On Mon, Sep 01, 2025 at 04:29:29PM +0200, Philipp Rudo wrote: Hi Philipp, Thank you for deep insight, please see the comments
> Hi Pingfan, > > thanks for sharing the updated version of the series. There are a few > small nits you can find in my comments to the individual patches. > > I also took an other look at the bigger picture. The way I see it the > series contains two major changes. > > 1. A generic mechanism to parse and run bpf programs during kexec. Thanks for your suggestion. This makes the whole design look more natural. Without it, using the PE format parser as a frontend to the image parser looks a bit awkward. > 2. A new loader for UEFI Applications building up on 1. > > Both those changes are currently smashed together as "PE image loader", > which IMHO is quite confusing. It's correct that UEFI Apps are PE > files. But the PE format is also used in many other ways and in the end > we are only interested in this specific use case. Plus the generic > mechanism to parse and run bpf programs during kexec can also be used > with any other file format, not just PE. > > In addition I noticed that hooking into kexec_file while loading the > image is too late. The problem is that in > kernel/kexec_file.c:kimage_file_prepare_segments the cmdline is > measured for IMA before the image is loaded. But we allow the > bpf_prog to change the cmdline. When that is done the IMA measurement > no longer is correct. So we need a new hook to run the bpf programs > after the initrd and cmdline were read but before the IMA measurement is > done. > This should be a issue when turning on IMA measurement on cmdline. And it can be perfectly addressed with your suggestion. > So my suggestions are: > > 1. Extend the kexec_file_ops by a new 'get_bpf_prog' hook. I'm not sure I agree with you on this. We both agree that the generic mechanism to parse and run BPF programs should be independent of the image parser and belong in kexec_file.c. However, kexec_file_ops is still a concept that belongs to the image parser layer. So I think that moving the logic to kexec_file.c is good enough. > 2. Move the mechanism to run bpf progs from kexec_pe_image.c to > kexec_file.c (with the new hook in the file_ops there shouldn't be > any problems). Yes, the logic of loading and runing bpf progs should be placed in kexec_file.c. > 3. Rename CONFIG_KEXEC_PE_IMAGE to CONFIG_KEXEC_BPF OK. > 4. Rename kexec_pe_image.c (and the functions within) to > kexec_uefi_app.c > OK. Thanks for your careful review and good suggestion. Best Regards, Pingfan > Thanks > Philipp > > On Tue, 19 Aug 2025 09:24:16 +0800 > Pingfan Liu <[email protected]> wrote: > > > Cc [email protected] so any UKI expert can comment > > > > *** Review the history *** > > > > Nowadays UEFI PE bootable image is more and more popular on the > > distribution. > > But it is still an open issue to load that kind of image by kexec with IMA > > enabled > > > > There are several approaches to reslove this issue, but none of them are > > accepted in upstream till now. > > > > The summary of those approaches: > > -1. UEFI service emulator for UEFI stub > > -2. PE format parser in kernel > > > > For the first one, I have tried a purgatory-style emulator [1]. But it > > confronts the hardware scaling trouble. For the second one, there are two > > choices, one is to implement it inside the kernel, the other is inside the > > user > > space. Both zboot-format [2] and UKI-format [3] parsers are rejected due to > > the concern that the variant format parsers will inflate the kernel code. > > And > > finally, we have these kinds of parsers in the user space 'kexec-tools'. > > > > > > *** The approach in this series *** > > > > This approach allows the various PE boot image to be parsed in the bpf-prog, > > as a result, the kexec kernel code to remain relatively stable. > > > > Benefits > > And it abstracts architecture independent part and > > the API is limitted > > > > To protect against malicious attacks on the BPF loader in user space, it > > employs BPF lskel to load and execute BPF programs from within the > > kernel. > > > > Each type of PE image contains a dedicated section '.bpf', which stores > > the bpf-prog designed to parse the format. This ensures that the PE's > > signature also protects the integrity of the '.bpf' section. > > > > > > The parsing process operates as a pipeline. The current BPF program > > parser attaches