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author | 2024-05-09 15:55:54 +0100 | |
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committer | 2024-05-09 15:55:54 +0100 | |
commit | a5a5ce57953b53e5ec5b9b9455176bc90253cfa8 (patch) | |
tree | f4b45d81018501b263e2e7716b10a1185a41a186 /arch/arm64 | |
parent | Merge branch 'for-next/misc' into for-next/core (diff) | |
parent | arm64/mm: Fix pud_user_accessible_page() for PGTABLE_LEVELS <= 2 (diff) | |
download | linux-a5a5ce57953b53e5ec5b9b9455176bc90253cfa8.tar.gz linux-a5a5ce57953b53e5ec5b9b9455176bc90253cfa8.tar.bz2 linux-a5a5ce57953b53e5ec5b9b9455176bc90253cfa8.zip |
Merge branch 'for-next/mm' into for-next/core
* for-next/mm:
arm64/mm: Fix pud_user_accessible_page() for PGTABLE_LEVELS <= 2
arm64/mm: Add uffd write-protect support
arm64/mm: Move PTE_PRESENT_INVALID to overlay PTE_NG
arm64/mm: Remove PTE_PROT_NONE bit
arm64/mm: generalize PMD_PRESENT_INVALID for all levels
arm64: mm: Don't remap pgtables for allocate vs populate
arm64: mm: Batch dsb and isb when populating pgtables
arm64: mm: Don't remap pgtables per-cont(pte|pmd) block
Diffstat (limited to 'arch/arm64')
-rw-r--r-- | arch/arm64/Kconfig | 1 | ||||
-rw-r--r-- | arch/arm64/include/asm/pgtable-prot.h | 19 | ||||
-rw-r--r-- | arch/arm64/include/asm/pgtable.h | 114 | ||||
-rw-r--r-- | arch/arm64/mm/mmu.c | 101 |
4 files changed, 157 insertions, 78 deletions
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 7b11c98b3e84..763e221f2169 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -255,6 +255,7 @@ config ARM64 select SYSCTL_EXCEPTION_TRACE select THREAD_INFO_IN_TASK select HAVE_ARCH_USERFAULTFD_MINOR if USERFAULTFD + select HAVE_ARCH_USERFAULTFD_WP if USERFAULTFD select TRACE_IRQFLAGS_SUPPORT select TRACE_IRQFLAGS_NMI_SUPPORT select HAVE_SOFTIRQ_ON_OWN_STACK diff --git a/arch/arm64/include/asm/pgtable-prot.h b/arch/arm64/include/asm/pgtable-prot.h index dd9ee67d1d87..b11cfb9fdd37 100644 --- a/arch/arm64/include/asm/pgtable-prot.h +++ b/arch/arm64/include/asm/pgtable-prot.h @@ -18,14 +18,21 @@ #define PTE_DIRTY (_AT(pteval_t, 1) << 55) #define PTE_SPECIAL (_AT(pteval_t, 1) << 56) #define PTE_DEVMAP (_AT(pteval_t, 1) << 57) -#define PTE_PROT_NONE (_AT(pteval_t, 1) << 58) /* only when !PTE_VALID */ /* - * This bit indicates that the entry is present i.e. pmd_page() - * still points to a valid huge page in memory even if the pmd - * has been invalidated. + * PTE_PRESENT_INVALID=1 & PTE_VALID=0 indicates that the pte's fields should be + * interpreted according to the HW layout by SW but any attempted HW access to + * the address will result in a fault. pte_present() returns true. */ -#define PMD_PRESENT_INVALID (_AT(pteval_t, 1) << 59) /* only when !PMD_SECT_VALID */ +#define PTE_PRESENT_INVALID (PTE_NG) /* only when !PTE_VALID */ + +#ifdef CONFIG_HAVE_ARCH_USERFAULTFD_WP +#define PTE_UFFD_WP (_AT(pteval_t, 1) << 58) /* uffd-wp tracking */ +#define PTE_SWP_UFFD_WP (_AT(pteval_t, 1) << 3) /* only for