Commit 3558a5ac authored by Dan Carpenter's avatar Dan Carpenter Committed by Steven Rostedt

tracing: Truncated output is better than nothing

The initial reason for this patch is that I noticed that:

	if (len > TRACE_BUF_SIZE)

is off by one.  In this code, if len == TRACE_BUF_SIZE, then it means we
have truncated the last character off the output string.  If we truncate
two or more characters then we exit without printing.

After some discussion, we decided that printing truncated data is better
than not printing at all so we should just use vscnprintf() and remove
the test entirely.  Also I have updated memcpy() to copy the NUL char
instead of setting the NUL in a separate step.

Link: http://lkml.kernel.org/r/20141127155752.GA21914@mwandaSigned-off-by: default avatarDan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent 8e1e1df2
...@@ -2158,9 +2158,7 @@ __trace_array_vprintk(struct ring_buffer *buffer, ...@@ -2158,9 +2158,7 @@ __trace_array_vprintk(struct ring_buffer *buffer,
goto out; goto out;
} }
len = vsnprintf(tbuffer, TRACE_BUF_SIZE, fmt, args); len = vscnprintf(tbuffer, TRACE_BUF_SIZE, fmt, args);
if (len > TRACE_BUF_SIZE)
goto out;
local_save_flags(flags); local_save_flags(flags);
size = sizeof(*entry) + len + 1; size = sizeof(*entry) + len + 1;
...@@ -2171,8 +2169,7 @@ __trace_array_vprintk(struct ring_buffer *buffer, ...@@ -2171,8 +2169,7 @@ __trace_array_vprintk(struct ring_buffer *buffer,
entry = ring_buffer_event_data(event); entry = ring_buffer_event_data(event);
entry->ip = ip; entry->ip = ip;
memcpy(&entry->buf, tbuffer, len); memcpy(&entry->buf, tbuffer, len + 1);
entry->buf[len] = '\0';
if (!call_filter_check_discard(call, entry, buffer, event)) { if (!call_filter_check_discard(call, entry, buffer, event)) {
__buffer_unlock_commit(buffer, event); __buffer_unlock_commit(buffer, event);
ftrace_trace_stack(buffer, flags, 6, pc); ftrace_trace_stack(buffer, flags, 6, pc);
......
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