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tracing: Add hook to function tracing for other subsystems to use

Currently Function traces can be only exported to the ring buffer. This adds a trace_export concept which can process traces and export them to a registered destination as an addition to the current one that outputs to Ftrace - i.e. ring buffer. In this way, if we want function traces to be sent to other destinations rather than only to the ring buffer, we just need to register a new trace_export and implement its own .write() function for writing traces to storage. With this patch, only function tracing (trace type is TRACE_FN) is supported. Link: http://lkml.kernel.org/r/1479715043-6534-2-git-send-email-zhang.chunyan@linaro.org

Chunyan Zhang committed 9 years ago

Commit 478409d1 parent 153aae52 files · +156 −1Browse files

Unified · Split

2 files
  1. include/linux/trace.h +28 −0
  2. kernel/trace/trace.c +128 −1
include/linux/trace.h+28−0
@@ -0,0 +1,28 @@
1#ifndef _LINUX_TRACE_H
2#define _LINUX_TRACE_H
3
4#ifdef CONFIG_TRACING
5/*
6 * The trace export - an export of Ftrace output. The trace_export
7 * can process traces and export them to a registered destination as
8 * an addition to the current only output of Ftrace - i.e. ring buffer.
9 *
10 * If you want traces to be sent to some other place rather than ring
11 * buffer only, just need to register a new trace_export and implement
12 * its own .write() function for writing traces to the storage.
13 *
14 * next - pointer to the next trace_export
15 * write - copy traces which have been delt with ->commit() to
16 * the destination
17 */
18struct trace_export {
19 struct trace_export __rcu *next;
20 void (*write)(const void *, unsigned int);
21};
22
23int register_ftrace_export(struct trace_export *export);
24int unregister_ftrace_export(struct trace_export *export);
25
26#endif /* CONFIG_TRACING */
27
28#endif /* _LINUX_TRACE_H */
kernel/trace/trace.c+128−1
@@ -40,6 +40,7 @@ · 39 unmodified lines
40#include <linux/poll.h>40#include <linux/poll.h>
41#include <linux/nmi.h>41#include <linux/nmi.h>
42#include <linux/fs.h>42#include <linux/fs.h>
43#include <linux/trace.h>
43#include <linux/sched/rt.h>44#include <linux/sched/rt.h>
44 45
45#include "trace.h"46#include "trace.h"
@@ -2128,6 +2129,129 @@ void trace_buffer_unlock_commit_regs(struct trace_array *tr, · 2082 unmodified lines
2128 ftrace_trace_userstack(buffer, flags, pc);2129 ftrace_trace_userstack(buffer, flags, pc);
2129}2130}
2130 2131
2132static void
2133trace_process_export(struct trace_export *export,
2134 struct ring_buffer_event *event)
2135{
2136 struct trace_entry *entry;
2137 unsigned int size = 0;
2138
2139 entry = ring_buffer_event_data(event);
2140 size = ring_buffer_event_length(event);
2141 export->write(entry, size);
2142}
2143
2144static DEFINE_MUTEX(ftrace_export_lock);
2145
2146static struct trace_export __rcu *ftrace_exports_list __read_mostly;
2147
2148static DEFINE_STATIC_KEY_FALSE(ftrace_exports_enabled);
2149
2150static inline void ftrace_exports_enable(void)
2151{
2152 static_branch_enable(&ftrace_exports_enabled);
2153}
2154
2155static inline void ftrace_exports_disable(void)
2156{
2157 static_branch_disable(&ftrace_exports_enabled);
2158}
2159
2160void ftrace_exports(struct ring_buffer_event *event)
2161{
2162 struct trace_export *export;
2163
2164 preempt_disable_notrace();
2165
2166 export = rcu_dereference_raw_notrace(ftrace_exports_list);
2167 while (export) {
2168 trace_process_export(export, event);
2169 export = rcu_dereference_raw_notrace(export->next);
2170 }
2171
2172 preempt_enable_notrace();
2173}
2174
2175static inline void
2176add_trace_export(struct trace_export **list, struct trace_export *export)
2177{
2178 rcu_assign_pointer(export->next, *list);
2179 /*
2180 * We are entering export into the list but another
2181 * CPU might be walking that list. We need to make sure
2182 * the export->next pointer is valid before another CPU sees
2183 * the export pointer included into the list.
2184 */
2185 rcu_assign_pointer(*list, export);
2186}
2187
2188static inline int
2189rm_trace_export(struct trace_export **list, struct trace_export *export)
2190{
2191 struct trace_export **p;
2192
2193 for (p = list; *p != NULL; p = &(*p)->next)
2194 if (*p == export)
2195 break;
2196
2197 if (*p != export)
2198 return -1;
2199
2200 rcu_assign_pointer(*p, (*p)->next);
2201
2202 return 0;
2203}
2204
2205static inline void
2206add_ftrace_export(struct trace_export **list, struct trace_export *export)
2207{
2208 if (*list == NULL)
2209 ftrace_exports_enable();
2210
2211 add_trace_export(list, export);
2212}
2213
2214static inline int
2215rm_ftrace_export(struct trace_export **list, struct trace_export *export)
2216{
2217 int ret;
2218
2219 ret = rm_trace_export(list, export);
2220 if (*list == NULL)
2221 ftrace_exports_disable();
2222
2223 return ret;
2224}
2225
2226int register_ftrace_export(struct trace_export *export)
2227{
2228 if (WARN_ON_ONCE(!export->write))
2229 return -1;
2230
2231 mutex_lock(&ftrace_export_lock);
2232
2233 add_ftrace_export(&ftrace_exports_list, export);
2234
2235 mutex_unlock(&ftrace_export_lock);
2236
2237 return 0;
2238}
2239EXPORT_SYMBOL_GPL(register_ftrace_export);
2240
2241int unregister_ftrace_export(struct trace_export *export)
2242{
2243 int ret;
2244
2245 mutex_lock(&ftrace_export_lock);
2246
2247 ret = rm_ftrace_export(&ftrace_exports_list, export);
2248
2249 mutex_unlock(&ftrace_export_lock);
2250
2251 return ret;
2252}
2253EXPORT_SYMBOL_GPL(unregister_ftrace_export);
2254
2131void2255void
2132trace_function(struct trace_array *tr,2256trace_function(struct trace_array *tr,
2133 unsigned long ip, unsigned long parent_ip, unsigned long flags,2257 unsigned long ip, unsigned long parent_ip, unsigned long flags,
@@ -2146,8 +2270,11 @@ trace_function(struct trace_array *tr, · 12 unmodified lines
2146 entry->ip = ip;2270 entry->ip = ip;
2147 entry->parent_ip = parent_ip;2271 entry->parent_ip = parent_ip;
2148 2272
2149 if (!call_filter_check_discard(call, entry, buffer, event))2273 if (!call_filter_check_discard(call, entry, buffer, event)) {
2274 if (static_branch_unlikely(&ftrace_exports_enabled))
2275 ftrace_exports(event);
2150 __buffer_unlock_commit(buffer, event);2276 __buffer_unlock_commit(buffer, event);
2277 }
2151}2278}
2152 2279
2153#ifdef CONFIG_STACKTRACE2280#ifdef CONFIG_STACKTRACE