swp ptes */ +#else +#define PTE_UFFD_WP (_AT(pteval_t, 0)) +#define PTE_SWP_UFFD_WP (_AT(pteval_t, 0)) +#endif /* CONFIG_HAVE_ARCH_USERFAULTFD_WP */ #define _PROT_DEFAULT (PTE_TYPE_PAGE | PTE_AF | PTE_SHARED) #define _PROT_SECT_DEFAULT (PMD_TYPE_SECT | PMD_SECT_AF | PMD_SECT_S) @@ -103,7 +110,7 @@ static inline bool __pure lpa2_is_enabled(void) __val; \ }) -#define PAGE_NONE __pgprot(((_PAGE_DEFAULT) & ~PTE_VALID) | PTE_PROT_NONE | PTE_RDONLY | PTE_NG | PTE_PXN | PTE_UXN) +#define PAGE_NONE __pgprot(((_PAGE_DEFAULT) & ~PTE_VALID) | PTE_PRESENT_INVALID | PTE_RDONLY | PTE_NG | PTE_PXN | PTE_UXN) /* shared+writable pages are clean by default, hence PTE_RDONLY|PTE_WRITE */ #define PAGE_SHARED __pgprot(_PAGE_SHARED) #define PAGE_SHARED_EXEC __pgprot(_PAGE_SHARED_EXEC) diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h index afdd56d26ad7..bde9fd179388 100644 --- a/arch/arm64/include/asm/pgtable.h +++ b/arch/arm64/include/asm/pgtable.h @@ -105,7 +105,7 @@ static inline pteval_t __phys_to_pte_val(phys_addr_t phys) /* * The following only work if pte_present(). Undefined behaviour otherwise. */ -#define pte_present(pte) (!!(pte_val(pte) & (PTE_VALID | PTE_PROT_NONE))) +#define pte_present(pte) (pte_valid(pte) || pte_present_invalid(pte)) #define pte_young(pte) (!!(pte_val(pte) & PTE_AF)) #define pte_special(pte) (!!(pte_val(pte) & PTE_SPECIAL)) #define pte_write(pte) (!!(pte_val(pte) & PTE_WRITE)) @@ -132,6 +132,8 @@ static inline pteval_t __phys_to_pte_val(phys_addr_t phys) #define pte_dirty(pte) (pte_sw_dirty(pte) || pte_hw_dirty(pte)) #define pte_valid(pte) (!!(pte_val(pte) & PTE_VALID)) +#define pte_present_invalid(pte) \ + ((pte_val(pte) & (PTE_VALID | PTE_PRESENT_INVALID)) == PTE_PRESENT_INVALID) /* * Execute-only user mappings do not have the PTE_USER bit set. All valid * kernel mappings have the PTE_UXN bit set. @@ -261,6 +263,13 @@ static inline pte_t pte_mkpresent(pte_t pte) return set_pte_bit(pte, __pgprot(PTE_VALID)); } +static inline pte_t pte_mkinvalid(pte_t pte) +{ + pte = set_pte_bit(pte, __pgprot(PTE_PRESENT_INVALID)); + pte = clear_pte_bit(pte, __pgprot(PTE_VALID)); + return pte; +} + static inline pmd_t pmd_mkcont(pmd_t pmd) { return __pmd(pmd_val(pmd) | PMD_SECT_CONT); @@ -271,9 +280,31 @@ static inline pte_t pte_mkdevmap(pte_t pte) return set_pte_bit(pte, __pgprot(PTE_DEVMAP | PTE_SPECIAL)); } -static inline void __set_pte(pte_t *ptep, pte_t pte) +#ifdef CONFIG_HAVE_ARCH_USERFAULTFD_WP +static inline int pte_uffd_wp(pte_t pte) +{ + return !!(pte_val(pte) & PTE_UFFD_WP); +} + +static inline pte_t pte_mkuffd_wp(pte_t pte) +{ + return pte_wrprotect(set_pte_bit(pte, __pgprot(PTE_UFFD_WP))); +} + +static inline pte_t pte_clear_uffd_wp(pte_t pte) +{ + return clear_pte_bit(pte, __pgprot(PTE_UFFD_WP)); +} +#endif /* CONFIG_HAVE_ARCH_USERFAULTFD_WP */ + +static inline void __set_pte_nosync(pte_t *ptep, pte_t pte) { WRITE_ONCE(*ptep, pte); +} + +static inline void __set_pte(pte_t *ptep, pte_t pte) +{ + __set_pte_nosync(ptep, pte); /* * Only if the new pte is valid and kernel, otherwise TLB maintenance @@ -463,13 +494,39 @@ static inline pte_t pte_swp_clear_exclusive(pte_t pte) return clear_pte_bit(pte, __pgprot(PTE_SWP_EXCLUSIVE)); } +#ifdef CONFIG_HAVE_ARCH_USERFAULTFD_WP +static inline pte_t pte_swp_mkuffd_wp(pte_t pte) +{ + return set_pte_bit(pte, __pgprot(PTE_SWP_UFFD_WP)); +} + +static inline int pte_swp_uffd_wp(pte_t pte) +{ + return !!