[Deepin-Kernel-SIG] [linux 6.18-y] [Upstream] arm64: mm: Add PTE_DIRTY back to PAGE_KERNEL* to fix kexec/hibernation#1557
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Commit 143937c ("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 aa57157 ("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: 143937c ("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> (cherry picked from commit c25c4aa3f79a488cc270507935a29c07dc6bddfc) Signed-off-by: Wentao Guan <guanwentao@uniontech.com>
Reviewer's guide (collapsed on small PRs)Reviewer's GuideThis PR updates the arm64 kernel page table protection macros so that all kernel linear-map PAGE_KERNEL* PTEs are created with the PTE_DIRTY bit set, restoring pre-5.4 behavior to ensure pte_mkwrite_novma() can correctly make temporary mappings writable for kexec/hibernation paths. Sequence diagram for kexec temporary mapping with updated PAGE_KERNEL PTE_DIRTY behaviorsequenceDiagram
participant CPU
participant kexec_reloc as kexec_relocation_code
participant trans_pgd as trans_pgd_create_copy
participant copy_pte as _copy_pte
participant pte_mkwrite as pte_mkwrite_novma
CPU->>kexec_reloc: Start kexec or hibernation restore
kexec_reloc->>trans_pgd: Create temporary linear map
trans_pgd->>copy_pte: Copy kernel PTE into trans PGD
copy_pte->>pte_mkwrite: Make PTE writable
alt Before_fix_PAGE_KERNEL_without_PTE_DIRTY
pte_mkwrite-->>copy_pte: Sees PTE without PTE_DIRTY
note over pte_mkwrite: Only clears PTE_RDONLY if PTE_DIRTY is set
pte_mkwrite-->>copy_pte: PTE remains read_only
copy_pte-->>trans_pgd: Temporary PTE is still read_only
trans_pgd-->>kexec_reloc: Map used for relocation
kexec_reloc->>CPU: Attempt in_kernel write to temp mapping
CPU-->>kexec_reloc: Page fault due to read_only PTE
else After_fix_PAGE_KERNEL_with_PTE_DIRTY
pte_mkwrite-->>copy_pte: Sees PTE with PTE_DIRTY set
pte_mkwrite-->>copy_pte: Clears PTE_RDONLY, keeps PTE_DIRTY
copy_pte-->>trans_pgd: Temporary PTE is writable
trans_pgd-->>kexec_reloc: Map used for relocation
kexec_reloc->>CPU: In_kernel write to temp mapping
CPU-->>kexec_reloc: Write succeeds, no fault
end
Flow diagram for pte_mkwrite_novma behavior with PAGE_KERNEL PTE_DIRTY changeflowchart TD
A[Start: _copy_pte calls pte_mkwrite_novma] --> B[Input PTE from PAGE_KERNEL* mapping]
B --> C{Does PTE have PTE_DIRTY set?}
subgraph Before_fix_PAGE_KERNEL_without_PTE_DIRTY
direction TB
C -- No --> D[Leave PTE_RDONLY set]
D --> E[Result: PTE stays read_only]
E --> F[Temporary linear map may fault on in_kernel writes]
end
subgraph After_fix_PAGE_KERNEL_with_PTE_DIRTY
direction TB
C -- Yes --> G[Clear PTE_RDONLY bit]
G --> H[Keep PTE_DIRTY set]
H --> I[Result: PTE becomes writable]
I --> J[Temporary linear map allows kexec/hibernation writes]
end
F --> K[End]
J --> K[End]
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Commit 143937c ("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 aa57157 ("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: 143937c ("arm64, mm: avoid always making PTE dirty in pte_mkwrite()")
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
(cherry picked from commit c25c4aa3f79a488cc270507935a29c07dc6bddfc)
Summary by Sourcery
Bug Fixes: