coredump: use task comm instead of (unknown)

If we don't know the file corresponding to the binary (i.e.  exe_file is
unknown), use "task->comm (path unknown)" instead of simple "(unknown)"
as suggested by ak.

The fallback is the same as %e except it will append "(path unknown)".

Signed-off-by: Jiri Slaby <[email protected]>
Cc: Alan Cox <[email protected]>
Cc: Al Viro <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: Oleg Nesterov <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

fs/exec.c

@@ -1657,7 +1657,7 @@ static int cn_print_exe_file(struct core_name *cn)
 
 	exe_file = get_mm_exe_file(current->mm);
 	if (!exe_file)
-		return cn_printf(cn, "(unknown)");
+		return cn_printf(cn, "%s (path unknown)", current->comm);
 
 	pathbuf = kmalloc(PATH_MAX, GFP_TEMPORARY);
 	if (!pathbuf) {