ktrace: Add help infrastructure

Add a help function that will be used to describe the commands in more
detail. Currently a very limited help is added, but it will be extended.

Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

4 files changed, 94 insertions, 0 deletions

diff --git a/include/ktrace.h b/include/ktrace.h
index 11e1b83..cb0d537 100644
--- a/include/ktrace.h
+++ b/include/ktrace.h
@@ -12,6 +12,18 @@
 
 #define ARRAY_SIZE(array) (sizeof(array) / sizeof((array)[0]))
 
+struct ktrace_commands {
+	const char		*command;
+	const char		*usage;
+	const char		*help;
+};
+
+int help_completion(struct ccli *ccli, const char *command,
+		    const char *line, int word,
+		    char *match, char ***list, void *data);
+int cmd_help(struct ccli *ccli, const char *command, const char *line,
+	     void *data, int argc, char **argv);
+
 int create_completion(struct ccli *ccli, const char *command,
 		      const char *line, int word,
 		      char *match, char ***list, void *data);
diff --git a/src/Makefile b/src/Makefile
index 8d4a373..8f282a0 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -4,6 +4,7 @@ include $(src)/scripts/utils.mk
 
 OBJS =
 OBJS += ktrace.o
+OBJS += help.o
 OBJS += create.o
 OBJS += enable.o
 
diff --git a/src/help.c b/src/help.c
new file mode 100644
index 0000000..05ce439
--- /dev/null
+++ b/src/help.c
@@ -0,0 +1,78 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2022 Google Inc, Steven Rostedt <rostedt@goodmis.org>
+ */
+#include "ktrace.h"
+
+static struct ktrace_commands ktrace_cmds[] = 
+{
+	{
+		"create",
+		"create (kprobe|eprobe|synthetic) options",
+		"  kprobe - to create a kernel probe event.\n"
+		"  eprobe - to create an event on top of another event.\n"
+		"  synthetic - to create a synthetic event",
+	},
+	{
+		"enable",
+		"enable (tracing|event)",
+		"  tracing - to enable tracing if it is stopped.\n"
+		"  event - to enable an event"
+	},
+	{
+		"disable",
+		"disable (tracing|event)",
+		"  tracing - to disable tracing, just stops writing to the ring buffer.\n"
+		"  event - stop an event."
+	}
+};
+
+int cmd_help(struct ccli *ccli, const char *command, const char *line,
+	     void *data, int argc, char **argv)
+{
+	int l = 1;
+	int i;
+
+	if (argc < 2) {
+		for (i = 0; l > 0 && i < ARRAY_SIZE(ktrace_cmds); i++) {
+			if (i)
+				l = ccli_page(ccli, l, "\n");
+			l = ccli_page(ccli, l, "command: %s\n",
+					 ktrace_cmds[i].command);
+			l = ccli_page(ccli, l, "usage: %s\n",
+					 ktrace_cmds[i].usage);
+			l = ccli_page(ccli, l, "%s\n",
+					 ktrace_cmds[i].help);
+		}
+		return 0;
+	}
+
+	for (i = 0; l > 0 && i < ARRAY_SIZE(ktrace_cmds); i++) {
+		if (strcmp(argv[1], ktrace_cmds[i].command) == 0) {
+			l = ccli_page(ccli, l, "usage: %s\n",
+					 ktrace_cmds[i].usage);
+			l = ccli_page(ccli, l, "%s\n",
+					 ktrace_cmds[i].help);
+			return 0;
+		}
+	}
+	return 0;
+}
+
+int help_completion(struct ccli *ccli, const char *command,
+		    const char *line, int word,
+		    char *match, char ***list, void *data)
+{
+	int cnt = 0;
+	int ret = 0;
+	int i;
+
+	if (word == 1) {
+		for (i = 0; ret >= 0 && i < ARRAY_SIZE(ktrace_cmds); i++)
+			ret = ccli_list_add(ccli, list, &cnt,
+					    ktrace_cmds[i].command);
+		return ret;
+	}
+	return 0;
+}
+
diff --git a/src/ktrace.c b/src/ktrace.c
index 3be95bb..7874ff0 100644
--- a/src/ktrace.c
+++ b/src/ktrace.c
@@ -106,6 +106,9 @@ int main (int argc, char **argv)
 
 	load_history(ccli);
 
+	ccli_register_command(ccli, "help", cmd_help, NULL);
+	ccli_register_completion(ccli, "help", help_completion);
+
 	ccli_register_command(ccli, "create", cmd_create, tep);
 	ccli_register_completion(ccli, "create", create_completion);