| Message ID | cover.1671098103.git.baskov@ispras.ru (mailing list archive) |
|---|---|
| Headers | show |
| Series | x86_64: Improvements at compressed kernel stage | expand |
On Thu, Dec 15, 2022 at 03:37:51PM +0300, Evgeniy Baskov wrote: > This patchset is aimed > * to improve UEFI compatibility of compressed kernel code for x86_64 > * to setup proper memory access attributes for code and rodata sections > * to implement W^X protection policy throughout the whole execution > of compressed kernel for EFISTUB code path. Hi Evgeniy, Aside from some minor patch fuzz in patch 6 due to building this in today's Fedora rawhide kernel rather than mainline, this patch set works for me. Thanks!
On 2022-12-15 22:21, Peter Jones wrote: > On Thu, Dec 15, 2022 at 03:37:51PM +0300, Evgeniy Baskov wrote: >> This patchset is aimed >> * to improve UEFI compatibility of compressed kernel code for x86_64 >> * to setup proper memory access attributes for code and rodata >> sections >> * to implement W^X protection policy throughout the whole execution >> of compressed kernel for EFISTUB code path. > > Hi Evgeniy, > > Aside from some minor patch fuzz in patch 6 due to building this in > today's Fedora rawhide kernel rather than mainline, this patch set > works > for me. > > Thanks! Nice to hear that, thank you for testing again!
This patchset is aimed * to improve UEFI compatibility of compressed kernel code for x86_64 * to setup proper memory access attributes for code and rodata sections * to implement W^X protection policy throughout the whole execution of compressed kernel for EFISTUB code path. Kernel is made to be more compatible with PE image specification [3], allowing it to be successfully loaded by stricter PE loader implementations like the one from [2]. There is at least one known implementation that uses that loader in production [4]. There are also ongoing efforts to upstream these changes. Also the patchset adds EFI_MEMORY_ATTTRIBUTE_PROTOCOL, included into EFI specification since version 2.10, as a better alternative to using DXE services for memory protection attributes manipulation, since it is defined by the UEFI specification itself and not UEFI PI specification. This protocol is not widely available so the code using DXE services is kept in place as a fallback in case specific implementation does not support the new protocol. One of EFI implementations that already support EFI_MEMORY_ATTTRIBUTE_PROTOCOL is Microsoft Project Mu [5]. Kernel image generation tool (tools/build.c) is refactored as a part of changes that makes PE image more compatible. The patchset implements memory protection for compressed kernel code while executing both inside EFI boot services and outside of them. For EFISTUB code path W^X protection policy is maintained throughout the whole execution of compressed kernel. The latter is achieved by extracting the kernel directly from EFI environment and jumping to it's head immediately after exiting EFI boot services. As a side effect of this change one page table rebuild and a copy of the kernel image is removed. Memory protection inside EFI environment is controlled by the CONFIG_DXE_MEM_ATTRIBUTES option, although with these patches this option also control the use EFI_MEMORY_ATTTRIBUTE_PROTOCOL and memory protection attributes of PE sections and not only DXE services as the name might suggest. Changes in v2: * Fix spelling. * Rebase code to current master. * Split huge patches into smaller ones. * Remove unneeded forward declarations. * Make direct extraction unconditional. * Also make it work for x86_32. * Reduce lower limit of KASLR to 64M. * Make callback interface more logically consistent. * Actually declare callbacks structure before using it. * Mention effect on x86_32 in commit message of "x86/build: Remove RWX sections and align on 4KB". * Clarify commit message of "x86/boot: Increase boot page table size". * Remove "startup32_" prefix on startup32_enable_nx_if_supported. * Move linker generated sections outside of function scope. * Drop some unintended changes. * Drop generating 2 reloc entries. (as I've misread the documentation and there's no need for this change.) * Set has_nx from enable_nx_if_supported correctly. * Move ELF header check to build time. * Set WP at the same time as PG in trampoline code, as it is more logically consistent. * Put x86-specific EFISTUB definitions in x86-stub.h header. * Catch presence of ELF segments violating W^X during build. * Move PE definitions from build.c to a new header file. * Fix generation of PE '.compat' section. I decided to keep protection of compressed kernel blob and '.rodata' separate from '.text' for now, since it does not really have a lot of overhead. Otherwise, all comments on v1 seems to