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

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Date:   Mon, 23 Dec 2019 15:13:01 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Joel Fernandes <joel@...lfernandes.org>
Cc:     Antonio Borneo <antonio.borneo@...com>,
        Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
        linux-stm32@...md-mailman.stormreply.com
Subject: Re: [PATCH] tracing: Fix printing ptrs in preempt/irq
 enable/disable events

On Sat, 21 Dec 2019 18:47:41 -0500
Joel Fernandes <joel@...lfernandes.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);