Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932435AbdLOPgx (ORCPT ); Fri, 15 Dec 2017 10:36:53 -0500 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:59586 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S932183AbdLOPgu (ORCPT ); Fri, 15 Dec 2017 10:36:50 -0500 From: Thomas Richter To: linux-kernel@vger.kernel.org, peterz@infradead.org Cc: heiko.carstens@de.ibm.com, schwidefsky@de.ibm.com, brueckner@linux.vnet.ibm.com, Thomas Richter Subject: [PATCH] trace/uprobes: fix output issue with address randomization Date: Fri, 15 Dec 2017 16:36:25 +0100 X-Mailer: git-send-email 2.13.5 X-TM-AS-GCONF: 00 x-cbid: 17121515-0016-0000-0000-0000050D98CD X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17121515-0017-0000-0000-00002849B727 Message-Id: <20171215153625.7657-1-tmricht@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-12-15_06:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 impostorscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1709140000 definitions=main-1712150219 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2058 Lines: 57 Commit ad67b74d2469 ("printk: hash addresses printed with %p") changed %p to hash pointers in order to avoid leaking kernel addresses. This breaks the tool perf probe. To set a uprobe on a function named inet_pton in libc library, obtain the address of the symbol inet_pton using command nm and then use the following command to set the uprobe: # echo "p:probe_libc/inet_pton /usr/lib64/libc-2.26.so:0x142060" > /sys/kernel/debug/tracing/uprobe_events However the output shows a randomized address: # cat /sys/kernel/debug/tracing/uprobe_events p:probe_libc/inet_pton /usr/lib64/libc-2.26.so:0x000000002d0f8952 The displayed address 0x000000002d0f8952 is incorrect and breaks tools post processing it: # linux/tools/perf/perf probe -l Failed to find debug information for address 2d0f8952 probe_libc:inet_pton (on 0x2d0f8952 in /usr/lib64/libc-2.26.so) Using the %px printk format string fixes this issue for root and shows the correct address allowing the perf probe tool to resolve the address to the symbol: # echo "p:probe_libc/inet_pton /usr/lib64/libc-2.26.so:0x142060" > /sys/kernel/debug/tracing/uprobe_events # cat /sys/kernel/debug/tracing/uprobe_events p:probe_libc/inet_pton /usr/lib64/libc-2.26.so:0x0000000000142060 # linux/tools/perf/perf probe -l probe_libc:inet_pton (on __inet_pton@resolv/inet_pton.c in /usr/lib64/libc-2.26.so) Signed-off-by: Thomas Richter Suggested-by: Peter Zijlstra --- kernel/trace/trace_uprobe.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c index 40592e7b3568..268029ae1be6 100644 --- a/kernel/trace/trace_uprobe.c +++ b/kernel/trace/trace_uprobe.c @@ -608,7 +608,7 @@ static int probes_seq_show(struct seq_file *m, void *v) /* Don't print "0x (null)" when offset is 0 */ if (tu->offset) { - seq_printf(m, "0x%p", (void *)tu->offset); + seq_printf(m, "0x%px", (void *)tu->offset); } else { switch (sizeof(void *)) { case 4: -- 2.13.4