[PATCH 4/12] maps4: introduce a generic page walker

Matt Mackall
2007-10-26T16:36:58Z

Introduce a general page table walker

Signed-off-by: Matt Mackall <mpm@selenic.com>

Index: l/include/linux/mm.h
===================================================================
--- l.orig/include/linux/mm.h 2007-10-26 11:19:36.000000000 -0500
+++ l/include/linux/mm.h 2007-10-26 11:20:37.000000000 -0500
@@ -773,6 +773,28 @@ unsigned long unmap_vmas(struct mmu_gath
struct vm_area_struct *start_vma, unsigned long start_addr,
unsigned long end_addr, unsigned long *nr_accounted,
struct zap_details *);
+
+/**
+ * mm_walk - callbacks for walk_page_range
+ * @pgd_entry: if set, called for each non-empty PGD (top-level) entry
+ * @pud_entry: if set, called for each non-empty PUD (2nd-level) entry
+ * @pmd_entry: if set, called for each non-empty PMD (3rd-level) entry
+ * @pte_entry: if set, called for each non-empty PTE (4th-level) entry
+ * @pte_hole: if set, called for each hole at all levels
+ *
+ * (see walk_page_range for more details)
+ */
+struct mm_walk {
+ int (*pgd_entry)(pgd_t *, unsigned long, unsigned long, void *);
+ int (*pud_entry)(pud_t *, unsigned long, unsigned long, void *);
+ int (*pmd_entry)(pmd_t *, unsigned long, unsigned long, void *);
+ int (*pte_entry)(pte_t *, unsigned long, unsigned long, void *);
+ int (*pte_hole)(unsigned long, unsigned long, void *);
+};
+
+int walk_page_range(const struct mm_struct *, unsigned long addr,
+ unsigned long end, const struct mm_walk *walk,
+ void *private);
void free_pgd_range(struct mmu_gather **tlb, unsigned long addr,
unsigned long end, unsigned long floor, unsigned long ceiling);
void free_pgtables(struct mmu_gather **tlb, struct vm_area_struct *start_vma,
Index: l/mm/Makefile
===================================================================
--- l.orig/mm/Makefile 2007-10-26 11:19:36.000000000 -0500
+++ l/mm/Makefile 2007-10-26 11:20:01.000000000 -0500
@@ -5,7 +5,7 @@
mmu-y := nommu.o
mmu-$(CONFIG_MMU) := fremap.o highmem.o madvise.o memory.o mincore.o \
mlock.o mmap.o mprotect.o mremap.o msync.o rmap.o \
- vmalloc.o
+ vmalloc.o pagewalk.o

obj-y := bootmem.o filemap.o mempool.o oom_kill.o fadvise.o \
page_alloc.o page-writeback.o pdflush.o \
Index: l/mm/pagewalk.c
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ l/mm/pagewalk.c 2007-10-26 11:20:01.000000000 -0500
@@ -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;
+}