tracing/boot: Add boot-time tracing

Setup tracing options via extra boot config in addition to kernel
command line.

This adds following commands support. These are applied to
the global trace instance.

 - ftrace.options = OPT1[,OPT2...]
   Enable given ftrace options.

 - ftrace.trace_clock = CLOCK
   Set given CLOCK to ftrace's trace_clock.

 - ftrace.buffer_size = SIZE
   Configure ftrace buffer size to SIZE. You can use "KB" or "MB"
   for that SIZE.

 - ftrace.events = EVENT[, EVENT2...]
   Enable given events on boot. You can use a wild card in EVENT.

 - ftrace.tracer = TRACER
   Set TRACER to current tracer on boot. (e.g. function)

Note that this is NOT replacing the kernel parameters, because
this boot config based setting is later than that. If you want to
trace earlier boot events, you still need kernel parameters.

Link: http://lkml.kernel.org/r/157867237723.17873.17494943526320587488.stgit@devnote2

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

1 files changed, 113 insertions, 0 deletions

diff --git a/kernel/trace/trace_boot.c b/kernel/trace/trace_boot.c
new file mode 100644
index 000000000000..4b41310184df
--- /dev/null
+++ b/kernel/trace/trace_boot.c
@@ -0,0 +1,113 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * trace_boot.c
+ * Tracing kernel boot-time
+ */
+
+#define pr_fmt(fmt)	"trace_boot: " fmt
+
+#include <linux/ftrace.h>
+#include <linux/init.h>
+#include <linux/bootconfig.h>
+
+#include "trace.h"
+
+#define MAX_BUF_LEN 256
+
+extern int trace_set_options(struct trace_array *tr, char *option);
+extern int tracing_set_tracer(struct trace_array *tr, const char *buf);
+extern ssize_t tracing_resize_ring_buffer(struct trace_array *tr,
+					  unsigned long size, int cpu_id);
+
+static void __init
+trace_boot_set_ftrace_options(struct trace_array *tr, struct xbc_node *node)
+{
+	struct xbc_node *anode;
+	const char *p;
+	char buf[MAX_BUF_LEN];
+	unsigned long v = 0;
+
+	/* Common ftrace options */
+	xbc_node_for_each_array_value(node, "options", anode, p) {
+		if (strlcpy(buf, p, ARRAY_SIZE(buf)) >= ARRAY_SIZE(buf)) {
+			pr_err("String is too long: %s\n", p);
+			continue;
+		}
+
+		if (trace_set_options(tr, buf) < 0)
+			pr_err("Failed to set option: %s\n", buf);
+	}
+
+	p = xbc_node_find_value(node, "trace_clock", NULL);
+	if (p && *p != '\0') {
+		if (tracing_set_clock(tr, p) < 0)
+			pr_err("Failed to set trace clock: %s\n", p);
+	}
+
+	p = xbc_node_find_value(node, "buffer_size", NULL);
+	if (p && *p != '\0') {
+		v = memparse(p, NULL);
+		if (v < PAGE_SIZE)
+			pr_err("Buffer size is too small: %s\n", p);
+		if (tracing_resize_ring_buffer(tr, v, RING_BUFFER_ALL_CPUS) < 0)
+			pr_err("Failed to resize trace buffer to %s\n", p);
+	}
+}
+
+#ifdef CONFIG_EVENT_TRACING
+extern int ftrace_set_clr_event(struct trace_array *tr, char *buf, int set);
+
+static void __init
+trace_boot_enable_events(struct trace_array *tr, struct xbc_node *node)
+{
+	struct xbc_node *anode;
+	char buf[MAX_BUF_LEN];
+	const char *p;
+
+	xbc_node_for_each_array_value(node, "events", anode, p) {
+		if (strlcpy(buf, p, ARRAY_SIZE(buf)) >= ARRAY_SIZE(buf)) {
+			pr_err("String is too long: %s\n", p);
+			continue;
+		}
+
+		if (ftrace_set_clr_event(tr, buf, 1) < 0)
+			pr_err("Failed to enable event: %s\n", p);
+	}
+}
+#else
+#define trace_boot_enable_events(tr, node) do {} while (0)
+#endif
+
+static void __init
+trace_boot_enable_tracer(struct trace_array *tr, struct xbc_node *node)
+{
+	const char *p;
+
+	p = xbc_node_find_value(node, "tracer", NULL);
+	if (p && *p != '\0') {
+		if (tracing_set_tracer(tr, p) < 0)
+			pr_err("Failed to set given tracer: %s\n", p);
+	}
+}
+
+static int __init trace_boot_init(void)
+{
+	struct xbc_node *trace_node;
+	struct trace_array *tr;
+
+	trace_node = xbc_find_node("ftrace");
+	if (!trace_node)
+		return 0;
+
+	tr = top_trace_array();
+	if (!tr)
+		return 0;
+
+	trace_boot_set_ftrace_options(tr, trace_node);
+	trace_boot_enable_events(tr, trace_node);
+	trace_boot_enable_tracer(tr, trace_node);
+
+	return 0;
+}
+
+fs_initcall(trace_boot_init);