NOMMU: Teach kobjsize() about VMA regions.

Now that we no longer use compound pages for all large allocations,
kobjsize() actively breaks things like binfmt_flat by always handing
back PAGE_SIZE for mmap'ed regions. Fix this up by looking up the
VMA region for non-compounds.

Ideally binfmt_flat wants to get rid of kobjsize() completely, but
this is an incremental step.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>
Signed-off-by: David Howells <dhowells@redhat.com>
Tested-by: Mike Frysinger <vapier.adi@gmail.com>

diff --git a/mm/nommu.c b/mm/nommu.c
index a6e8ccfbd40013df6dcb71899e25deaaf7d5c706..60ed8375c986f56604e1551836fcf0f48d1273a3 100644 (file)
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -148,6 +148,20 @@ unsigned int kobjsize(const void *objp)
        if (PageSlab(page))
                return ksize(objp);
 
+       /*
+        * If it's not a compound page, see if we have a matching VMA
+        * region. This test is intentionally done in reverse order,
+        * so if there's no VMA, we still fall through and hand back
+        * PAGE_SIZE for 0-order pages.
+        */
+       if (!PageCompound(page)) {
+               struct vm_area_struct *vma;
+
+               vma = find_vma(current->mm, (unsigned long)objp);
+               if (vma)
+                       return vma->vm_end - vma->vm_start;
+       }
+
        /*
         * The ksize() function is only guaranteed to work for pointers
         * returned by kmalloc(). So handle arbitrary pointers here.