user/sven/linux.git/scripts/Makefile.lib, branch v6.14.9

objtool: Silence more KCOV warnings, part 2

2025-05-02T06:02:15Z

commit 55c78035a1a8dfb05f1472018ce2a651701adb7d upstream. Similar to GCOV, KCOV can leave behind dead code and undefined behavior. Warnings related to those should be ignored. The previous commit: 6b023c784204 ("objtool: Silence more KCOV warnings") ... only did so for CONFIG_CGOV_KERNEL. Also do it for CONFIG_KCOV, but for real this time. Fixes the following warning: vmlinux.o: warning: objtool: synaptics_report_mt_data: unexpected end of section .text.synaptics_report_mt_data Fixes: 6b023c784204 ("objtool: Silence more KCOV warnings") Reported-by: kernel test robot Signed-off-by: Josh Poimboeuf Signed-off-by: Ingo Molnar Cc: Linus Torvalds Link: https://lore.kernel.org/r/a44ba16e194bcbc52c1cef3d3cd9051a62622723.1743481539.git.jpoimboe@kernel.org Closes: https://lore.kernel.org/oe-kbuild-all/202503282236.UhfRsF3B-lkp@intel.com/ Signed-off-by: Greg Kroah-Hartman

kbuild: fix misspelling in scripts/Makefile.lib

2025-02-06T10:28:14Z

Signed-off-by: Oleh Zadorozhnyi Signed-off-by: Masahiro Yamada

kbuild: fix Clang LTO with CONFIG_OBJTOOL=n

2025-01-31T19:28:05Z

Since commit bede169618c6 ("kbuild: enable objtool for *.mod.o and additional kernel objects"), Clang LTO builds do not perform any optimizations when CONFIG_OBJTOOL is disabled (e.g., for ARCH=arm64). This is because every LLVM bitcode file is immediately converted to ELF format before the object files are linked together. This commit fixes the breakage. Fixes: bede169618c6 ("kbuild: enable objtool for *.mod.o and additional kernel objects") Reported-by: Yonghong Song Signed-off-by: Masahiro Yamada Tested-by: Yonghong Song

kbuild: Strip runtime const RELA sections correctly

2025-01-31T19:28:05Z

Due to the fact that runtime const ELF sections are named without a leading period or double underscore, the RSTRIP logic that removes the static RELA sections from vmlinux fails to identify them. This results in a situation like below, where some sections that were supposed to get removed are left behind. [Nr] Name Type Address Off Size ES Flg Lk Inf Al [58] runtime_shift_d_hash_shift PROGBITS ffffffff83500f50 2900f50 000014 00 A 0 0 1 [59] .relaruntime_shift_d_hash_shift RELA 0000000000000000 55b6f00 000078 18 I 70 58 8 [60] runtime_ptr_dentry_hashtable PROGBITS ffffffff83500f68 2900f68 000014 00 A 0 0 1 [61] .relaruntime_ptr_dentry_hashtable RELA 0000000000000000 55b6f78 000078 18 I 70 60 8 [62] runtime_ptr_USER_PTR_MAX PROGBITS ffffffff83500f80 2900f80 000238 00 A 0 0 1 [63] .relaruntime_ptr_USER_PTR_MAX RELA 0000000000000000 55b6ff0 000d50 18 I 70 62 8 So tweak the match expression to strip all sections starting with .rel. While at it, consolidate the logic used by RISC-V, s390 and x86 into a single shared Makefile library command. Link: https://lore.kernel.org/all/CAHk-=wjk3ynjomNvFN8jf9A1k=qSc=JFF591W00uXj-qqNUxPQ@mail.gmail.com/ Signed-off-by: Ard Biesheuvel Reviewed-by: Charlie Jenkins Tested-by: Charlie Jenkins Tested-by: Alexander Gordeev Signed-off-by: Masahiro Yamada

kbuild: switch from lz4c to lz4 for compression

2024-11-27T23:11:56Z

Replace lz4c with lz4 for kernel image compression. Although lz4 and lz4c are functionally similar, lz4c has been deprecated upstream since 2018. Since as early as Ubuntu 16.04 and Fedora 25, lz4 and lz4c have been packaged together, making it safe to update the requirement from lz4c to lz4. Consequently, some distributions and build systems, such as OpenEmbedded, have fully transitioned to using lz4. OpenEmbedded core adopted this change in commit fe167e082cbd ("bitbake.conf: require lz4 instead of lz4c"), causing compatibility issues when building the mainline kernel in the latest OpenEmbedded environment, as seen in the errors below. This change also updates the LZ4 compression commands to make it backward compatible by replacing stdin and stdout with the '-' option, due to some unclear reason, the stdout keyword does not work for lz4 and '-' works for both. In addition, this modifies the legacy '-c1' with '-9' which is also compatible with both. This fixes the mainline kernel build failures with the latest master OpenEmbedded builds associated with the mentioned compatibility issues. LZ4 arch/arm/boot/compressed/piggy_data /bin/sh: 1: lz4c: not found ... ... ERROR: oe_runmake failed Link: https://github.com/lz4/lz4/pull/553 Suggested-by: Francesco Dolcini Signed-off-by: Parth Pancholi Signed-off-by: Masahiro Yamada

kbuild: enable objtool for *.mod.o and additional kernel objects

2024-11-27T23:11:55Z

Currently, objtool is disabled in scripts/Makefile.{modfinal,vmlinux}. This commit moves rule_cc_o_c and rule_as_o_S to scripts/Makefile.lib and set objtool-enabled to y there. With this change, *.mod.o, .module-common.o, builtin-dtb.o, and vmlinux.export.o will now be covered by objtool. Signed-off-by: Masahiro Yamada

kbuild: move cmd_cc_o_c and cmd_as_o_S to scripts/Malefile.lib

2024-11-27T23:11:55Z

The cmd_cc_o_c and cmd_as_o_S macros are duplicated in scripts/Makefile.{build,modfinal,vmlinux}. This commit factors them out to scripts/Makefile.lib. No functional changes are intended. Signed-off-by: Masahiro Yamada

kbuild: support building external modules in a separate build directory

2024-11-27T23:11:55Z

There has been a long-standing request to support building external modules in a separate build directory. This commit introduces a new environment variable, KBUILD_EXTMOD_OUTPUT, and its shorthand Make variable, MO. A simple usage: $ make -C M= MO= Signed-off-by: Masahiro Yamada Reviewed-by: Nicolas Schier

kbuild: Add Propeller configuration for kernel build

2024-11-27T00:38:27Z

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 commit is limited to x86 platforms that support PMU features like LBR on Intel machines and AMD Zen3 BRS. 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 Tested-by: Yonghong Song Tested-by: Nathan Chancellor Reviewed-by: Kees Cook Signed-off-by: Masahiro Yamada

kbuild: Add AutoFDO support for Clang build

2024-11-06T13:41:09Z

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 --out= 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 Tested-by: Yonghong Song Tested-by: Yabin Cui Tested-by: Nathan Chancellor Reviewed-by: Kees Cook Tested-by: Peter Jung Signed-off-by: Masahiro Yamada