Provide functions to clear page-table entries in a decorated page-table
for a specified VA range. Functions also check that the clearing
effectively happens in the decorated page-table and there is no crossing
of the decorated page-table boundary (through references to another page
table), so that another page table is not modified by mistake.
As information (address, size, page-table level) about VA ranges mapped
to the decorated page-table is tracked, clearing is done with just
specifying the start address of the range.
Signed-off-by: Alexandre Chartre <alexandre.chartre@xxxxxxxxxx>
---
arch/x86/include/asm/dpt.h | 1 +
arch/x86/mm/dpt.c | 135 +++++++++++++++++++++++++++++++++++++
2 files changed, 136 insertions(+)
diff --git a/arch/x86/include/asm/dpt.h b/arch/x86/include/asm/dpt.h
index 0d74afb10141..01727ef0577e 100644
--- a/arch/x86/include/asm/dpt.h
+++ b/arch/x86/include/asm/dpt.h
@@ -56,6 +56,7 @@ extern void dpt_destroy(struct dpt *dpt);
extern int dpt_map_range(struct dpt *dpt, void *ptr, size_t size,
enum page_table_level level);
extern int dpt_map(struct dpt *dpt, void *ptr, unsigned long size);
+extern void dpt_unmap(struct dpt *dpt, void *ptr);
static inline int dpt_map_module(struct dpt *dpt, char *module_name)
{
diff --git a/arch/x86/mm/dpt.c b/arch/x86/mm/dpt.c
index 12eb0d794d84..c495c9b59b3e 100644
--- a/arch/x86/mm/dpt.c
+++ b/arch/x86/mm/dpt.c
@@ -636,6 +636,141 @@ int dpt_map(struct dpt *dpt, void *ptr, unsigned long size)
}
EXPORT_SYMBOL(dpt_map);
+static void dpt_clear_pte_range(struct dpt *dpt, pmd_t *pmd,
+ unsigned long addr, unsigned long end)
+{
+ pte_t *pte;
+
+ pte = dpt_pte_offset(dpt, pmd, addr);
+ if (IS_ERR(pte))
+ return;
+
+ do {
+ pte_clear(NULL, addr, pte);
+ } while (pte++, addr += PAGE_SIZE, addr < end);
+}
+
+static void dpt_clear_pmd_range(struct dpt *dpt, pud_t *pud,
+ unsigned long addr, unsigned long end,
+ enum page_table_level level)
+{
+ unsigned long next;
+ pmd_t *pmd;
+
+ pmd = dpt_pmd_offset(dpt, pud, addr);
+ if (IS_ERR(pmd))
+ return;
+
+ do {
+ next = pmd_addr_end(addr, end);
+ if (pmd_none(*pmd))
+ continue;
+ if (level == PGT_LEVEL_PMD || pmd_trans_huge(*pmd) ||
+ pmd_devmap(*pmd) || !pmd_present(*pmd)) {
+ pmd_clear(pmd);
+ continue;
+ }
+ dpt_clear_pte_range(dpt, pmd, addr, next);
+ } while (pmd++, addr = next, addr < end);
+}
+
+static void dpt_clear_pud_range(struct dpt *dpt, p4d_t *p4d,
+ unsigned long addr, unsigned long end,
+ enum page_table_level level)
+{
+ unsigned long next;
+ pud_t *pud;
+
+ pud = dpt_pud_offset(dpt, p4d, addr);
+ if (IS_ERR(pud))
+ return;
+
+ do {
+ next = pud_addr_end(addr, end);
+ if (pud_none(*pud))
+ continue;
+ if (level == PGT_LEVEL_PUD || pud_trans_huge(*pud) ||
+ pud_devmap(*pud)) {
+ pud_clear(pud);
+ continue;
+ }
+ dpt_clear_pmd_range(dpt, pud, addr, next, level);
+ } while (pud++, addr = next, addr < end);
+}
+
+static void dpt_clear_p4d_range(struct dpt *dpt, pgd_t *pgd,
+ unsigned long addr, unsigned long end,
+ enum page_table_level level)
+{
+ unsigned long next;
+ p4d_t *p4d;
+
+ p4d = dpt_p4d_offset(dpt, pgd, addr);
+ if (IS_ERR(p4d))
+ return;
+
+ do {
+ next = p4d_addr_end(addr, end);
+ if (p4d_none(*p4d))
+ continue;
+ if (level == PGT_LEVEL_P4D) {
+ p4d_clear(p4d);
+ continue;
+ }
+ dpt_clear_pud_range(dpt, p4d, addr, next, level);
+ } while (p4d++, addr = next, addr < end);
+}
+
+static void dpt_clear_pgd_range(struct dpt *dpt, pgd_t *pagetable,
+ unsigned long addr, unsigned long end,
+ enum page_table_level level)
+{
+ unsigned long next;
+ pgd_t *pgd;
+
+ pgd = pgd_offset_pgd(pagetable, addr);
+ do {
+ next = pgd_addr_end(addr, end);
+ if (pgd_none(*pgd))
+ continue;
+ if (level == PGT_LEVEL_PGD) {
+ pgd_clear(pgd);
+ continue;
+ }
+ dpt_clear_p4d_range(dpt, pgd, addr, next, level);
+ } while (pgd++, addr = next, addr < end);
+}
+
+/*
+ * Clear page table entries in the specified decorated page-table.
+ */
+void dpt_unmap(struct dpt *dpt, void *ptr)
+{
+ struct dpt_range_mapping *range_mapping;
+ unsigned long addr, end;
+ unsigned long flags;
+
+ spin_lock_irqsave(&dpt->lock, flags);
+
+ range_mapping = dpt_get_range_mapping(dpt, ptr);
+ if (!range_mapping) {
+ pr_debug("DPT %p: UNMAP %px - not mapped\n", dpt, ptr);
+ goto done;
+ }
+
+ addr = (unsigned long)range_mapping->ptr;
+ end = addr + range_mapping->size;
+ pr_debug("DPT %p: UNMAP %px/%lx/%d\n", dpt, ptr,
+ range_mapping->size, range_mapping->level);
+ dpt_clear_pgd_range(dpt, dpt->pagetable, addr, end,
+ range_mapping->level);
+ list_del(&range_mapping->list);
+ kfree(range_mapping);
+done:
+ spin_unlock_irqrestore(&dpt->lock, flags);
+}
+EXPORT_SYMBOL(dpt_unmap);
+
/*
* dpt_create - allocate a page-table and create a corresponding
* decorated page-table. The page-table is allocated and aligned
--
2.18.2
