[PATCH v2 1/2] tracing: preserve repeated boot-time tracing parameters

[Wesley Atwell <atwellwea@gmail.com>]

Bootconfig expands arrays into repeated param=value entries, and the
kernel command line can repeat the same tracing parameter as well.
Several tracing __setup() handlers still overwrite their boot buffers,
so only the last ftrace filter, graph filter, trace option, kprobe
event, or trace trigger entry survives boot.

Preserve repeated values in the format their existing parsers already
consume: comma-delimited lists for ftrace filters and trace options,
semicolon-delimited lists for kprobe events, and per-chunk parsing for
trace_trigger=. The trace_trigger parser tokenizes its storage in
place, so keep a running length and only parse the newly appended
chunk into bootup_triggers[].

Fixes: 2af15d6a44b8 ("ftrace: add kernel command line function filtering")
Fixes: 7bcfaf54f591 ("tracing: Add trace_options kernel command line parameter")
Fixes: a01fdc897fa5 ("tracing: Add trace_trigger kernel command line option")
Fixes: 970988e19eb0 ("tracing/kprobe: Add kprobe_event= boot parameter")
Signed-off-by: Wesley Atwell <atwellwea@gmail.com>
---
v2:
- No changes

 kernel/trace/ftrace.c       | 29 +++++++++++++++++++++++++----
 kernel/trace/trace.c        | 23 ++++++++++++++++++++++-
 kernel/trace/trace_events.c | 23 ++++++++++++++++++++---
 kernel/trace/trace_kprobe.c | 23 ++++++++++++++++++++++-
 4 files changed, 89 insertions(+), 9 deletions(-)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 8df69e702706..cdd46f639333 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -6835,13 +6835,34 @@ EXPORT_SYMBOL_GPL(ftrace_set_global_notrace);
 static char ftrace_notrace_buf[FTRACE_FILTER_SIZE] __initdata;
 static char ftrace_filter_buf[FTRACE_FILTER_SIZE] __initdata;
 
+static void __init append_ftrace_boot_param(char *buf, const char *str,
+					    char sep)
+{
+	size_t len, str_len;
+
+	if (buf[0] == '\0') {
+		strscpy(buf, str, FTRACE_FILTER_SIZE);
+		return;
+	}
+
+	len = strlen(buf);
+	str_len = strlen(str);
+	if (!str_len)
+		return;
+	if (str_len >= FTRACE_FILTER_SIZE - len - 1)
+		return;
+
+	buf[len] = sep;
+	strscpy(buf + len + 1, str, FTRACE_FILTER_SIZE - len - 1);
+}
+
 /* Used by function selftest to not test if filter is set */
 bool ftrace_filter_param __initdata;
 
 static int __init set_ftrace_notrace(char *str)
 {
 	ftrace_filter_param = true;
-	strscpy(ftrace_notrace_buf, str, FTRACE_FILTER_SIZE);
+	append_ftrace_boot_param(ftrace_notrace_buf, str, ',');
 	return 1;
 }
 __setup("ftrace_notrace=", set_ftrace_notrace);
@@ -6849,7 +6870,7 @@ __setup("ftrace_notrace=", set_ftrace_notrace);
 static int __init set_ftrace_filter(char *str)
 {
 	ftrace_filter_param = true;
-	strscpy(ftrace_filter_buf, str, FTRACE_FILTER_SIZE);
+	append_ftrace_boot_param(ftrace_filter_buf, str, ',');
 	return 1;
 }
 __setup("ftrace_filter=", set_ftrace_filter);
@@ -6861,14 +6882,14 @@ static int ftrace_graph_set_hash(struct ftrace_hash *hash, char *buffer);
 
 static int __init set_graph_function(char *str)
 {
-	strscpy(ftrace_graph_buf, str, FTRACE_FILTER_SIZE);
+	append_ftrace_boot_param(ftrace_graph_buf, str, ',');
 	return 1;
 }
 __setup("ftrace_graph_filter=", set_graph_function);
 
 static int __init set_graph_notrace_function(char *str)
 {
-	strscpy(ftrace_graph_notrace_buf, str, FTRACE_FILTER_SIZE);
+	append_ftrace_boot_param(ftrace_graph_notrace_buf, str, ',');
 	return 1;
 }
 __setup("ftrace_graph_notrace=", set_graph_notrace_function);
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index ebd996f8710e..42d03d36ae39 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -327,9 +327,30 @@ __setup("trace_instance=", boot_instance);
 
 static char trace_boot_options_buf[MAX_TRACER_SIZE] __initdata;
 
