kcore: register vmemmap range

Benjamin Herrenschmidt <benh@kernel.crashing.org> pointed out that vmemmap
range is not included in KCORE_RAM, KCORE_VMALLOC ....

This adds KCORE_VMEMMAP if SPARSEMEM_VMEMMAP is used.  By this, vmemmap
can be readable via /proc/kcore

Because it's not vmalloc area, vread/vwrite cannot be used.  But the range
is static against the memory layout, this patch handles vmemmap area by
the same scheme with physical memory.

This patch assumes SPARSEMEM_VMEMMAP range is not in VMALLOC range.  It's
correct now.

[akpm@linux-foundation.org: fix typo]
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Jiri Slaby <jirislaby@gmail.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: WANG Cong <xiyou.wangcong@gmail.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 51 insertions, 2 deletions

diff --git a/fs/proc/kcore.c b/fs/proc/kcore.c
index 802de33d6341..78970e6f715c 100644
--- a/fs/proc/kcore.c
+++ b/fs/proc/kcore.c
@@ -103,7 +103,7 @@ static void free_kclist_ents(struct list_head *head)
         }
 }
 /*
- * Replace all KCORE_RAM information with passed list.
+ * Replace all KCORE_RAM/KCORE_VMEMMAP information with passed list.
  */
 static void __kcore_update_ram(struct list_head *list)
 {
@@ -113,7 +113,8 @@ static void __kcore_update_ram(struct list_head *list)
         write_lock(&kclist_lock);
         if (kcore_need_update) {
                 list_for_each_entry_safe(pos, tmp, &kclist_head, list) {
-                        if (pos->type == KCORE_RAM)
+                        if (pos->type == KCORE_RAM
+                                || pos->type == KCORE_VMEMMAP)
                                 list_move(&pos->list, &garbage);
                 }
                 list_splice_tail(list, &kclist_head);
@@ -151,6 +152,47 @@ static int kcore_update_ram(void)
 
 #else /* !CONFIG_HIGHMEM */
 
+#ifdef CONFIG_SPARSEMEM_VMEMMAP
+/* calculate vmemmap's address from given system ram pfn and register it */
+int get_sparsemem_vmemmap_info(struct kcore_list *ent, struct list_head *head)
+{
+        unsigned long pfn = __pa(ent->addr) >> PAGE_SHIFT;
+        unsigned long nr_pages = ent->size >> PAGE_SHIFT;
+        unsigned long start, end;
+        struct kcore_list *vmm, *tmp;
+
+
+        start = ((unsigned long)pfn_to_page(pfn)) & PAGE_MASK;
+        end = ((unsigned long)pfn_to_page(pfn + nr_pages)) - 1;
+        end = ALIGN(end, PAGE_SIZE);
+        /* overlap check (because we have to align page */
+        list_for_each_entry(tmp, head, list) {
+                if (tmp->type != KCORE_VMEMMAP)
+                        continue;
+                if (start < tmp->addr + tmp->size)
+                        if (end > tmp->addr)
+                                end = tmp->addr;
+        }
+        if (start < end) {
+                vmm = kmalloc(sizeof(*vmm), GFP_KERNEL);
+                if (!vmm)
+                        return 0;
+                vmm->addr = start;
+                vmm->size = end - start;
+                vmm->type = KCORE_VMEMMAP;
+                list_add_tail(&vmm->list, head);
+        }
+        return 1;
+
+}
+#else
+int get_sparsemem_vmemmap_info(struct kcore_list *ent, struct list_head *head)
+{
+        return 1;
+}
+
+#endif
+
 static int
 kclist_add_private(unsigned long pfn, unsigned long nr_pages, void *arg)
 {
@@ -181,6 +223,12 @@ kclist_add_private(unsigned long pfn, unsigned long nr_pages, void *arg)
 
         ent->type = KCORE_RAM;
         list_add_tail(&ent->list, head);
+
+        if (!get_sparsemem_vmemmap_info(ent, head)) {
+                list_del(&ent->list);
+                goto free_out;
+        }
+
         return 0;
 free_out:
         kfree(ent);
diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h
index bd7b840765a0..379eaed72d4b 100644
--- a/include/linux/proc_fs.h
+++ b/include/linux/proc_fs.h
@@ -82,6 +82,7 @@ enum kcore_type {
         KCORE_TEXT,
         KCORE_VMALLOC,
         KCORE_RAM,
+        KCORE_VMEMMAP,
         KCORE_OTHER,
 };