#include <linux/elfcore.h>
 #include <linux/vmalloc.h>
 #include <linux/highmem.h>
+#include <linux/bootmem.h>
 #include <linux/init.h>
 #include <asm/uaccess.h>
 #include <asm/io.h>
 #include <linux/list.h>
+#include <linux/ioport.h>
+#include <linux/mm.h>
+#include <linux/memory.h>
 #include <asm/sections.h>
 
 #define CORE_STR "CORE"
 
 static struct proc_dir_entry *proc_root_kcore;
 
-static int open_kcore(struct inode * inode, struct file * filp)
-{
-       return capable(CAP_SYS_RAWIO) ? 0 : -EPERM;
-}
-
-static ssize_t read_kcore(struct file *, char __user *, size_t, loff_t *);
-
-static const struct file_operations proc_kcore_operations = {
-       .read           = read_kcore,
-       .open           = open_kcore,
-};
 
 #ifndef kc_vaddr_to_offset
 #define        kc_vaddr_to_offset(v) ((v) - PAGE_OFFSET)
 
 static LIST_HEAD(kclist_head);
 static DEFINE_RWLOCK(kclist_lock);
+static int kcore_need_update = 1;
 
 void
 kclist_add(struct kcore_list *new, void *addr, size_t size, int type)
        return size + *elf_buflen;
 }
 
+static void free_kclist_ents(struct list_head *head)
+{
+       struct kcore_list *tmp, *pos;
+
+       list_for_each_entry_safe(pos, tmp, head, list) {
+               list_del(&pos->list);
+               kfree(pos);
+       }
+}
+/*
+ * Replace all KCORE_RAM information with passed list.
+ */
+static void __kcore_update_ram(struct list_head *list)
+{
+       struct kcore_list *tmp, *pos;
+       LIST_HEAD(garbage);
+
+       write_lock(&kclist_lock);
+       if (kcore_need_update) {
+               list_for_each_entry_safe(pos, tmp, &kclist_head, list) {
+                       if (pos->type == KCORE_RAM)
+                               list_move(&pos->list, &garbage);
+               }
+               list_splice_tail(list, &kclist_head);
+       } else
+               list_splice(list, &garbage);
+       kcore_need_update = 0;
+       write_unlock(&kclist_lock);
+
+       free_kclist_ents(&garbage);
+}
+
+
+#ifdef CONFIG_HIGHMEM
+/*
+ * If no highmem, we can assume [0...max_low_pfn) continuous range of memory
+ * because memory hole is not as big as !HIGHMEM case.
+ * (HIGHMEM is special because part of memory is _invisible_ from the kernel.)
+ */
+static int kcore_update_ram(void)
+{
+       LIST_HEAD(head);
+       struct kcore_list *ent;
+       int ret = 0;
+
+       ent = kmalloc(sizeof(*ent), GFP_KERNEL);
+       if (!ent)
+               return -ENOMEM;
+       ent->addr = (unsigned long)__va(0);
+       ent->size = max_low_pfn << PAGE_SHIFT;
+       ent->type = KCORE_RAM;
+       list_add(&ent->list, &head);
+       __kcore_update_ram(&head);
+       return ret;
+}
+
+#else /* !CONFIG_HIGHMEM */
+
+static int
+kclist_add_private(unsigned long pfn, unsigned long nr_pages, void *arg)
+{
+       struct list_head *head = (struct list_head *)arg;
+       struct kcore_list *ent;
+
+       ent = kmalloc(sizeof(*ent), GFP_KERNEL);
+       if (!ent)
+               return -ENOMEM;
+       ent->addr = (unsigned long)__va((pfn << PAGE_SHIFT));
+       ent->size = nr_pages << PAGE_SHIFT;
+
+       /* Sanity check: Can happen in 32bit arch...maybe */
+       if (ent->addr < (unsigned long) __va(0))
+               goto free_out;
+
+       /* cut not-mapped area. ....from ppc-32 code. */
+       if (ULONG_MAX - ent->addr < ent->size)
+               ent->size = ULONG_MAX - ent->addr;
+
+       /* cut when vmalloc() area is higher than direct-map area */
+       if (VMALLOC_START > (unsigned long)__va(0)) {
+               if (ent->addr > VMALLOC_START)
+                       goto free_out;
+               if (VMALLOC_START - ent->addr < ent->size)
+                       ent->size = VMALLOC_START - ent->addr;
+       }
+
+       ent->type = KCORE_RAM;
+       list_add_tail(&ent->list, head);
+       return 0;
+free_out:
+       kfree(ent);
+       return 1;
+}
+
+static int kcore_update_ram(void)
+{
+       int nid, ret;
+       unsigned long end_pfn;
+       LIST_HEAD(head);
+
+       /* Not inialized....update now */
+       /* find out "max pfn" */
+       end_pfn = 0;
+       for_each_node_state(nid, N_HIGH_MEMORY) {
+               unsigned long node_end;
+               node_end  = NODE_DATA(nid)->node_start_pfn +
+                       NODE_DATA(nid)->node_spanned_pages;
+               if (end_pfn < node_end)
+                       end_pfn = node_end;
+       }
+       /* scan 0 to max_pfn */
+       ret = walk_system_ram_range(0, end_pfn, &head, kclist_add_private);
+       if (ret) {
+               free_kclist_ents(&head);
+               return -ENOMEM;
+       }
+       __kcore_update_ram(&head);
+       return ret;
+}
+#endif /* CONFIG_HIGHMEM */
 
 /*****************************************************************************/
 /*
        return acc;
 }
 
+
+static int open_kcore(struct inode *inode, struct file *filp)
+{
+       if (!capable(CAP_SYS_RAWIO))
+               return -EPERM;
+       if (kcore_need_update)
+               kcore_update_ram();
+       return 0;
+}
+
+
+static const struct file_operations proc_kcore_operations = {
+       .read           = read_kcore,
+       .open           = open_kcore,
+};
+
+#ifdef CONFIG_MEMORY_HOTPLUG
+/* just remember that we have to update kcore */
+static int __meminit kcore_callback(struct notifier_block *self,
+                                   unsigned long action, void *arg)
+{
+       switch (action) {
+       case MEM_ONLINE:
+       case MEM_OFFLINE:
+               write_lock(&kclist_lock);
+               kcore_need_update = 1;
+               write_unlock(&kclist_lock);
+       }
+       return NOTIFY_OK;
+}
+#endif
+
+
 static struct kcore_list kcore_vmalloc;
 
 #ifdef CONFIG_ARCH_PROC_KCORE_TEXT
 
 static int __init proc_kcore_init(void)
 {
-       proc_root_kcore = proc_create("kcore", S_IRUSR, NULL, &proc_kcore_operations);
+       proc_root_kcore = proc_create("kcore", S_IRUSR, NULL,
+                                     &proc_kcore_operations);
+       /* Store text area if it's special */
        proc_kcore_text_init();
+       /* Store vmalloc area */
        kclist_add(&kcore_vmalloc, (void *)VMALLOC_START,
                VMALLOC_END - VMALLOC_START, KCORE_VMALLOC);
+       /* Store direct-map area from physical memory map */
+       kcore_update_ram();
+       hotplug_memory_notifier(kcore_callback, 0);
+       /* Other special area, area-for-module etc is arch specific. */
+
        return 0;
 }
 module_init(proc_kcore_init);