[PATCH v3 1/2] tracing: preserve repeated boot-time tracing parameters

[Wesley Atwell <atwellwea@gmail.com>]

Some tracing boot parameters already accept delimited value lists, but
their __setup() handlers keep only the last instance seen at boot.
Make repeated instances append to the same boot-time buffer in the
format each parser already consumes, and document that behavior in
admin-guide/kernel-parameters.txt.

Use a shared trace_append_boot_param() helper for the ftrace filters,
trace_options, and kprobe_event boot parameters. trace_trigger=
tokenizes its backing storage in place, so keep a running offset and
only parse the newly appended chunk into bootup_triggers[].

This also lets Bootconfig array values work naturally when they expand
to repeated param=value entries.

Signed-off-by: Wesley Atwell <atwellwea@gmail.com>
---
 .../admin-guide/kernel-parameters.txt         | 18 ++++++++++--
 kernel/trace/ftrace.c                         | 12 +++++---
 kernel/trace/trace.c                          |  3 +-
 kernel/trace/trace.h                          | 29 +++++++++++++++++++
 kernel/trace/trace_events.c                   | 26 +++++++++++++++--
 kernel/trace/trace_kprobe.c                   |  3 +-
 6 files changed, 79 insertions(+), 12 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 55ffc0f8858a..203863c1839b 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1803,13 +1803,15 @@ Kernel parameters
 			tracer at boot up. function-list is a comma-separated
 			list of functions. This list can be changed at run
 			time by the set_ftrace_filter file in the debugfs
-			tracing directory.
+			tracing directory. Repeated instances append more
+			functions to the same list.
 
 	ftrace_notrace=[function-list]
 			[FTRACE] Do not trace the functions specified in
 			function-list. This list can be changed at run time
 			by the set_ftrace_notrace file in the debugfs
-			tracing directory.
+			tracing directory. Repeated instances append more
+			functions to the same list.
 
 	ftrace_graph_filter=[function-list]
 			[FTRACE] Limit the top level callers functions traced
@@ -1817,12 +1819,16 @@ Kernel parameters
 			function-list is a comma-separated list of functions
 			that can be changed at run time by the
 			set_graph_function file in the debugfs tracing directory.
+			Repeated instances append more functions to the same
+			list.
 
 	ftrace_graph_notrace=[function-list]
 			[FTRACE] Do not trace from the functions specified in
 			function-list.  This list is a comma-separated list of
 			functions that can be changed at run time by the
 			set_graph_notrace file in the debugfs tracing directory.
+			Repeated instances append more functions to the same
+			list.
 
 	ftrace_graph_max_depth=<uint>
 			[FTRACE] Used with the function graph tracer. This is
@@ -3053,6 +3059,8 @@ Kernel parameters
 			The probe-list is a semicolon delimited list of probe
 			definitions. Each definition is same as kprobe_events
 			interface, but the parameters are comma delimited.
+			Repeated instances append more probe definitions to
+			the same boot-time list.
 			For example, to add a kprobe event on vfs_read with
 			arg1 and arg2, add to the command line;
 
@@ -7820,6 +7828,9 @@ Kernel parameters
 
 			    /sys/kernel/tracing/trace_options
 
+			Repeated instances append more options to the same
+			boot-time list.
+
 			For example, to enable stacktrace option (to dump the
 			stack trace of each event), add to the command line:
 
@@ -7831,7 +7842,8 @@ Kernel parameters
 	trace_trigger=[trigger-list]
 			[FTRACE] Add an event trigger on specific events.
 			Set a trigger on top of a specific event, with an optional
-			filter.
+			filter. Repeated instances append more triggers to
+			the same boot-time list.
 
