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arm64/mm: Avoid ID mapping of kpti flag if it is no longer needed 

arm64_use_ng_mappings will be set to 'true' by the early boot code if it
decides to use non-global (nG) attributes for all kernel mappings,
typically when enabling KASLR on a system that does not implement E0PD.

In this case, the G-to-nG update routines are never called, and so there
is no reason to create the writable mapping of the associated status
flag in the ID map.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20240301104046.1234309-6-ardb+git@google.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
This commit is contained in:
Ard Biesheuvel 2024-03-01 11:40:49 +01:00 committed by Catalin Marinas
parent 3137db4c66
commit 27f2b9fcdd
1 changed files with 1 additions and 1 deletions
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2
arch/arm64/mm/mmu.c
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@ -777,7 +777,7 @@ static void __init create_idmap(void)
IDMAP_ROOT_LEVEL, (pte_t *)idmap_pg_dir, false,
__phys_to_virt(ptep) - ptep);
if (IS_ENABLED(CONFIG_UNMAP_KERNEL_AT_EL0)) {
if (IS_ENABLED(CONFIG_UNMAP_KERNEL_AT_EL0) && !arm64_use_ng_mappings) {
extern u32 __idmap_kpti_flag;
u64 pa = __pa_symbol(&__idmap_kpti_flag);