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authorLi Zefan <lizf@cn.fujitsu.com>2009-08-07 10:33:43 +0800
committerSteven Rostedt <rostedt@goodmis.org>2009-08-26 00:32:07 -0400
commit87a342f5db69d53ea70493bb1ec69c9047677038 (patch)
tree89ec97b3a32d6508d10f1598201e48a24c08c46e /kernel
parent43b51ead3f752a3935116e5b1a94254b8573734f (diff)
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 <lizf@cn.fujitsu.com> LKML-Reference: <4A7B9287.90205@cn.fujitsu.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/trace/trace_events_filter.c26
1 files changed, 23 insertions, 3 deletions
diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
index 8a8e576733fc..9f03082c81d8 100644
--- a/kernel/trace/trace_events_filter.c
+++ b/kernel/trace/trace_events_filter.c
@@ -163,6 +163,20 @@ static int filter_pred_string(struct filter_pred *pred, void *event,
return match;
}
+/* Filter predicate for char * pointers */
+static int filter_pred_pchar(struct filter_pred *pred, void *event,
+ int val1, int val2)
+{
+ char **addr = (char **)(event + pred->offset);
+ int cmp, match;
+
+ cmp = strncmp(*addr, pred->str_val, pred->str_len);
+
+ match = (!cmp) ^ pred->not;
+
+ return match;
+}
+
/*
* Filter predicate for dynamic sized arrays of characters.
* These are implemented through a list of strings at the end
@@ -489,7 +503,8 @@ int filter_assign_type(const char *type)
static bool is_string_field(struct ftrace_event_field *field)
{
return field->filter_type == FILTER_DYN_STRING ||
- field->filter_type == FILTER_STATIC_STRING;
+ field->filter_type == FILTER_STATIC_STRING ||
+ field->filter_type == FILTER_PTR_STRING;
}
static int is_legal_op(struct ftrace_event_field *field, int op)
@@ -579,11 +594,16 @@ static int filter_add_pred(struct filter_parse_state *ps,
}
if (is_string_field(field)) {
+ pred->str_len = field->size;
+
if (field->filter_type == FILTER_STATIC_STRING)
fn = filter_pred_string;
- else
+ else if (field->filter_type == FILTER_DYN_STRING)
fn = filter_pred_strloc;
- pred->str_len = field->size;
+ else {
+ fn = filter_pred_pchar;
+ pred->str_len = strlen(pred->str_val);
+ }
} else {
if (field->is_signed)
ret = strict_strtoll(pred->str_val, 0, &val);