maps4: introduce a generic page walker
Introduce a general page table walker
Signed-off-by: Matt Mackall <mpm@selenic.com>
Cc: Dave Hansen <haveblue@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/pagewalk.c b/mm/pagewalk.c
new file mode 100644
index 0000000..b4f27d2
--- /dev/null
+++ b/mm/pagewalk.c
@@ -0,0 +1,131 @@
+#include <linux/mm.h>
+#include <linux/highmem.h>
+#include <linux/sched.h>
+
+static int walk_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
+ const struct mm_walk *walk, void *private)
+{
+ pte_t *pte;
+ int err = 0;
+
+ pte = pte_offset_map(pmd, addr);
+ do {
+ err = walk->pte_entry(pte, addr, addr + PAGE_SIZE, private);
+ if (err)
+ break;
+ } while (pte++, addr += PAGE_SIZE, addr != end);
+
+ pte_unmap(pte);
+ return err;
+}
+
+static int walk_pmd_range(pud_t *pud, unsigned long addr, unsigned long end,
+ const struct mm_walk *walk, void *private)
+{
+ pmd_t *pmd;
+ unsigned long next;
+ int err = 0;
+
+ pmd = pmd_offset(pud, addr);
+ do {
+ next = pmd_addr_end(addr, end);
+ if (pmd_none_or_clear_bad(pmd)) {
+ if (walk->pte_hole)
+ err = walk->pte_hole(addr, next, private);
+ if (err)
+ break;
+ continue;
+ }
+ if (walk->pmd_entry)
+ err = walk->pmd_entry(pmd, addr, next, private);
+ if (!err && walk->pte_entry)
+ err = walk_pte_range(pmd, addr, next, walk, private);
+ if (err)
+ break;
+ } while (pmd++, addr = next, addr != end);
+
+ return err;
+}
+
+static int walk_pud_range(pgd_t *pgd, unsigned long addr, unsigned long end,
+ const struct mm_walk *walk, void *private)
+{
+ pud_t *pud;
+ unsigned long next;
+ int err = 0;
+
+ pud = pud_offset(pgd, addr);
+ do {
+ next = pud_addr_end(addr, end);
+ if (pud_none_or_clear_bad(pud)) {
+ if (walk->pte_hole)
+ err = walk->pte_hole(addr, next, private);
+ if (err)
+ break;
+ continue;
+ }
+ if (walk->pud_entry)
+ err = walk->pud_entry(pud, addr, next, private);
+ if (!err && (walk->pmd_entry || walk->pte_entry))
+ err = walk_pmd_range(pud, addr, next, walk, private);
+ if (err)
+ break;
+ } while (pud++, addr = next, addr != end);
+
+ return err;
+}
+
+/**
+ * walk_page_range - walk a memory map's page tables with a callback
+ * @mm - memory map to walk
+ * @addr - starting address
+ * @end - ending address
+ * @walk - set of callbacks to invoke for each level of the tree
+ * @private - private data passed to the callback function
+ *
+ * Recursively walk the page table for the memory area in a VMA,
+ * calling supplied callbacks. Callbacks are called in-order (first
+ * PGD, first PUD, first PMD, first PTE, second PTE... second PMD,
+ * etc.). If lower-level callbacks are omitted, walking depth is reduced.
+ *
+ * Each callback receives an entry pointer, the start and end of the
+ * associated range, and a caller-supplied private data pointer.
+ *
+ * No locks are taken, but the bottom level iterator will map PTE
+ * directories from highmem if necessary.
+ *
+ * If any callback returns a non-zero value, the walk is aborted and
+ * the return value is propagated back to the caller. Otherwise 0 is returned.
+ */
+int walk_page_range(const struct mm_struct *mm,
+ unsigned long addr, unsigned long end,
+ const struct mm_walk *walk, void *private)
+{
+ pgd_t *pgd;
+ unsigned long next;
+ int err = 0;
+
+ if (addr >= end)
+ return err;
+
+ pgd = pgd_offset(mm, addr);
+ do {
+ next = pgd_addr_end(addr, end);
+ if (pgd_none_or_clear_bad(pgd)) {
+ if (walk->pte_hole)
+ err = walk->pte_hole(addr, next, private);
+ if (err)
+ break;
+ continue;
+ }
+ if (walk->pgd_entry)
+ err = walk->pgd_entry(pgd, addr, next, private);
+ if (!err &&
+ (walk->pud_entry || walk->pmd_entry || walk->pte_entry))
+ err = walk_pud_range(pgd, addr, next, walk, private);
+ if (err)
+ break;
+ } while (pgd++, addr = next, addr != end);
+
+ return err;
+}
