[PATCH v2 4/4] tracing/uprobes: Do not print '0x (null)' when offset is 0

[Wang Nan]

When manually added uprobe point with zero address, 'uprobe_events' output
'(null)' instead of 0x00000000:

 # echo p:probe_libc/abs_0 /path/to/lib.bin:0x0 arg1=%ax > \
            /sys/kernel/debug/tracing/uprobe_events

 # cat /sys/kernel/debug/tracing/uprobe_events
   p:probe_libc/abs_0 /path/to/lib.bin:0x          (null) arg1=%ax

This patch fixes this behavior:

 # cat /sys/kernel/debug/tracing/uprobe_events
 p:probe_libc/abs_0 /path/to/lib.bin:0x0000000000000000

Signed-off-by: Wang Nan <wangnan0@xxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@xxxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
---
 kernel/trace/trace_uprobe.c | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
index f97479f..d2f6d0b 100644
--- a/kernel/trace/trace_uprobe.c
+++ b/kernel/trace/trace_uprobe.c
@@ -601,7 +601,22 @@ static int probes_seq_show(struct seq_file *m, void *v)
 
 	seq_printf(m, "%c:%s/%s", c, tu->tp.call.class->system,
 			trace_event_name(&tu->tp.call));
-	seq_printf(m, " %s:0x%p", tu->filename, (void *)tu->offset);
+	seq_printf(m, " %s:", tu->filename);
+
+	/* Don't print "0x  (null)" when offset is 0 */
+	if (tu->offset) {
+		seq_printf(m, "0x%p", (void *)tu->offset);
+	} else {
+		switch (sizeof(void *)) {
+		case 4:
+			seq_printf(m, "0x00000000");
+			break;
+		case 8:
+		default:
+			seq_printf(m, "0x0000000000000000");
+			break;
+		}
+	}
 
 	for (i = 0; i < tu->tp.nr_args; i++)
 		seq_printf(m, " %s=%s", tu->tp.args[i].name, tu->tp.args[i].comm);
-- 
1.8.3.4

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