Hi Pingfan, On Tue, 16 Sep 2025 10:00:41 +0800 Pingfan Liu <pi...@redhat.com> wrote:
> 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. I'm not sure I get your point here. My rational is, that the bpf_prog can be included in different file formats. So we still need a mechanism to parse it from the different formats. Plus we need a file_ops that is "responsible" for a file type. All in all it makes most sense to me to have a file_ops that only has a .probe and .get_bpf_prog. But yes, maybe I'm missing something. I'm curious on seeing your v6. Thanks Philipp > > > 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 <pi...@redhat.com> wrote: > > > > > Cc systemd-de...@lists.freedesktop.org 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/20240819145417.23367-1-pi...@redhat.com/T/ > > > [2]: > > > https://lore.kernel.org/kexec/20230306030305.15595-1-kernelf...@gmail.com/ > > > [3]: https://lore.kernel.org/lkml/20230911052535.335770-1-ker...@jfarr.cc/ > > > [4]: > > > https://lore.kernel.org/linux-arm-kernel/20230921133703.39042-2-kernelf...@gmail.com/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 > > >
