mm: prepare VM_DONTDUMP for using in drivers

Rename VM_NODUMP into VM_DONTDUMP: this name matches other negative flags:
VM_DONTEXPAND, VM_DONTCOPY. Currently this flag used only for
sys_madvise. The next patch will use it for replacing the outdated flag
VM_RESERVED.

Also forbid madvise(MADV_DODUMP) for special kernel mappings VM_SPECIAL
(VM_IO | VM_DONTEXPAND | VM_RESERVED | VM_PFNMAP)

Signed-off-by: Konstantin Khlebnikov <[e-mail]>
Cc: Alexander Viro <[e-mail]>
Cc: Carsten Otte <[e-mail]>
Cc: Chris Metcalf <[e-mail]>
Cc: Cyrill Gorcunov <[e-mail]>
Cc: Eric Paris <[e-mail]>
Cc: H. Peter Anvin <[e-mail]>
Cc: Hugh Dickins <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: James Morris <[e-mail]>
Cc: Jason Baron <[e-mail]>
Cc: Kentaro Takeda <[e-mail]>
Cc: Matt Helsley <[e-mail]>
Cc: Nick Piggin <[e-mail]>
Cc: Oleg Nesterov <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Robert Richter <[e-mail]>
Cc: Suresh Siddha <[e-mail]>
Cc: Tetsuo Handa <[e-mail]>
Cc: Venkatesh Pallipadi <[e-mail]>
Acked-by: Linus Torvalds <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

fs/binfmt_elf.c

···
 	if (always_dump_vma(vma))
 		goto whole;
 
-	if (vma->vm_flags & VM_NODUMP)
+	if (vma->vm_flags & VM_DONTDUMP)
 		return 0;
 
 	/* Hugetlb memory check */

include/linux/mm.h

···
 #define VM_HUGETLB	0x00400000	/* Huge TLB Page VM */
 #define VM_NONLINEAR	0x00800000	/* Is non-linear (remap_file_pages) */
 #define VM_ARCH_1	0x01000000	/* Architecture-specific flag */
-#define VM_NODUMP	0x04000000	/* Do not include in the core dump */
+#define VM_DONTDUMP	0x04000000	/* Do not include in the core dump */
 
 #define VM_MIXEDMAP	0x10000000	/* Can contain "struct page" and pure PFN pages */
 #define VM_HUGEPAGE	0x20000000	/* MADV_HUGEPAGE marked this vma */

mm/madvise.c

···
 		new_flags &= ~VM_DONTCOPY;
 		break;
 	case MADV_DONTDUMP:
-		new_flags |= VM_NODUMP;
+		new_flags |= VM_DONTDUMP;
 		break;
 	case MADV_DODUMP:
-		new_flags &= ~VM_NODUMP;
+		if (new_flags & VM_SPECIAL) {
+			error = -EINVAL;
+			goto out;
+		}
+		new_flags &= ~VM_DONTDUMP;
 		break;
 	case MADV_MERGEABLE:
 	case MADV_UNMERGEABLE: