FAILED: patch "[PATCH] tracing/eprobes: Fix reading of string fields" failed to apply to 5.15-stable tree

The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From f04dec93466a0481763f3b56cdadf8076e28bfbf Mon Sep 17 00:00:00 2001
From: "Steven Rostedt (Google)" <[email protected]>
Date: Sat, 20 Aug 2022 09:43:19 -0400
Subject: [PATCH] tracing/eprobes: Fix reading of string fields

Currently when an event probe (eprobe) hooks to a string field, it does not display it as a string, but instead as a number. This makes the field rather useless. Handle the different kinds of strings, dynamic, static, relational/dynamic etc.

Now when a string field is used, the ":string" type can be used to display it:

echo "e:sw sched/sched_switch comm=$next_comm:string" > dynamic_events

index 550671985fd1..a1d3423ab74f 100644
@@ -311,6 +311,27 @@ static unsigned long get_event_field(struct fetch_insn *code, void *rec)
 
 	addr = rec + field->offset;
 
+	if (is_string_field(field)) {
+		switch (field->filter_type) {
+		case FILTER_DYN_STRING:
+			val = (unsigned long)(rec + (*(unsigned int *)addr & 0xffff));
+			break;
+		case FILTER_RDYN_STRING:
+			val = (unsigned long)(addr + (*(unsigned int *)addr & 0xffff));
+			break;
+		case FILTER_STATIC_STRING:
+			val = (unsigned long)addr;
+			break;
+		case FILTER_PTR_STRING:
+			val = (unsigned long)(*(char *)addr);
+			break;
+		default:
+			WARN_ON_ONCE(1);
+			return 0;
+		}
+		return val;
+	}
+
 	switch (field->size) {
 	case 1:
 		if (field->is_signed)

This is the backport to 5.15.

-- Steve

------------------ original commit in Linus's tree ------------------

From: "Steven Rostedt (Google)" <[email protected]>
Date: Sat, 20 Aug 2022 09:43:19 -0400
Subject: [PATCH] tracing/eprobes: Fix reading of string fields

Currently when an event probe (eprobe) hooks to a string field, it does not display it as a string, but instead as a number. This makes the field rather useless. Handle the different kinds of strings, dynamic, static, relational/dynamic etc.

Now when a string field is used, the ":string" type can be used to display it:

echo "e:sw sched/sched_switch comm=$next_comm:string" > dynamic_events

---
 kernel/trace/trace_eprobe.c |   18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

Index: linux-test.git/kernel/trace/trace_eprobe.c
===================================================================
@@ -320,6 +320,24 @@ static unsigned long get_event_field(str
 
 	addr = rec + field->offset;
 
+	if (is_string_field(field)) {
+		switch (field->filter_type) {
+		case FILTER_DYN_STRING:
+			val = (unsigned long)(rec + (*(unsigned int *)addr & 0xffff));
+			break;
+		case FILTER_STATIC_STRING:
+			val = (unsigned long)addr;
+			break;
+		case FILTER_PTR_STRING:
+			val = (unsigned long)(*(char *)addr);
+			break;
+		default:
+			WARN_ON_ONCE(1);
+			return 0;
+		}
+		return val;
+	}
+
 	switch (field->size) {
 	case 1:
 		if (field->is_signed)

Now queued up, thanks.

greg k-h