Subject: [PATCH RFC v8 06/24] arm64: set_memory: Implement set_memory_pkey()

From: Kevin Brodsky <[email-masked]>
Date: Tue, 26 May 2026 12:15:55 +0100

Implement set_memory_pkey() using POE.

Signed-off-by: Kevin Brodsky <[email-masked]>
---
 arch/arm64/include/asm/set_memory.h |  4 ++++
 arch/arm64/mm/pageattr.c            | 26 ++++++++++++++++++++++++++
 2 files changed, 30 insertions(+)

diff --git a/arch/arm64/include/asm/set_memory.h b/arch/arm64/include/asm/set_memory.h
index 90f61b17275e..b6cd6de34abf 100644
--- a/arch/arm64/include/asm/set_memory.h
+++ b/arch/arm64/include/asm/set_memory.h
@@ -19,4 +19,8 @@ bool kernel_page_present(struct page *page);
 int set_memory_encrypted(unsigned long addr, int numpages);
 int set_memory_decrypted(unsigned long addr, int numpages);
 
+#ifdef CONFIG_ARCH_HAS_KPKEYS
+int set_memory_pkey(unsigned long addr, int numpages, int pkey);
+#endif
+
 #endif /* _ASM_ARM64_SET_MEMORY_H */
diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c
index ce035e1b4eaf..8f3519400bd1 100644
--- a/arch/arm64/mm/pageattr.c
+++ b/arch/arm64/mm/pageattr.c
@@ -9,6 +9,8 @@
 #include <linux/sched.h>
 #include <linux/vmalloc.h>
 #include <linux/pagewalk.h>
+#include <linux/pkeys.h>
+#include <linux/kpkeys.h>
 
 #include <asm/cacheflush.h>
 #include <asm/pgtable-prot.h>
@@ -365,6 +367,30 @@ int set_direct_map_valid_noflush(struct page *page, unsigned nr, bool valid)
 	return set_memory_valid(addr, nr, valid);
 }
 
+#ifdef CONFIG_ARCH_HAS_KPKEYS
+int set_memory_pkey(unsigned long addr, int numpages, int pkey)
+{
+	unsigned long set_prot = 0;
+
+	if (!kpkeys_enabled())
+		return 0;
+
+	if (!__is_lm_address(kasan_reset_tag((void *)addr)))
+		return -EINVAL;
+
+	if (pkey < 0 || pkey >= arch_max_pkey())
+		return -EINVAL;
+
+	set_prot |= pkey & BIT(0) ? PTE_PO_IDX_0 : 0;
+	set_prot |= pkey & BIT(1) ? PTE_PO_IDX_1 : 0;
+	set_prot |= pkey & BIT(2) ? PTE_PO_IDX_2 : 0;
+
+	return __change_memory_common(addr, PAGE_SIZE * numpages,
+				      __pgprot(set_prot),
+				      __pgprot(PTE_PO_IDX_MASK));
+}
+#endif
+
 #ifdef CONFIG_DEBUG_PAGEALLOC
 /*
  * This is - apart from the return value - doing the same

-- 
2.51.2