to bpf_handle_pefile() and detaches at the end of the > > current stage via disarm_bpf_prog(). The results parsed by the current > > BPF program are buffered in the kernel through prepare_nested_pe() and > > then delivered to the next stage. For each stage of the pipeline, the > > BPF bytecode is stored in the '.bpf' section of the PE file. That means > > a vmlinuz.efi embeded in UKI format can be handled. > > > > > > Special thanks to Philipp Rudo, who spent significant time evaluating > > the practicality of my solution, and to Viktor Malik, who guided me > > toward using BPF light skeleton to prevent malicious attacks from user > > space. > > > > *** Test result *** > > Configured with RHEL kernel debug file, which turns on most of locking, > > memory debug option, I have not seen any warning or bug for 1000 times. > > > > Test approach: > > -1. compile kernel > > -2. get the zboot image with bpf-prog by 'make -C tools/kexec zboot' > > -3. compile kexec-tools from > > https://github.com/pfliu/kexec-tools/pull/new/pe_bpf > > > > The rest process is the common convention to use kexec. > > > > > > [1]: https://lore.kernel.org/lkml/[email protected]/T/ > > [2]: > > https://lore.kernel.org/kexec/[email protected]/ > > [3]: https://lore.kernel.org/lkml/[email protected]/ > > [4]: > > https://lore.kernel.org/linux-arm-kernel/[email protected]/T/ > > > > v4 -> v5 > > - rebased onto Linux 6.17-rc2 > > - [1/12], use a separate CONFIG_KEEP_COMPRESSOR to decide the section > > of decompressor method > > - [10/12], add Catalin's acked-by (Thanks Catalin!) > > > > v3 -> v4 > > - Use dynamic allocator in decompression ([4/12]) > > - Fix issue caused by Identical Code Folding ([5/12]) > > - Integrate the image generator tool in the kernel tree ([11,12/12]) > > - Address the issue according to Philipp's comments in v3 reviewing. > > Thanks Philipp! > > > > RFCv2 -> v3 > > - move the introduced bpf kfuncs to kernel/bpf/* and mark them sleepable > > - use listener and publisher model to implement bpf_copy_to_kernel() > > - keep each introduced kfunc under the control of memcg > > > > RFCv1 -> RFCv2 > > - Use bpf kfunc instead of helper > > - Use C source code to generate the light skeleton file > > > > > > *** BLURB HERE *** > > > > Pingfan Liu (12): > > kexec_file: Make kexec_image_load_default global visible > > lib/decompress: Keep decompressor when CONFIG_KEEP_COMPRESSOR > > bpf: Introduce bpf_copy_to_kernel() to buffer the content from bpf-prog > > bpf: Introduce decompressor kfunc > > kexec: Introduce kexec_pe_image to parse and load PE file > > kexec: Integrate with the introduced bpf kfuncs > > kexec: Introduce a bpf-prog lskel to parse PE file > > kexec: Factor out routine to find a symbol in ELF > > kexec: Integrate bpf light skeleton to load zboot image > > arm64/kexec: Add PE image format support > > tools/kexec: Introduce a bpf-prog to parse zboot image format > > tools/kexec: Add a zboot image building tool > > > > arch/arm64/Kconfig | 1 + > > arch/arm64/include/asm/kexec.h | 1 + > > arch/arm64/kernel/machine_kexec_file.c | 3 + > > include/linux/bpf.h | 42 ++ > > include/linux/decompress/mm.h | 7 + > > include/linux/kexec.h | 10 + > > kernel/Kconfig.kexec | 9 + > > kernel/Makefile | 2 + > > kernel/bpf/Makefile | 3 + > > kernel/bpf/helpers.c | 230 +++++++++ > > kernel/bpf/helpers_carrier.c | 215 +++++++++ > > kernel/kexec_bpf/Makefile | 71 +++ > > kernel/kexec_bpf/kexec_pe_parser_bpf.c | 67 +++ > > kernel/kexec_bpf/kexec_pe_parser_bpf.lskel.h | 147 ++++++ > > kernel/kexec_file.c | 88 ++-- > > kernel/kexec_pe_image.c | 463 +++++++++++++++++++ > > lib/Kconfig | 3 + > > lib/decompress.c | 6 +- > > tools/kexec/Makefile | 90 ++++ > > tools/kexec/pe.h | 177 +++++++ > > tools/kexec/zboot_image_builder.c | 280 +++++++++++ > > tools/kexec/zboot_parser_bpf.c | 158 +++++++ > > 22 files changed, 2029 insertions(+), 44 deletions(-) > > create mode 100644 kernel/bpf/helpers_carrier.c > > create mode 100644 kernel/kexec_bpf/Makefile > > create mode 100644 kernel/kexec_bpf/kexec_pe_parser_bpf.c > > create mode 100644 kernel/kexec_bpf/kexec_pe_parser_bpf.lskel.h > > create mode 100644 kernel/kexec_pe_image.c > > create mode 100644 tools/kexec/Makefile > > create mode 100644 tools/kexec/pe.h > > create mode 100644 tools/kexec/zboot_image_builder.c > > create mode 100644 tools/kexec/zboot_parser_bpf.c > > > > > > base-commit: c17b750b3ad9f45f2b6f7e6f7f4679844244f0b9 >
