received: from mail-yw1-f201.google.com (mail-yw1-f201.google.com [209.85.128.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 18F2B1CF7AC for ; Thu, 10 Oct 2024 19:24:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728588250; cv=none; b=JdggiCDFN5rHsm25JqWf9FCRHN3ceu3tBeHoaR5w42Y7v3/R6mbx7ddA7qlUp8rER2VY2zFQ6k/OfQLvRFp9KvjVMhnHp0StyqWn6428M0oUsXwlHj9u6U9zIFlhXrDSvj/FDjzrLdRmw2rquw7CERbXZNXpsjN1o3CbN57qahk= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728588250; c=relaxed/simple; bh=4aV4Vf4Dnlms7H78qFliS5vnmDmCAFO20W4kAwl8veI=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=qcMKu4MhQnduND//pTT+GYI92NbPDghBRpMnkTqRh+3ZZWWfFRg1W8XEuhEjmiYsWielYAxxzBvPr6/M1bJHlUKAqFp1yKqkXYZN+U9A75rrzX9WPu3e5x7ks/3p4y5v+suTSnro1bwAPxYvw+QK8b4Vuhi0qzWo7s8itfmeq74= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--xur.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=DKbyADYO; arc=none smtp.client-ip=209.85.128.201 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--xur.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="DKbyADYO" Received: by mail-yw1-f201.google.com with SMTP id 00721157ae682-6e20e22243dso23351057b3.1 for ; Thu, 10 Oct 2024 12:24:07 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1728588247; x=1729193047; darn=vger.kernel.org; h=content-transfer-encoding:cc:to:from:subject:message-id:references :mime-version:in-reply-to:date:from:to:cc:subject:date:message-id :reply-to; bh=XX/6HD4slzBTzGEwcNiNs+1L0zFh7B6w5scbjoGcHw4=; b=DKbyADYO9DRkWYd69M+c1u1muRjSJOtgTTC60yKZlVA9k4iH1fnfxP/7v4RFAm53wx 2/EJZaW4ZvdIXPtlM7RHjMexn1It3o5fn2BIGztzt6+pDxFA17lNtclPgkEokJ4q+xsM /b5A5ZexJN3nCtzr8l/hSRRM7/ppRcdcs+hYho1yYrcoMo9bMzh7k7uvUlbsZkw4MeSq Xxoym2cDBF2KspB8xofjCjlB8yp1rxFsoTLaV5X77Q28AuCi6do185kFxMyV9vpqiNEU by1ccl5rWGSnKk6ojcIY++1zV/EnacuxGF9JBPMV2WuGhCXR4gCkv8faTCV2fhBUNTxj WH8Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1728588247; x=1729193047; h=content-transfer-encoding:cc:to:from:subject:message-id:references :mime-version:in-reply-to:date:x-gm-message-state:from:to:cc:subject :date:message-id:reply-to; bh=XX/6HD4slzBTzGEwcNiNs+1L0zFh7B6w5scbjoGcHw4=; b=TdUrn8D7fPhiOfFINuEDlvrL13DUuFOEyFdtc1mfnSi4KnYPIx+xyvvg/b5Q1RrJNT kaoUqP+7tbhivP7u92iHoVHietIlRB4c0AYi3EZv/J2JsT5372d1MaClKH9wbFMCYIud nODaYNImX6VOFmZJdSNAdkLcH0+fLmDwJfihe0r+iuhEiBm5m4ByJd2p94eqSP4uKQ5f sm2/oY0SOp0wB5CDrxiI/F/7kodE3mQfXLm6za1273fKoxcLtfv4U1T9epmsjPQIR3pU X5wjGcQXnYYrwvZIxOSGZv/kfDqqqMbqg0cF2Fe29Rg3h4i51PtPdpNexfgt64x4aXi4 DILQ== X-Forwarded-Encrypted: i=1; AJvYcCVMxksx55sjTvqI0/EFm8B8z42csRkSjNAkN/M+z9hsopz+qxHgNraT+FgryXhldrDQMPl8xn88iuOdMAQ=@vger.kernel.org X-Gm-Message-State: AOJu0YyAAvvyreggZSW3J1paFAHRKD0qdnu1fSLBt02v6W7ucbEeZTFz q1tX7zutke7kyazcMgTy+My2IDgNiL13Z3wBWszyLTM/NAVdLAJjvf+26xD5SV5QAQ== X-Google-Smtp-Source: AGHT+IGyWjvgMgjNWbkOgO7lLoUZEFijLdQklOL6eZgBelbYevlja9yvXhNh71Ny3sIrfPmpes+4ZXM= X-Received: from xur.c.googlers.com ([fda3:e722:ac3:cc00:20:ed76:c0a8:2330]) (user=xur job=sendgmr) by 2002:a05:690c:731:b0:6b0:d571:3540 with SMTP id 00721157ae682-6e32217dfb7mr181217b3.6.1728588246387; Thu, 10 Oct 2024 12:24:06 -0700 (PDT) Date: Thu, 10 Oct 2024 12:23:53 -0700 In-Reply-To: <20241010192400.451187-1-xur@google.com> Precedence: bulk X-Mailing-List: linux-kbuild@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20241010192400.451187-1-xur@google.com> X-Mailer: git-send-email 2.47.0.rc1.288.g06298d1525-goog Message-ID: <20241010192400.451187-2-xur@google.com> Subject: [PATCH v3 1/6] Add AutoFDO support for Clang build From: Rong Xu To: 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 , Kees Cook , Masahiro Yamada , "Mike Rapoport (IBM)" , Nathan Chancellor , Nick Desaulniers , Nicolas Schier , "Paul E. McKenney" , Peter Zijlstra , Rong Xu , Sami Tolvanen , Thomas Gleixner , Wei Yang , workflows@vger.kernel.org, Miguel Ojeda , Maksim Panchenko Cc: x86@kernel.org, linux-arch@vger.kernel.org, linux-doc@vger.kernel.org, linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, llvm@lists.linux.dev, Sriraman Tallam , Krzysztof Pszeniczny , Stephane Eranian Add the build support for using Clang's AutoFDO. Building the kernel with AutoFDO does not reduce the optimization level from the compiler. AutoFDO uses hardware sampling to gather information about the frequency of execution of different code paths within a binary. This information is then used to guide the compiler's optimization decisions, resulting in a more efficient binary. Experiments showed that the kernel can improve up to 10% in latency. The support requires a Clang compiler after LLVM 17. This submission is limited to x86 platforms that support PMU features like LBR on Intel machines and AMD Zen3 BRS. Support for SPE on ARM 1, and BRBE on ARM 1 is part of planned future work. Here is an example workflow for AutoFDO kernel: 1) Build the kernel on the HOST machine with LLVM enabled, for example, $ make menuconfig LLVM=1 Turn on AutoFDO build config: CONFIG_AUTOFDO_CLANG=y With a configuration that has LLVM enabled, use the following command: scripts/config -e AUTOFDO_CLANG After getting the config, build with $ make LLVM=1 2) Install the kernel on the TEST machine. 3) Run the load tests. The '-c' option in perf specifies the sample event period. We suggest using a suitable prime number, like 500009, for this purpose. For Intel platforms: $ perf record -e BR_INST_RETIRED.NEAR_TAKEN:k -a -N -b -c \ -o -- For AMD platforms: The supported system are: Zen3 with BRS, or Zen4 with amd_lbr_v2 For Zen3: $ cat proc/cpuinfo | grep " brs" For Zen4: $ cat proc/cpuinfo | grep amd_lbr_v2 $ perf record --pfm-events RETIRED_TAKEN_BRANCH_INSTRUCTIONS:k -a \ -N -b -c -o -- 4) (Optional) Download the raw perf file to the HOST machine. 5) To generate an AutoFDO profile, two offline tools are available: create_llvm_prof and llvm_profgen. The create_llvm_prof tool is part of the AutoFDO project and can be found on GitHub (https://github.com/google/autofdo), version v0.30.1 or later. The llvm_profgen tool is included in the LLVM compiler itself. It's important to note that the version of llvm_profgen doesn't need to match the version of Clang. It needs to be the LLVM 19 release or later, or from the LLVM trunk. $ llvm-profgen --kernel --binary= --perfdata= \ -o or $ create_llvm_prof --binary= --profile= \ --format=extbinary -o Note that multiple AutoFDO profile files can be merged into one via: $ llvm-profdata merge -o ... 6) Rebuild the kernel using the AutoFDO profile file with the same config as step 1, (Note CONFIG_AUTOFDO_CLANG needs to be enabled): $ make LLVM=1 CLANG_AUTOFDO_PROFILE= Co-developed-by: Han Shen Signed-off-by: Han Shen Signed-off-by: Rong Xu Suggested-by: Sriraman Tallam Suggested-by: Krzysztof Pszeniczny Suggested-by: Nick Desaulniers Suggested-by: Stephane Eranian --- Documentation/dev-tools/autofdo.rst | 165 ++++++++++++++++++++++++++++ Documentation/dev-tools/index.rst | 1 + MAINTAINERS | 7 ++ Makefile | 1 + arch/Kconfig | 20 ++++ arch/x86/Kconfig | 1 + scripts/Makefile.autofdo | 23 ++++ scripts/Makefile.lib | 10 ++ tools/objtool/check.c | 1 + 9 files changed, 229 insertions(+) create mode 100644 Documentation/dev-tools/autofdo.rst create mode 100644 scripts/Makefile.autofdo diff --git a/Documentation/dev-tools/autofdo.rst b/Documentation/dev-tools/autofdo.rst new file mode 100644 index 000000000000..c244e2b697a4 --- /dev/null +++ b/Documentation/dev-tools/autofdo.rst @@ -0,0 +1,165 @@ +.. SPDX-License-Identifier: GPL-2.0 + +=================================== +Using AutoFDO with the Linux kernel +=================================== + +This enables AutoFDO build support for the kernel when using +the Clang compiler. AutoFDO (Auto-Feedback-Directed Optimization) +is a type of profile-guided optimization (PGO) used to enhance the +performance of binary executables. It gathers information about the +frequency of execution of various code paths within a binary using +hardware sampling. This data is then used to guide the compiler's +optimization decisions, resulting in a more efficient binary. AutoFDO +is a powerful optimization technique, and data indicates that it can +significantly improve kernel performance. It's especially beneficial +for workloads affected by front-end stalls. + +For AutoFDO builds, unlike non-FDO builds, the user must supply a +profile. Acquiring an AutoFDO profile can be done in several ways. +AutoFDO profiles are created by converting hardware sampling using +the "perf" tool. It is crucial that the workload used to create these +perf files is representative; they must exhibit runtime +characteristics similar to the workloads that are intended to be +optimized. Failure to do so will result in the compiler optimizing +for the wrong objective. + +The AutoFDO profile often encapsulates the program's behavior. If the +performance-critical codes are architecture-independent, the profile +can be applied across platforms to achieve performance gains. For +instance, using the profile generated on Intel architecture to build +a kernel for AMD architecture can also yield performance improvements. + +There are two methods for acquiring a representative profile: +(1) Sample real workloads using a production environment. +(2) Generate the profile using a representative load test. +When enabling the AutoFDO build configuration without providing an +AutoFDO profile, the compiler only modifies the dwarf information in +the kernel without impacting runtime performance. It's advisable to +use a kernel binary built with the same AutoFDO configuration to +collect the perf profile. While it's possible to use a kernel built +with different options, it may result in inferior performance. + +One can collect profiles using AutoFDO build for the previous kernel. +AutoFDO employs relative line numbers to match the profiles, offering +some tolerance for source changes. This mode is commonly used in a +production environment for profile collection. + +In a profile collection based on a load test, the AutoFDO collection +process consists of the following steps: + +#. Initial build: The kernel is built with AutoFDO options + without a profile. + +#. Profiling: The above kernel is then run with a representative + workload to gather execution frequency data. This data is + collected using hardware sampling, via perf. AutoFDO is most + effective on platforms supporting advanced PMU features like + LBR on Intel machines. + +#. AutoFDO profile generation: Perf output file is converted to + the AutoFDO profile via offline tools. + +The support requires a Clang compiler LLVM 17 or later. + +Preparation +=========== + +Configure the kernel with:: + + CONFIG_AUTOFDO_CLANG=y + +Customization +============= + +You can enable or disable AutoFDO build for individual file and directories by +adding a line similar to the following to the respective kernel Makefile: + +- For enabling a single file (e.g. foo.o) :: + + AUTOFDO_PROFILE_foo.o := y + +- For enabling all files in one directory :: + + AUTOFDO_PROFILE := y + +- For disabling one file :: + + AUTOFDO_PROFILE_foo.o := n + +- For disabling all files in one directory :: + + AUTOFDO_PROFILE := n + +Workflow +======== + +Here is an example workflow for AutoFDO kernel: + +1) Build the kernel on the HOST machine with LLVM enabled, + for example, :: + + $ make menuconfig LLVM=1 + + Turn on AutoFDO build config:: + + CONFIG_AUTOFDO_CLANG=y + + With a configuration that with LLVM enabled, use the following command:: + + $ scripts/config -e AUTOFDO_CLANG + + After getting the config, build with :: + + $ make LLVM=1 + +2) Install the kernel on the TEST machine. + +3) Run the load tests. The '-c' option in perf specifies the sample + event period. We suggest using a suitable prime number, like 500009, + for this purpose. + + - For Intel platforms:: + + $ perf record -e BR_INST_RETIRED.NEAR_TAKEN:k -a -N -b -c -o -- + + - For AMD platforms: For Intel platforms: + The supported systems are: Zen3 with BRS, or Zen4 with amd_lbr_v2. To check, + For Zen3:: + + $ cat proc/cpuinfo | grep " brs" + + For Zen4:: + + $ cat proc/cpuinfo | grep amd_lbr_v2 + + The following command generated the perf data file:: + + $ perf record --pfm-events RETIRED_TAKEN_BRANCH_INSTRUCTIONS:k -a -N -b -c -o -- + +4) (Optional) Download the raw perf file to the HOST machine. + +5) To generate an AutoFDO profile, two offline tools are available: + create_llvm_prof and llvm_profgen. The create_llvm_prof tool is part + of the AutoFDO project and can be found on GitHub + (https://github.com/google/autofdo), version v0.30.1 or later. + The llvm_profgen tool is included in the LLVM compiler itself. It's + important to note that the version of llvm_profgen doesn't need to match + the version of Clang. It needs to be the LLVM 19 release of Clang + or later, or just from the LLVM trunk. :: + + $ llvm-profgen --kernel --binary= --perfdata= -o + + or :: + + $ create_llvm_prof --binary= --profile= --format=extbinary -o + + Note that multiple AutoFDO profile files can be merged into one via:: + + $ llvm-profdata merge -o ... + +6) Rebuild the kernel using the AutoFDO profile file with the same config as step 1, + (Note CONFIG_AUTOFDO_CLANG needs to be enabled):: + + $ make LLVM=1 CLANG_AUTOFDO_PROFILE= + diff --git a/Documentation/dev-tools/index.rst b/Documentation/dev-tools/index.rst index 53d4d124f9c5..6945644f7008 100644 --- a/Documentation/dev-tools/index.rst +++ b/Documentation/dev-tools/index.rst @@ -34,6 +34,7 @@ Documentation/dev-tools/testing-overview.rst ktap checkuapi gpio-sloppy-logic-analyzer + autofdo .. only:: subproject and html diff --git a/MAINTAINERS b/MAINTAINERS index d01256208c9f..1b8db863031f 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -3678,6 +3678,13 @@ F: kernel/audit* F: lib/*audit.c K: \baudit_[a-z_0-9]\+\b +AUTOFDO BUILD +M: Rong Xu +M: Han Shen +S: Supported +F: Documentation/dev-tools/autofdo.rst +F: scripts/Makefile.autofdo + AUXILIARY BUS DRIVER M: Greg Kroah-Hartman R: Dave Ertman diff --git a/Makefile b/Makefile index c5493c0c0ca1..bbb6ec68f5dc 100644 --- a/Makefile +++ b/Makefile @@ -1018,6 +1018,7 @@ include-$(CONFIG_KMSAN) += scripts/Makefile.kmsan include-$(CONFIG_UBSAN) += scripts/Makefile.ubsan include-$(CONFIG_KCOV) += scripts/Makefile.kcov include-$(CONFIG_RANDSTRUCT) += scripts/Makefile.randstruct +include-$(CONFIG_AUTOFDO_CLANG) += scripts/Makefile.autofdo include-$(CONFIG_GCC_PLUGINS) += scripts/Makefile.gcc-plugins include $(addprefix $(srctree)/, $(include-y)) diff --git a/arch/Kconfig b/arch/Kconfig index 8af374ea1adc..5e9604960cbb 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -811,6 +811,26 @@ config LTO_CLANG_THIN If unsure, say Y. endchoice +config ARCH_SUPPORTS_AUTOFDO_CLANG + bool + +config AUTOFDO_CLANG + bool "Enable Clang's AutoFDO build (EXPERIMENTAL)" + depends on ARCH_SUPPORTS_AUTOFDO_CLANG + depends on CC_IS_CLANG && CLANG_VERSION >= 170000 + help + This option enables Clang’s AutoFDO build. When + an AutoFDO profile is specified in variable + CLANG_AUTOFDO_PROFILE during the build process, + Clang uses the profile to optimize the kernel. + + If no profile is specified, AutoFDO options are + still passed to Clang to facilitate the collection + of perf data for creating an AutoFDO profile in + subsequent builds. + + If unsure, say N. + config ARCH_SUPPORTS_CFI_CLANG bool help diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 2852fcd82cbd..503a0268155a 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -126,6 +126,7 @@ config X86 select ARCH_SUPPORTS_LTO_CLANG select ARCH_SUPPORTS_LTO_CLANG_THIN select ARCH_SUPPORTS_RT + select ARCH_SUPPORTS_AUTOFDO_CLANG select ARCH_USE_BUILTIN_BSWAP select ARCH_USE_CMPXCHG_LOCKREF if X86_CMPXCHG64 select ARCH_USE_MEMTEST diff --git a/scripts/Makefile.autofdo b/scripts/Makefile.autofdo new file mode 100644 index 000000000000..1c9f224bc221 --- /dev/null +++ b/scripts/Makefile.autofdo @@ -0,0 +1,23 @@ +# SPDX-License-Identifier: GPL-2.0 + +# Enable available and selected Clang AutoFDO features. + +CFLAGS_AUTOFDO_CLANG := -fdebug-info-for-profiling -mllvm -enable-fs-discriminator=true -mllvm -improved-fs-discriminator=true + +# If CONFIG_DEBUG_INFO is not enabled, set -gmlt option. +ifndef CONFIG_DEBUG_INFO + CFLAGS_AUTOFDO_CLANG += -gmlt +endif + +ifdef CLANG_AUTOFDO_PROFILE + CFLAGS_AUTOFDO_CLANG += -fprofile-sample-use=$(CLANG_AUTOFDO_PROFILE) +endif + +ifdef CONFIG_LTO_CLANG_THIN + ifdef CLANG_AUTOFDO_PROFILE + KBUILD_LDFLAGS += --lto-sample-profile=$(CLANG_AUTOFDO_PROFILE) + endif + KBUILD_LDFLAGS += --mllvm=-enable-fs-discriminator=true --mllvm=-improved-fs-discriminator=true -plugin-opt=thinlto +endif + +export CFLAGS_AUTOFDO_CLANG diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib index 01a9f567d5af..e85d6ac31bd9 100644 --- a/scripts/Makefile.lib +++ b/scripts/Makefile.lib @@ -191,6 +191,16 @@ _c_flags += $(if $(patsubst n%,, \ -D__KCSAN_INSTRUMENT_BARRIERS__) endif +# +# Enable Clang's AutoFDO build flags for a file or directory depending on +# variables AUTOFDO_PROFILE_obj.o and AUTOFDO_PROFILE. +# +ifeq ($(CONFIG_AUTOFDO_CLANG),y) +_c_flags += $(if $(patsubst n%,, \ + $(AUTOFDO_PROFILE_$(target-stem).o)$(AUTOFDO_PROFILE)$(is-kernel-object)), \ + $(CFLAGS_AUTOFDO_CLANG)) +endif + # $(src) for including checkin headers from generated source files # $(obj) for including generated headers from checkin source files ifeq ($(KBUILD_EXTMOD),) diff --git a/tools/objtool/check.c b/tools/objtool/check.c index 6604f5d038aa..4c5229991e1e 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -4557,6 +4557,7 @@ static int validate_ibt(struct objtool_file *file) !strcmp(sec->name, "__jump_table") || !strcmp(sec->name, "__mcount_loc") || !strcmp(sec->name, ".kcfi_traps") || + !strcmp(sec->name, ".llvm.call-graph-profile") || strstr(sec->name, "__patchable_function_entries")) continue; From patchwork Thu Oct 10 19:23:54 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Rong Xu X-Patchwork-Id: 13830916 Received: from mail-yb1-f202.google.com (mail-yb1-f202.google.com [209.85.219.202]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D468A1CF7D6 for ; Thu, 10 Oct 2024 19:24:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.219.202 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728588251; cv=none; b=bJcsRacwtCA/5LqsCjbHsm7Q6R1TdtL1LKpiZVyLY4HDPe40lJIoiy7t08iWTmFyiIKzuu67VxjCA/WgSD5nM23k71pdV0/t/2QHWocjrjHnJOJ5GaEaU+9qRQmBSRYdFiQ1K0tw3njPze+LDG1/KLAaF1dCfhe+/PCCpTu18Jc= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728588251; c=relaxed/simple; bh=B/fTpCzd8QlJMQ3iEfz2aTZvNZTM1lTyUzt5b6yEoHA=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=Yy6XZw4KoRqdOFWvhGuFSpS3TNH7T451kTLqFugg9siqAqOr0r8Rm6Y7WFYQnqo3mOMib3F78vE+JGN7U9gWEoKjdSdRD05aiwuSkmD7JhRnjVLGv7pi3LLYFr8VkyCtuCu/pxsLsXMUyz42wf4kgDX2dA9hFRWKlh2B038KKog= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--xur.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=qs5hkC9D; arc=none smtp.client-ip=209.85.219.202 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--xur.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="qs5hkC9D" Received: by mail-yb1-f202.google.com with SMTP id 3f1490d57ef6-e2913beeddaso699871276.0 for ; Thu, 10 Oct 2024 12:24:09 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1728588249; x=1729193049; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=pwVGeNhEiYELCNV51bxA2EzTaJbA2K5Fr027Br3jO4Q=; b=qs5hkC9DxaPqNC52LcXmgLYggJaqQWSGbKzkQ45ToHblTiJPSYXLIQIzZbZg5jNgTi z/NTFdYp8ufpUA7vRvPtnYnlNEOwNi74wqSF4nDmJsnkmTlHPfG0lh7Ns9a50fyhaFbu jF6xnNLBVPbLQ0r8ueDs+/W6Qf8yYBrxx0YUBK9jCHiyW1UMW6LkSeBnFArdtpcE7U48 zV7TEQq2kpj/DPwKjbMBKG+ZpQ5eoK1htw3FCFqTPAQDb7/WqF5LRuTI5ApS7XGuj35B HIHDRlsa0yIk3XMf8gS4Wbz9HltVsTq6zF0zgDtAouu2sX9G5BQYSF5rsVwXC2bKBKju ZsGw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1728588249; x=1729193049; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=pwVGeNhEiYELCNV51bxA2EzTaJbA2K5Fr027Br3jO4Q=; b=YlQdyDT+S4puBStXVIYrUsYyPGJMYhxpeLz379UU0bnATlJOhk1b6Gp8NgRujaw54w z8lMdWYbAhPHt1L9jsXb47zwbDWNCyFXMGENbq0IbmpdIsGJCzMkc2eX5PsKCOOO4Xw3 yYWVXlTfnOQI49yB8U3KAico2tC8n8DER6NIR4RIaAxVD0u8qyJ3pEmDWr/IAcdbHHVd CJ60pyLD4sXgK/PqsCoTd0kxySqde/U91H89m6j/t2+FPaUeSfaQhb3D9JUq4HfkDlPp Vsv/41C8GRZ1w1ebF0UE3zNfeXJsbZW6ogodnn5SLuWCmWuDgcrV/qC1N7rXlQThzGbK D+kQ== X-Forwarded-Encrypted: i=1; AJvYcCVRRvpihP8K0Nks+3Ce5gSaz7w5q+s9JAW8rTozVNmwc4G4di7fsbjkyZds7rHb6J+kdvmqn+5Vx2wUmhc=@vger.kernel.org X-Gm-Message-State: AOJu0YyK73b0ckT6ebJqXFufT7Xg4HSIY6fHJPc5pdq6E9hOKigx3PIZ 7xyUlyId26ZAP1OiJy+vZ5gDkzbnrViXBKhFRDkXlrTdO7j3i2JiVczyf2XZlS90DA== X-Google-Smtp-Source: AGHT+IET7ynYxoh2WLaFTqujq1dsN8li9OFmo1T7KNB2xR5JtuPPo+YvvfF+NvnbjuFxvNf7cf4DObk= X-Received: from xur.c.googlers.com ([fda3:e722:ac3:cc00:20:ed76:c0a8:2330]) (user=xur job=sendgmr) by 2002:a25:b104:0:b0:e29:a86:fd0d with SMTP id 3f1490d57ef6-e290bb40627mr73646276.5.1728588248551; Thu, 10 Oct 2024 12:24:08 -0700 (PDT) Date: Thu, 10 Oct 2024 12:23:54 -0700 In-Reply-To: <20241010192400.451187-1-xur@google.com> Precedence: bulk X-Mailing-List: linux-kbuild@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20241010192400.451187-1-xur@google.com> X-Mailer: git-send-email 2.47.0.rc1.288.g06298d1525-goog Message-ID: <20241010192400.451187-3-xur@google.com> Subject: [PATCH v3 2/6] objtool: Fix unreachable instruction warnings for weak funcitons From: Rong Xu To: 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 , Kees Cook , Masahiro Yamada , "Mike Rapoport (IBM)" , Nathan Chancellor , Nick Desaulniers , Nicolas Schier , "Paul E. McKenney" , Peter Zijlstra , Rong Xu , Sami Tolvanen , Thomas Gleixner , Wei Yang , workflows@vger.kernel.org, Miguel Ojeda , Maksim Panchenko Cc: x86@kernel.org, linux-arch@vger.kernel.org, linux-doc@vger.kernel.org, linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, llvm@lists.linux.dev, Sriraman Tallam , Krzysztof Pszeniczny In the presence of both weak and strong function definitions, the linker drops the weak symbol in favor of a strong symbol, but leaves the code in place. Code in ignore_unreachable_insn() has some heuristics to suppress the warning, but it does not work when -ffunction-sections is enabled. Suppose function foo has both strong and weak definitions. Case 1: The strong definition has an annotated section name, like .init.text. Only the weak definition will be placed into .text.foo. But since the section has no symbols, there will be no "hole" in the section. Case 2: Both sections are without an annotated section name. Both will be placed into .text.foo section, but there will be only one symbol (the strong one). If the weak code is before the strong code, there is no "hole" as it fails to find the right-most symbol before the offset. The fix is to use the first node to compute the hole if hole.sym is empty. If there is no symbol in the section, the first node will be NULL, in which case, -1 is returned to skip the whole section. Co-developed-by: Han Shen Signed-off-by: Han Shen Signed-off-by: Rong Xu Suggested-by: Sriraman Tallam Suggested-by: Krzysztof Pszeniczny --- tools/objtool/elf.c | 15 ++++++++++----- 1 file changed, 10 insertions(+), 5 deletions(-) diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c index 3d27983dc908..6f64d611faea 100644 --- a/tools/objtool/elf.c +++ b/tools/objtool/elf.c @@ -224,12 +224,17 @@ int find_symbol_hole_containing(const struct section *sec, unsigned long offset) if (n) return 0; /* not a hole */ - /* didn't find a symbol for which @offset is after it */ - if (!hole.sym) - return 0; /* not a hole */ + /* + * @offset >= sym->offset + sym->len, find symbol after it. + * When hole.sym is empty, use the first node to compute the hole. + * If there is no symbol in the section, the first node will be NULL, + * in which case, -1 is returned to skip the whole section. + */ + if (hole.sym) + n = rb_next(&hole.sym->node); + else + n = rb_first_cached(&sec->symbol_tree); - /* @offset >= sym->offset + sym->len, find symbol after it */ - n = rb_next(&hole.sym->node); if (!n) return -1; /* until end of address space */ From patchwork Thu Oct 10 19:23:55 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Rong Xu X-Patchwork-Id: 13830917 Received: from mail-yw1-f201.google.com (mail-yw1-f201.google.com [209.85.128.