tracing: Use seq_buf for string concatenation

In preparation for removing the strlcat API[1], replace the string concatenation logic with a struct seq_buf, which tracks the current position and the remaining space internally. Use seq_buf_str() to NUL-terminate before passing to early_enable_events(). Link: https://github.com/KSPP/linux/issues/370 [1]

Woradorn Laodhanadhaworn committed 4 months ago

Commit efdcfd91 parent dca6a221 file · +13 −3Browse files

Showing the changes to kernel (1 of 1 file). Show all

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kernel/trace/trace_events.c+13−3

@@ -14,6 +14,7 @@ · 13 unmodified lines
14	14	#include <linux/workqueue.h>
15	15	#include <linux/security.h>
16	16	#include <linux/spinlock.h>
	17	+#include <linux/seq_buf.h>
17	18	#include <linux/kthread.h>
18	19	#include <linux/tracefs.h>
19	20	#include <linux/uaccess.h>
@@ -4604,13 +4605,20 @@ extern struct trace_event_call *__start_ftrace_events[]; · 4584 unmodified lines
4604	4605	extern struct trace_event_call *__stop_ftrace_events[];
4605	4606
4606	4607	static char bootup_event_buf[COMMAND_LINE_SIZE] __initdata;
	4608	+static struct seq_buf bootup_event_seq __initdata = {
	4609	+ .buffer = bootup_event_buf,
	4610	+ .size = sizeof(bootup_event_buf),
	4611	+};
4607	4612
4608	4613	static __init int setup_trace_event(char *str)
4609	4614	{
4610		− if (bootup_event_buf[0] != '\0')
4611		− strlcat(bootup_event_buf, ",", COMMAND_LINE_SIZE);
	4615	+ if (seq_buf_used(&bootup_event_seq) > 0)
	4616	+ seq_buf_puts(&bootup_event_seq, ",");
	4617	+
	4618	+ seq_buf_puts(&bootup_event_seq, str);
4612	4619
4613		− strlcat(bootup_event_buf, str, COMMAND_LINE_SIZE);
	4620	+ if (seq_buf_has_overflowed(&bootup_event_seq))
	4621	+ return -ENOMEM;
4614	4622
4615	4623	trace_set_ring_buffer_expanded(NULL);
4616	4624	disable_tracing_selftest("running event tracing");
@@ -4869,6 +4877,7 @@ static __init int event_trace_enable(void) · 252 unmodified lines
4869	4877	*/
4870	4878	__trace_early_add_events(tr);
4871	4879
	4880	+ seq_buf_str(&bootup_event_seq);
4872	4881	early_enable_events(tr, bootup_event_buf, false);
4873	4882
4874	4883	trace_printk_start_comm();
@@ -4897,6 +4906,7 @@ static __init int event_trace_enable_again(void) · 22 unmodified lines
4897	4906	if (!tr)
4898	4907	return -ENODEV;
4899	4908
	4909	+ seq_buf_str(&bootup_event_seq);
4900	4910	early_enable_events(tr, bootup_event_buf, true);
4901	4911
4902	4912	return 0;