[PATCH v5 0/3] LoongArch: Move KASLR to EFI stub to avoid initrd overlap

[WANG Rui]

Changes since [v4]:
  * Add a comment above kaslr_disabled() introducing the terms
    "strictly-defined KASLR" and "broadly-defined KASLR", and
    explaining what kaslr_disabled() returns. (Huacai Chen)
  * Set efi_nokaslr when "resume=<devname>" is present, since
    LoongArch hibernation does not support KASLR. (Huacai Chen)
  * Adjust local variable declarations, comment wording, and
    function placement. (Huacai Chen)

Changes since [v3]:
  * Minor cleanups based on review comments.

Changes since [v2]:
  * Add a new patch to prevent initrd overlap during relocation.
  * Revert changes to the CONFIG_RANDOMIZE_BASE_MAX_OFFSET range.

Changes since [v1]:
  * Drop the patch "LoongArch: Allow rdtime_h() and rdtime_l() in 64-bit builds".
  * Use random_get_entropy() instead of rdtime_l().

This series addresses a potential overlap issue between the kernel
image and the initrd when KASLR is enabled.

In the normal boot flow, the bootloader is responsible for loading
both vmlinux and the initrd, and it can guarantee that the two do
not overlap in memory. However, this assumption only holds as long
as neither image changes its location afterwards.

The in-kernel KASLR implementation breaks that assumption. When the
initrd is placed close to the kernel image, randomizing the kernel
location at runtime may move it into the initrd region, leading to
memory corruption early during boot.

To fix this, this series moves the KASLR logic out of the kernel
proper and into the EFI stub. With this change, the final placement
of both the kernel image and the initrd is determined by the EFI
memory allocator. This ensures that the two allocations are
coordinated and cannot overlap.

Functionally, the kernel still supports KASLR as before, but the
randomization now happens before the kernel is entered, rather than
during early kernel relocation.

[v4]: https://lore.kernel.org/loongarch/20260429120300.1786210-1-r@xxxxxx
[v3]: https://lore.kernel.org/loongarch/20260429051318.1581350-1-r@xxxxxx
[v2]: https://lore.kernel.org/loongarch/20260428040159.1065822-1-r@xxxxxx
[v1]: https://lore.kernel.org/loongarch/20260427104721.47724-1-r@xxxxxx

WANG Rui (3):
  efi/loongarch: Randomize kernel preferred address for KASLR
  LoongArch: Skip relocation-time KASLR if already applied
  LoongArch: Avoid initrd overlap during kernel relocation

 arch/loongarch/include/asm/efi.h              |  4 +-
 arch/loongarch/kernel/relocate.c              | 50 +++++++++++++++++++
 .../firmware/efi/libstub/efi-stub-helper.c    |  4 ++
 drivers/firmware/efi/libstub/loongarch.c      | 16 ++++++
 4 files changed, 73 insertions(+), 1 deletion(-)

-- 
2.54.0