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

mhiramathitachi · Ingo Molnar · commit d81b4253b0f0 · 2014-07-18T06:23:40.000+02:00
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 <tony.luck@gmail.com> Fixed-by: Suzuki K. Poulose <suzuki@in.ibm.com> Tested-by: Tony Luck <tony.luck@intel.com> Tested-by: Michael Ellerman <mpe@ellerman.id.au> Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Acked-by: Michael Ellerman <mpe@ellerman.id.au> (for powerpc) Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Jeremy Fitzhardinge <jeremy@goop.org> Cc: sparse@chrisli.org Cc: Paul Mackerras <paulus@samba.org> Cc: akataria@vmware.com Cc: anil.s.keshavamurthy@intel.com Cc: Fenghua Yu <fenghua.yu@intel.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Rusty Russell <rusty@rustcorp.com.au> Cc: Chris Wright <chrisw@sous-sol.org> Cc: yrl.pp-manager.tt@hitachi.com Cc: Kevin Hao <haokexin@gmail.com> Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: rdunlap@infradead.org Cc: dl9pf@gmx.de Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: David S. Miller <davem@davemloft.net> Cc: linux-ia64@vger.kernel.org Cc: linuxppc-dev@lists.ozlabs.org Link: http://lkml.kernel.org/r/20140717114411.13401.2632.stgit@kbuild-fedora.novalocal Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
@@ -2037,19 +2037,23 @@ static int __init populate_kprobe_blacklist(unsigned long *start,
 {
 	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);
 	}
