By extending the filter rules by more generic fields
we can write triggers filters like
echo 'stacktrace if cpu == 1' > \
/sys/kernel/debug/tracing/events/raw_syscalls/sys_enter/trigger
or
echo 'stacktrace if comm == sshd' > \
/sys/kernel/debug/tracing/events/raw_syscalls/sys_enter/trigger
CPU and COMM are not part of struct trace_entry. We could add the two
new fields to ftrace_common_field list and fix up all depending
sides. But that looks pretty ugly. Another thing I would like to
avoid that the 'format' file contents changes.
All this can be avoided by introducing another list which contains
non field members of struct trace_entry.
Signed-off-by: Daniel Wagner <[email protected]>
Cc: Steven Rostedt <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: [email protected]
---
kernel/trace/trace_events.c | 25 ++++++++++++++++++
kernel/trace/trace_events_filter.c | 54 ++++++++++++++++++++++++++++++++++++--
2 files changed, 77 insertions(+), 2 deletions(-)
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 404a372..7ca09cd 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -30,6 +30,7 @@
DEFINE_MUTEX(event_mutex);
LIST_HEAD(ftrace_events);
+static LIST_HEAD(ftrace_generic_fields);
static LIST_HEAD(ftrace_common_fields);
#define GFP_TRACE (GFP_KERNEL | __GFP_ZERO)
@@ -94,6 +95,10 @@ trace_find_event_field(struct trace_event_call *call, char *name)
struct ftrace_event_field *field;
struct list_head *head;
+ field = __find_event_field(&ftrace_generic_fields, name);
+ if (field)
+ return field;
+
field = __find_event_field(&ftrace_common_fields, name);
if (field)
return field;
@@ -144,6 +149,13 @@ int trace_define_field(struct trace_event_call *call, const char *type,
}
EXPORT_SYMBOL_GPL(trace_define_field);
+#define __generic_field(type, item, filter_type) \
+ ret = __trace_define_field(&ftrace_generic_fields, #type, \
+ #item, 0, 0, is_signed_type(type), \
+ filter_type); \
+ if (ret) \
+ return ret;
+
#define __common_field(type, item) \
ret = __trace_define_field(&ftrace_common_fields, #type, \
"common_" #item, \
@@ -153,6 +165,16 @@ EXPORT_SYMBOL_GPL(trace_define_field);
if (ret) \
return ret;
+static int trace_define_generic_fields(void)
+{
+ int ret;
+
+ __generic_field(int, cpu, FILTER_OTHER);
+ __generic_field(char *, comm, FILTER_PTR_STRING);
+
+ return ret;
+}
+
static int trace_define_common_fields(void)
{
int ret;
@@ -2671,6 +2693,9 @@ static __init int event_trace_init(void)
if (!entry)
pr_warn("Could not create tracefs 'available_events' entry\n");
+ if (trace_define_generic_fields())
+ pr_warn("tracing: Failed to allocated generic fields");
+
if (trace_define_common_fields())
pr_warn("tracing: Failed to allocate common fields");
diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
index d81d6f3..bd1bf18 100644
--- a/kernel/trace/trace_events_filter.c
+++ b/kernel/trace/trace_events_filter.c
@@ -252,6 +252,50 @@ static int filter_pred_strloc(struct filter_pred *pred, void *event)
return match;
}
+/* Filter predicate for CPUs. */
+static int filter_pred_cpu(struct filter_pred *pred, void *event)
+{
+ int cpu, cmp;
+ int match = 0;
+
+ cpu = raw_smp_processor_id();
+ cmp = pred->val;
+
+ switch (pred->op) {
+ case OP_EQ:
+ match = cpu == cmp;
+ break;
+ case OP_LT:
+ match = cpu < cmp;
+ break;
+ case OP_LE:
+ match = cpu <= cmp;
+ break;
+ case OP_GT:
+ match = cpu > cmp;
+ break;
+ case OP_GE:
+ match = cpu >= cmp;
+ break;
+ default:
+ break;
+ }
+
+ return !!match == !pred->not;
+}
+
+/* Filter predicate for COMM. */
+static int filter_pred_comm(struct filter_pred *pred, void *event)
+{
+ int cmp, match;
+
+ cmp = pred->regex.match(current->comm, &pred->regex,
+ pred->regex.field_len);
+ match = cmp ^ pred->not;
+
+ return match;
+}
+
static int filter_pred_none(struct filter_pred *pred, void *event)
{
return 0;
@@ -1002,7 +1046,10 @@ static int init_pred(struct filter_parse_state *ps,
if (is_string_field(field)) {
filter_build_regex(pred);
- if (field->filter_type == FILTER_STATIC_STRING) {
+ if (!strcmp(field->name, "comm")) {
+ fn = filter_pred_comm;
+ pred->regex.field_len = TASK_COMM_LEN;
+ } else if (field->filter_type == FILTER_STATIC_STRING) {
fn = filter_pred_string;
pred->regex.field_len = field->size;
} else if (field->filter_type == FILTER_DYN_STRING)
@@ -1025,7 +1072,10 @@ static int init_pred(struct filter_parse_state *ps,
}
pred->val = val;
- fn = select_comparison_fn(pred->op, field->size,
+ if (!strcmp(field->name, "cpu"))
+ fn = filter_pred_cpu;
+ else
+ fn = select_comparison_fn(pred->op, field->size,
field->is_signed);
if (!fn) {
parse_error(ps, FILT_ERR_INVALID_OP, 0);
--
2.4.3
On Mon, 10 Aug 2015 14:35:46 +0200
Daniel Wagner <[email protected]> wrote:
> By extending the filter rules by more generic fields
> we can write triggers filters like
>
> echo 'stacktrace if cpu == 1' > \
> /sys/kernel/debug/tracing/events/raw_syscalls/sys_enter/trigger
>
> or
>
> echo 'stacktrace if comm == sshd' > \
> /sys/kernel/debug/tracing/events/raw_syscalls/sys_enter/trigger
>
> CPU and COMM are not part of struct trace_entry. We could add the two
> new fields to ftrace_common_field list and fix up all depending
> sides. But that looks pretty ugly. Another thing I would like to
> avoid that the 'format' file contents changes.
>
> All this can be avoided by introducing another list which contains
> non field members of struct trace_entry.
>
> Signed-off-by: Daniel Wagner <[email protected]>
> Cc: Steven Rostedt <[email protected]>
> Cc: Ingo Molnar <[email protected]>
> Cc: [email protected]
v0? Expect more revisions? ;-)
Looks fine. I pulled it into my queue.
-- Steve