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author | Li Zefan <lizf@cn.fujitsu.com> | 2009-08-07 10:33:43 +0800 |
---|---|---|
committer | Steven Rostedt <rostedt@goodmis.org> | 2009-08-26 00:32:07 -0400 |
commit | 87a342f5db69d53ea70493bb1ec69c9047677038 (patch) | |
tree | 89ec97b3a32d6508d10f1598201e48a24c08c46e /kernel/trace/trace_events_filter.c | |
parent | 43b51ead3f752a3935116e5b1a94254b8573734f (diff) | |
download | op-kernel-dev-87a342f5db69d53ea70493bb1ec69c9047677038.zip op-kernel-dev-87a342f5db69d53ea70493bb1ec69c9047677038.tar.gz |
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/trace/trace_events_filter.c')
-rw-r--r-- | kernel/trace/trace_events_filter.c | 26 |
1 files changed, 23 insertions, 3 deletions
diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c index 8a8e576..9f03082 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); |