[BUGFIX][PATCH] prevent boosting kprobes on exception address

From: Masami Hiramatsu <mhiramat@redhat.com>
To: Andrew Morton <akpm@linux-foundation.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Greg KH <greg@kroah.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
	Ananth N Mavinakayanahalli <ananth@in.ibm.com>,
	Jim Keniston <jkenisto@us.ibm.com>,
	systemtap-ml <systemtap@sources.redhat.com>,
	"Frank Ch. Eigler" <fche@redhat.com>
Subject: [BUGFIX][PATCH] prevent boosting kprobes on exception address
Date: Mon, 16 Mar 2009 18:57:22 -0400	[thread overview]
Message-ID: <49BED952.2050809@redhat.com> (raw)
In-Reply-To: <20090128181053.GC9908@Krystal>

Don't boost at the addresses which are listed on exception tables,
because major page fault will occur on those addresses. In that case,
kprobes can not ensure that when instruction buffer can be freed
since some processes will sleep on the buffer.
(kprobes-ia64 already has same check.)

Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
---
 arch/x86/kernel/kprobes.c |    3 +++
 1 file changed, 3 insertions(+)

Index: mmotm/arch/x86/kernel/kprobes.c
===================================================================

--- mmotm.orig/arch/x86/kernel/kprobes.c
+++ mmotm/arch/x86/kernel/kprobes.c
@@ -193,6 +193,9 @@ static int __kprobes can_boost(kprobe_op
 	kprobe_opcode_t opcode;
 	kprobe_opcode_t *orig_opcodes = opcodes;

+	if (search_exception_tables(opcodes))
+		return 0;	/* Page fault may occur on this address. */
+
 retry:
 	if (opcodes - orig_opcodes > MAX_INSN_SIZE - 1)
 		return 0;
-- 
Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America) Inc.
Software Solutions Division

e-mail: mhiramat@redhat.com


