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2020-11-25kbuild: Skip module BTF generation for out-of-tree external modulesAndrii Nakryiko1-2/+7
In some modes of operation, Kbuild allows to build modules without having vmlinux image around. In such case, generation of module BTF is impossible. This patch changes the behavior to emit a warning about impossibility of generating kernel module BTF, instead of breaking the build. This is especially important for out-of-tree external module builds. In vmlinux-less mode: $ make clean $ make modules_prepare $ touch drivers/acpi/button.c $ make M=drivers/acpi ... CC [M] drivers/acpi/button.o MODPOST drivers/acpi/Module.symvers LD [M] drivers/acpi/button.ko BTF [M] drivers/acpi/button.ko Skipping BTF generation for drivers/acpi/button.ko due to unavailability of vmlinux ... $ readelf -S ~/linux-build/default/drivers/acpi/button.ko | grep BTF -A1 ... empty ... Now with normal build: $ make all ... LD [M] drivers/acpi/button.ko BTF [M] drivers/acpi/button.ko ... $ readelf -S ~/linux-build/default/drivers/acpi/button.ko | grep BTF -A1 [60] .BTF PROGBITS 0000000000000000 00029310 000000000000ab3f 0000000000000000 0 0 1 Fixes: 5f9ae91f7c0d ("kbuild: Build kernel module BTFs if BTF is enabled and pahole supports it") Reported-by: Bruce Allan <bruce.w.allan@intel.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Cc: Jessica Yu <jeyu@kernel.org> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Masahiro Yamada <yamada.masahiro@socionext.com> Link: https://lore.kernel.org/bpf/20201121070829.2612884-1-andrii@kernel.org
2020-11-10kbuild: Build kernel module BTFs if BTF is enabled and pahole supports itAndrii Nakryiko1-2/+18
Detect if pahole supports split BTF generation, and generate BTF for each selected kernel module, if it does. This is exposed to Makefiles and C code as CONFIG_DEBUG_INFO_BTF_MODULES flag. Kernel module BTF has to be re-generated if either vmlinux's BTF changes or module's .ko changes. To achieve that, I needed a helper similar to if_changed, but that would allow to filter out vmlinux from the list of updated dependencies for .ko building. I've put it next to the only place that uses and needs it, but it might be a better idea to just add it along the other if_changed variants into scripts/Kbuild.include. Each kernel module's BTF deduplication is pretty fast, as it does only incremental BTF deduplication on top of already deduplicated vmlinux BTF. To show the added build time, I've first ran make only just built kernel (to establish the baseline) and then forced only BTF re-generation, without regenerating .ko files. The build was performed with -j60 parallelization on 56-core machine. The final time also includes bzImage building, so it's not a pure BTF overhead. $ time make -j60 ... make -j60 27.65s user 10.96s system 782% cpu 4.933 total $ touch ~/linux-build/default/vmlinux && time make -j60 ... make -j60 123.69s user 27.85s system 1566% cpu 9.675 total So 4.6 seconds real time, with noticeable part spent in compressed vmlinux and bzImage building. To show size savings, I've built my kernel configuration with about 700 kernel modules with full BTF per each kernel module (without deduplicating against vmlinux) and with split BTF against deduplicated vmlinux (approach in this patch). Below are top 10 modules with biggest BTF sizes. And total size of BTF data across all kernel modules. It shows that split BTF "compresses" 115MB down to 5MB total. And the biggest kernel modules get a downsize from 500-570KB down to 200-300KB. FULL BTF ======== $ for f in $(find . -name '*.ko'); do size -A -d $f | grep BTF | awk '{print $2}'; done | awk '{ s += $1 } END { print s }' 115710691 $ for f in $(find . -name '*.ko'); do printf "%s %d\n" $f $(size -A -d $f | grep BTF | awk '{print $2}'); done | sort -nr -k2 | head -n10 ./drivers/gpu/drm/i915/i915.ko 570570 ./drivers/net/ethernet/mellanox/mlx5/core/mlx5_core.ko 520240 ./drivers/gpu/drm/radeon/radeon.ko 503849 ./drivers/infiniband/hw/mlx5/mlx5_ib.ko 491777 ./fs/xfs/xfs.ko 411544 ./drivers/net/ethernet/intel/i40e/i40e.ko 403904 ./drivers/net/ethernet/broadcom/bnx2x/bnx2x.ko 398754 ./drivers/infiniband/core/ib_core.ko 397224 ./fs/cifs/cifs.ko 386249 ./fs/nfsd/nfsd.ko 379738 SPLIT BTF ========= $ for f in $(find . -name '*.ko'); do size -A -d $f | grep BTF | awk '{print $2}'; done | awk '{ s += $1 } END { print s }' 5194047 $ for f in $(find . -name '*.ko'); do printf "%s %d\n" $f $(size -A -d $f | grep BTF | awk '{print $2}'); done | sort -nr -k2 | head -n10 ./drivers/gpu/drm/i915/i915.ko 293206 ./drivers/gpu/drm/radeon/radeon.ko 282103 ./fs/xfs/xfs.ko 222150 ./drivers/net/ethernet/mellanox/mlx5/core/mlx5_core.ko 198503 ./drivers/infiniband/hw/mlx5/mlx5_ib.ko 198356 ./drivers/net/ethernet/broadcom/bnx2x/bnx2x.ko 113444 ./fs/cifs/cifs.ko 109379 ./arch/x86/kvm/kvm.ko 100225 ./drivers/gpu/drm/drm.ko 94827 ./drivers/infiniband/core/ib_core.ko 91188 Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20201110011932.3201430-4-andrii@kernel.org
2020-09-25kbuild: preprocess module linker scriptMasahiro Yamada1-3/+2
There was a request to preprocess the module linker script like we do for the vmlinux one. (https://lkml.org/lkml/2020/8/21/512) The difference between vmlinux.lds and module.lds is that the latter is needed for external module builds, thus must be cleaned up by 'make mrproper' instead of 'make clean'. Also, it must be created by 'make modules_prepare'. You cannot put it in arch/$(SRCARCH)/kernel/, which is cleaned up by 'make clean'. I moved arch/$(SRCARCH)/kernel/module.lds to arch/$(SRCARCH)/include/asm/module.lds.h, which is included from scripts/module.lds.S. scripts/module.lds is fine because 'make clean' keeps all the build artifacts under scripts/. You can add arch-specific sections in <asm/module.lds.h>. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Tested-by: Jessica Yu <jeyu@kernel.org> Acked-by: Will Deacon <will@kernel.org> Acked-by: Geert Uytterhoeven <geert@linux-m68k.org> Acked-by: Palmer Dabbelt <palmerdabbelt@google.com> Reviewed-by: Kees Cook <keescook@chromium.org> Acked-by: Jessica Yu <jeyu@kernel.org>
2019-08-22kbuild: move modkern_{c,a}flags to Makefile.lib from Makefile.buildMasahiro Yamada1-3/+3
Makefile.lib is included by Makefile.modfinal as well as Makefile.build. Move modkern_cflags to Makefile.lib in order to simplify cmd_cc_o_c in Makefile.modfinal. Move modkern_cflags as well for consistency. Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
2019-08-22kbuild: split final module linking out into Makefile.modfinalMasahiro Yamada1-0/+60
I think splitting the modpost and linking modules into separate Makefiles will be useful especially when more complex build steps come in. The main motivation of this commit is to integrate the proposed klp-convert feature cleanly. I moved the logging 'Building modules, stage 2.' to Makefile.modpost to avoid the code duplication although I do not know whether or not this message is needed in the first place. Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>