[RFT PATCH -next v3] [BUGFIX] kprobes: Fix "Failed to find blacklist" error on ia64 and ppc64

Masami Hiramatsu masami.hiramatsu.pt at hitachi.com
Fri May 30 13:18:38 EST 2014

On ia64 and ppc64, the function pointer does not point the
entry address of the function, but the address of function
discriptor (which contains the entry address and misc
data.) Since the kprobes passes the function pointer stored
by NOKPROBE_SYMBOL() to kallsyms_lookup_size_offset() for
initalizing its blacklist, it fails and reports many errors
as below.

  Failed to find blacklist 0001013168300000
  Failed to find blacklist 0001013000f0a000
  Failed to find blacklist 000101315f70a000
  Failed to find blacklist 000101324c80a000
  Failed to find blacklist 0001013063f0a000
  Failed to find blacklist 000101327800a000
  Failed to find blacklist 0001013277f0a000
  Failed to find blacklist 000101315a70a000
  Failed to find blacklist 0001013277e0a000
  Failed to find blacklist 000101305a20a000
  Failed to find blacklist 0001013277d0a000
  Failed to find blacklist 00010130bdc0a000
  Failed to find blacklist 00010130dc20a000
  Failed to find blacklist 000101309a00a000
  Failed to find blacklist 0001013277c0a000
  Failed to find blacklist 0001013277b0a000
  Failed to find blacklist 0001013277a0a000
  Failed to find blacklist 000101327790a000
  Failed to find blacklist 000101303140a000
  Failed to find blacklist 0001013a3280a000

To fix this bug, this introduces function_entry() macro to
retrieve the entry address from the given function pointer,
and uses for kallsyms_lookup_size_offset() while initializing

Changes in v3:
 - Fix a bug to get blacklist address based on function entry
   instead of function descriptor. (Suzuki's work, Thanks!)

Changes in V2:
 - Use function_entry() macro when lookin up symbols instead
   of storing it.
 - Update for the latest -next.

Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt at hitachi.com>
Signed-off-by: Suzuki K. Poulose <suzuki at in.ibm.com>
Reported-by: Tony Luck <tony.luck at gmail.com>
Cc: Suzuki K. Poulose <suzuki at in.ibm.com>
Cc: Tony Luck <tony.luck at intel.com>
Cc: Fenghua Yu <fenghua.yu at intel.com>
Cc: Benjamin Herrenschmidt <benh at kernel.crashing.org>
Cc: Paul Mackerras <paulus at samba.org>
Cc: Ananth N Mavinakayanahalli <ananth at in.ibm.com>
Cc: Kevin Hao <haokexin at gmail.com>
Cc: linux-ia64 at vger.kernel.org
Cc: linux-kernel at vger.kernel.org
Cc: linuxppc-dev at lists.ozlabs.org
 arch/ia64/include/asm/types.h    |    2 ++
 arch/powerpc/include/asm/types.h |   11 +++++++++++
 include/linux/types.h            |    4 ++++
 kernel/kprobes.c                 |   11 +++++++----
 4 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/arch/ia64/include/asm/types.h b/arch/ia64/include/asm/types.h
index 4c351b1..95279dd 100644
--- a/arch/ia64/include/asm/types.h
+++ b/arch/ia64/include/asm/types.h
@@ -27,5 +27,7 @@ struct fnptr {
 	unsigned long gp;
+#define function_entry(fn) (((struct fnptr *)(fn))->ip)
 #endif /* !__ASSEMBLY__ */
 #endif /* _ASM_IA64_TYPES_H */
diff --git a/arch/powerpc/include/asm/types.h b/arch/powerpc/include/asm/types.h
index bfb6ded..8b89d65 100644
--- a/arch/powerpc/include/asm/types.h
+++ b/arch/powerpc/include/asm/types.h
@@ -25,6 +25,17 @@ typedef struct {
 	unsigned long env;
 } func_descr_t;
+#if defined(CONFIG_PPC64) && (!defined(_CALL_ELF) || _CALL_ELF == 1)
+ * On PPC64 ABIv1 the function pointer actually points to the
+ * function's descriptor. The first entry in the descriptor is the
+ * address of the function text.
+ */
+#define function_entry(fn)	(((func_descr_t *)(fn))->entry)
+#define function_entry(fn)	((unsigned long)(fn))
 #endif /* __ASSEMBLY__ */
 #endif /* _ASM_POWERPC_TYPES_H */
diff --git a/include/linux/types.h b/include/linux/types.h
index a0bb704..3b95369 100644
--- a/include/linux/types.h
+++ b/include/linux/types.h
@@ -213,5 +213,9 @@ struct callback_head {
 #define rcu_head callback_head
+#ifndef function_entry
+#define function_entry(fn)	((unsigned long)(fn))
 #endif /*  __ASSEMBLY__ */
 #endif /* _LINUX_TYPES_H */
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 2ac9f13..3f2d6d4 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -32,6 +32,7 @@
  *		<prasanna at in.ibm.com> added function-return probes.
 #include <linux/kprobes.h>
+#include <linux/types.h>
 #include <linux/hash.h>
 #include <linux/init.h>
 #include <linux/slab.h>
@@ -2042,16 +2043,18 @@ static int __init populate_kprobe_blacklist(unsigned long *start,
 	unsigned long 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);
+		unsigned long entry = function_entry(*iter);
+		if (!kallsyms_lookup_size_offset(entry, &size, &offset)) {
+			pr_err("Failed to find blacklist at %p\n",
+			       (void *)entry);
 		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;
 		list_add_tail(&ent->list, &kprobe_blacklist);

More information about the Linuxppc-dev mailing list