Hello all, This patchset makes it possible to use bpftrace with kprobes on kernels built without loadable module support. On a Raspberry Pi 4b, this saves about 700KB of memory where BPF is needed but loadable module support is not. These two kernels had identical configurations, except CONFIG_MODULE was off in the second: - Linux version 6.8.0-rc7 - Memory: 3330672K/4050944K available (16576K kernel code, 2390K rwdata, - 12364K rodata, 5632K init, 675K bss, 195984K reserved, 524288K cma-reserved) + Linux version 6.8.0-rc7-00003-g2af01251ca21 + Memory: 3331400K/4050944K available (16512K kernel code, 2384K rwdata, + 11728K rodata, 5632K init, 673K bss, 195256K reserved, 524288K cma-reserved) I don't intend to present an exhaustive list of !MODULES usecases, since I'm sure there are many I'm not aware of. Performance is a common one, the primary justification being that static text is mapped on hugepages and module text is not. Security is another, since rootkits are much harder to implement without modules. The first patch is the interesting one: it moves module_alloc() into its own file with its own Kconfig option, so it can be utilized even when loadable module support is disabled. I got the idea from an unmerged patch from a few years ago I found on lkml (see [1/4] for details). I think this also has value in its own right, since I suspect there are potential users beyond bpf, hopefully we will hear from some. Patches 2-3 are proofs of concept to demonstrate the first patch is sufficient to achieve my goal (full ebpf functionality without modules). Patch 4 adds a new "-n" argument to vmtest.sh to run the BPF selftests without modules, so the prior three patches can be rigorously tested. If something like the first patch were to eventually be merged, the rest could go through the normal bpf-next process as I clean them up: I've only based them on Linus' tree and combined them into a series here to introduce the idea. If you prefer to fetch the patches via git: [1/4] https://github.com/jcalvinowens/linux.git work/module-alloc +[2/4]+[3/4] https://github.com/jcalvinowens/linux.git work/nomodule-bpf +[4/4] https://github.com/jcalvinowens/linux.git testing/nomodule-bpf-ci In addition to the automated BPF selftests, I've lightly tested this on my laptop (x86_64), a Raspberry Pi 4b (arm64), and a Raspberry Pi Zero W (arm). The other architectures have only been compile tested. I didn't want to spam all the arch maintainers with what I expect will be a discussion mostly about modules and bpf, so I've left them off this first submission. I will be sure to add them on future submissions of the first patch. Of course, feedback on the arch bits is welcome here. In addition to feedback on the patches themselves, I'm interested in hearing from anybody else who might find this functionality useful. Thanks, Calvin Calvin Owens (4): module: mm: Make module_alloc() generally available bpf: Allow BPF_JIT with CONFIG_MODULES=n kprobes: Allow kprobes with CONFIG_MODULES=n selftests/bpf: Support testing the !MODULES case arch/Kconfig | 4 +- arch/arm/kernel/module.c | 35 ----- arch/arm/mm/Makefile | 2 + arch/arm/mm/module_alloc.c | 40 ++++++ arch/arm64/kernel/module.c | 127 ----------------- arch/arm64/mm/Makefile | 1 + arch/arm64/mm/module_alloc.c | 130 ++++++++++++++++++ arch/loongarch/kernel/module.c | 6 - arch/loongarch/mm/Makefile | 2 + arch/loongarch/mm/module_alloc.c | 10 ++ arch/mips/kernel/module.c | 10 -- arch/mips/mm/Makefile | 2 + arch/mips/mm/module_alloc.c | 13 ++ arch/nios2/kernel/module.c | 20 --- arch/nios2/mm/Makefile | 2 + arch/nios2/mm/module_alloc.c | 22 +++ arch/parisc/kernel/module.c | 12 -- arch/parisc/mm/Makefile | 1 + arch/parisc/mm/module_alloc.c | 15 ++ arch/powerpc/kernel/module.c | 36 ----- arch/powerpc/mm/Makefile | 1 + arch/powerpc/mm/module_alloc.c | 41 ++++++ arch/riscv/kernel/module.c | 11 -- arch/riscv/mm/Makefile | 1 + arch/riscv/mm/module_alloc.c | 17 +++ arch/s390/kernel/module.c | 37 ----- arch/s390/mm/Makefile | 1 + arch/s390/mm/module_alloc.c | 42 ++++++ arch/sparc/kernel/module.c | 31 ----- arch/sparc/mm/Makefile | 2 + arch/sparc/mm/module_alloc.c | 31 +++++ arch/x86/kernel/ftrace.c | 2 +- arch/x86/kernel/module.c | 56 -------- arch/x86/mm/Makefile | 2 + arch/x86/mm/module_alloc.c | 59 ++++++++ fs/proc/kcore.c | 2 +- include/trace/events/bpf_testmod.h | 1 + kernel/bpf/Kconfig | 11 +- kernel/bpf/Makefile | 2 + kernel/bpf/bpf_struct_ops.c | 28 +++- kernel/bpf/bpf_testmod/Makefile | 1 + kernel/bpf/bpf_testmod/bpf_testmod.c | 1 + kernel/bpf/bpf_testmod/bpf_testmod.h | 1 + kernel/bpf/bpf_testmod/bpf_testmod_kfunc.h | 1 + kernel/kprobes.c | 22 +++ kernel/module/Kconfig | 1 + kernel/module/main.c | 17 --- kernel/trace/trace_kprobe.c | 11 ++ mm/Kconfig | 3 + mm/Makefile | 1 + mm/module_alloc.c | 21 +++ mm/vmalloc.c | 2 +- net/bpf/test_run.c | 2 + tools/testing/selftests/bpf/Makefile | 28 ++-- .../selftests/bpf/bpf_testmod/Makefile | 2 +- .../bpf/bpf_testmod/bpf_testmod-events.h | 6 + .../selftests/bpf/bpf_testmod/bpf_testmod.c | 4 + .../bpf/bpf_testmod/bpf_testmod_kfunc.h | 2 + tools/testing/selftests/bpf/config | 5 - tools/testing/selftests/bpf/config.mods | 5 + tools/testing/selftests/bpf/config.nomods | 1 + .../selftests/bpf/progs/btf_type_tag_percpu.c | 2 + .../selftests/bpf/progs/btf_type_tag_user.c | 2 + tools/testing/selftests/bpf/progs/core_kern.c | 2 + .../selftests/bpf/progs/iters_testmod_seq.c | 2 + .../bpf/progs/test_core_reloc_module.c | 2 + .../selftests/bpf/progs/test_ldsx_insn.c | 2 + .../selftests/bpf/progs/test_module_attach.c | 3 + .../selftests/bpf/progs/tracing_struct.c | 2 + tools/testing/selftests/bpf/testing_helpers.c | 14 ++ tools/testing/selftests/bpf/vmtest.sh | 24 +++- 71 files changed, 636 insertions(+), 424 deletions(-) create mode 100644 arch/arm/mm/module_alloc.c create mode 100644 arch/arm64/mm/module_alloc.c create mode 100644 arch/loongarch/mm/module_alloc.c create mode 100644 arch/mips/mm/module_alloc.c create mode 100644 arch/nios2/mm/module_alloc.c create mode 100644 arch/parisc/mm/module_alloc.c create mode 100644 arch/powerpc/mm/module_alloc.c create mode 100644 arch/riscv/mm/module_alloc.c create mode 100644 arch/s390/mm/module_alloc.c create mode 100644 arch/sparc/mm/module_alloc.c create mode 100644 arch/x86/mm/module_alloc.c create mode 120000 include/trace/events/bpf_testmod.h create mode 100644 kernel/bpf/bpf_testmod/Makefile create mode 120000 kernel/bpf/bpf_testmod/bpf_testmod.c create mode 120000 kernel/bpf/bpf_testmod/bpf_testmod.h create mode 120000 kernel/bpf/bpf_testmod/bpf_testmod_kfunc.h create mode 100644 mm/module_alloc.c create mode 100644 tools/testing/selftests/bpf/config.mods create mode 100644 tools/testing/selftests/bpf/config.nomods -- 2.43.0
