tracing/syscalls: Fix the output of syscalls with no arguments

Before:

  # echo 1 > events/syscalls/sys_enter_sync/enable
  # cat events/syscalls/sys_enter_sync/format
  ...
        field:int nr;   offset:12;      size:4;

  print fmt: "# sync
  # cat trace
  ...
            sync-8950  [000]  2366.087670: sys_sync(

After:

  # echo 1 > events/syscalls/sys_enter_sync/enable
  # cat events/syscalls/sys_enter_sync/format
  ...
        field:int nr;   offset:12;      size:4;

  print fmt: ""
  # sync
  # cat trace
            sync-2134  [001]   136.780735: sys_sync()

Reported-by: Masami Hiramatsu <mhiramat@redhat.com>
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Jason Baron <jbaron@redhat.com>
Cc: Masami Hiramatsu <mhiramat@redhat.com>
LKML-Reference: <4A8D05AF.20103@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 16 insertions, 9 deletions

diff --git a/kernel/trace/trace_syscalls.c b/kernel/trace/trace_syscalls.c
index 28e4dae4af21..46c1b977a2cb 100644
--- a/kernel/trace/trace_syscalls.c
+++ b/kernel/trace/trace_syscalls.c
@@ -46,15 +46,22 @@ print_syscall_enter(struct trace_iterator *iter, int flags)
                                 return TRACE_TYPE_PARTIAL_LINE;
                 }
                 /* parameter values */
-                ret = trace_seq_printf(s, "%s: %lx%s ", entry->args[i],
+                ret = trace_seq_printf(s, "%s: %lx%s", entry->args[i],
                                        trace->args[i],
-                                       i == entry->nb_args - 1 ? ")" : ",");
+                                       i == entry->nb_args - 1 ? "" : ", ");
                 if (!ret)
                         return TRACE_TYPE_PARTIAL_LINE;
         }
 
+        ret = trace_seq_putc(s, ')');
+        if (!ret)
+                return TRACE_TYPE_PARTIAL_LINE;
+
 end:
-        trace_seq_printf(s, "\n");
+        ret =  trace_seq_putc(s, '\n');
+        if (!ret)
+                return TRACE_TYPE_PARTIAL_LINE;
+
         return TRACE_TYPE_HANDLED;
 }
 
@@ -129,24 +136,24 @@ int syscall_enter_format(struct ftrace_event_call *call, struct trace_seq *s)
                 offset += sizeof(unsigned long);
         }
 
-        trace_seq_printf(s, "\nprint fmt: \"");
+        trace_seq_puts(s, "\nprint fmt: \"");
         for (i = 0; i < entry->nb_args; i++) {
                 ret = trace_seq_printf(s, "%s: 0x%%0%zulx%s", entry->args[i],
                                         sizeof(unsigned long),
-                                        i == entry->nb_args - 1 ? "\", " : ", ");
+                                        i == entry->nb_args - 1 ? "" : ", ");
                 if (!ret)
                         return 0;
         }
+        trace_seq_putc(s, '"');
 
         for (i = 0; i < entry->nb_args; i++) {
-                ret = trace_seq_printf(s, "((unsigned long)(REC->%s))%s",
-                                        entry->args[i],
-                                        i == entry->nb_args - 1 ? "\n" : ", ");
+                ret = trace_seq_printf(s, ", ((unsigned long)(REC->%s))",
+                                       entry->args[i]);
                 if (!ret)
                         return 0;
         }
 
-        return ret;
+        return trace_seq_putc(s, '\n');
 }
 
 int syscall_exit_format(struct ftrace_event_call *call, struct trace_seq *s)