[PATCH v5 0/4] x86/boot/KASLR: Restrict kernel to be randomized in mirror regions
From: Baoquan He
Date: Thu Jul 13 2017 - 10:20:03 EST
Our customer reported that Kernel text may be located on non-mirror
region (movable zone) when both address range mirroring feature and
KASLR are enabled.
The functions of address range mirroring feature are as follows.
- The physical memory region whose descriptors in EFI memory map have
EFI_MEMORY_MORE_RELIABLE attribute (bit: 16) are mirrored
- The function arranges such mirror region into normal zone and other region
into movable zone in order to locate kernel code and data on mirror region
So we need restrict kernel to be located inside mirror regions if it
The method is very simple. If efi is enabled, just iterate all efi
memory map and pick mirror region to process for adding candidate
of slot. No matter how many mirror regions or what size of mirror region
are found, as long as mirror region is found, we won't enter into e820
processing code though mirror region might not big enough to provide
different position for kernel. If efi disabled or no mirror region
existed, still process e820 memory map. This won't bring much efficiency
loss, at worst we just go through all efi memory maps and found no mirror.
Refactor process_efi_entries code according to Kees's suggestion.
Rearrange the old patch 1/2 to make it be done in three steps for
easier review addcording to Kees's suggestion.
Put process_efi_entry invocation inside the #ifdef CONFIG_EFI according
to tglx's suggestion. Since the efi related code is meaningful only if
Removed debug code.
Taku suggested that we should put kernel to mirrored region always
whether or not "kernelcore=mirror" is specified since kernel text is
important and mirrored region is reliable.
Change code according to kbuild report and Chao Fan's comment.
Baoquan He (4):
x86/boot/KASLR: Wrap e820 entries walking code into new function
x86/boot/KASLR: Switch to pass struct mem_vector to
x86/boot/KASLR: Rename process_e820_entry() into process_mem_region()
x86/boot/KASLR: Restrict kernel to be randomized in mirror regions
arch/x86/boot/compressed/kaslr.c | 125 ++++++++++++++++++++++++++++++---------
1 file changed, 98 insertions(+), 27 deletions(-)