(pte_val(pte) & PTE_SWP_UFFD_WP); +} + +static inline pte_t pte_swp_clear_uffd_wp(pte_t pte) +{ + return clear_pte_bit(pte, __pgprot(PTE_SWP_UFFD_WP)); +} +#endif /* CONFIG_HAVE_ARCH_USERFAULTFD_WP */ + #ifdef CONFIG_NUMA_BALANCING /* * See the comment in include/linux/pgtable.h */ static inline int pte_protnone(pte_t pte) { - return (pte_val(pte) & (PTE_VALID | PTE_PROT_NONE)) == PTE_PROT_NONE; + /* + * pte_present_invalid() tells us that the pte is invalid from HW + * perspective but present from SW perspective, so the fields are to be + * interpretted as per the HW layout. The second 2 checks are the unique + * encoding that we use for PROT_NONE. It is insufficient to only use + * the first check because we share the same encoding scheme with pmds + * which support pmd_mkinvalid(), so can be present-invalid without + * being PROT_NONE. + */ + return pte_present_invalid(pte) && !pte_user(pte) && !pte_user_exec(pte); } static inline int pmd_protnone(pmd_t pmd) @@ -478,12 +535,7 @@ static inline int pmd_protnone(pmd_t pmd) } #endif -#define pmd_present_invalid(pmd) (!!(pmd_val(pmd) & PMD_PRESENT_INVALID)) - -static inline int pmd_present(pmd_t pmd) -{ - return pte_present(pmd_pte(pmd)) || pmd_present_invalid(pmd); -} +#define pmd_present(pmd) pte_present(pmd_pte(pmd)) /* * THP definitions. @@ -508,14 +560,16 @@ static inline int pmd_trans_huge(pmd_t pmd) #define pmd_mkclean(pmd) pte_pmd(pte_mkclean(pmd_pte(pmd))) #define pmd_mkdirty(pmd) pte_pmd(pte_mkdirty(pmd_pte(pmd))) #define pmd_mkyoung(pmd) pte_pmd(pte_mkyoung(pmd_pte(pmd))) - -static inline pmd_t pmd_mkinvalid(pmd_t pmd) -{ - pmd = set_pmd_bit(pmd, __pgprot(PMD_PRESENT_INVALID)); - pmd = clear_pmd_bit(pmd, __pgprot(PMD_SECT_VALID)); - - return pmd; -} +#define pmd_mkinvalid(pmd) pte_pmd(pte_mkinvalid(pmd_pte(pmd))) +#ifdef CONFIG_HAVE_ARCH_USERFAULTFD_WP +#define pmd_uffd_wp(pmd) pte_uffd_wp(pmd_pte(pmd)) +#define pmd_mkuffd_wp(pmd) pte_pmd(pte_mkuffd_wp(pmd_pte(pmd))) +#define pmd_clear_uffd_wp(pmd) pte_pmd(pte_clear_uffd_wp(pmd_pte(pmd))) +#define pmd_swp_uffd_wp(pmd) pte_swp_uffd_wp(pmd_pte(pmd)) +#define pmd_swp_mkuffd_wp(pmd) pte_pmd(pte_swp_mkuffd_wp(pmd_pte(pmd))) +#define pmd_swp_clear_uffd_wp(pmd) \ + pte_pmd(pte_swp_clear_uffd_wp(pmd_pte(pmd))) +#endif /* CONFIG_HAVE_ARCH_USERFAULTFD_WP */ #define pmd_thp_or_huge(pmd) (pmd_huge(pmd) || pmd_trans_huge(pmd)) @@ -760,6 +814,7 @@ static inline pmd_t *pud_pgtable(pud_t pud) #else +#define pud_valid(pud) false #define pud_page_paddr(pud) ({ BUILD_BUG(); 0; }) #define pud_user_exec(pud) pud_user(pud) /* Always 