KVM: arm64: Add header_page userspace descriptor for nVHE tracing
Added userspace file that describes the content of each hyp tracing
ring-buffer page. This follows the same format as the descriptor found
in the tracefs root to ensure compatibility with userspace trace tools.
Signed-off-by: Vincent Donnefort <vdonnefort@google.com>
diff --git a/arch/arm64/kvm/hyp_events.c b/arch/arm64/kvm/hyp_events.c
index 193d97a..c2f4c84 100644
--- a/arch/arm64/kvm/hyp_events.c
+++ b/arch/arm64/kvm/hyp_events.c
@@ -161,6 +161,30 @@ static const struct file_operations hyp_event_format_fops = {
.release = single_release,
};
+static ssize_t hyp_header_page_read(struct file *filp, char __user *ubuf,
+ size_t cnt, loff_t *ppos)
+{
+ struct trace_seq *s;
+ ssize_t r;
+
+ s = kmalloc(sizeof(*s), GFP_KERNEL);
+ if (!s)
+ return -ENOMEM;
+
+ trace_seq_init(s);
+ ring_buffer_print_page_header(s);
+ r = simple_read_from_buffer(ubuf, cnt, ppos, s->buffer,
+ trace_seq_used(s));
+ kfree(s);
+
+ return r;
+}
+
+static const struct file_operations hyp_header_page_fops = {
+ .read = hyp_header_page_read,
+ .llseek = default_llseek,
+};
+
static char early_events[COMMAND_LINE_SIZE];
static __init int setup_hyp_event_early(char *str)
@@ -216,6 +240,9 @@ void hyp_trace_init_event_tracefs(struct dentry *parent)
return;
}
+ tracefs_create_file("header_page", 0400, parent, NULL,
+ &hyp_header_page_fops);
+
parent = tracefs_create_dir("hyp", parent);
if (!parent) {
pr_err("Failed to create tracefs folder for hyp events\n");
