[PATCH v6 09/13] ring-buffer: Save text and data locations in mapped meta data

Steven Rostedt
2024-06-12T23:20:07Z

When a ring buffer is mapped to a specific address, save the address of a
text function and some data. This will be used to determine the delta
between the last boot and the current boot for pointers to functions as
well as to data.

Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
kernel/trace/ring_buffer.c | 16 ++++++++++++++++
1 file changed, 16 insertions(+)

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 804dfbdeef84..8c287430411d 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -45,6 +45,8 @@
static void update_pages_handler(struct work_struct *work);

struct ring_buffer_meta {
+ unsigned long text_addr;
+ unsigned long data_addr;
unsigned long first_buffer;
unsigned long head_buffer;
unsigned long commit_buffer;
@@ -542,6 +544,9 @@ struct trace_buffer {
unsigned long range_addr_start;
unsigned long range_addr_end;

+ long last_text_delta;
+ long last_data_delta;
+
unsigned int subbuf_size;
unsigned int subbuf_order;
unsigned int max_data_size;
@@ -1821,10 +1826,15 @@ static void rb_meta_validate_events(struct ring_buffer_per_cpu *cpu_buffer)
}
}

+/* Used to calculate data delta */
+static char rb_data_ptr[] = "";
+
static void rb_range_meta_init(struct trace_buffer *buffer, int nr_pages)
{
struct ring_buffer_meta *meta;
unsigned long delta;
+ unsigned long this_text = (unsigned long)rb_range_meta_init;
+ unsigned long this_data = (unsigned long)rb_data_ptr;
void *subbuf;
int cpu;
int i;
@@ -1841,6 +1851,10 @@ static void rb_range_meta_init(struct trace_buffer *buffer, int nr_pages)
meta->first_buffer += delta;
meta->head_buffer += delta;
meta->commit_buffer += delta;
+ buffer->last_text_delta = this_text - meta->text_addr;
+ buffer->last_data_delta = this_data - meta->data_addr;
+ meta->text_addr = this_text;
+ meta->data_addr = this_data;
continue;
}

@@ -1857,6 +1871,8 @@ static void rb_range_meta_init(struct trace_buffer *buffer, int nr_pages)
subbuf = rb_subbufs_from_meta(meta);

meta->first_buffer = (unsigned long)subbuf;
+ meta->text_addr = this_text;
+ meta->data_addr = this_data;

/*
* The buffers[] array holds the order of the sub-buffers
--
2.43.0