[PATCH 11/15] tracing: Add kho serialization of trace buffers

@@ -212,4 +212,6 @@ int trace_rb_cpu_prepare(unsigned int cpu, struct hlist_node *node);
 #define trace_rb_cpu_prepare	NULL
 #endif
 
+int trace_kho_write_trace_buffer(void *fdt, struct trace_buffer *buffer);
+
 #endif /* _LINUX_RING_BUFFER_H */

@@ -20,6 +20,7 @@
 #include <linux/percpu.h>
 #include <linux/mutex.h>
 #include <linux/delay.h>
+#include <linux/kexec.h>
 #include <linux/slab.h>
 #include <linux/init.h>
 #include <linux/hash.h>

@@ -5921,6 +5922,94 @@ int trace_rb_cpu_prepare(unsigned int cpu, struct hlist_node *node)
 	return 0;
 }
 
+#ifdef CONFIG_FTRACE_KHO
+static int trace_kho_write_cpu(void *fdt, struct trace_buffer *buffer, int cpu)
+{
+	int i = 0;
+	int err = 0;
+	struct list_head *tmp;
+	const char compatible[] = "ftrace,cpu-v1";
+	char name[] = "cpuffffffff";
+	int nr_pages;
+	struct ring_buffer_per_cpu *cpu_buffer;
+	bool first_loop = true;
+	struct kho_mem *mem;
+	uint64_t mem_len;
+
+	if (!cpumask_test_cpu(cpu, buffer->cpumask))
+		return 0;
+
+	cpu_buffer = buffer->buffers[cpu];
+
+	nr_pages = cpu_buffer->nr_pages;
+	mem_len = sizeof(*mem) * nr_pages * 2;
+	mem = vmalloc(mem_len);
+
+	snprintf(name, sizeof(name), "cpu%x", cpu);
+
+	err |= fdt_begin_node(fdt, name);
+	err |= fdt_property(fdt, "compatible", compatible, sizeof(compatible));
+	err |= fdt_property(fdt, "cpu", &cpu, sizeof(cpu));
+
+	for (tmp = rb_list_head(cpu_buffer->pages);
+	     tmp != rb_list_head(cpu_buffer->pages) || first_loop;
+	     tmp = rb_list_head(tmp->next), first_loop = false) {
+		struct buffer_page *bpage = (struct buffer_page *)tmp;
+
+		/* Ring is larger than it should be? */
+		if (i >= (nr_pages * 2)) {
+			pr_err("ftrace ring has more pages than nr_pages (%d / %d)", i, nr_pages);
+			err = -EINVAL;
+			break;
+		}
+
+		/* First describe the bpage */
+		mem[i++] = (struct kho_mem) {
+			.addr = __pa(bpage),
+			.len = sizeof(*bpage)
+		};
+
+		/* Then the data page */
+		mem[i++] = (struct kho_mem) {
+			.addr = __pa(bpage->page),
+			.len = PAGE_SIZE
+		};
+	}
+
+	err |= fdt_property(fdt, "mem", mem, mem_len);
+	err |= fdt_end_node(fdt);
+
+	vfree(mem);
+	return err;
+}
+
+int trace_kho_write_trace_buffer(void *fdt, struct trace_buffer *buffer)
+{
+	const char compatible[] = "ftrace,buffer-v1";
+	char name[] = "buffer";
+	int err;
+	int i;
+
+	err = fdt_begin_node(fdt, name);
+	if (err)
+		return err;
+
+	fdt_property(fdt, "compatible", compatible, sizeof(compatible));
+
+	for (i = 0; i < buffer->cpus; i++) {
+		err = trace_kho_write_cpu(fdt, buffer, i);
+		if (err)
+			return err;
+	}
+
+	err =  fdt_end_node(fdt);
+	if (err)
+		return err;
+
+	return 0;
+}
+#endif
+
 #ifdef CONFIG_RING_BUFFER_STARTUP_TEST
 /*
  * This is a basic integrity check of the ring buffer.

@@ -10597,6 +10597,21 @@ void __init early_trace_init(void)
 }
 
 #ifdef CONFIG_FTRACE_KHO
+static int trace_kho_write_trace_array(void *fdt, struct trace_array *tr)
+{
+	const char *name = tr->name ? tr->name : "global_trace";
+	const char compatible[] = "ftrace,array-v1";
+	int err = 0;
+
+	err |= fdt_begin_node(fdt, name);
+	err |= fdt_property(fdt, "compatible", compatible, sizeof(compatible));
+	err |= fdt_property(fdt, "trace_flags", &tr->trace_flags, sizeof(tr->trace_flags));
+	err |= trace_kho_write_trace_buffer(fdt, tr->array_buffer.buffer);
+	err |= fdt_end_node(fdt);
+
+	return err;
+}
+
 static int trace_kho_notifier(struct notifier_block *self,
 			      unsigned long cmd,
 			      void *v)

@@ -10623,6 +10638,7 @@ static int trace_kho_notifier(struct notifier_block *self,
 
 	err |= fdt_begin_node(fdt, "ftrace");
 	err |= fdt_property(fdt, "compatible", compatible, sizeof(compatible));
+	err |= trace_kho_write_trace_array(fdt, &global_trace);
 	err |= fdt_end_node(fdt);
 
 	if (!err) {