 			The format is "trace_trigger=<event>.<trigger>[ if <filter>],..."
 			Where more than one trigger may be specified that are comma delimited.
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 8df69e702706..d0a486b63ed6 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -6841,7 +6841,8 @@ 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);
+	trace_append_boot_param(ftrace_notrace_buf, str, ',',
+				FTRACE_FILTER_SIZE);
 	return 1;
 }
 __setup("ftrace_notrace=", set_ftrace_notrace);
@@ -6849,7 +6850,8 @@ __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);
+	trace_append_boot_param(ftrace_filter_buf, str, ',',
+				FTRACE_FILTER_SIZE);
 	return 1;
 }
 __setup("ftrace_filter=", set_ftrace_filter);
@@ -6861,14 +6863,16 @@ 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);
+	trace_append_boot_param(ftrace_graph_buf, str, ',',
+				FTRACE_FILTER_SIZE);
 	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);
+	trace_append_boot_param(ftrace_graph_notrace_buf, str, ',',
+				FTRACE_FILTER_SIZE);
 	return 1;
 }
 __setup("ftrace_graph_notrace=", set_graph_notrace_function);
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index ebd996f8710e..5086239a75dc 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -329,7 +329,8 @@ static char trace_boot_options_buf[MAX_TRACER_SIZE] __initdata;
 
 static int __init set_trace_boot_options(char *str)
 {
-	strscpy(trace_boot_options_buf, str, MAX_TRACER_SIZE);
+	trace_append_boot_param(trace_boot_options_buf, str, ',',
+				MAX_TRACER_SIZE);
 	return 1;
 }
 __setup("trace_options=", set_trace_boot_options);
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index b8f3804586a0..4f5abac4bd19 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -23,6 +23,7 @@
 #include <linux/once_lite.h>
 #include <linux/ftrace_regs.h>
 #include <linux/llist.h>
+#include <linux/string.h>
 
 #include "pid_list.h"
 
@@ -262,6 +263,34 @@ static inline bool still_need_pid_events(int type, struct trace_pid_list *pid_li
 		(!(type & TRACE_NO_PIDS) && no_pid_list);
 }
 
+/*
+ * Repeated boot parameters, including Bootconfig array expansions, need
+ * to stay in the delimiter form that the existing parser consumes.
+ */
+static inline void __init trace_append_boot_param(char *buf, const char *str,
+						  char sep, size_t size)
+{
+	size_t len, str_len;
+
+	if (buf[0] == '\0') {
+		strscpy(buf, str, size);
+		return;
+	}
+
+	str_len = strlen(str);
+	if (!str_len)
+		return;
+
+	len = strlen(buf);
+	if (len >= size - 1)
+		return;
+	if (str_len >= size - len - 1)
+		return;
+
+	buf[len] = sep;
+	strscpy(buf + len + 1, str, size - len - 1);
+}
+
 typedef bool (*cond_update_fn_t)(struct trace_array *tr, void *cond_data);
 
 /**
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 249d1cba72c0..5f72be33f2d1 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -3679,20 +3679,40 @@ static struct boot_triggers {
 } bootup_triggers[MAX_BOOT_TRIGGERS];
 
 static char bootup_trigger_buf[COMMAND_LINE_SIZE];
+static size_t bootup_trigger_buf_len;
 static int nr_boot_triggers;
 
 static __init int setup_trace_triggers(char *str)
 {
 	char *trigger;
 	char *buf;
+	size_t start, str_len;
 	int i;
 
-	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;
+
+	str_len = strlen(str);
+	if (start && str_len >= COMMAND_LINE_SIZE - start)
+		return 1;
+
+	/*
+	 * trace_trigger= parsing tokenizes the backing storage in place.
+	 * Copy each repeated parameter into fresh space and only parse that
+	 * newly copied chunk here.
+	 */
+	trace_append_boot_param(bootup_trigger_buf + start, str, '\0',
+				COMMAND_LINE_SIZE - start);
+	bootup_trigger_buf_len += strlen(bootup_trigger_buf + start) + 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..e9f1c55aea64 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -31,7 +31,8 @@ static char kprobe_boot_events_buf[COMMAND_LINE_SIZE] __initdata;
 
 static int __init set_kprobe_boot_events(char *str)
 {
-	strscpy(kprobe_boot_events_buf, str, COMMAND_LINE_SIZE);
+	trace_append_boot_param(kprobe_boot_events_buf, str, ';',
+				COMMAND_LINE_SIZE);
 	disable_tracing_selftest("running kprobe events");
 
 	return 1;
-- 
2.34.1