From: Scott Moser <smoser@redhat.com>
Subject: [RHEL5.1 PATCH] bz238465 [PPC] handle <.symbol> lookup for kprobes
Date: Fri, 25 May 2007 10:44:57 -0400 (EDT)
Bugzilla: 238465
Message-Id: <Pine.LNX.4.64.0705251043410.5134@squad5-lp1.lab.boston.redhat.com>
Changelog: [PPC] handle <.symbol> lookup for kprobes


RHBZ#: 238465
------
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=238465

Description:
------------
  [POWERPC] Transparently handle <.symbol> lookup for kprobes
  
  When data symbols are not present in kernel image, user needs to add
  dot(".") before function name explicitly, that he wants to probe in kprobe
  module on ppc64.
  
  for ex:-
  When data symbols are missing on ppc64,
  ====================
  [root@llm27lp1 ~]# cat /proc/kallsyms | grep do_fork
  c00000000006283c T .do_fork
  ==============================
  User needs add "." to "do_fork"
  
  kp.symbol_name = ".do_fork";
  ============================
  
  This makes kprobe module source unportable.  This fixes the problem.
  
  Signed-off-by: Srinivasa Ds <srinivasa@in.ibm.com>
  Signed-off-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
  Signed-off-by: Paul Mackerras <paulus@samba.org>


RHEL Version Found:
-------------------
bug against 5.0

Upstream Status:
----------------
This code is upstream for 2.6.22
git commit [1] eb609e52d188775da738a1ffd1e982e6212c77d7


Test Status:
------------
These patches have been built against 2.6.18-19.el5, and successfully
built in brew task 794835 [2].

Test has been done by Srinivasa Ds of IBM.

Proposed Patch:
----------------
Please review and ACK for RHEL5.1

-- 
[1] http://git.kernel.org/gitweb.cgi?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=eb609e52d188775da738a1ffd1e982e6212c77d7
[2] http://brewweb.devel.redhat.com/brew/taskinfo?taskID=794835

---
 include/asm-powerpc/kprobes.h |    6 ++++++
 1 file changed, 6 insertions(+)

Index: b/include/asm-powerpc/kprobes.h
===================================================================
--- a/include/asm-powerpc/kprobes.h
+++ b/include/asm-powerpc/kprobes.h
@@ -63,6 +63,12 @@ typedef unsigned int kprobe_opcode_t;
 				addr = *(kprobe_opcode_t **)addr;	\
 		} else if (name[0] != '.')				\
 			addr = *(kprobe_opcode_t **)addr;		\
+	} else {							\
+		char dot_name[KSYM_NAME_LEN+1];				\
+		dot_name[0] = '.';					\
+		dot_name[1] = '\0';					\
+		strncat(dot_name, name, KSYM_NAME_LEN);			\
+		addr = (kprobe_opcode_t *)kallsyms_lookup_name(dot_name); \
 	}								\
 }