Re: [PATCH] tracing: Fix printing ptrs in preempt/irq enable/disable events

Steven Rostedt
2019-12-23T20:13:07Z

On Sat, 21 Dec 2019 18:47:41 -0500
Joel Fernandes <joel@joelfernandes.org> wrote:

> On Wed, Dec 04, 2019 at 09:21:15AM -0500, Steven Rostedt wrote:
> >
> > Joel,
> >
> > Any comments on this patch?
>
> Steve, it looks like this issue happens with trace-cmd not knowing what
> _stext is. If I do cat trace_pipe , then I don't see the issue as _stext is
> looked up correctly but the reporter of the bug is using trace-cmd. Is there
> a way to solve this within trace-cmd? Not knowing much about trace-cmd
> internals, I will have to defer to you on this though..
>
> Other than this, I need to make the offset to _stext as s32 instead of u32
> type so that the problem of the symbol location being before _stext does not
> cause overflow.
>
> Lastly, I am not super convinced that we need to store the full pointer just
> to handle a case where the offset of the symbol might be more than +-2G from
> _stext. Once we see such issue, then we can handle it. But right now the size
> of the trace buffer is utilized better by just storing the offset IMHO.
>

Does this fix it for you?

-- Steve

diff --git a/lib/traceevent/event-parse.c b/lib/traceevent/event-parse.c
index 4fd3907e..dc705dd2 100644
--- a/lib/traceevent/event-parse.c
+++ b/lib/traceevent/event-parse.c
@@ -3595,6 +3595,45 @@ tep_find_event_by_name(struct tep_handle *tep,
return event;
}

+static unsigned long long test_for_symbol(struct tep_handle *tep,
+ struct tep_print_arg *arg)
+{
+ unsigned long long val = 0;
+ struct func_list *item = tep->funclist;
+ char *func;
+ int i;
+
+ if (isdigit(arg->atom.atom[0]))
+ return 0;
+
+ for (i = 0; i < (int)tep->func_count; i++) {
+ unsigned long long addr;
+ const char *name;
+
+ if (tep->func_map) {
+ addr = tep->func_map[i].addr;
+ name = tep->func_map[i].func;
+ } else if (item) {
+ addr = item->addr;
+ name = item->func;
+ item = item->next;
+ } else
+ break;
+
+ if (strcmp(arg->atom.atom, name) == 0) {
+ val = addr;
+ break;
+ }
+ }
+
+ func = realloc(arg->atom.atom, 32);
+ if (func) {
+ snprintf(func, 32, "%lld", val);
+ arg->atom.atom = func;
+ }
+ return val;
+}
+
static unsigned long long
eval_num_arg(void *data, int size, struct tep_event *event, struct tep_print_arg *arg)
{
@@ -3611,7 +3650,10 @@ eval_num_arg(void *data, int size, struct tep_event *event, struct tep_print_arg
/* ?? */
return 0;
case TEP_PRINT_ATOM:
- return strtoull(arg->atom.atom, NULL, 0);
+ val = strtoull(arg->atom.atom, NULL, 0);
+ if (!val)
+ val = test_for_symbol(tep, arg);
+ return val;
case TEP_PRINT_FIELD:
if (!arg->field.field) {
arg->field.field = tep_find_any_field(event, arg->field.name);