[PATCH 5.15.y 2/2] arm64: mm: Add PTE_DIRTY back to PAGE_KERNEL* to fix kexec/hibernation

[Sasha Levin <sashal@kernel.org>]

From: Catalin Marinas <catalin.marinas@arm.com>

[ Upstream commit c25c4aa3f79a488cc270507935a29c07dc6bddfc ]

Commit 143937ca51cc ("arm64, mm: avoid always making PTE dirty in
pte_mkwrite()") changed pte_mkwrite_novma() to only clear PTE_RDONLY
when PTE_DIRTY is set. This was to allow writable-clean PTEs for swap
pages that haven't actually been written.

However, this broke kexec and hibernation for some platforms. Both go
through trans_pgd_create_copy() -> _copy_pte(), which calls
pte_mkwrite_novma() to make the temporary linear-map copy fully
writable. With the updated pte_mkwrite_novma(), read-only kernel pages
(without PTE_DIRTY) remain read-only in the temporary mapping.
While such behaviour is fine for user pages where hardware DBM or
trapping will make them writeable, subsequent in-kernel writes by the
kexec relocation code will fault.

Add PTE_DIRTY back to all _PAGE_KERNEL* protection definitions. This was
the case prior to 5.4, commit aa57157be69f ("arm64: Ensure
VM_WRITE|VM_SHARED ptes are clean by default"). With the kernel
linear-map PTEs always having PTE_DIRTY set, pte_mkwrite_novma()
correctly clears PTE_RDONLY.

Fixes: 143937ca51cc ("arm64, mm: avoid always making PTE dirty in pte_mkwrite()")
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: stable@vger.kernel.org
Reported-by: Jianpeng Chang <jianpeng.chang.cn@windriver.com>
Link: https://lore.kernel.org/r/20251204062722.3367201-1-jianpeng.chang.cn@windriver.com
Cc: Will Deacon <will@kernel.org>
Cc: Huang, Ying <ying.huang@linux.alibaba.com>
Cc: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Huang Ying <ying.huang@linux.alibaba.com>
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 arch/arm64/include/asm/pgtable-prot.h | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/include/asm/pgtable-prot.h b/arch/arm64/include/asm/pgtable-prot.h
index 2c49c93663f1f..cdec09baf74e7 100644
--- a/arch/arm64/include/asm/pgtable-prot.h
+++ b/arch/arm64/include/asm/pgtable-prot.h
@@ -44,11 +44,11 @@
 
 #define _PAGE_DEFAULT		(_PROT_DEFAULT | PTE_ATTRINDX(MT_NORMAL))
 
-#define _PAGE_KERNEL		(PROT_NORMAL)
-#define _PAGE_KERNEL_RO		((PROT_NORMAL & ~PTE_WRITE) | PTE_RDONLY)
-#define _PAGE_KERNEL_ROX	((PROT_NORMAL & ~(PTE_WRITE | PTE_PXN)) | PTE_RDONLY)
-#define _PAGE_KERNEL_EXEC	(PROT_NORMAL & ~PTE_PXN)
-#define _PAGE_KERNEL_EXEC_CONT	((PROT_NORMAL & ~PTE_PXN) | PTE_CONT)
+#define _PAGE_KERNEL		(PROT_NORMAL | PTE_DIRTY)
+#define _PAGE_KERNEL_RO		((PROT_NORMAL & ~PTE_WRITE) | PTE_RDONLY | PTE_DIRTY)
+#define _PAGE_KERNEL_ROX	((PROT_NORMAL & ~(PTE_WRITE | PTE_PXN)) | PTE_RDONLY | PTE_DIRTY)
+#define _PAGE_KERNEL_EXEC	((PROT_NORMAL & ~PTE_PXN) | PTE_DIRTY)
+#define _PAGE_KERNEL_EXEC_CONT	((PROT_NORMAL & ~PTE_PXN) | PTE_CONT | PTE_DIRTY)
 
 #define _PAGE_SHARED		(_PAGE_DEFAULT | PTE_USER | PTE_RDONLY | PTE_NG | PTE_PXN | PTE_UXN | PTE_WRITE)
 #define _PAGE_SHARED_EXEC	(_PAGE_DEFAULT | PTE_USER | PTE_RDONLY | PTE_NG | PTE_PXN | PTE_WRITE)
-- 
2.51.0