A new function, remove_pgd_mapping(), is added. It allows us to unmap a specific portion of kernel mapping later as far as the mapping is made using create_pgd_mapping() and unless we try to free a sub-set of memory range within a section mapping.
This function will be used in a later kdump patch to implement the protection against corrupting crash dump kernel memory which is to be set aside. Signed-off-by: AKASHI Takahiro <[email protected]> --- arch/arm64/include/asm/mmu.h | 2 + arch/arm64/mm/mmu.c | 130 +++++++++++++++++++++++++++++++++++++++++-- 2 files changed, 127 insertions(+), 5 deletions(-) diff --git a/arch/arm64/include/asm/mmu.h b/arch/arm64/include/asm/mmu.h index 47619411f0ff..04eb240736d8 100644 --- a/arch/arm64/include/asm/mmu.h +++ b/arch/arm64/include/asm/mmu.h @@ -36,6 +36,8 @@ extern void init_mem_pgprot(void); extern void create_pgd_mapping(struct mm_struct *mm, phys_addr_t phys, unsigned long virt, phys_addr_t size, pgprot_t prot, bool page_mappings_only); +extern void remove_pgd_mapping(struct mm_struct *mm, unsigned long virt, + phys_addr_t size); extern void *fixmap_remap_fdt(phys_addr_t dt_phys); #endif diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c index 17243e43184e..9d3cea1db3b4 100644 --- a/arch/arm64/mm/mmu.c +++ b/arch/arm64/mm/mmu.c @@ -334,12 +334,10 @@ static void __init create_mapping_noalloc(phys_addr_t phys, unsigned long virt, __create_pgd_mapping(init_mm.pgd, phys, virt, size, prot, NULL, false); } -void __init create_pgd_mapping(struct mm_struct *mm, phys_addr_t phys, - unsigned long virt, phys_addr_t size, - pgprot_t prot, bool page_mappings_only) +void create_pgd_mapping(struct mm_struct *mm, phys_addr_t phys, + unsigned long virt, phys_addr_t size, + pgprot_t prot, bool page_mappings_only) { - BUG_ON(mm == &init_mm); - __create_pgd_mapping(mm->pgd, phys, virt, size, prot, pgd_pgtable_alloc, page_mappings_only); } @@ -357,6 +355,128 @@ static void create_mapping_late(phys_addr_t phys, unsigned long virt, NULL, debug_pagealloc_enabled()); } +static bool pgtable_is_cleared(void *pgtable) +{ + unsigned long *desc, *end; + + for (desc = pgtable, end = (unsigned long *)(pgtable + PAGE_SIZE); + desc < end; desc++) + if (*desc) + return false; + + return true; +} + +static void clear_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end) +{ + pte_t *pte; + + if (WARN_ON(pmd_bad(*pmd))) + return; + + pte = pte_set_fixmap_offset(pmd, addr); + + do { + pte_clear(NULL, NULL, pte); + } while (pte++, addr += PAGE_SIZE, addr != end); + + pte_clear_fixmap(); +} + +static void clear_pmd_range(pud_t *pud, unsigned long addr, unsigned long end) +{ + pmd_t *pmd; + unsigned long next; + + if (WARN_ON(pud_bad(*pud))) + return; + + pmd = pmd_set_fixmap_offset(pud, addr); + + do { + next = pmd_addr_end(addr, end); + + if (pmd_table(*pmd)) { + clear_pte_range(pmd, addr, next); + if (((next - addr) == PMD_SIZE) || + pgtable_is_cleared(__va(pmd_page_paddr(*pmd)))) { + __free_page(pmd_page(*pmd)); + pmd_clear(pmd); + } + } else { + if (WARN_ON((next - addr) != PMD_SIZE)) + return; + pmd_clear(pmd); + } + } while (pmd++, addr = next, addr != end); + + pmd_clear_fixmap(); +} + +static void clear_pud_range(pgd_t *pgd, unsigned long addr, unsigned long end) +{ + pud_t *pud; + unsigned long next; + + if (WARN_ON(pgd_bad(*pgd))) + return; + + pud = pud_set_fixmap_offset(pgd, addr); + + do { + next = pud_addr_end(addr, end); + + if (pud_table(*pud)) { + clear_pmd_range(pud, addr, next); +#if CONFIG_PGTABLE_LEVELS > 2 + if (((next - addr) == PUD_SIZE) || + pgtable_is_cleared(__va(pud_page_paddr(*pud)))) { + __free_page(pud_page(*pud)); + pud_clear(pud); + } +#endif + } else { +#if CONFIG_PGTABLE_LEVELS > 2 + if (WARN_ON((next - addr) != PUD_SIZE)) + return; + pud_clear(pud); +#endif + } + } while (pud++, addr = next, addr != end); + + pud_clear_fixmap(); +} + +static void __remove_pgd_mapping(pgd_t *pgdir, unsigned long virt, + phys_addr_t size) +{ + unsigned long addr, length, end, next; + pgd_t *pgd = pgd_offset_raw(pgdir, virt); + + addr = virt & PAGE_MASK; + length = PAGE_ALIGN(size + (virt & ~PAGE_MASK)); + + end = addr + length; + do { + next = pgd_addr_end(addr, end); + clear_pud_range(pgd, addr, next); + +#if CONFIG_PGTABLE_LEVELS > 3 + if (((next - addr) == PGD_SIZE) || + pgtable_is_cleared(__va(pgd_page_paddr(*pgd)))) { + __free_page(pgd_page(*pgd)); + pgd_clear(pgd); + } +#endif + } while (pgd++, addr = next, addr != end); +} + +void remove_pgd_mapping(struct mm_struct *mm, unsigned long virt, + phys_addr_t size) +{ + __remove_pgd_mapping(mm->pgd, virt, size); +} + static void __init __map_memblock(pgd_t *pgd, phys_addr_t start, phys_addr_t end) { unsigned long kernel_start = __pa(_text); -- 2.11.0 _______________________________________________ kexec mailing list [email protected] http://lists.infradead.org/mailman/listinfo/kexec
