tracing: Remove comparing of NULL to va_list in trace_array_vprintk()

Olof Johansson stated the following:

  Comparing a va_list with NULL is bogus. It's supposed to be treated like
  an opaque type and only be manipulated with va_* accessors.

Olof noticed that this code broke the ARM builds:

    kernel/trace/trace.c: In function 'trace_array_vprintk':
    kernel/trace/trace.c:1364: error: invalid operands to binary == (have 'va_list' and 'void *')
    kernel/trace/trace.c: In function 'tracing_mark_write':
    kernel/trace/trace.c:3349: error: incompatible type for argument 3 of 'trace_vprintk'

This patch partly reverts c13d2f7c3231e873f30db92b96c8caa48f100f33 and
re-installs the original mark_printk() mechanism.

Reported-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Carsten Emde <C.Emde@osadl.org>
LKML-Reference: <4B1BAB74.104@osadl.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 12 insertions, 6 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 484114d70743..88bd9ae2a9ed 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1361,11 +1361,7 @@ int trace_array_vprintk(struct trace_array *tr,
         pause_graph_tracing();
         raw_local_irq_save(irq_flags);
         __raw_spin_lock(&trace_buf_lock);
-        if (args == NULL) {
-                strncpy(trace_buf, fmt, TRACE_BUF_SIZE);
-                len = strlen(trace_buf);
-        } else
-                len = vsnprintf(trace_buf, TRACE_BUF_SIZE, fmt, args);
+        len = vsnprintf(trace_buf, TRACE_BUF_SIZE, fmt, args);
 
         size = sizeof(*entry) + len + 1;
         buffer = tr->buffer;
@@ -3353,6 +3349,16 @@ tracing_entries_write(struct file *filp, const char __user *ubuf,
         return cnt;
 }
 
+static int mark_printk(const char *fmt, ...)
+{
+        int ret;
+        va_list args;
+        va_start(args, fmt);
+        ret = trace_vprintk(0, fmt, args);
+        va_end(args);
+        return ret;
+}
+
 static ssize_t
 tracing_mark_write(struct file *filp, const char __user *ubuf,
                                         size_t cnt, loff_t *fpos)
@@ -3379,7 +3385,7 @@ tracing_mark_write(struct file *filp, const char __user *ubuf,
         } else
                 buf[cnt] = '\0';
 
-        cnt = trace_vprintk(0, buf, NULL);
+        cnt = mark_printk("%s", buf);
         kfree(buf);
         *fpos += cnt;