[RFC 0/7] UEFI emulator for kexec
Pingfan Liu
piliu at redhat.com
Fri Jul 19 06:02:18 PDT 2024
On Thu, Jul 18, 2024 at 4:58 PM Pingfan Liu <piliu at redhat.com> wrote:
>
>
> *** Background ***
>
> As more PE format kernel images are introduced, it post challenge to kexec to
> cope with the new format.
>
> In my attempt to add support for arm64 zboot image in the kernel [1],
> Ard suggested using an emulator to tackle this issue. Last year, when
> Jan tried to introduce UKI support in the kernel [2], Ard mentioned the
> emulator approach again [3]
>
> After discussion, Ard's approach seems to be a more promising solution
> to handle PE format kernels once and for all. This series follows that
> approach and implements an emulator to emulate EFI boot time services,
> allowing the efistub kernel to self-extract and boot.
>
>
>
> *** Overview of implement ***
> The whole model consits of three parts:
>
> -1. The emulator
> It is a self-relocatable PIC code, which is finally linked into kernel, but not
> export any internal symbol to kernel. It mainly contains: a PE file parser,
> which loads PE format kernel, a group of functions to emulate efi boot service.
>
> -2. inside kernel, PE-format loader
> Its main task is to set up two extra kexec_segment, one for emulator, the other
> for passing information from the first kernel to emulator.
>
> -3. set up identity mapping only for the memory used by the emulator.
> Here it relies on kimage_alloc_control_pages() to get pages, which will not
> stamped during the process of kexec relocate (cp from src to dst). And since the
> mapping only covers a small range of memory, it cost small amount memory.
>
>
> *** To do ***
>
> Currently, it only works on arm64 _zboot_ image on arm64 virt machine. For
> arm64 UKI, I have not completed it. But it should be easy to archieve by
Not familiar with UKI, after going through the
systemd/src/boot/efi/initrd.c, I guess systemd-stub plays as a EFI
application, it calls initrd_register() to install the initrd
information. After systemd-stub transmits the control to the efistub
linux kernel, the efistub will get the initrd. So all should spin
around the EFI_LOAD_FILE2_PROTOCOL. Am I right?
Thanks,
Pingfan
> implementing EFI_LOAD_FILE2_PROTOCOL.LoadFile(). And with a slightly
> improvement, it would work on x86.
>
> Besides that, as POC, I skip four functions in efistub: setup_graphics(),
> efi_random_get_seed() and efi_enable_reset_attack_mitigation(),
> efi_retrieve_eventlog(). Hence skipping the corresponding boot services.
>
> Also, this series does not implement a memory allocator, which I plan to
> implement with the help of bitmap.
>
> About console, currently it hard code for arm64 virt machine, later it should
> extract the information through ACPI table.
>
> [1]: https://lore.kernel.org/linux-arm-kernel/ZBvKSis+dfnqa+Vz@piliu.users.ipa.redhat.com/T/#m42abb0ad3c10126b8b3bfae8a596deb707d6f76e
> [2]: https://lore.kernel.org/lkml/20230918173607.421d2616@rotkaeppchen/T/
> [3]: https://lore.kernel.org/lkml/20230918173607.421d2616@rotkaeppchen/T/#mc60aa591cb7616ceb39e1c98f352383f9ba6e985
>
>
> Cc: Ard Biesheuvel <ardb at kernel.org>
> Cc: Jan Hendrik Farr <kernel at jfarr.cc>
> Cc: Philipp Rudo <prudo at redhat.com>
> Cc: Lennart Poettering <mzxreary at 0pointer.de>
> Cc: Jarkko Sakkinen <jarkko at kernel.org>
> Cc: Baoquan He <bhe at redhat.com>
> Cc: Dave Young <dyoung at redhat.com>
> Cc: Mark Rutland <mark.rutland at arm.com>
> Cc: Will Deacon <will at kernel.org>
> Cc: Catalin Marinas <catalin.marinas at arm.com>
> To: linux-arm-kernel at lists.infradead.org
> To: kexec at lists.infradead.org
