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