[PATCH 12/13] 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 3164f327d4d8..0b44636b6eea 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"
@@ -1057,6 +1059,124 @@ static int dump_on_oops_show(struct seq_file *s, void *unused)
 }
 DEFINE_SHOW_STORE_ATTRIBUTE(dump_on_oops);
 
+static char trace_remote_cmdline[COMMAND_LINE_SIZE];
+
+static int __init set_trace_remote_cmdline(char *str)
+{
+	static int idx;
+
+	if (!str)
+		return 0;
+
+	strscpy(trace_remote_cmdline + idx, str, COMMAND_LINE_SIZE - idx);
+	idx += strlen(str);
+	trace_remote_cmdline[idx++] = '\t';
+	return 1;
+}
+__setup("trace_remote=", set_trace_remote_cmdline);
+
+static void trace_remote_apply_cmdline_opts(struct trace_remote *remote, char *cmdline)
+{
+	bool printk_on = false;
+	char *opt;
+	int ret;
+
+	while ((opt = strsep(&cmdline, "^"))) {
+		if (!*opt)
+			continue;
+
+		if (!strcmp(opt, "dump_on_oops")) {
+			remote->panic_on = true;
+		} else if (!strcmp(opt, "printk")) {
+			printk_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 {
+			pr_warn("Unknown trace remote option '%s'\n", opt);
+		}
+	}
+
+	if (printk_on) {
+		ret = trace_remote_enable_printk(remote, true);
+		if (ret)
+			pr_warn("Failed to enable trace remote printk (%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 struct dentry *tracefs_root;
 static DEFINE_MUTEX(tracefs_lock);
 static u64 tracefs_root_count;
@@ -1228,6 +1348,7 @@ int trace_remote_register(const char *name, struct trace_remote_callbacks *cbs,
 		goto err_unregister_events;
 	}
 
+	trace_remote_apply_cmdline(name, remote);
 	no_free_ptr(remote);
 	return 0;
 
@@ -1708,3 +1829,15 @@ 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;
+}
-- 
2.54.0.1032.g2f8565e1d1-goog