I'm not in fact the maintainer covering this file.. On Fri, Dec 15, 2017 at 04:36:25PM +0100, Thomas Richter wrote: > 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:
So I had a wee peek and afaict this ends up at: trace_create_file("uprobe_events", 0644, d_tracer, NULL, &uprobe_events_ops); which is a world readable file. Doesn't that leak the kaslr offset?