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C3BD61D04B9 for ; Thu, 10 Oct 2024 19:24:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728588253; cv=none; b=Ut5NjX0DBUxRUG/sBAsL4VRh7MM1pHcJ8isCwZpeTA9FvOXXg/76dcfEi7Stiid0faDWu0fOIyK2XQSHzdPHWjpMQIoXDI5gIiMFthbe57n/HsZvlRgf7d/c2361WNmu1UO60+M+Cq47Zc0jd5LW8OfIJwAzS86K+AhlC2fSEq4= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728588253; c=relaxed/simple; bh=LqcsOVQmv5GpC5shRDpw1q19kzqKid+XE2EfW/9oI3s=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=eSB//A4nzEf4clFVtVOmbH9o7Zwd2Ha2QylXDNJtrIwdytoyTYhdYAinz0IUqX5WXBk9fiEW29Wm9Gko1/MCQ8xK9GuRpdHqlwSg8RtfxOeldx0lyU7/h5J89xfsXjf43ER2pXd40mD/dJsH6UAaEF/6x2gxddvLw1ZTYdYVNVs= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--xur.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=UV8mHI9k; arc=none smtp.client-ip=209.85.128.201 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--xur.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="UV8mHI9k" Received: by mail-yw1-f201.google.com with SMTP id 00721157ae682-6d9e31e66eeso27977847b3.1 for ; Thu, 10 Oct 2024 12:24:11 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1728588251; x=1729193051; darn=vger.kernel.org; h=content-transfer-encoding:cc:to:from:subject:message-id:references :mime-version:in-reply-to:date:from:to:cc:subject:date:message-id :reply-to; bh=3BOqTSYvoekh3ysMWFRZqW1diZJBhOLc/W4rCwg+Ukg=; b=UV8mHI9kyjtUFrXS3BNmZ17sfu7X2IK5Ot50foKxp75pzrC9SJACTptnlCLRKZ6Zkx UIMD9toG0hcWAddEHT/sE0c1Bg3YgG3nvfb1+u1szGlFnR/1fImL/hXgJ5gYulmku9WZ aQwTlwE24yl0vCpWh3gM0ZQOFSXytZigMAJ//iEcMQJS/1+piF1UE8A2rooFG3tG4g3H tQHTmDFDUCZzz9RIyvDF87Up+AhmZVuTRKzTBbrWWlykpvcORivzMV+ZMOyHKuWGmuIM MS4B7MgWHPI/HGDy6g12CMv2vthKO183UR4LpxM0SBS0xhEt9QU989EHM2Qs7t7qcPRs GkSQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1728588251; x=1729193051; h=content-transfer-encoding:cc:to:from:subject:message-id:references :mime-version:in-reply-to:date:x-gm-message-state:from:to:cc:subject :date:message-id:reply-to; bh=3BOqTSYvoekh3ysMWFRZqW1diZJBhOLc/W4rCwg+Ukg=; b=WP7YEVs7PTL9f0Zl2urz99mWZ28z9MzM/TGjElxHEd8yuZwrmSJ6ujYCl038/wxAjM tDAu4uIET18m3i8iKw72kJ2DPxQ2ZzNjlusccu7T0Yj5FQjfq9Q5sKi5NFr6qzAvZb+q XvG9o1LAJNAuezONxAOG4G6NUbN5IIiIIQP6yfg7RCdKu6ngpkvnVFibGYevucqLcZlk XhG1HO6FkjARgSXAg0LevCp/nwumGWRxhw/kM1c6zmS4qhj2277i4jTay+tAIkLTpYOY iDbvsyZx08uqG2ER6TpNZoLd5rK3sI1fHinw67LOc1/AU+se3FkMaAuD4PnKZqCurXh7 4x6w== X-Forwarded-Encrypted: i=1; AJvYcCXiRUkgMamNAAgyQunJiKSvG/PJvmKX5QLaN1S3Vv9qGPfOMld1NUBGNaIOk4W+ZEcW5KjvL55BZGmqS4M=@vger.kernel.org X-Gm-Message-State: AOJu0Yzmps7r1H8H+BuASrECrWwGboYSRlzkb5J2r4wNzhoHLgGJ2SyY UTyGuV9sVf27QiwN655XA/aNvwuawS7bCFbztx6LElS3a2GPf5e8HQ102WDovqWV8g== X-Google-Smtp-Source: AGHT+IHEhJDc7jYHTPhzM4J4p0+oM2iW7zVVsM3E55tbL5mucatmOoOEuvmUjkSCKz7r7tlVC7+ixFs= X-Received: from xur.c.googlers.com ([fda3:e722:ac3:cc00:20:ed76:c0a8:2330]) (user=xur job=sendgmr) by 2002:a81:b04d:0:b0:6e3:2693:ca6b with SMTP id 00721157ae682-6e32693d36bmr176997b3.2.1728588250242; Thu, 10 Oct 2024 12:24:10 -0700 (PDT) Date: Thu, 10 Oct 2024 12:23:55 -0700 In-Reply-To: <20241010192400.451187-1-xur@google.com> Precedence: bulk X-Mailing-List: linux-kbuild@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20241010192400.451187-1-xur@google.com> X-Mailer: git-send-email 2.47.0.rc1.288.g06298d1525-goog Message-ID: <20241010192400.451187-4-xur@google.com> Subject: [PATCH v3 3/6] Change the symbols order when --ffuntion-sections is enabled From: Rong Xu To: 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 , Kees Cook , Masahiro Yamada , "Mike Rapoport (IBM)" , Nathan Chancellor , Nick Desaulniers , Nicolas Schier , "Paul E. McKenney" , Peter Zijlstra , Rong Xu , Sami Tolvanen , Thomas Gleixner , Wei Yang , workflows@vger.kernel.org, Miguel Ojeda , Maksim Panchenko Cc: x86@kernel.org, linux-arch@vger.kernel.org, linux-doc@vger.kernel.org, linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, llvm@lists.linux.dev, Sriraman Tallam , Krzysztof Pszeniczny 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 "..". This patch modifies the order of subsections within the text output section when the -ffunction-sections flag is enabled. Specifically, it repositions sections with certain fixed patterns (for example .text.unlikely) before TEXT_MAIN, ensuring that they are grouped and matched together. 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. Co-developed-by: Han Shen Signed-off-by: Han Shen Signed-off-by: Rong Xu Suggested-by: Sriraman Tallam Suggested-by: Krzysztof Pszeniczny --- include/asm-generic/vmlinux.lds.h | 17 +++++++++++++++-- 1 file changed, 15 insertions(+), 2 deletions(-) diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index eeadbaeccf88..5df589c60401 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -554,9 +554,21 @@ * 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. + * code elimination or function-section is enabled. Match these symbols + * first when in these builds. */ +#if defined(CONFIG_LD_DEAD_CODE_DATA_ELIMINATION) || defined(CONFIG_LTO_CLANG) +#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) \ + NOINSTR_TEXT \ + *(.ref.text) +#else #define TEXT_TEXT \ ALIGN_FUNCTION(); \ *(.text.hot .text.hot.*) \ @@ -566,6 +578,7 @@ NOINSTR_TEXT \ *(.ref.text) \ *(.text.asan.* .text.tsan.*) +#endif /* sched.text is aling to function alignment to secure we have same From patchwork Thu Oct 10 19:23:56 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Rong Xu X-Patchwork-Id: 13830918 Received: from mail-yw1-f202.google.com (mail-yw1-f202.google.com [209.85.128.202]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7D2FA1E00AC for ; Thu, 10 Oct 2024 19:24:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.202 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728588255; cv=none; b=nf/PyC6nnx8iXzuXvgW2ZHvcjVLW52VrIJg7MEj4YDVUz6rFzGAjRwa8GoiHGtCK64SMG0tm+LyPbIX56xo+U9MSSLiyi6tk289Regy3Yr9rPZu2I52voWcrK3syDXujpAO4jy0gRGhSFzbN+dgZO/2RvEYHpPTHYuIBjXafNYw= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728588255; c=relaxed/simple; bh=zVodnoYgNm1DYBK5hKpuTtqHMKwNmjLuCknrbH33Aow=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=RvJgoeXyvbbDghoiqHorefcCHeEf93PdW/xQHwr+cOi2qxQ2T+TpSgfCsmaGM6TNcXNKvyDQARMUb9RGznGsbj9T2hXMOmtwx63gobHZBKuLn21Gd2VKUkc0W03d+eC7E2rCjjrwkTNZkVo07a1AeI8T4skvqYhbaT1Pyi+7NPc= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--xur.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=g1ULejyr; arc=none smtp.client-ip=209.85.128.202 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--xur.