The following KASLR implementation allows to randomize the kernel mapping: - virtually: we expect the bootloader to provide a seed in the device-tree - physically: only implemented in the EFI stub, it relies on the firmware to provide a seed using EFI_RNG_PROTOCOL. arm64 has a similar implementation hence the patch 3 factorizes KASLR related functions for riscv to take advantage. The new virtual kernel location is limited by the early page table that only has one PUD and with the PMD alignment constraint, the kernel can only take < 512 positions. Note that the patch "riscv: Use PUD/P4D/PGD pages for the linear mapping" is necessary to retrieve the memory below the physical kernel address, so that the EFI stub does not have to try to relocate the kernel as close as possible to the start of dram. This patchset is rebased on top of: Introduce 64b relocatable kernel (https://lore.kernel.org/lkml/20230215143626.453491-1-alexghiti@xxxxxxxxxxxx/) RISC-V kasan rework (https://lore.kernel.org/lkml/Y6TTvku%2FyuSjm42j@spud/T/) riscv: Use PUD/P4D/PGD pages for the linear mapping (https://lore.kernel.org/lkml/20230125114229.hrhsyw4aegrnmoau@orel/T/) riscv: Allow to downgrade paging mode from the command line (https://lore.kernel.org/lkml/CAHVXubjeSMvfTPnvrnYRupOGx6+vUvUGfRS3piTeo=TH2cHKNg@xxxxxxxxxxxxxx/) base-commit-tag: v6.2-rc7 This patchset was tested with u-boot boottime service for the seed on: - ubuntu defconfig + kasan outline (sv39, sv48, sv57): OK - ubuntu defconfig + kasan inline (sv39, sv48, sv57): OK - ubuntu defconfg (sv39, sv48, sv57): OK Alexandre Ghiti (4): riscv: Introduce virtual kernel mapping KASLR riscv: Dump out kernel offset information on panic arm64: libstub: Move KASLR handling functions to efi-stub-helper.c riscv: libstub: Implement KASLR by using generic functions arch/riscv/Kconfig | 18 +++ arch/riscv/include/asm/page.h | 1 + arch/riscv/kernel/pi/Makefile | 2 +- arch/riscv/kernel/pi/cmdline_early.c | 12 ++ arch/riscv/kernel/pi/fdt_early.c | 23 +++ arch/riscv/kernel/setup.c | 25 +++ arch/riscv/mm/init.c | 31 +++- drivers/firmware/efi/libstub/arm64-stub.c | 110 +------------ .../firmware/efi/libstub/efi-stub-helper.c | 147 ++++++++++++++++++ drivers/firmware/efi/libstub/efistub.h | 8 + drivers/firmware/efi/libstub/riscv-stub.c | 27 ++-- 11 files changed, 281 insertions(+), 123 deletions(-) create mode 100644 arch/riscv/kernel/pi/fdt_early.c -- 2.37.2
