[PATCH v3 12/13] tracing: Update function tracing output for previous boot buffer

[Steven Rostedt]

From: "Steven Rostedt (Google)" <rostedt@xxxxxxxxxxx>

For a persistent ring buffer that is saved across boots, if function
tracing was performed in the previous boot, it only saves the address of
the functions and uses "%pS" to print their names. But the current boot,
those functions may be in different locations. The persistent meta-data
saves the text delta between the two boots and can be used to find the
address of the saved function of where it is located in the current boot.

Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
---
 kernel/trace/trace_output.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
index d8b302d01083..b9d2c64c0648 100644
--- a/kernel/trace/trace_output.c
+++ b/kernel/trace/trace_output.c
@@ -990,8 +990,11 @@ enum print_line_t trace_nop_print(struct trace_iterator *iter, int flags,
 }
 
 static void print_fn_trace(struct trace_seq *s, unsigned long ip,
-			   unsigned long parent_ip, int flags)
+			   unsigned long parent_ip, long delta, int flags)
 {
+	ip += delta;
+	parent_ip += delta;
+
 	seq_print_ip_sym(s, ip, flags);
 
 	if ((flags & TRACE_ITER_PRINT_PARENT) && parent_ip) {
@@ -1009,7 +1012,7 @@ static enum print_line_t trace_fn_trace(struct trace_iterator *iter, int flags,
 
 	trace_assign_type(field, iter->ent);
 
-	print_fn_trace(s, field->ip, field->parent_ip, flags);
+	print_fn_trace(s, field->ip, field->parent_ip, iter->tr->text_delta, flags);
 	trace_seq_putc(s, '\n');
 
 	return trace_handle_return(s);
@@ -1674,7 +1677,7 @@ trace_func_repeats_print(struct trace_iterator *iter, int flags,
 
 	trace_assign_type(field, iter->ent);
 
-	print_fn_trace(s, field->ip, field->parent_ip, flags);
+	print_fn_trace(s, field->ip, field->parent_ip, iter->tr->text_delta, flags);
 	trace_seq_printf(s, " (repeats: %u, last_ts:", field->count);
 	trace_print_time(s, iter,
 			 iter->ts - FUNC_REPEATS_GET_DELTA_TS(field));
-- 
2.43.0