arm64: trans_pgd: clone only the linear map that exists at runtime

kexec_file_load() fails on arm64 if we have CONFIG_ARM64_VA_BITS_52 but
it runs on a !FEAT_LPA2 host (such as my loving Grace machine).

That is because trans_pgd_create_copy() uses the compile time
PAGE_OFFSET (VA 52) instead of the actual VA size (48 -- due to the lack
of LPA2). With the fifth level folded, pgd_none() is always false, so
the walk cannot skip the 15 extra PGDIR_SIZE slots, and they all alias
back to the same table: the whole kernel page table gets cloned 16
times, KASAN shadow included. Without KASAN it does not blow up, it just
wastes ~RAM/32 in page tables.

Fix it by copying the linear map that is the actual one, not the
compiled one.

Fixes: a6bbf5d4d9d1 ("arm64: mm: Add definitions to support 5 levels of paging")
Signed-off-by: Breno Leitao <leitao@debian.org>
Tested-by: Yury Smirnov <yurymonzon@gmail.com>
Signed-off-by: Will Deacon <will@kernel.org>

0 files changed, 0 insertions, 0 deletions