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="g1ULejyr" Received: by mail-yw1-f202.google.com with SMTP id 00721157ae682-6e2e5e376fcso28134457b3.2 for ; Thu, 10 Oct 2024 12:24:13 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1728588252; x=1729193052; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=bXvfnp7Z+BLB7t8cyHpKNDqx6J3lf8zmPrAsIDA7Ieo=; b=g1ULejyr20RZg5oj0I5IOugHg7+y4on1aNrHB9qRb4tEIWQ6YvsKZDBzLHcvFXs+n1 ngz5fjpEl/tIDKehqBFevDLb0xJjjx9XVV6cmPuNbvDb41HAfUZ9pvBLtqfKvfwGhhoe rbsL1pHozUmFAEB2I6TfSPb++tOhJ53H5eZM127k1mf/dOW7ku+mH5gfT03x6SBm338d +4qDQVGgwa+Pgh0kEfft+K4CUwzrDcJAGkvxhoYEBvOwAOrbsRxatWDLuFafnAicy4W6 oNW/LVdIqG2gbV/Ix3WZz3e3nMGdybdBAU0lp/l24EjDbQI4WxnHzTUJ2z1JXIW5lnr+ eVAQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1728588252; x=1729193052; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=bXvfnp7Z+BLB7t8cyHpKNDqx6J3lf8zmPrAsIDA7Ieo=; b=S9+hcJRRC8wF7VK566Xz5NgGH9v8ToNjOAigxCXnyRAONF3klUnWtZRDgiUoFzRCpr 0UsWTv03lIr7nBdq0gsHKsdpSuj+NzDDLPKX/a6MILqeVcwZQBpKo+51rn0UoLiY30QJ TJApLNrkHLK2yPAER9QkEfLek9OJqDKChn2piLNkc1BcLylGGr6dq0WXSb644S8x0h61 eDVFAeQtP9/5FTf+qJ5AyR5w6ktJJEJHkatkT8eveUHyd3HnEQk0hJEyZZjxGhVjkRWU NUvQEF5gczwGBDenRkunC+RBZbiKlxtiD9UatBvbFUAE3LeuNoNFb5Au1VoEVRh8K/fM E8Vw== X-Forwarded-Encrypted: i=1; AJvYcCVh4XRdIp5Q4PDJDBcUnah9oM27Gvp06zAS3aBHyZssIA3PUwaPaa0kdz2CegVND7qD9nThKty5TYTZPiw=@vger.kernel.org X-Gm-Message-State: AOJu0Yw0fKnlXj1i2L72mAHomW64G5h0bRsmwhoBRJHEYl4wW3BuOpQf QbPjlK15ETHZAk7wDkpJh0qOQQCRZY3bDRlJKvOn8ntlszriWNatsYzalx03gHUBRw== X-Google-Smtp-Source: AGHT+IGMu32Wgj2a9dn+nhr1MFY2d/lT0LJJ8GMl/nvZiUcXkvZk1kPhfz7t2WYIwd1XNqtF7GeWJaE= X-Received: from xur.c.googlers.com ([fda3:e722:ac3:cc00:20:ed76:c0a8:2330]) (user=xur job=sendgmr) by 2002:a25:d084:0:b0:e25:cea9:b0e with SMTP id 3f1490d57ef6-e2919fe8406mr8276.9.1728588252247; Thu, 10 Oct 2024 12:24:12 -0700 (PDT) Date: Thu, 10 Oct 2024 12:23:56 -0700 In-Reply-To: <20241010192400.451187-1-xur@google.com> Precedence: bulk X-Mailing-List: linux-kbuild@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20241010192400.451187-1-xur@google.com> X-Mailer: git-send-email 2.47.0.rc1.288.g06298d1525-goog Message-ID: <20241010192400.451187-5-xur@google.com> Subject: [PATCH v3 4/6] AutoFDO: Enable -ffunction-sections for the AutoFDO build From: Rong Xu To: 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 , Kees Cook , Masahiro Yamada , "Mike Rapoport (IBM)" , Nathan Chancellor , Nick Desaulniers , Nicolas Schier , "Paul E. McKenney" , Peter Zijlstra , Rong Xu , Sami Tolvanen , Thomas Gleixner , Wei Yang , workflows@vger.kernel.org, Miguel Ojeda , Maksim Panchenko Cc: x86@kernel.org, linux-arch@vger.kernel.org, linux-doc@vger.kernel.org, linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, llvm@lists.linux.dev, Sriraman Tallam Enable -ffunction-sections by default for the AutoFDO build. With -ffunction-sections, the compiler places each function in its own section named .text.function_name instead of placing all functions in the .text section. In the AutoFDO build, this allows the linker to utilize profile information to reorganize functions for improved utilization of iCache and iTLB. Co-developed-by: Han Shen Signed-off-by: Han Shen Signed-off-by: Rong Xu Suggested-by: Sriraman Tallam --- include/asm-generic/vmlinux.lds.h | 37 ++++++++++++++++++++++++------- scripts/Makefile.autofdo | 2 +- 2 files changed, 30 insertions(+), 9 deletions(-) diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index 5df589c60401..ace617d1af9b 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -95,18 +95,25 @@ * With LTO_CLANG, the linker also splits sections by default, so we need * these macros to combine the sections during the final link. * + * With LTO_CLANG, the linker also splits sections by default, so we need + * these macros to combine the sections during the final link. + * * RODATA_MAIN is not used because existing code already defines .rodata.x * sections to be brought in with rodata. */ -#if defined(CONFIG_LD_DEAD_CODE_DATA_ELIMINATION) || defined(CONFIG_LTO_CLANG) +#if defined(CONFIG_LD_DEAD_CODE_DATA_ELIMINATION) || defined(CONFIG_LTO_CLANG) || \ +defined(CONFIG_AUTOFDO_CLANG) #define TEXT_MAIN .text .text.[0-9a-zA-Z_]* +#else +#define TEXT_MAIN .text +#endif +#if defined(CONFIG_LD_DEAD_CODE_DATA_ELIMINATION) || defined(CONFIG_LTO_CLANG) #define DATA_MAIN .data .data.[0-9a-zA-Z_]* .data..L* .data..compoundliteral* .data.$__unnamed_* .data.$L* #define SDATA_MAIN .sdata .sdata.[0-9a-zA-Z_]* #define RODATA_MAIN .rodata .rodata.[0-9a-zA-Z_]* .rodata..L* #define BSS_MAIN .bss .bss.[0-9a-zA-Z_]* .bss..L* .bss..compoundliteral* #define SBSS_MAIN .sbss .sbss.[0-9a-zA-Z_]* #else -#define TEXT_MAIN .text #define DATA_MAIN .data #define SDATA_MAIN .sdata #define RODATA_MAIN .rodata @@ -549,6 +556,20 @@ __cpuidle_text_end = .; \ __noinstr_text_end = .; +#ifdef CONFIG_AUTOFDO_CLANG +#define TEXT_HOT \ + __hot_text_start = .; \ + *(.text.hot .text.hot.*) \ + __hot_text_end = .; +#define TEXT_UNLIKELY \ + __unlikely_text_start = .; \ + *(.text.unlikely .text.unlikely.*) \ + __unlikely_text_end = .; +#else +#define TEXT_HOT *(.text.hot .text.hot.*) +#define TEXT_UNLIKELY *(.text.unlikely .text.unlikely.*) +#endif + /* * .text section. Map to function alignment to avoid address changes * during second ld run in second ld pass when generating System.map @@ -557,30 +578,30 @@ * code elimination or function-section is enabled. Match these symbols * first when in these builds. */ -#if defined(CONFIG_LD_DEAD_CODE_DATA_ELIMINATION) || defined(CONFIG_LTO_CLANG) +#if defined(CONFIG_LD_DEAD_CODE_DATA_ELIMINATION) || defined(CONFIG_LTO_CLANG) || \ +defined(CONFIG_AUTOFDO_CLANG) #define TEXT_TEXT \ ALIGN_FUNCTION(); \ *(.text.asan.* .text.tsan.*) \ *(.text.unknown .text.unknown.*) \ - *(.text.unlikely .text.unlikely.*) \ + TEXT_UNLIKELY \ . = ALIGN(PAGE_SIZE); \ - *(.text.hot .text.hot.*) \ + TEXT_HOT \ *(TEXT_MAIN .text.fixup) \ NOINSTR_TEXT \ *(.ref.text) #else #define TEXT_TEXT \ ALIGN_FUNCTION(); \ - *(.text.hot .text.hot.*) \ + TEXT_HOT \ *(TEXT_MAIN .text.fixup) \ - *(.text.unlikely .text.unlikely.*) \ + TEXT_UNLIKELY \ *(.text.unknown .text.unknown.*) \ NOINSTR_TEXT \ *(.ref.text) \ *(.text.asan.* .text.tsan.*) #endif - /* sched.text is aling to function alignment to secure we have same * address even at second ld pass when generating System.map */ #define SCHED_TEXT \ diff --git a/scripts/Makefile.autofdo b/scripts/Makefile.autofdo index 1c9f224bc221..9c9a530ef090 100644 --- a/scripts/Makefile.autofdo +++ b/scripts/Makefile.autofdo @@ -10,7 +10,7 @@ ifndef CONFIG_DEBUG_INFO endif ifdef CLANG_AUTOFDO_PROFILE - CFLAGS_AUTOFDO_CLANG += -fprofile-sample-use=$(CLANG_AUTOFDO_PROFILE) + CFLAGS_AUTOFDO_CLANG += -fprofile-sample-use=$(CLANG_AUTOFDO_PROFILE) -ffunction-sections endif ifdef CONFIG_LTO_CLANG_THIN From patchwork Thu Oct 10 19:23:57 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Rong Xu X-Patchwork-Id: 13830919 Received: from mail-yb1-f202.google.com (mail-yb1-f202.google.com [209.85.219.202]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1415A1E1C15 for ; Thu, 10 Oct 2024 19:24:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.219.202 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728588257; cv=none; b=c1PFzvtSoow8wrW3NxJCojf5hSkfFkA+EzR1cIIJbs0/RNK2knnzUiR2+oJ54Me9U3JyOioRtXvfsDSJ0wWBhY8pxGVKfD+QCx+FReWhPJNewhaWc3YcnpBQf0x8tI2NgCeyVmEX/zuVPb4PeiD6Pxfb6bKQFjS5G+6Cb7Kmnwk= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728588257; c=relaxed/simple; bh=sTdPsc9TlDcP9fj9qZnzf9a6N2MHYfNB5acRtfCguZg=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=u4QdCuwPc3XfjMHMvWw3Kdoyacrzomhf/DukMufa37KbvwbkzfWdu+WrfsYv/mwsFIphvKttqWm4uQUco/mvnpc7zmlaOfo37nvijXGfKBghlOviBc9MTKlsqaaPixBbIqzcfy1HGVq5QwMRsrll/QsZTN4E99gOe6Jp/pxPT9Q= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--xur.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=PSJSPEGc; arc=none smtp.client-ip=209.85.219.202 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--xur.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="PSJSPEGc" Received: by mail-yb1-f202.google.com with SMTP id 3f1490d57ef6-e165fc5d94fso1987942276.2 for ; Thu, 10 Oct 2024 12:24:14 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1728588254; x=1729193054; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=56GXdyw+jn4VfhhYEfGPQRjvArCzv+g18r0M8mTXpxs=; b=PSJSPEGc1ICrZR4kXlEtx0Rwvct4gMl1FL6geWt9CoeT31Aj1Htur6L9rMoVeQUSnC wEOAUkj+OzZnmuAf4Er9O7m3jfET+nuGYRjubK6+XOeQrQA+zLwWOnKBkfB1zdtEIUQS mgbaw9Y22REIA/D7bfTUQqn+aK9Tv/1SnHgJhzD9VjnmGHFKZdu34Z9BBTgphuBcq/4D JnsHDFbOrBdjbPqQUOL4F2Q/mwSaCXVWXMlN+cKk8SKoAwd5kfM93RRC2jbFfEC0EUFN BltEnFDFdo8lesO9AY4SZAtg374VFe6aKn5iV0MgCINFELLDM548NlZtxIZbqTQxV53/ eX+w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1728588254; x=1729193054; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=56GXdyw+jn4VfhhYEfGPQRjvArCzv+g18r0M8mTXpxs=; b=OAc969GfHAMD3yPQXWqFBRcmPpNM5JNXm4p5jNaN8K65J1802IP8GnxowY6XmhvL6E 8Rgd+UI2Cd6aNH9sk84E6etUTXidJd59M4HrO3qr2JU5Wc+CGZ+kKnc5I7lj9fV+Fgu4 xsXTdifYdqBym9mOxrfTbnlxWRb0uahRoFbr4I0/Edc1b+6cjv3df/wO3Id6whO+sNeZ gxend1vJousdo6J4A9ND9tgZzjYePAICdSl/eWVkNl5OV5vp9mp8Kqxcs319G96a9SwT 8rs+Cl5mXs55uR/7/49986ojawRA7NIlXtqDKZCPgYKJ5ri57Bl1gEcaLwuDoKJyCksX /F7Q== X-Forwarded-Encrypted: i=1; AJvYcCUnzsvkKT7SBOYV2l2EC8EwDXo3b5Uc699Yn8u4O7aAjJeyw5YNhQS/xWcOc0osxHl1nMRqviJV9uawlPo=@vger.kernel.org X-Gm-Message-State: AOJu0YycCKFMYYkRub3yz+BZYrsnAJLDTs0HUXrLKJiZptQ5uNd9adNL JUL2vPNVxrJ2933TxG9G6wzGSPxBV4AatWwMg97iL3c7RaA12AUa2MDuEzNwrzREKg== X-Google-Smtp-Source: AGHT+IFESUDnoxkBRGGFEsil5vwwqQnr0M2E/rzO5Ah3pXUbKQzjO+St/IUq3wX79za0eMMedUk/mMc= X-Received: from xur.c.googlers.com ([fda3:e722:ac3:cc00:20:ed76:c0a8:2330]) (user=xur job=sendgmr) by 2002:a5b:94c:0:b0:e28:ef8f:7424 with SMTP id 3f1490d57ef6-e28fe44d418mr60122276.11.1728588254050; Thu, 10 Oct 2024 12:24:14 -0700 (PDT) Date: Thu, 10 Oct 2024 12:23:57 -0700 In-Reply-To: <20241010192400.451187-1-xur@google.com> Precedence: bulk X-Mailing-List: linux-kbuild@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20241010192400.451187-1-xur@google.com> X-Mailer: git-send-email 2.47.0.rc1.288.g06298d1525-goog Message-ID: <20241010192400.451187-6-xur@google.com> Subject: [PATCH v3 5/6] AutoFDO: Enable machine function split optimization for AutoFDO From: Rong Xu To: 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 , Kees Cook , Masahiro Yamada , "Mike Rapoport (IBM)" , Nathan Chancellor , Nick Desaulniers , Nicolas Schier , "Paul E. McKenney" , Peter Zijlstra , Rong Xu , Sami Tolvanen , Thomas Gleixner , Wei Yang , workflows@vger.kernel.org, Miguel Ojeda , Maksim Panchenko Cc: x86@kernel.org, linux-arch@vger.kernel.org, linux-doc@vger.kernel.org, linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, llvm@lists.linux.dev, Sriraman Tallam , Krzysztof Pszeniczny Enable the machine function split optimization for AutoFDO in Clang. Machine function split (MFS) is a pass in the Clang compiler that splits a function into hot and cold parts. The linker groups all cold blocks across functions together. This decreases hot code fragmentation and improves iCache and iTLB utilization. MFS requires a profile so this is enabled only for the AutoFDO builds. Co-developed-by: Han Shen Signed-off-by: Han Shen Signed-off-by: Rong Xu Suggested-by: Sriraman Tallam Suggested-by: Krzysztof Pszeniczny --- include/asm-generic/vmlinux.lds.h | 6 ++++++ scripts/Makefile.autofdo | 2 ++ 2 files changed, 8 insertions(+) diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index ace617d1af9b..20e46c0917db 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -565,9 +565,14 @@ defined(CONFIG_AUTOFDO_CLANG) __unlikely_text_start = .; \ *(.text.unlikely .text.unlikely.*) \ __unlikely_text_end = .; +#define TEXT_SPLIT \ + __split_text_start = .; \ + *(.text.split .text.split.[0-9a-zA-Z_]*) \ + __split_text_end = .; #else #define TEXT_HOT *(.text.hot .text.hot.*) #define TEXT_UNLIKELY *(.text.unlikely .text.unlikely.*) +#define TEXT_SPLIT #endif /* @@ -584,6 +589,7 @@ defined(CONFIG_AUTOFDO_CLANG) ALIGN_FUNCTION(); \ *(.text.asan.* .text.tsan.*) \ *(.text.unknown .text.unknown.*) \ + TEXT_SPLIT \ TEXT_UNLIKELY \ . = ALIGN(PAGE_SIZE); \ TEXT_HOT \ diff --git a/scripts/Makefile.autofdo b/scripts/Makefile.autofdo index 9c9a530ef090..380042a301cc 100644 --- a/scripts/Makefile.autofdo +++ b/scripts/Makefile.autofdo @@ -11,6 +11,7 @@ endif ifdef CLANG_AUTOFDO_PROFILE CFLAGS_AUTOFDO_CLANG += -fprofile-sample-use=$(CLANG_AUTOFDO_PROFILE) -ffunction-sections + CFLAGS_AUTOFDO_CLANG += -fsplit-machine-functions endif ifdef CONFIG_LTO_CLANG_THIN @@ -18,6 +19,7 @@ ifdef CONFIG_LTO_CLANG_THIN KBUILD_LDFLAGS += --lto-sample-profile=$(CLANG_AUTOFDO_PROFILE) endif KBUILD_LDFLAGS += --mllvm=-enable-fs-discriminator=true --mllvm=-improved-fs-discriminator=true -plugin-opt=thinlto + KBUILD_LDFLAGS += -plugin-opt=-split-machine-functions endif export CFLAGS_AUTOFDO_CLANG From patchwork Thu Oct 10 19:23:58 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Rong Xu X-Patchwork-Id: 13830920 Received: from mail-yw1-f202.google.com (mail-yw1-f202.google.com [209.85.128.202]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0004E1E376E for ; Thu, 10 Oct 2024 19:24:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.202 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728588260; cv=none; b=F8Q1StlotFySGI8CSkcPTwg49pLUT01ehqf6qrdL+B8afGRIRrJTWXbJu9v/MtWm9ajBx0sFsMMH6sBPdyHMCrbkMvFEP9WvCrmicZxLlQTFRiAR+Uz0AfBlo75RatFuY7rL+XLO6Dncr8uLZpFT87t3EykfKWzRE/P8zEiaLdM= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728588260; c=relaxed/simple; bh=9E0liJxCpmlS5aOXNfbBO6uFs+bNG8FjVuC7X5ymlNU=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=FP7LBuUNgXMdYceUpahOxQprTs0dF1vJV0x/Wj58BzMhsqvPm0FkDLFi44LVaHSfYrKDD6iZXU3YFzeVvjTpHjjAhlpoZftbi0wOgt26lKBKd3+Rv1dRCcu6AQPeIM1yegaIa4thu1dVhm1vEp2LjrIj5yJCSWRGlHIqvedwDQg= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--xur.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=xxT8ZrAn; arc=none smtp.client-ip=209.85.128.202 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--xur.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="xxT8ZrAn" Received: by mail-yw1-f202.google.com with SMTP id 00721157ae682-6e315a5b199so25268097b3.2 for ; Thu, 10 Oct 2024 12:24:16 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1728588256; x=1729193056; darn=vger.kernel.org; h=content-transfer-encoding:cc:to:from:subject:message-id:references :mime-version:in-reply-to:date:from:to:cc:subject:date:message-id :reply-to; bh=Hk6fAtuHbaC8EX1j2qoTsmRqhh2KQ8nox4P5fnjnegY=; b=xxT8ZrAn/66Prjvcbu+OVDr/bRou1BGehXafu1oxARyaYqg/qZaU4OAM0kk4t9x7e5 7zxQdcXmwFsrsBhDscd3Gkp8/FVg5sB4F5tzauktt9ehvSCBT/vVbeAKcyj3r7yIiwXF SOJTp7Gzbmlw2t+GHR2DwoARgXQzwk+KrzX32zijCDo4kGJTzx1lptO+I5nT9eyKKK5U FzyWEGoy96DtCoC4z65MHbUTSVA8Kny9CezfNDb4J9dPWmQC2REZZfm0CHEIXQf7WLGS mSg8U9cs2v6/mLa7uFR1DdAoEZY1z7mXNiKqjgIy1MrRbhdma0LUaM+PO1ZfW0+mgo1S MKDg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1728588256; x=1729193056; h=content-transfer-encoding:cc:to:from:subject:message-id:references :mime-version:in-reply-to:date:x-gm-message-state:from:to:cc:subject :date:message-id:reply-to; bh=Hk6fAtuHbaC8EX1j2qoTsmRqhh2KQ8nox4P5fnjnegY=; b=qFyaFiQG9oKBs5eTG896kHd55DTCQBbsN8ugNwoOjvz4dYgEy403NJwnftYEGdlyV4 YTzrFLLob51jPSpToHfVjMGZk/v0ba0mJrIefVAIQS3sTmUi04HPA/iI4aWhbEaxStSv hJ6Bx9ywo8GLsc39oDrciMereF5YqvQzprPV4IDRvhrmvQQbYaZTsnb5ajeRmIWDVi0p NKAjcOlPeyhLddxTM2dxk7hOSg0dix0xNuOo+K5MA4cQ55pl+1Ar1Lu8p6kZlfNC5CqH cry8Ka+bDPEx2z5khg4piUdw92tfjteKc7y0SwDagJ560w1plNwfMvwSpQDyYQLAgnUS dddA== X-Forwarded-Encrypted: i=1; AJvYcCXqSinuNXIj1Z4fT4iuEx2AS3tcXTmrihC6nYo36VCF5eWuA7A+6pWAid6VN5tb1JrqkuM4S9NrZHLYNKs=@vger.kernel.org X-Gm-Message-State: AOJu0Yyn++Ws4Jd50A/+QU4CeRU01tysw6PGMU/pNAWwzu0LiPQUGPVO polk3Ya2K501LCPfTiv+zItP/RJNi7QPpKckmGkfCCW3n1qE9MYibQsh4RVeem0CjA== X-Google-Smtp-Source: AGHT+IHSNMGekjiTKTKxih5YxbXCag9dv8Q/k6Q02RfV9JEZtmfvz4QEahWbmrMjbYAYZOE3VqnfVfM= X-Received: from xur.c.googlers.com ([fda3:e722:ac3:cc00:20:ed76:c0a8:2330]) (user=xur job=sendgmr) by 2002:a05:690c:424a:b0:6e3:f12:1ad3 with SMTP id 00721157ae682-6e3224d30b8mr248907b3.6.1728588255760; Thu, 10 Oct 2024 12:24:15 -0700 (PDT) Date: Thu, 10 Oct 2024 12:23:58 -0700 In-Reply-To: <20241010192400.451187-1-xur@google.com> Precedence: bulk X-Mailing-List: linux-kbuild@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20241010192400.451187-1-xur@google.com> X-Mailer: git-send-email 2.47.0.rc1.288.g06298d1525-goog Message-ID: <20241010192400.451187-7-xur@google.com> Subject: [PATCH v3 6/6] Add Propeller configuration for kernel build. From: Rong Xu To: 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 , Kees Cook , Masahiro Yamada , "Mike Rapoport (IBM)" , Nathan Chancellor , Nick Desaulniers , Nicolas Schier , "Paul E. McKenney" , Peter Zijlstra , Rong Xu , Sami Tolvanen , Thomas Gleixner , Wei Yang , workflows@vger.kernel.org, Miguel Ojeda , Maksim Panchenko Cc: x86@kernel.org, linux-arch@vger.kernel.org, linux-doc@vger.kernel.org, linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, llvm@lists.linux.dev, Sriraman Tallam , Krzysztof Pszeniczny , Stephane Eranian Add the build support for using Clang's Propeller optimizer. Like AutoFDO, Propeller uses hardware sampling to gather information about the frequency of execution of different code paths within a binary. This information is then used to guide the compiler's optimization decisions, resulting in a more efficient binary. The support requires a Clang compiler LLVM 19 or later, and the create_llvm_prof tool (https://github.com/google/autofdo/releases/tag/v0.30.1). This submission is limited to x86 platforms that support PMU features like LBR on Intel machines and AMD Zen3 BRS. For Arm, we plan to send patches for SPE-based Propeller when AutoFDO for Arm is ready. Here is an example workflow for building an AutoFDO+Propeller optimized kernel: 1) Build the kernel on the HOST machine, with AutoFDO and Propeller build config CONFIG_AUTOFDO_CLANG=y CONFIG_PROPELLER_CLANG=y then $ make LLVM=1 CLANG_AUTOFDO_PROFILE= “” is the profile collected when doing a non-Propeller AutoFDO build. This step builds a kernel that has the same optimization level as AutoFDO, plus a metadata section that records basic block information. This kernel image runs as fast as an AutoFDO optimized kernel. 2) Install the kernel on test/production machines. 3) Run the load tests. The '-c' option in perf specifies the sample event period. We suggest using a suitable prime number, like 500009, for this purpose. For Intel platforms: $ perf record -e BR_INST_RETIRED.NEAR_TAKEN:k -a -N -b -c \ -o -- For AMD platforms: The supported system are: Zen3 with BRS, or Zen4 with amd_lbr_v2 # To see if Zen3 support LBR: $ cat proc/cpuinfo | grep " brs" # To see if Zen4 support LBR: $ cat proc/cpuinfo | grep amd_lbr_v2 # If the result is yes, then collect the profile using: $ perf record --pfm-events RETIRED_TAKEN_BRANCH_INSTRUCTIONS:k -a \ -N -b -c -o -- 4) (Optional) Download the raw perf file to the HOST machine. 5) Generate Propeller profile: $ create_llvm_prof --binary= --profile= \ --format=propeller --propeller_output_module_name \ --out=_cc_profile.txt \ --propeller_symorder=_ld_profile.txt “create_llvm_prof” is the profile conversion tool, and a prebuilt binary for linux can be found on https://github.com/google/autofdo/releases/tag/v0.30.1 (can also build from source). "" can be something like "/home/user/dir/any_string". This command generates a pair of Propeller profiles: "_cc_profile.txt" and "_ld_profile.txt". 6) Rebuild the kernel using the AutoFDO and Propeller profile files. CONFIG_AUTOFDO_CLANG=y CONFIG_PROPELLER_CLANG=y and $ make LLVM=1 CLANG_AUTOFDO_PROFILE= \ CLANG_PROPELLER_PROFILE_PREFIX= Co-developed-by: Han Shen Signed-off-by: Han Shen Signed-off-by: Rong Xu Suggested-by: Sriraman Tallam Suggested-by: Krzysztof Pszeniczny Suggested-by: Nick Desaulniers Suggested-by: Stephane Eranian --- Documentation/dev-tools/index.rst | 1 + Documentation/dev-tools/propeller.rst | 161 ++++++++++++++++++++++++++ MAINTAINERS | 7 ++ Makefile | 1 + arch/Kconfig | 22 ++++ arch/x86/Kconfig | 1 + arch/x86/kernel/vmlinux.lds.S | 4 + include/asm-generic/vmlinux.lds.h | 10 +- scripts/Makefile.lib | 10 ++ scripts/Makefile.propeller | 28 +++++ tools/objtool/check.c | 1 + 11 files changed, 241 insertions(+), 5 deletions(-) create mode 100644 Documentation/dev-tools/propeller.rst create mode 100644 scripts/Makefile.propeller diff --git a/Documentation/dev-tools/index.rst b/Documentation/dev-tools/index.rst index 6945644f7008..3c0ac08b2709 100644 --- a/Documentation/dev-tools/index.rst +++ b/Documentation/dev-tools/index.rst @@ -35,6 +35,7 @@ Documentation/dev-tools/testing-overview.rst checkuapi gpio-sloppy-logic-analyzer autofdo + propeller .. only:: subproject and html diff --git a/Documentation/dev-tools/propeller.rst b/Documentation/dev-tools/propeller.rst new file mode 100644 index 000000000000..a217354e0f95 --- /dev/null +++ b/Documentation/dev-tools/propeller.rst @@ -0,0 +1,161 @@ +.. SPDX-License-Identifier: GPL-2.0 + +===================================== +Using Propeller with the Linux kernel +===================================== + +This enables Propeller build support for the kernel when using Clang +compiler. Propeller is a profile-guided optimization (PGO) method used +to optimize binary executables. Like AutoFDO, it utilizes hardware +sampling to gather information about the frequency of execution of +different code paths within a binary. Unlike AutoFDO, this information +is then used right before linking phase to optimize (among others) +block layout within and across functions. + +A few important notes about adopting Propeller optimization: + +#. Although it can be used as a standalone optimization step, it is + strongly recommended to apply Propeller on top of AutoFDO, + AutoFDO+ThinLTO or Instrument FDO. The rest of this document + assumes this paradigm. + +#. Propeller uses another round of profiling on top of + AutoFDO/AutoFDO+ThinLTO/iFDO. The whole build process involves + "build-afdo - train-afdo - build-propeller - train-propeller - + build-optimized". + +#. Propeller requires LLVM 19 release or later for Clang/Clang++ + and the linker(ld.lld). + +#. In addition to LLVM toolchain, Propeller requires a profiling + conversion tool: https://github.com/google/autofdo with a release + after v0.30.1: https://github.com/google/autofdo/releases/tag/v0.30.1. + +The Propeller optimization process involves the following steps: + +#. Initial building: Build the AutoFDO or AutoFDO+ThinLTO binary as + you would normally do, but with a set of compile-time / link-time + flags, so that a special metadata section is created within the + kernel binary. The special section is only intend to be used by the + profiling tool, it is not part of the runtime image, nor does it + change kernel run time text sections. + +#. Profiling: The above kernel is then run with a representative + workload to gather execution frequency data. This data is collected + using hardware sampling, via perf. Propeller is most effective on + platforms supporting advanced PMU features like LBR on Intel + machines. This step is the same as profiling the kernel for AutoFDO + (the exact perf parameters can be different). + +#. Propeller profile generation: Perf output file is converted to a + pair of Propeller profiles via an offline tool. + +#. Optimized build: Build the AutoFDO or AutoFDO+ThinLTO optimized + binary as you would normally do, but with a compile-time / + link-time flag to pick up the Propeller compile time and link time + profiles. This build step uses 3 profiles - the AutoFDO profile, + the Propeller compile-time profile and the Propeller link-time + profile. + +#. Deployment: The optimized kernel binary is deployed and used + in production environments, providing improved performance + and reduced latency. + +Preparation +=========== + +Configure the kernel with:: + + CONFIG_AUTOFDO_CLANG=y + CONFIG_PROPELLER_CLANG=y + +Customization +============= + +You can enable or disable Propeller build for individual file and +directories by adding a line similar to the following to the +respective kernel Makefile: + +- For enabling a single file (e.g. foo.o):: + + PROPELLER_PROFILE_foo.o := y + +- For enabling all files in one directory:: + + PROPELLER_PROFILE := y + +- For disabling one file:: + + PROPELLER_PROFILE_foo.o := n + +- For disabling all files in one directory:: + + PROPELLER__PROFILE := n + + +Workflow +======== + +Here is an example workflow for building an AutoFDO+Propeller kernel: + +1) Assuming an AutoFDO profile is already collected following + instructions in the AutoFDO document, build the kernel on the HOST + machine, with AutoFDO and Propeller build configs :: + + CONFIG_AUTOFDO_CLANG=y + CONFIG_PROPELLER_CLANG=y + + and :: + + $ make LLVM=1 CLANG_AUTOFDO_PROFILE= + +2) Install the kernel on the TEST machine. + +3) Run