1 files changed, 36 insertions, 0 deletions

diff --git a/kernel/resource.c b/kernel/resource.c
index 46322019ab7d..0bcebffc4e77 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -491,6 +491,42 @@ int __weak page_is_ram(unsigned long pfn)
 }
 EXPORT_SYMBOL_GPL(page_is_ram);
 
+/*
+ * Search for a resouce entry that fully contains the specified region.
+ * If found, return 1 if it is RAM, 0 if not.
+ * If not found, or region is not fully contained, return -1
+ *
+ * Used by the ioremap functions to ensure the user is not remapping RAM and is
+ * a vast speed up over walking through the resource table page by page.
+ */
+int region_is_ram(resource_size_t start, unsigned long size)
+{
+        struct resource *p;
+        resource_size_t end = start + size - 1;
+        int flags = IORESOURCE_MEM | IORESOURCE_BUSY;
+        const char *name = "System RAM";
+        int ret = -1;
+
+        read_lock(&resource_lock);
+        for (p = iomem_resource.child; p ; p = p->sibling) {
+                if (end < p->start)
+                        continue;
+
+                if (p->start <= start && end <= p->end) {
+                        /* resource fully contains region */
+                        if ((p->flags != flags) || strcmp(p->name, name))
+                                ret = 0;
+                        else
+                                ret = 1;
+                        break;
+                }
+                if (p->end < start)
+                        break;  /* not found */
+        }
+        read_unlock(&resource_lock);
+        return ret;
+}
+
 void __weak arch_remove_reservations(struct resource *avail)
 {
 }