Add wrappers around the p4d/pud/pmd/pte offset kernel functions which
ensure that page-table pointers are in the specified decorated page-table.
Signed-off-by: Alexandre Chartre <alexandre.chartre@xxxxxxxxxx>
---
arch/x86/mm/dpt.c | 66 +++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 66 insertions(+)
diff --git a/arch/x86/mm/dpt.c b/arch/x86/mm/dpt.c
index 6df2d4fde8ec..44aad99bc3dc 100644
--- a/arch/x86/mm/dpt.c
+++ b/arch/x86/mm/dpt.c
@@ -82,6 +82,72 @@ static bool dpt_valid_offset(struct dpt *dpt, void *offset)
return valid;
}
+/*
+ * dpt_pXX_offset() functions are equivalent to kernel pXX_offset()
+ * functions but, in addition, they ensure that page table pointers
+ * are in the specified decorated page table. Otherwise an error is
+ * returned.
+ */
+
+static pte_t *dpt_pte_offset(struct dpt *dpt,
+ pmd_t *pmd, unsigned long addr)
+{
+ pte_t *pte;
+
+ pte = pte_offset_map(pmd, addr);
+ if (!dpt_valid_offset(dpt, pte)) {
+ pr_err("DPT %p: PTE %px not found\n", dpt, pte);
+ return ERR_PTR(-EINVAL);
+ }
+
+ return pte;
+}
+
+static pmd_t *dpt_pmd_offset(struct dpt *dpt,
+ pud_t *pud, unsigned long addr)
+{
+ pmd_t *pmd;
+
+ pmd = pmd_offset(pud, addr);
+ if (!dpt_valid_offset(dpt, pmd)) {
+ pr_err("DPT %p: PMD %px not found\n", dpt, pmd);
+ return ERR_PTR(-EINVAL);
+ }
+
+ return pmd;
+}
+
+static pud_t *dpt_pud_offset(struct dpt *dpt,
+ p4d_t *p4d, unsigned long addr)
+{
+ pud_t *pud;
+
+ pud = pud_offset(p4d, addr);
+ if (!dpt_valid_offset(dpt, pud)) {
+ pr_err("DPT %p: PUD %px not found\n", dpt, pud);
+ return ERR_PTR(-EINVAL);
+ }
+
+ return pud;
+}
+
+static p4d_t *dpt_p4d_offset(struct dpt *dpt,
+ pgd_t *pgd, unsigned long addr)
+{
+ p4d_t *p4d;
+
+ p4d = p4d_offset(pgd, addr);
+ /*
+ * p4d is the same has pgd if we don't have a 5-level page table.
+ */
+ if ((p4d != (p4d_t *)pgd) && !dpt_valid_offset(dpt, p4d)) {
+ pr_err("DPT %p: P4D %px not found\n", dpt, p4d);
+ return ERR_PTR(-EINVAL);
+ }
+
+ return p4d;
+}
+
/*
* dpt_create - allocate a page-table and create a corresponding
* decorated page-table. The page-table is allocated and aligned
--
2.18.2