the load tests. The '-c' option in perf specifies the sample + event period. We suggest using a suitable prime number, like 500009, + for this purpose. + + - For Intel platforms:: + + $ perf record -e BR_INST_RETIRED.NEAR_TAKEN:k -a -N -b -c -o -- + + - For AMD platforms:: + + $ perf record --pfm-event RETIRED_TAKEN_BRANCH_INSTRUCTIONS:k -a -N -b -c -o -- + + Note you can repeat the above steps to collect multiple s. + +4) (Optional) Download the raw perf file(s) to the HOST machine. + +5) Use the create_llvm_prof tool (https://github.com/google/autofdo) to + generate Propeller profile. :: + + $ create_llvm_prof --binary= --profile= + --format=propeller --propeller_output_module_name + --out=_cc_profile.txt + --propeller_symorder=_ld_profile.txt + + "" can be something like "/home/user/dir/any_string". + + This command generates a pair of Propeller profiles: + "_cc_profile.txt" and + "_ld_profile.txt". + + If there are more than 1 perf_file collected in the previous step, + you can create a temp list file "" with each line + containing one perf file name and run:: + + $ create_llvm_prof --binary= --profile=@ + --format=propeller --propeller_output_module_name + --out=_cc_profile.txt + --propeller_symorder=_ld_profile.txt + +6) Rebuild the kernel using the AutoFDO and Propeller + profiles. :: + + CONFIG_AUTOFDO_CLANG=y + CONFIG_PROPELLER_CLANG=y + + and :: + + $ make LLVM=1 CLANG_AUTOFDO_PROFILE= CLANG_PROPELLER_PROFILE_PREFIX= diff --git a/MAINTAINERS b/MAINTAINERS index 1b8db863031f..f4cc6dd6c4d8 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -18560,6 +18560,13 @@ S: Maintained F: include/linux/psi* F: kernel/sched/psi.c +PROPELLER BUILD +M: Rong Xu +M: Han Shen +S: Supported +F: Documentation/dev-tools/propeller.rst +F: scripts/Makefile.propeller + PRINTK M: Petr Mladek R: Steven Rostedt diff --git a/Makefile b/Makefile index bbb6ec68f5dc..2d2f688c21c6 100644 --- a/Makefile +++ b/Makefile @@ -1019,6 +1019,7 @@ include-$(CONFIG_UBSAN) += scripts/Makefile.ubsan include-$(CONFIG_KCOV) += scripts/Makefile.kcov include-$(CONFIG_RANDSTRUCT) += scripts/Makefile.randstruct include-$(CONFIG_AUTOFDO_CLANG) += scripts/Makefile.autofdo +include-$(CONFIG_PROPELLER_CLANG) += scripts/Makefile.propeller include-$(CONFIG_GCC_PLUGINS) += scripts/Makefile.gcc-plugins include $(addprefix $(srctree)/, $(include-y)) diff --git a/arch/Kconfig b/arch/Kconfig index 5e9604960cbb..fdeb5f173a10 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -831,6 +831,28 @@ config AUTOFDO_CLANG If unsure, say N. +config ARCH_SUPPORTS_PROPELLER_CLANG + bool + +config PROPELLER_CLANG + bool "Enable Clang's Propeller build" + depends on ARCH_SUPPORTS_PROPELLER_CLANG + depends on AUTOFDO_CLANG + depends on CC_IS_CLANG && CLANG_VERSION >= 190000 + help + This option enables Clang’s Propeller build which + is on top of AutoFDO build. When the Propeller profiles + is specified in variable CLANG_PROPELLER_PROFILE_PREFIX + during the build process, Clang uses the profiles to + optimize the kernel. + + If no profile is specified, Proepller options are + still passed to Clang to facilitate the collection + of perf data for creating the Propeller profiles in + subsequent builds. + + If unsure, say N. + config ARCH_SUPPORTS_CFI_CLANG bool help diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 503a0268155a..da47164bfddc 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -127,6 +127,7 @@ config X86 select ARCH_SUPPORTS_LTO_CLANG_THIN select ARCH_SUPPORTS_RT select ARCH_SUPPORTS_AUTOFDO_CLANG + select ARCH_SUPPORTS_PROPELLER_CLANG if X86_64 select ARCH_USE_BUILTIN_BSWAP select ARCH_USE_CMPXCHG_LOCKREF if X86_CMPXCHG64 select ARCH_USE_MEMTEST diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S index 6726be89b7a6..7ecc21c569be 100644 --- a/arch/x86/kernel/vmlinux.lds.S +++ b/arch/x86/kernel/vmlinux.lds.S @@ -442,6 +442,10 @@ SECTIONS STABS_DEBUG DWARF_DEBUG +#ifdef CONFIG_PROPELLER_CLANG + .llvm_bb_addr_map : { *(.llvm_bb_addr_map) } +#endif + ELF_DETAILS DISCARDS diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index 20e46c0917db..5986dd4cfb14 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -95,14 +95,14 @@ * With LTO_CLANG, the linker also splits sections by default, so we need * these macros to combine the sections during the final link. * - * With LTO_CLANG, the linker also splits sections by default, so we need - * these macros to combine the sections during the final link. + * CONFIG_AUTOFD_CLANG and CONFIG_PROPELLER_CLANG will also split text sections + * and cluster them in the linking time. * * RODATA_MAIN is not used because existing code already defines .rodata.x * sections to be brought in with rodata. */ #if defined(CONFIG_LD_DEAD_CODE_DATA_ELIMINATION) || defined(CONFIG_LTO_CLANG) || \ -defined(CONFIG_AUTOFDO_CLANG) +defined(CONFIG_AUTOFDO_CLANG) || defined(CONFIG_PROPELLER_CLANG) #define TEXT_MAIN .text .text.[0-9a-zA-Z_]* #else #define TEXT_MAIN .text @@ -556,7 +556,7 @@ defined(CONFIG_AUTOFDO_CLANG) __cpuidle_text_end = .; \ __noinstr_text_end = .; -#ifdef CONFIG_AUTOFDO_CLANG +#if defined(CONFIG_AUTOFDO_CLANG) || defined(CONFIG_PROPELLER_CLANG) #define TEXT_HOT \ __hot_text_start = .; \ *(.text.hot .text.hot.*) \ @@ -584,7 +584,7 @@ defined(CONFIG_AUTOFDO_CLANG) * first when in these builds. */ #if defined(CONFIG_LD_DEAD_CODE_DATA_ELIMINATION) || defined(CONFIG_LTO_CLANG) || \ -defined(CONFIG_AUTOFDO_CLANG) +defined(CONFIG_AUTOFDO_CLANG) || defined(CONFIG_PROPELLER_CLANG) #define TEXT_TEXT \ ALIGN_FUNCTION(); \ *(.text.asan.* .text.tsan.*) \ diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib index e85d6ac31bd9..60354c476956 100644 --- a/scripts/Makefile.lib +++ b/scripts/Makefile.lib @@ -201,6 +201,16 @@ _c_flags += $(if $(patsubst n%,, \ $(CFLAGS_AUTOFDO_CLANG)) endif +# +# Enable Clang's Propeller build flags for a file or directory depending on +# variables AUTOFDO_PROPELLER_obj.o and PROPELLER_PROFILE. +# +ifeq ($(CONFIG_PROPELLER_CLANG),y) +_c_flags += $(if $(patsubst n%,, \ + $(AUTOFDO_PROFILE_$(target-stem).o)$(AUTOFDO_PROFILE)$(PROPELLER_PROFILE))$(is-kernel-object), \ + $(CFLAGS_PROPELLER_CLANG)) +endif + # $(src) for including checkin headers from generated source files # $(obj) for including generated headers from checkin source files ifeq ($(KBUILD_EXTMOD),) diff --git a/scripts/Makefile.propeller b/scripts/Makefile.propeller new file mode 100644 index 000000000000..344190717e47 --- /dev/null +++ b/scripts/Makefile.propeller @@ -0,0 +1,28 @@ +# SPDX-License-Identifier: GPL-2.0 + +# Enable available and selected Clang Propeller features. +ifdef CLANG_PROPELLER_PROFILE_PREFIX + CFLAGS_PROPELLER_CLANG := -fbasic-block-sections=list=$(CLANG_PROPELLER_PROFILE_PREFIX)_cc_profile.txt -ffunction-sections + KBUILD_LDFLAGS += --symbol-ordering-file=$(CLANG_PROPELLER_PROFILE_PREFIX)_ld_profile.txt --no-warn-symbol-ordering +else + CFLAGS_PROPELLER_CLANG := -fbasic-block-sections=labels +endif + +# Propeller requires debug information to embed module names in the profiles. +# If CONFIG_DEBUG_INFO is not enabled, set -gmlt option. Skip this for AutoFDO, +# as the option should already be set. +ifndef CONFIG_DEBUG_INFO + ifndef CONFIG_AUTOFDO_CLANG + CFLAGS_PROPELLER_CLANG += -gmlt + endif +endif + +ifdef CONFIG_LTO_CLANG_THIN + ifdef CLANG_PROPELLER_PROFILE_PREFIX + KBUILD_LDFLAGS += --lto-basic-block-sections=$(CLANG_PROPELLER_PROFILE_PREFIX)_cc_profile.txt + else + KBUILD_LDFLAGS += --lto-basic-block-sections=labels + endif +endif + +export CFLAGS_PROPELLER_CLANG diff --git a/tools/objtool/check.c b/tools/objtool/check.c index 4c5229991e1e..05a0fb4a3d1a 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -4558,6 +4558,7 @@ static int validate_ibt(struct objtool_file *file) !strcmp(sec->name, "__mcount_loc") || !strcmp(sec->name, ".kcfi_traps") || !strcmp(sec->name, ".llvm.call-graph-profile") || + !strcmp(sec->name, ".llvm_bb_addr_map") || strstr(sec->name, "__patchable_function_entries")) continue;