From 87a342f5db69d53ea70493bb1ec69c9047677038 Mon Sep 17 00:00:00 2001 From: Li Zefan Date: Fri, 7 Aug 2009 10:33:43 +0800 Subject: tracing/filters: Support filtering for char * strings Usually, char * entries are dangerous in traces because the string can be released whereas a pointer to it can still wait to be read from the ring buffer. But sometimes we can assume it's safe, like in case of RO data (eg: __file__ or __line__, used in bkl trace event). If these RO data are in a module and so is the call to the trace event, then it's safe, because the ring buffer will be flushed once this module get unloaded. To allow char * to be treated as a string: TRACE_EVENT(..., TP_STRUCT__entry( __field_ext(const char *, name, FILTER_PTR_STRING) ... ) ... ); The filtering will not dereference "char *" unless the developer explicitly sets FILTER_PTR_STR in __field_ext. Signed-off-by: Li Zefan LKML-Reference: <4A7B9287.90205@cn.fujitsu.com> Signed-off-by: Steven Rostedt --- include/linux/ftrace_event.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/linux/ftrace_event.h') diff --git a/include/linux/ftrace_event.h b/include/linux/ftrace_event.h index 0440bea..ace2da9 100644 --- a/include/linux/ftrace_event.h +++ b/include/linux/ftrace_event.h @@ -144,6 +144,7 @@ enum { FILTER_OTHER = 0, FILTER_STATIC_STRING, FILTER_DYN_STRING, + FILTER_PTR_STRING, }; extern int trace_define_field(struct ftrace_event_call *call, -- cgit v1.1