[RFC PATCH 15/16] arm64: Enable kpkeys_hardened_pgtables support

Kevin Brodsky
2024-12-06T10:14:01Z

kpkeys_hardened_pgtables should be enabled as early as possible (if
selected). It does however require kpkeys being available, which
means on arm64 POE being detected and enabled. POE is a boot
feature, so calling kpkeys_hardened_pgtables_enable() just after
setup_boot_cpu_features() in smp_prepare_boot_cpu() is the best we
can do.

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 ++
2 files changed, 3 insertions(+)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index f35964641c1a..dac2f9a64826 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -2184,6 +2184,7 @@ 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 3b3f6b56e733..074cab55f9db 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>
@@ -468,6 +469,7 @@ void __init smp_prepare_boot_cpu(void)
if (system_uses_irq_prio_masking())
init_gic_priority_masking();

+ kpkeys_hardened_pgtables_enable();
kasan_init_hw_tags();
/* Init percpu seeds for random tags after cpus are set up. */
kasan_init_sw_tags();
--
2.47.0