From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Message-Id: <20070822123643.989489295@de.ibm.com> References: <20070822123603.501231302@de.ibm.com> Date: Wed, 22 Aug 2007 14:36:12 +0200 From: Martin Schwidefsky Subject: [patch 09/10] kprobes: fix instruction length calculation Content-Disposition: inline; filename=009-kprobe-iln.diff Sender: linux-kernel-owner@vger.kernel.org List-Archive: List-Post: To: linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org Cc: David Wilder , Martin Schwidefsky , Heiko Carstens List-ID: From: David Wilder Placing a kprobe on "bc" instruction (s390/s390x) can cause an oops. The instruction length is encoded into the first two bits of the s390 instruction. Kprobe is incorrectly computing the instruction length. The instruction length is used for determining what type of "fix-up" is needed for conditional branch instruction. The problem can bee seen by placing a kprobe on a "bc" instruction that will not branch. The results is that Kprobe incorrectly computes the new instruction pointer (psw.addr) after single stepping the instruction. The problem is corrected with this patch. Signed-off-by: David Wilder Signed-off-by: Martin Schwidefsky Signed-off-by: Heiko Carstens --- arch/s390/kernel/kprobes.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) Index: quilt-2.6/arch/s390/kernel/kprobes.c =================================================================== --- quilt-2.6.orig/arch/s390/kernel/kprobes.c +++ quilt-2.6/arch/s390/kernel/kprobes.c @@ -85,7 +85,7 @@ void __kprobes get_instruction_type(stru ainsn->reg = (*ainsn->insn & 0xf0) >> 4; /* save the instruction length (pop 5-5) in bytes */ - switch (*(__u8 *) (ainsn->insn) >> 4) { + switch (*(__u8 *) (ainsn->insn) >> 6) { case 0: ainsn->ilen = 2; break; -- blue skies, Martin. "Reality continues to ruin my life." - Calvin.