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 <tmri...@linux.vnet.ibm.com>
Suggested-by: Peter Zijlstra <pet...@infradead.org>
---
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