be addressed. Changes in v3: * Setup IDT before issuing cpuid so that AMD SEV #VC handler is set. * Replace memcpy with strncpy to prevent out-of-bounds reads in tools/build.c. * Zero BSS before entering efi_main(), since it can contain garbage when booting via EFI handover protocol. * When booting via EFI don't require init_size of RAM, since in-place unpacking is not used anyway with that interface. This saves ~40M of memory for debian .config. * Setup sections memory protection in efi_main() to cover EFI handover protocol, where EFI sections are likely not properly protected. Changes in v4: * Add one missing identity mapping. * Include following patches improving the use of DXE services: - efi/x86: don't try to set page attributes on 0-sized regions. - efi/x86: don't set unsupported memory attributes Patch "x86/boot: Support 4KB pages for identity mapping" needs review from x86/mm team. I have also included Peter's patches [6-8] into the series for simplicity. Many thanks to Ard Biesheuvel <ardb@kernel.org> and Andrew Cooper <Andrew.Cooper3@citrix.com> for reviewing the patches, and to Peter Jones <pjones@redhat.com>, Mario Limonciello <mario.limonciello@amd.com> and Joey Lee <jlee@suse.com> for additional testing! [1] https://lkml.org/lkml/2022/8/1/1314 [2] https://github.com/acidanthera/audk/tree/secure_pe [3] https://download.microsoft.com/download/9/c/5/9c5b2167-8017-4bae-9fde-d599bac8184a/pecoff_v83.docx [4] https://www.ispras.ru/en/technologies/asperitas/ [5] https://github.com/microsoft/mu_tiano_platforms [6] https://lkml.org/lkml/2022/10/18/1178 [7] https://lkml.org/lkml/2022/12/13/840 [8] https://lkml.org/lkml/2022/12/13/841 Evgeniy Baskov (23): x86/boot: Align vmlinuz sections on page size x86/build: Remove RWX sections and align on 4KB x86/boot: Set cr0 to known state in trampoline x86/boot: Increase boot page table size x86/boot: Support 4KB pages for identity mapping x86/boot: Setup memory protection for bzImage code x86/build: Check W^X of vmlinux during build x86/boot: Map memory explicitly x86/boot: Remove mapping from page fault handler efi/libstub: Move helper function to related file x86/boot: Make console interface more abstract x86/boot: Make kernel_add_identity_map() a pointer x86/boot: Split trampoline and pt init code x86/boot: Add EFI kernel extraction interface efi/x86: Support extracting kernel from libstub x86/boot: Reduce lower limit of physical KASLR x86/boot: Reduce size of the DOS stub tools/include: Add simplified version of pe.h x86/build: Cleanup tools/build.c x86/build: Make generated PE more spec compliant efi/x86: Explicitly set sections memory attributes efi/libstub: Add memory attribute protocol definitions efi/libstub: Use memory attribute protocol Peter Jones (3): efi/libstub: make memory protection warnings include newlines. efi/x86: don't try to set page attributes on 0-sized regions. efi/x86: don't set unsupported memory attributes arch/x86/boot/Makefile | 2 +- arch/x86/boot/compressed/Makefile | 8 +- arch/x86/boot/compressed/acpi.c | 25 +- arch/x86/boot/compressed/efi.c | 19 +- arch/x86/boot/compressed/head_32.S | 53 +- arch/x86/boot/compressed/head_64.S | 89 ++- arch/x86/boot/compressed/ident_map_64.c | 122 ++-- arch/x86/boot/compressed/kaslr.c | 8 +- arch/x86/boot/compressed/misc.c | 278 ++++----- arch/x86/boot/compressed/misc.h | 23 +- arch/x86/boot/compressed/pgtable.h | 20 - arch/x86/boot/compressed/pgtable_64.c | 75 ++- arch/x86/boot/compressed/putstr.c | 130 ++++ arch/x86/boot/compressed/sev.c | 6 +- arch/x86/boot/compressed/vmlinux.lds.S | 6 + arch/x86/boot/header.S | 110 +--- arch/x86/boot/tools/build.c | 569 +++++++++++------- arch/x86/include/asm/boot.h | 26 +- arch/x86/include/asm/efi.h | 7 + arch/x86/include/asm/init.h | 1 + arch/x86/include/asm/shared/extract.h | 26 + arch/x86/include/asm/shared/pgtable.h | 29 + arch/x86/kernel/vmlinux.lds.S | 15 +- arch/x86/mm/ident_map.c | 185 +++++- drivers/firmware/efi/Kconfig | 2 + drivers/firmware/efi/libstub/Makefile | 2 +- drivers/firmware/efi/libstub/efistub.h | 26 + drivers/firmware/efi/libstub/mem.c | 194 ++++++ .../firmware/efi/libstub/x86-extract-direct.c | 208 +++++++ drivers/firmware/efi/libstub/x86-stub.c | 231 ++----- drivers/firmware/efi/libstub/x86-stub.h | 14 + include/linux/efi.h | 1 + tools/include/linux/pe.h | 150 +++++ 33 files changed, 1860 insertions(+), 800 deletions(-) delete mode 100644 arch/x86/boot/compressed/pgtable.h create mode 100644 arch/x86/boot/compressed/putstr.c create mode 100644 arch/x86/include/asm/shared/extract.h create mode 100644 arch/x86/include/asm/shared/pgtable.h create mode 100644 drivers/firmware/efi/libstub/x86-extract-direct.c create mode 100644 drivers/firmware/efi/libstub/x86-stub.h create mode 100644 tools/include/linux/pe.h