> To: linux-efi at vger.kernel.org
>
> Pingfan Liu (7):
> efi/libstub: Ask efi_random_alloc() to skip unusable memory
> debug/libstub: cheats to step around some boot service
> efi/emulator: Initial rountines to emulate EFI boot time service
> efi/emulator: Turn on mmu for arm64
> arm64: mm: Change to prototype of
> arm64: kexec: Prepare page table for emulator
> kexec: Introduce kexec_pe_image to parse and load PE file
>
> arch/arm64/include/asm/kexec.h | 3 +
> arch/arm64/include/asm/mmu.h | 6 +
> arch/arm64/kernel/Makefile | 2 +-
> arch/arm64/kernel/kexec_image.c | 1 +
> arch/arm64/kernel/kexec_pe_image.c | 519 ++++++++++++++++++
> arch/arm64/kernel/machine_kexec.c | 90 ++-
> arch/arm64/kernel/machine_kexec_file.c | 1 +
> arch/arm64/mm/mmu.c | 67 ++-
> drivers/firmware/efi/Makefile | 1 +
> drivers/firmware/efi/efi_emulator/Makefile | 98 ++++
> .../firmware/efi/efi_emulator/amba-pl011.c | 80 +++
> .../efi_emulator/arm64_emulator_service.lds | 45 ++
> .../firmware/efi/efi_emulator/arm64_proc.S | 172 ++++++
> .../firmware/efi/efi_emulator/config_table.c | 23 +
> drivers/firmware/efi/efi_emulator/core.c | 211 +++++++
> drivers/firmware/efi/efi_emulator/earlycon.h | 19 +
> .../firmware/efi/efi_emulator/efi_emulator.S | 12 +
> drivers/firmware/efi/efi_emulator/emulator.h | 66 +++
> drivers/firmware/efi/efi_emulator/entry.c | 64 +++
> drivers/firmware/efi/efi_emulator/head.S | 10 +
> drivers/firmware/efi/efi_emulator/initrd.c | 15 +
> drivers/firmware/efi/efi_emulator/lib.c | 73 +++
> drivers/firmware/efi/efi_emulator/memory.c | 27 +
> .../firmware/efi/efi_emulator/memory_api.c | 73 +++
> drivers/firmware/efi/efi_emulator/misc.c | 76 +++
> drivers/firmware/efi/efi_emulator/pe_loader.c | 124 +++++
> drivers/firmware/efi/efi_emulator/printf.c | 389 +++++++++++++
> .../efi/efi_emulator/runtime_service.c | 28 +
> .../firmware/efi/libstub/efi-stub-helper.c | 3 +
> drivers/firmware/efi/libstub/efi-stub.c | 2 +
> drivers/firmware/efi/libstub/random.c | 2 +
> drivers/firmware/efi/libstub/randomalloc.c | 5 +
> drivers/firmware/efi/libstub/tpm.c | 4 +
> include/linux/efi_emulator.h | 46 ++
> include/linux/kexec.h | 5 +
> 35 files changed, 2327 insertions(+), 35 deletions(-)
> create mode 100644 arch/arm64/kernel/kexec_pe_image.c
> create mode 100644 drivers/firmware/efi/efi_emulator/Makefile
> create mode 100644 drivers/firmware/efi/efi_emulator/amba-pl011.c
> create mode 100644 drivers/firmware/efi/efi_emulator/arm64_emulator_service.lds
> create mode 100644 drivers/firmware/efi/efi_emulator/arm64_proc.S
> create mode 100644 drivers/firmware/efi/efi_emulator/config_table.c
> create mode 100644 drivers/firmware/efi/efi_emulator/core.c
> create mode 100644 drivers/firmware/efi/efi_emulator/earlycon.h
> create mode 100644 drivers/firmware/efi/efi_emulator/efi_emulator.S
> create mode 100644 drivers/firmware/efi/efi_emulator/emulator.h
> create mode 100644 drivers/firmware/efi/efi_emulator/entry.c
> create mode 100644 drivers/firmware/efi/efi_emulator/head.S
> create mode 100644 drivers/firmware/efi/efi_emulator/initrd.c
> create mode 100644 drivers/firmware/efi/efi_emulator/lib.c
> create mode 100644 drivers/firmware/efi/efi_emulator/memory.c
> create mode 100644 drivers/firmware/efi/efi_emulator/memory_api.c
> create mode 100644 drivers/firmware/efi/efi_emulator/misc.c
> create mode 100644 drivers/firmware/efi/efi_emulator/pe_loader.c
> create mode 100644 drivers/firmware/efi/efi_emulator/printf.c
> create mode 100644 drivers/firmware/efi/efi_emulator/runtime_service.c
> create mode 100644 include/linux/efi_emulator.h
>
> --
> 2.41.0
>
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