[PATCH v4 16/18] tracing/remotes: Add trace_remote cmdline options

[Vincent Donnefort <vdonnefort@google.com>]

Following the same format as trace_instance, add a cmdline to configure
a trace remote on registration:

  trace_remote=<remote>^<opt1>^<opt2>,<evt1>,<evt2>

Enabling events automatically turns on tracing.

Signed-off-by: Vincent Donnefort <vdonnefort@google.com>

diff --git a/kernel/trace/trace_remote.c b/kernel/trace/trace_remote.c
index ccdac9fa106a..e72ee6ecf473 100644
--- a/kernel/trace/trace_remote.c
+++ b/kernel/trace/trace_remote.c
@@ -13,6 +13,8 @@
 #include <linux/trace_seq.h>
 #include <linux/types.h>
 
+#include <asm/setup.h>
+
 #include "trace.h"
 
 #define TRACEFS_DIR		"remotes"
@@ -1169,6 +1171,125 @@ static int poll_ms_show(struct seq_file *s, void *unused)
 }
 DEFINE_TRACE_REMOTE_ATTRIBUTE(poll_ms);
 
+static char trace_remote_cmdline[COMMAND_LINE_SIZE];
+
+static int __init set_trace_remote_cmdline(char *str)
+{
+	trace_append_boot_param(trace_remote_cmdline, str, '\t', COMMAND_LINE_SIZE);
+	return 1;
+}
+__setup("trace_remote=", set_trace_remote_cmdline);
+
+static void trace_remote_apply_cmdline_opts(struct trace_remote *remote, char *cmdline)
+{
+	bool dmesg_on = false;
+	char *opt;
+	int ret;
+
+	while ((opt = strsep(&cmdline, "^"))) {
+		if (!*opt)
+			continue;
+
+		if (!strcmp(opt, "dump_on_panic")) {
+			remote->panic_on = true;
+		} else if (!strcmp(opt, "dmesg")) {
+			dmesg_on = true;
+		} else if (!strncmp(opt, "buf_size=", 9)) {
+			/* buf_size can only be applied if the buffer is unloaded */
+			if (!WARN_ON(trace_remote_loaded(remote)))
+				remote->trace_buffer_size = memparse(opt + 9, NULL);
+		} else if (!strncmp(opt, "poll=", 5)) {
+			unsigned int poll_ms;
+
+			if (!kstrtouint(opt + 5, 10, &poll_ms) && poll_ms > 0)
+				remote->poll_ms = poll_ms;
+			else
+				pr_warn("Invalid trace remote poll '%s'\n", opt);
+		} else {
+			pr_warn("Unknown trace remote option '%s'\n", opt);
+		}
+	}
+
+	if (dmesg_on) {
+		ret = trace_remote_enable_dmesg(remote, true);
+		if (ret)
+			pr_warn("Failed to enable trace remote dmesg (%d)\n", ret);
+	}
+}
+
+static struct remote_event *
+trace_remote_find_event_by_name(struct trace_remote *remote, const char *name);
+
+static int
+trace_remote_enable_event(struct trace_remote *remote, struct remote_event *evt, bool enable);
+
+static void trace_remote_apply_cmdline_events(struct trace_remote *remote, char *cmdline)
+{
+	bool tracing_on = false;
+	char *token;
+	int ret;
+
+	while ((token = strsep(&cmdline, ","))) {
+		struct remote_event *evt;
+
+		if (!*token)
+			continue;
+
+		evt = trace_remote_find_event_by_name(remote, token);
+		if (!evt) {
+			pr_warn("trace remote event '%s' not found\n", token);
+			continue;
+		}
+
+		ret = trace_remote_enable_event(remote, evt, true);
+		if (ret)
+			pr_warn("Failed to enable trace remote event '%s' (%d)\n", token, ret);
+		else
+			tracing_on = true;
+	}
+
+	if (tracing_on) {
+		ret = trace_remote_enable_tracing(remote);
+		if (ret)
+			pr_warn("Failed to enable trace remote tracing (%d)\n", ret);
+	}
+}
+
+static void trace_remote_apply_cmdline(const char *name, struct trace_remote *remote)
+{
+	char *cmdline __free(kfree) = NULL;
+	char *events_cmdline = NULL;
+	char *opts_cmdline = NULL;
+	char *curr, *next;
+
+	if (!trace_remote_cmdline[0])
+		return;
+
+	cmdline = kstrdup(trace_remote_cmdline, GFP_KERNEL);
+	if (!cmdline)
+		return;
+
+	next = cmdline;
+	while ((curr = strsep(&next, "\t"))) {
+		char *token = strsep(&curr, ",");
+		char *rname = strsep(&token, "^");
+
+		if (strcmp(rname, name) == 0) {
+			opts_cmdline = token;
+			events_cmdline = curr;
+			break;
+		}
+	}
+
+	guard(mutex)(&remote->lock);
+
+	if (opts_cmdline)
+		trace_remote_apply_cmdline_opts(remote, opts_cmdline);
+	if (events_cmdline)
+		trace_remote_apply_cmdline_events(remote, events_cmdline);
+}
+
+
 static int trace_remote_init_tracefs(const char *name, struct trace_remote *remote)
 {
 	struct dentry *remote_d, *percpu_d, *d;
@@ -1345,6 +1466,7 @@ int trace_remote_register(const char *name, struct trace_remote_callbacks *cbs,
 	}
 
 	list_add(&remote->node, &trace_remotes);
+	trace_remote_apply_cmdline(name, remote);
 	retain_and_null_ptr(remote);
 
 	return 0;
@@ -1828,3 +1950,15 @@ static struct remote_event *trace_remote_find_event(struct trace_remote *remote,
 	return bsearch((const void *)(unsigned long)id, remote->events, remote->nr_events,
 		       sizeof(*remote->events), __cmp_events);
 }
+
+static struct remote_event *
+trace_remote_find_event_by_name(struct trace_remote *remote, const char *name)
+{
+	int i;
+
+	for (i = 0; i < remote->nr_events; i++) {
+		if (!strcmp(remote->events[i].name, name))
+			return &remote->events[i];
+	}
+	return NULL;
+}
-- 
2.55.0.571.g244d577d93-goog