0 with folding */ @@ -1005,6 +1060,8 @@ static inline p4d_t *p4d_offset_kimg(pgd_t *pgdp, u64 addr) static inline bool pgtable_l5_enabled(void) { return false; } +#define p4d_index(addr) (((addr) >> P4D_SHIFT) & (PTRS_PER_P4D - 1)) + /* Match p4d_offset folding in <asm/generic/pgtable-nop4d.h> */ #define p4d_set_fixmap(addr) NULL #define p4d_set_fixmap_offset(p4dp, addr) ((p4d_t *)p4dp) @@ -1027,8 +1084,8 @@ static inline pte_t pte_modify(pte_t pte, pgprot_t newprot) * in MAIR_EL1. The mask below has to include PTE_ATTRINDX_MASK. */ const pteval_t mask = PTE_USER | PTE_PXN | PTE_UXN | PTE_RDONLY | - PTE_PROT_NONE | PTE_VALID | PTE_WRITE | PTE_GP | - PTE_ATTRINDX_MASK; + PTE_PRESENT_INVALID | PTE_VALID | PTE_WRITE | + PTE_GP | PTE_ATTRINDX_MASK; /* preserve the hardware dirty information */ if (pte_hw_dirty(pte)) pte = set_pte_bit(pte, __pgprot(PTE_DIRTY)); @@ -1076,17 +1133,17 @@ static inline int pgd_devmap(pgd_t pgd) #ifdef CONFIG_PAGE_TABLE_CHECK static inline bool pte_user_accessible_page(pte_t pte) { - return pte_present(pte) && (pte_user(pte) || pte_user_exec(pte)); + return pte_valid(pte) && (pte_user(pte) || pte_user_exec(pte)); } static inline bool pmd_user_accessible_page(pmd_t pmd) { - return pmd_leaf(pmd) && !pmd_present_invalid(pmd) && (pmd_user(pmd) || pmd_user_exec(pmd)); + return pmd_valid(pmd) && !pmd_table(pmd) && (pmd_user(pmd) || pmd_user_exec(pmd)); } static inline bool pud_user_accessible_page(pud_t pud) { - return pud_leaf(pud) && (pud_user(pud) || pud_user_exec(pud)); + return pud_valid(pud) && !pud_table(pud) && (pud_user(pud) || pud_user_exec(pud)); } #endif @@ -1248,15 +1305,16 @@ static inline pmd_t pmdp_establish(struct vm_area_struct *vma, * Encode and decode a swap entry: * bits 0-1: present (must be zero) * bits 2: remember PG_anon_exclusive - * bits 3-7: swap type - * bits 8-57: swap offset - * bit 58: PTE_PROT_NONE (must be zero) + * bit 3: remember uffd-wp state + * bits 6-10: swap type + * bit 11: PTE_PRESENT_INVALID (must be zero) + * bits 12-61: swap offset */ -#define __SWP_TYPE_SHIFT 3 +#define __SWP_TYPE_SHIFT 6 #define __SWP_TYPE_BITS 5 -#define __SWP_OFFSET_BITS 50 #define __SWP_TYPE_MASK ((1 << __SWP_TYPE_BITS) - 1) -#define __SWP_OFFSET_SHIFT (__SWP_TYPE_BITS + __SWP_TYPE_SHIFT) +#define __SWP_OFFSET_SHIFT 12 +#define __SWP_OFFSET_BITS 50 #define __SWP_OFFSET_MASK ((1UL << __SWP_OFFSET_BITS) - 1) #define __swp_type(x) (((x).val >> __SWP_TYPE_SHIFT) & __SWP_TYPE_MASK) diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c index 495b732d5af3..c927e9312f10 100644 --- a/arch/arm64/mm/mmu.c +++ b/arch/arm64/mm/mmu.c @@ -109,28 +109,12 @@ EXPORT_SYMBOL(phys_mem_access_prot); static phys_addr_t __init early_pgtable_alloc(int shift) { phys_addr_t phys; - void *ptr; phys = memblock_phys_alloc_range(PAGE_SIZE, PAGE_SIZE, 0, MEMBLOCK_ALLOC_NOLEAKTRACE); if (!phys) panic("Failed to allocate page table page\n"); - /* - * The FIX_{PGD,PUD,PMD} slots may be in active use, but the FIX_PTE - * slot will be free, so we can (ab)use the FIX_PTE slot to initialise - * any level of table. - */ - ptr = pte_set_fixmap(phys); - - memset(ptr, 0, PAGE_SIZE); - - /* - * Implicit barriers also ensure the zeroed page is visible to the page - * table walker - */ - pte_clear_fixmap(); - return phys; } @@ -172,16 +156,25 @@ bool pgattr_change_is_safe(u64 old, u64 new) return ((old ^ new) & ~mask) == 0; } -static void init_pte(pmd_t *pmdp, unsigned long addr, unsigned long end, - phys_addr_t phys, pgprot_t prot) +static void init_clear_pgtable(void *table) { - pte_t *ptep; + clear_page(table); - ptep = pte_set_fixmap_offset(pmdp, addr); + /* Ensure the zeroing is observed by page table walks. */ + dsb(ishst); +} + +static void init_pte(pte_t *ptep, unsigned long addr, unsigned long end, + phys_addr_t phys, pgprot_t prot) +{ do { pte_t old_pte = __ptep_get(ptep); - __set_pte(ptep, pfn_pte(__phys_to_pfn(phys), prot)); + /* + * Required barriers to make this visible to the table walker + * are deferred to the end of alloc_init_cont_pte(). + */ + __set_pte_nosync(ptep, pfn_pte(__phys_to_pfn(phys), prot)); /* * After the PTE entry has been populated once, we @@ -192,8 +185,6 @@ static void init_pte(pmd_t *pmdp, unsigned long addr, unsigned long end, phys += PAGE_SIZE; } while (ptep++, addr += PAGE_SIZE, addr != end); - - pte_clear_fixmap(); } static void alloc_init_cont_pte(pmd_t *pmdp, unsigned long addr, @@ -204,6 +195,7 @@ static void alloc_init_cont_pte(pmd_t *pmdp, unsigned long addr, { unsigned long next; pmd_t pmd = READ_ONCE(*pmdp); + pte_t *ptep; BUG_ON(pmd_sect(pmd)); if (pmd_none(pmd)) { @@ -214,10 +206,14 @@ static void alloc_init_cont_pte(pmd_t *pmdp, unsigned long addr, pmdval |= PMD_TABLE_PXN; BUG_ON(!pgtable_alloc); pte_phys = pgtable_alloc(PAGE_SHIFT); + ptep = pte_set_fixmap(pte_phys); + init_clear_pgtable(ptep); + ptep += pte_index(addr); __pmd_populate(pmdp, pte_phys, pmdval); - pmd = READ_ONCE(*pmdp); + } else { + BUG_ON(pmd_bad(pmd)); + ptep = pte_set_fixmap_offset(pmdp, addr); } - BUG_ON(pmd_bad(pmd)); do { pgprot_t __prot = prot; @@ -229,20 +225,26 @@ static void alloc_init_cont_pte(pmd_t *pmdp, unsigned long addr, (flags & NO_CONT_MAPPINGS) == 0) __prot = __pgprot(pgprot_val(prot) | PTE_CONT); - init_pte(pmdp, addr, next, phys, __prot); + init_pte(ptep, addr, next, phys, __prot); + ptep += pte_index(next) - pte_index(addr); phys += next - addr; } while (addr = next, addr != end); + + /* + * Note: barriers and maintenance necessary to clear the fixmap slot + * ensure that all previous pgtable writes are visible to the table + * walker. + */ + pte_clear_fixmap(); } -static void init_pmd(pud_t *pudp, unsigned long addr, unsigned long end, +static void init_pmd(pmd_t *pmdp, unsigned long addr, unsigned long end, phys_addr_t phys, pgprot_t prot, phys_addr_t (*pgtable_alloc)(int), int flags) { unsigned long next; - pmd_t *pmdp; - pmdp = pmd_set_fixmap_offset(pudp, addr); do { pmd_t old_pmd = READ_ONCE(*pmdp); @@ -268,8 +270,6 @@ static void init_pmd(pud_t *pudp, unsigned long addr, unsigned long end, } phys += next - addr; } while (pmdp++, addr = next, addr != end); - - pmd_clear_fixmap(); } static void alloc_init_cont_pmd(pud_t *pudp, unsigned long addr, @@ -279,6 +279,7 @@ static void alloc_init_cont_pmd(pud_t *pudp, unsigned long addr, { unsigned long next; pud_t pud = READ_ONCE(*pudp); + pmd_t *pmdp; /* * Check for initial section mappings in the pgd/pud. @@ -292,10 +293,14 @@ static void alloc_init_cont_pmd(pud_t *pudp, unsigned long addr, pudval |= PUD_TABLE_PXN; BUG_ON(!pgtable_alloc); pmd_phys = pgtable_alloc(PMD_SHIFT); + pmdp = pmd_set_fixmap(pmd_phys); + init_clear_pgtable(pmdp); + pmdp += pmd_index(addr); __pud_populate(pudp, pmd_phys, pudval); - pud = READ_ONCE(*pudp); + } else { + BUG_ON(pud_bad(pud)); + pmdp = pmd_set_fixmap_offset(pudp, addr); } - BUG_ON(pud_bad(pud)); do { pgprot_t __prot = prot; @@ -307,10 +312,13 @@ static void alloc_init_cont_pmd(pud_t *pudp, unsigned long addr, (flags & NO_CONT_MAPPINGS) == 0) __prot = __pgprot(pgprot_val(prot) | PTE_CONT); - init_pmd(pudp, addr, next, phys, __prot, pgtable_alloc, flags); + init_pmd(pmdp, addr, next, phys, __prot, pgtable_alloc, flags); + pmdp += pmd_index(next) - pmd_index(addr); phys += next - addr; } while (addr = next, addr != end); + + pmd_clear_fixmap(); } static void alloc_init_pud(p4d_t *p4dp, unsigned long addr, unsigned long end, @@ -330,12 +338,15 @@ static void alloc_init_pud(p4d_t *p4dp, unsigned long addr, unsigned long end, p4dval |= P4D_TABLE_PXN; BUG_ON(!pgtable_alloc); pud_phys = pgtable_alloc(PUD_SHIFT); + pudp = pud_set_fixmap(pud_phys); + init_clear_pgtable(pudp); + pudp += pud_index(addr); __p4d_populate(p4dp, pud_phys, p4dval); - p4d = READ_ONCE(*p4dp); + } else { + BUG_ON(p4d_bad(p4d)); + pudp = pud_set_fixmap_offset(p4dp, addr); } - BUG_ON(p4d_bad(p4d)); - pudp = pud_set_fixmap_offset(p4dp, addr); do { pud_t old_pud = READ_ONCE(*pudp); @@ -385,12 +396,15 @@ static void alloc_init_p4d(pgd_t *pgdp, unsigned long addr, unsigned long end, pgdval |= PGD_TABLE_PXN; BUG_ON(!pgtable_alloc); p4d_phys = pgtable_alloc(P4D_SHIFT); + p4dp = p4d_set_fixmap(p4d_phys); + init_clear_pgtable(p4dp); + p4dp += p4d_index(addr); __pgd_populate(pgdp, p4d_phys, pgdval); - pgd = READ_ONCE(*pgdp); + } else { + BUG_ON(pgd_bad(pgd)); + p4dp = p4d_set_fixmap_offset(pgdp, addr); } - BUG_ON(pgd_bad(pgd)); - p4dp = p4d_set_fixmap_offset(pgdp, addr); do { p4d_t old_p4d = READ_ONCE(*p4dp); @@ -457,11 +471,10 @@ void create_kpti_ng_temp_pgd(pgd_t *pgdir, phys_addr_t phys, unsigned long virt, static phys_addr_t __pgd_pgtable_alloc(int shift) { - void *ptr = (void *)__get_free_page(GFP_PGTABLE_KERNEL); - BUG_ON(!ptr); + /* Page is zeroed by init_clear_pgtable() so don't duplicate effort. */ + void *ptr = (void *)__get_free_page(GFP_PGTABLE_KERNEL & ~__GFP_ZERO); - /* Ensure the zeroed page is visible to the page table walker */ - dsb(ishst); + BUG_ON(!ptr); return __pa(ptr); } |