| Message ID | 20210308181535.16230-4-ardb@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | arm64: use hierarchical XN permissions for all page tables | expand |
On 3/8/21 11:45 PM, Ard Biesheuvel wrote: > As the kernel and user space page tables are strictly mutually exclusive > when it comes to executable permissions, we can set the UXN table attribute > on all table entries that are created while creating kernel mappings in the > swapper page tables, and the PXN table attribute on all table entries that > are created while creating user space mappings in user space page tables. > > While at it, get rid of a redundant comment. > > Signed-off-by: Ard Biesheuvel <ardb@kernel.org> Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com> > --- > arch/arm64/include/asm/pgalloc.h | 19 ++++++++++++------- > 1 file changed, 12 insertions(+), 7 deletions(-) > > diff --git a/arch/arm64/include/asm/pgalloc.h b/arch/arm64/include/asm/pgalloc.h > index 27cc643d0509..31fbab3d6f99 100644 > --- a/arch/arm64/include/asm/pgalloc.h > +++ b/arch/arm64/include/asm/pgalloc.h > @@ -27,7 +27,10 @@ static inline void __pud_populate(pud_t *pudp, phys_addr_t pmdp, pudval_t prot) > > static inline void pud_populate(struct mm_struct *mm, pud_t *pudp, pmd_t *pmdp) > { > - __pud_populate(pudp, __pa(pmdp), PUD_TYPE_TABLE); > + pudval_t pudval = PUD_TYPE_TABLE; > + > + pudval |= (mm == &init_mm) ? PUD_TABLE_UXN : PUD_TABLE_PXN; > + __pud_populate(pudp, __pa(pmdp), pudval); > } > #else > static inline void __pud_populate(pud_t *pudp, phys_addr_t pmdp, pudval_t prot) > @@ -45,7 +48,10 @@ static inline void __p4d_populate(p4d_t *p4dp, phys_addr_t pudp, p4dval_t prot) > > static inline void p4d_populate(struct mm_struct *mm, p4d_t *p4dp, pud_t *pudp) > { > - __p4d_populate(p4dp, __pa(pudp), P4D_TYPE_TABLE); > + p4dval_t p4dval = P4D_TYPE_TABLE; > + > + p4dval |= (mm == &init_mm) ? P4D_TABLE_UXN : P4D_TABLE_PXN; > + __p4d_populate(p4dp, __pa(pudp), p4dval); > } > #else > static inline void __p4d_populate(p4d_t *p4dp, phys_addr_t pudp, p4dval_t prot) > @@ -70,16 +76,15 @@ static inline void __pmd_populate(pmd_t *pmdp, phys_addr_t ptep, > static inline void > pmd_populate_kernel(struct mm_struct *mm, pmd_t *pmdp, pte_t *ptep) > { > - /* > - * The pmd must be loaded with the physical address of the PTE table > - */ > - __pmd_populate(pmdp, __pa(ptep), PMD_TYPE_TABLE); > + VM_BUG_ON(mm != &init_mm); > + __pmd_populate(pmdp, __pa(ptep), PMD_TYPE_TABLE | PMD_TABLE_UXN); > } > > static inline void > pmd_populate(struct mm_struct *mm, pmd_t *pmdp, pgtable_t ptep) > { > - __pmd_populate(pmdp, page_to_phys(ptep), PMD_TYPE_TABLE); > + VM_BUG_ON(mm == &init_mm); > + __pmd_populate(pmdp, page_to_phys(ptep), PMD_TYPE_TABLE | PMD_TABLE_PXN); > } > #define pmd_pgtable(pmd) pmd_page(pmd) > >
diff --git a/arch/arm64/include/asm/pgalloc.h b/arch/arm64/include/asm/pgalloc.h index 27cc643d0509..31fbab3d6f99 100644 --- a/arch/arm64/include/asm/pgalloc.h +++ b/arch/arm64/include/asm/pgalloc.h @@ -27,7 +27,10 @@ static inline void __pud_populate(pud_t *pudp, phys_addr_t pmdp, pudval_t prot) static inline void pud_populate(struct mm_struct *mm, pud_t *pudp, pmd_t *pmdp) { - __pud_populate(pudp, __pa(pmdp), PUD_TYPE_TABLE); + pudval_t pudval = PUD_TYPE_TABLE; + + pudval |= (mm == &init_mm) ? PUD_TABLE_UXN : PUD_TABLE_PXN; + __pud_populate(pudp, __pa(pmdp), pudval); } #else static inline void __pud_populate(pud_t *pudp, phys_addr_t pmdp, pudval_t prot) @@ -45,7 +48,10 @@ static inline void __p4d_populate(p4d_t *p4dp, phys_addr_t pudp, p4dval_t prot) static inline void p4d_populate(struct mm_struct *mm, p4d_t *p4dp, pud_t *pudp) { - __p4d_populate(p4dp, __pa(pudp), P4D_TYPE_TABLE); + p4dval_t p4dval = P4D_TYPE_TABLE; + + p4dval |= (mm == &init_mm) ? P4D_TABLE_UXN : P4D_TABLE_PXN; + __p4d_populate(p4dp, __pa(pudp), p4dval); } #else static inline void __p4d_populate(p4d_t *p4dp, phys_addr_t pudp, p4dval_t prot) @@ -70,16 +76,15 @@ static inline void __pmd_populate(pmd_t *pmdp, phys_addr_t ptep, static inline void pmd_populate_kernel(struct mm_struct *mm, pmd_t *pmdp, pte_t *ptep) { - /* - * The pmd must be loaded with the physical address of the PTE table - */ - __pmd_populate(pmdp, __pa(ptep), PMD_TYPE_TABLE); + VM_BUG_ON(mm != &init_mm); + __pmd_populate(pmdp, __pa(ptep), PMD_TYPE_TABLE | PMD_TABLE_UXN); } static inline void pmd_populate(struct mm_struct *mm, pmd_t *pmdp, pgtable_t ptep) { - __pmd_populate(pmdp, page_to_phys(ptep), PMD_TYPE_TABLE); + VM_BUG_ON(mm == &init_mm); + __pmd_populate(pmdp, page_to_phys(ptep), PMD_TYPE_TABLE | PMD_TABLE_PXN); } #define pmd_pgtable(pmd) pmd_page(pmd)
As the kernel and user space page tables are strictly mutually exclusive when it comes to executable permissions, we can set the UXN table attribute on all table entries that are created while creating kernel mappings in the swapper page tables, and the PXN table attribute on all table entries that are created while creating user space mappings in user space page tables. While at it, get rid of a redundant comment. Signed-off-by: Ard Biesheuvel <ardb@kernel.org> --- arch/arm64/include/asm/pgalloc.h | 19 ++++++++++++------- 1 file changed, 12 insertions(+), 7 deletions(-)