mm: add get_dump_page

[pandora-kernel.git] / mm / memory.c

diff --git a/mm/memory.c b/mm/memory.c
index 4b5200f..a8430ff 100644 (file)
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1423,9 +1423,40 @@ int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
 
        return __get_user_pages(tsk, mm, start, nr_pages, flags, pages, vmas);
 }
-
 EXPORT_SYMBOL(get_user_pages);
 
+/**
+ * get_dump_page() - pin user page in memory while writing it to core dump
+ * @addr: user address
+ *
+ * Returns struct page pointer of user page pinned for dump,
+ * to be freed afterwards by page_cache_release() or put_page().
+ *
+ * Returns NULL on any kind of failure - a hole must then be inserted into
+ * the corefile, to preserve alignment with its headers; and also returns
+ * NULL wherever the ZERO_PAGE, or an anonymous pte_none, has been found -
+ * allowing a hole to be left in the corefile to save diskspace.
+ *
+ * Called without mmap_sem, but after all other threads have been killed.
+ */
+#ifdef CONFIG_ELF_CORE
+struct page *get_dump_page(unsigned long addr)
+{
+       struct vm_area_struct *vma;
+       struct page *page;
+
+       if (__get_user_pages(current, current->mm, addr, 1,
+                               GUP_FLAGS_FORCE, &page, &vma) < 1)
+               return NULL;
+       if (page == ZERO_PAGE(0)) {
+               page_cache_release(page);
+               return NULL;
+       }
+       flush_cache_page(vma, addr, page_to_pfn(page));
+       return page;
+}
+#endif /* CONFIG_ELF_CORE */
+
 pte_t *get_locked_pte(struct mm_struct *mm, unsigned long addr,
                        spinlock_t **ptl)
 {