kprobes: Fix "Failed to find blacklist" probing errors on ia64 and ppc64

On ia64 and ppc64, function pointers do not point to the
entry address of the function, but to the address of a
function descriptor (which contains the entry address and misc
data).

Since the kprobes code passes the function pointer stored
by NOKPROBE_SYMBOL() to kallsyms_lookup_size_offset() for
initalizing its blacklist, it fails and reports many errors,
such as:

Failed to find blacklist 0001013168300000
Failed to find blacklist 0001013000f0a000
[...]

To fix this bug, use arch_deref_entry_point() to get the
function entry address for kallsyms_lookup_size_offset()
instead of the raw function pointer.

Suzuki also pointed out that blacklist entries should also
be updated as well.

Reported-by: Tony Luck <[e-mail]>
Fixed-by: Suzuki K. Poulose <[e-mail]>
Tested-by: Tony Luck <[e-mail]>
Tested-by: Michael Ellerman <[e-mail]>
Signed-off-by: Masami Hiramatsu <[e-mail]>
Acked-by: Michael Ellerman <[e-mail]> (for powerpc)
Acked-by: Benjamin Herrenschmidt <[e-mail]>
Cc: Jeremy Fitzhardinge <[e-mail]>
Cc: [e-mail]
Cc: Paul Mackerras <[e-mail]>
Cc: [e-mail]
Cc: [e-mail]
Cc: Fenghua Yu <[e-mail]>
Cc: Arnd Bergmann <[e-mail]>
Cc: Rusty Russell <[e-mail]>
Cc: Chris Wright <[e-mail]>
Cc: [e-mail]
Cc: Kevin Hao <[e-mail]>
Cc: Ananth N Mavinakayanahalli <[e-mail]>
Cc: [e-mail]
Cc: [e-mail]
Cc: Linus Torvalds <[e-mail]>
Cc: David S. Miller <[e-mail]>
Cc: [e-mail]
Cc: [e-mail]
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Ingo Molnar <[e-mail]>

kernel/kprobes.c

···
 {
 	unsigned long *iter;
 	struct kprobe_blacklist_entry *ent;
-	unsigned long offset = 0, size = 0;
+	unsigned long entry, offset = 0, size = 0;
 
 	for (iter = start; iter < end; iter++) {
-		if (!kallsyms_lookup_size_offset(*iter, &size, &offset)) {
-			pr_err("Failed to find blacklist %p\n", (void *)*iter);
+		entry = arch_deref_entry_point((void *)*iter);
+
+		if (!kernel_text_address(entry) ||
+		    !kallsyms_lookup_size_offset(entry, &size, &offset)) {
+			pr_err("Failed to find blacklist at %p\n",
+				(void *)entry);
 			continue;
 		}
 
 		ent = kmalloc(sizeof(*ent), GFP_KERNEL);
 		if (!ent)
 			return -ENOMEM;
-		ent->start_addr = *iter;
-		ent->end_addr = *iter + size;
+		ent->start_addr = entry;
+		ent->end_addr = entry + size;
 		INIT_LIST_HEAD(&ent->list);
 		list_add_tail(&ent->list, &kprobe_blacklist);
 	}