ftrace.c

 1// SPDX-License-Identifier: GPL-2.0
 2/*
 3 * Simple kernel driver to link kernel Ftrace and an STM device
 4 * Copyright (c) 2016, Linaro Ltd.
 5 *
 6 * STM Ftrace will be registered as a trace_export.
 7 */
 8
 9#include <linux/module.h>
10#include <linux/stm.h>
11#include <linux/trace.h>
12
13#define STM_FTRACE_NR_CHANNELS 1
14#define STM_FTRACE_CHAN 0
15
16static int stm_ftrace_link(struct stm_source_data *data);
17static void stm_ftrace_unlink(struct stm_source_data *data);
18
19static struct stm_ftrace {
20	struct stm_source_data	data;
21	struct trace_export	ftrace;
22} stm_ftrace = {
23	.data	= {
24		.name		= "ftrace",
25		.nr_chans	= STM_FTRACE_NR_CHANNELS,
26		.type		= STM_FTRACE,
27		.link		= stm_ftrace_link,
28		.unlink		= stm_ftrace_unlink,
29	},
30};
31
32/**
33 * stm_ftrace_write() - write data to STM via 'stm_ftrace' source
34 * @buf:	buffer containing the data packet
35 * @len:	length of the data packet
36 */
37static void notrace
38stm_ftrace_write(struct trace_export *export, const void *buf, unsigned int len)
39{
40	struct stm_ftrace *stm = container_of(export, struct stm_ftrace, ftrace);
41	/* This is called from trace system with preemption disabled */
42	unsigned int cpu = smp_processor_id();
43
44	stm_source_write(&stm->data, STM_FTRACE_CHAN + cpu, buf, len);
45}
46
47static int stm_ftrace_link(struct stm_source_data *data)
48{
49	struct stm_ftrace *sf = container_of(data, struct stm_ftrace, data);
50
51	sf->ftrace.write = stm_ftrace_write;
52	sf->ftrace.flags = TRACE_EXPORT_FUNCTION | TRACE_EXPORT_EVENT
53			| TRACE_EXPORT_MARKER;
54
55	return register_ftrace_export(&sf->ftrace);
56}
57
58static void stm_ftrace_unlink(struct stm_source_data *data)
59{
60	struct stm_ftrace *sf = container_of(data, struct stm_ftrace, data);
61
62	unregister_ftrace_export(&sf->ftrace);
63}
64
65static int __init stm_ftrace_init(void)
66{
67	int ret;
68
69	stm_ftrace.data.nr_chans = roundup_pow_of_two(num_possible_cpus());
70	ret = stm_source_register_device(NULL, &stm_ftrace.data);
71	if (ret)
72		pr_err("Failed to register stm_source - ftrace.\n");
73
74	return ret;
75}
76
77static void __exit stm_ftrace_exit(void)
78{
79	stm_source_unregister_device(&stm_ftrace.data);
80}
81
82module_init(stm_ftrace_init);
83module_exit(stm_ftrace_exit);
84
85MODULE_LICENSE("GPL v2");
86MODULE_DESCRIPTION("stm_ftrace driver");
87MODULE_AUTHOR("Chunyan Zhang <zhang.chunyan@linaro.org>");