[PATCH] Add VM_ALWAYSDUMP

This patch adds the VM_ALWAYSDUMP flag for vm_flags in vm_area_struct.  This
provides a clean explicit way to have a vma always included in core dumps, as
is needed for vDSO's.
Signed-off-by: NRoland McGrath <roland@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

fs/binfmt_elf.c

@@ -1178,6 +1178,10 @@ static int dump_seek(struct file *file, loff_t off)
  */
 static int maydump(struct vm_area_struct *vma)
 {
+	/* The vma can be set up to tell us the answer directly.  */
+	if (vma->vm_flags & VM_ALWAYSDUMP)
+		return 1;
+
 	/* Do not dump I/O mapped devices or special mappings */
 	if (vma->vm_flags & (VM_IO | VM_RESERVED))
 		return 0;

include/linux/mm.h

@@ -168,6 +168,7 @@ extern unsigned int kobjsize(const void *objp);
 #define VM_NONLINEAR	0x00800000	/* Is non-linear (remap_file_pages) */
 #define VM_MAPPED_COPY	0x01000000	/* T if mapped copy of data (nommu mmap) */
 #define VM_INSERTPAGE	0x02000000	/* The vma has had "vm_insert_page()" done on it */
+#define VM_ALWAYSDUMP	0x04000000	/* Always include in core dumps */
 
 #ifndef VM_STACK_DEFAULT_FLAGS		/* arch can override this */
 #define VM_STACK_DEFAULT_FLAGS VM_DATA_DEFAULT_FLAGS