tracing/syscalls: Init print_fmt for syscall events

This is part of a patch set that removes the show_format method
in the ftrace event macros.

Add the print_fmt initialization to the syscall events.
The print_fmt is still not used, but will be in the follow up
patches.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
LKML-Reference: <4B273D41.609@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 67 insertions, 1 deletions

diff --git a/kernel/trace/trace_syscalls.c b/kernel/trace/trace_syscalls.c
index 75289f372dd2..1352b0a36fac 100644
--- a/kernel/trace/trace_syscalls.c
+++ b/kernel/trace/trace_syscalls.c
@@ -191,6 +191,67 @@ int syscall_enter_format(struct ftrace_event_call *call, struct trace_seq *s)
         return trace_seq_putc(s, '\n');
 }
 
+static
+int  __set_enter_print_fmt(struct syscall_metadata *entry, char *buf, int len)
+{
+        int i;
+        int pos = 0;
+
+        /* When len=0, we just calculate the needed length */
+#define LEN_OR_ZERO (len ? len - pos : 0)
+
+        pos += snprintf(buf + pos, LEN_OR_ZERO, "\"");
+        for (i = 0; i < entry->nb_args; i++) {
+                pos += snprintf(buf + pos, LEN_OR_ZERO, "%s: 0x%%0%zulx%s",
+                                entry->args[i], sizeof(unsigned long),
+                                i == entry->nb_args - 1 ? "" : ", ");
+        }
+        pos += snprintf(buf + pos, LEN_OR_ZERO, "\"");
+
+        for (i = 0; i < entry->nb_args; i++) {
+                pos += snprintf(buf + pos, LEN_OR_ZERO,
+                                ", ((unsigned long)(REC->%s))", entry->args[i]);
+        }
+
+#undef LEN_OR_ZERO
+
+        /* return the length of print_fmt */
+        return pos;
+}
+
+static int set_syscall_print_fmt(struct ftrace_event_call *call)
+{
+        char *print_fmt;
+        int len;
+        struct syscall_metadata *entry = call->data;
+
+        if (entry->enter_event != call) {
+                call->print_fmt = "\"0x%lx\", REC->ret";
+                return 0;
+        }
+
+        /* First: called with 0 length to calculate the needed length */
+        len = __set_enter_print_fmt(entry, NULL, 0);
+
+        print_fmt = kmalloc(len + 1, GFP_KERNEL);
+        if (!print_fmt)
+                return -ENOMEM;
+
+        /* Second: actually write the @print_fmt */
+        __set_enter_print_fmt(entry, print_fmt, len + 1);
+        call->print_fmt = print_fmt;
+
+        return 0;
+}
+
+static void free_syscall_print_fmt(struct ftrace_event_call *call)
+{
+        struct syscall_metadata *entry = call->data;
+
+        if (entry->enter_event == call)
+                kfree(call->print_fmt);
+}
+
 int syscall_exit_format(struct ftrace_event_call *call, struct trace_seq *s)
 {
         int ret;
@@ -386,9 +447,14 @@ int init_syscall_trace(struct ftrace_event_call *call)
 {
         int id;
 
+        if (set_syscall_print_fmt(call) < 0)
+                return -ENOMEM;
+
         id = register_ftrace_event(call->event);
-        if (!id)
+        if (!id) {
+                free_syscall_print_fmt(call);
                 return -ENODEV;
+        }
         call->id = id;
         INIT_LIST_HEAD(&call->fields);
         return 0;