+static void __init append_trace_boot_options(const char *str)
+{
+	size_t len, str_len;
+
+	if (trace_boot_options_buf[0] == '\0') {
+		strscpy(trace_boot_options_buf, str, MAX_TRACER_SIZE);
+		return;
+	}
+
+	len = strlen(trace_boot_options_buf);
+	str_len = strlen(str);
+	if (!str_len)
+		return;
+	if (str_len >= MAX_TRACER_SIZE - len - 1)
+		return;
+
+	trace_boot_options_buf[len] = ',';
+	strscpy(trace_boot_options_buf + len + 1, str,
+		MAX_TRACER_SIZE - len - 1);
+}
+
 static int __init set_trace_boot_options(char *str)
 {
-	strscpy(trace_boot_options_buf, str, MAX_TRACER_SIZE);
+	append_trace_boot_options(str);
 	return 1;
 }
 __setup("trace_options=", set_trace_boot_options);
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 249d1cba72c0..c3981f62e4bc 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -3679,20 +3679,37 @@ static struct boot_triggers {
 } bootup_triggers[MAX_BOOT_TRIGGERS];
 
 static char bootup_trigger_buf[COMMAND_LINE_SIZE];
+static int bootup_trigger_buf_len;
 static int nr_boot_triggers;
 
 static __init int setup_trace_triggers(char *str)
 {
 	char *trigger;
 	char *buf;
+	ssize_t copied;
 	int i;
+	int start;
 
-	strscpy(bootup_trigger_buf, str, COMMAND_LINE_SIZE);
+	if (bootup_trigger_buf_len >= COMMAND_LINE_SIZE)
+		return 1;
+
+	start = bootup_trigger_buf_len;
+	if (start && !*str)
+		return 1;
+
+	copied = strscpy(bootup_trigger_buf + start, str,
+			 COMMAND_LINE_SIZE - start);
+	if (copied < 0) {
+		if (start)
+			return 1;
+		copied = strlen(bootup_trigger_buf + start);
+	}
+	bootup_trigger_buf_len += copied + 1;
 	trace_set_ring_buffer_expanded(NULL);
 	disable_tracing_selftest("running event triggers");
 
-	buf = bootup_trigger_buf;
-	for (i = 0; i < MAX_BOOT_TRIGGERS; i++) {
+	buf = bootup_trigger_buf + start;
+	for (i = nr_boot_triggers; i < MAX_BOOT_TRIGGERS; i++) {
 		trigger = strsep(&buf, ",");
 		if (!trigger)
 			break;
diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index a5dbb72528e0..a63a56b55570 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -29,9 +29,30 @@
 /* Kprobe early definition from command line */
 static char kprobe_boot_events_buf[COMMAND_LINE_SIZE] __initdata;
 
+static void __init append_kprobe_boot_event(const char *str)
+{
+	size_t len, str_len;
+
+	if (kprobe_boot_events_buf[0] == '\0') {
+		strscpy(kprobe_boot_events_buf, str, COMMAND_LINE_SIZE);
+		return;
+	}
+
+	len = strlen(kprobe_boot_events_buf);
+	str_len = strlen(str);
+	if (!str_len)
+		return;
+	if (str_len >= COMMAND_LINE_SIZE - len - 1)
+		return;
+
+	kprobe_boot_events_buf[len] = ';';
+	strscpy(kprobe_boot_events_buf + len + 1, str,
+		COMMAND_LINE_SIZE - len - 1);
+}
+
 static int __init set_kprobe_boot_events(char *str)
 {
-	strscpy(kprobe_boot_events_buf, str, COMMAND_LINE_SIZE);
+	append_kprobe_boot_event(str);
 	disable_tracing_selftest("running kprobe events");
 
 	return 1;
-- 
2.34.1