[PATCH v6 29/30] arm64: kpkeys: Enable kpkeys_hardened_pgtables support

Kevin Brodsky
2026-02-27T17:58:03Z

The kpkeys_hardened_pgtables feature needs to be initialised in two
stages:

1. As soon as the buddy allocator becomes available. The canonical
place to handle this is mem_init().

2. As soon as the linear map can be split. With BBML2-noabort, this
requires CPU detection to be completed on all CPUs.
The earliest point is therefore after setup_system_features() has
been called.

With that done, all the bits are in place and we can advertise
support for kpkeys_hardened_pgtables by selecting
ARCH_HAS_KPKEYS_HARDENED_PGTABLES if ARM64_POE is enabled.

Signed-off-by: Kevin Brodsky <kevin.brodsky@arm.com>
---
arch/arm64/Kconfig | 1 +
arch/arm64/kernel/smp.c | 2 ++
arch/arm64/mm/mmu.c | 5 +++++
3 files changed, 8 insertions(+)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 732d4dbbab20..2faf082cc1d0 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -2165,6 +2165,7 @@ config ARM64_POE
select ARCH_USES_HIGH_VMA_FLAGS
select ARCH_HAS_PKEYS
select ARCH_HAS_KPKEYS
+ select ARCH_HAS_KPKEYS_HARDENED_PGTABLES
help
The Permission Overlay Extension is used to implement Memory
Protection Keys. Memory Protection Keys provides a mechanism for
diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
index 1aa324104afb..b2efff7a82ef 100644
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -35,6 +35,7 @@
#include <linux/kgdb.h>
#include <linux/kvm_host.h>
#include <linux/nmi.h>
+#include <linux/kpkeys.h>

#include <asm/alternative.h>
#include <asm/atomic.h>
@@ -441,6 +442,7 @@ void __init smp_cpus_done(unsigned int max_cpus)
hyp_mode_check();
setup_system_features();
setup_user_features();
+ kpkeys_hardened_pgtables_init_late();
mark_linear_text_alias_ro();
}

diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 1e2cf0166c1d..1a96c186c4a3 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -2273,3 +2273,8 @@ int arch_set_user_pkey_access(struct task_struct *tsk, int pkey, unsigned long i
return 0;
}
#endif
+
+void __init mem_init(void)
+{
+ kpkeys_hardened_pgtables_init();
+}
--
2.51.2