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Subject[PATCH 2/2] tracing/filters: use strcmp() instead of strncmp()
Trace filter is not working normally:

# echo 'name == et' > tracing/events/irq/irq_handler_entry/filter
# echo 1 > tracing/events/irq/irq_handler_entry/enable
# cat trace_pipe
<idle>-0 [001] 1363.423175: irq_handler_entry: irq=18 handler=eth0
<idle>-0 [001] 1363.934528: irq_handler_entry: irq=18 handler=eth0
...

It's because we pass to trace_define_field() the information of
__str_loc_##item, but not the actual string, so pred->str_len == field->size
== sizeof(unsigned short), thus it always compare at most 2 bytes when
filtering on __string() field.

Since __string() is dynamic size, we are not able to set field->size to
string length. Thus this patch uses strcmp() instead of strncmp().

[ Impact: make filter facility working normally for __string() field ]

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
---
kernel/trace/trace.h | 1 -
kernel/trace/trace_events_filter.c | 7 ++-----
2 files changed, 2 insertions(+), 6 deletions(-)

diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 6e735d4..ec8970b 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -758,7 +758,6 @@ struct filter_pred {
filter_pred_fn_t fn;
u64 val;
char str_val[MAX_FILTER_STR_VAL];
- int str_len;
char *field_name;
int offset;
int not;
diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
index a854eed..8362586 100644
--- a/kernel/trace/trace_events_filter.c
+++ b/kernel/trace/trace_events_filter.c
@@ -158,7 +158,7 @@ static int filter_pred_string(struct filter_pred *pred, void *event,
char *addr = (char *)(event + pred->offset);
int cmp, match;

- cmp = strncmp(addr, pred->str_val, pred->str_len);
+ cmp = strcmp(addr, pred->str_val);

match = (!cmp) ^ pred->not;

@@ -182,7 +182,7 @@ static int filter_pred_strloc(struct filter_pred *pred, void *event,
char *addr = (char *)(event + str_loc);
int cmp, match;

- cmp = strncmp(addr, pred->str_val, pred->str_len);
+ cmp = strcmp(addr, pred->str_val);

match = (!cmp) ^ pred->not;

@@ -341,7 +341,6 @@ static void filter_clear_pred(struct filter_pred *pred)
{
kfree(pred->field_name);
pred->field_name = NULL;
- pred->str_len = 0;
}

static int filter_set_pred(struct filter_pred *dest,
@@ -576,7 +575,6 @@ static int filter_add_pred(struct filter_parse_state *ps,
fn = filter_pred_string;
else
fn = filter_pred_strloc;
- pred->str_len = field->size;
if (pred->op == OP_NE)
pred->not = 1;
return filter_add_pred_fn(ps, call, pred, fn);
@@ -957,7 +955,6 @@ static struct filter_pred *create_pred(int op, char *operand1, char *operand2)
}

strcpy(pred->str_val, operand2);
- pred->str_len = strlen(operand2);

pred->op = op;

--
1.5.4.rc3


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