Re: [PATCHV5 1/3] tracing: add a possibility of exporting function trace to other places instead of ring buffer only

2016-08-30 Thread Chunyan Zhang 
On 30 August 2016 at 22:30, Steven Rostedt  wrote:
> On Tue, 30 Aug 2016 16:07:28 +0800
> Chunyan Zhang  wrote:
>
>> Currently Function traces can be only exported to ring buffer, this
>> patch added trace_export concept which can process traces and export
>> them to a registered destination as an addition to the current only
>> output of Ftrace - i.e. ring buffer.
>>
>> In this way, if we want Function traces to be sent to other destination
>> rather than ring buffer only, we just need to register a new
>> trace_export and implement its own .commit() callback or just use
>> 'trace_generic_commit()' which this patch also added and hooks up its
>> own .write() function for writing traces to the storage.
>>
>> With this patch, only Function trace (trace type is TRACE_FN)
>> is supported.
>>
>> Signed-off-by: Chunyan Zhang 
>> ---
>>  include/linux/trace.h |  35 
>>  kernel/trace/trace.c  | 155 
>> +-
>>  kernel/trace/trace.h  |   1 +
>>  3 files changed, 190 insertions(+), 1 deletion(-)
>>  create mode 100644 include/linux/trace.h
>>
>> diff --git a/include/linux/trace.h b/include/linux/trace.h
>> new file mode 100644
>> index 000..30ded92
>> --- /dev/null
>> +++ b/include/linux/trace.h
>> @@ -0,0 +1,35 @@
>> +#ifndef _LINUX_TRACE_H
>> +#define _LINUX_TRACE_H
>> +
>> +#include 
>> +struct trace_array;
>> +
>> +#ifdef CONFIG_TRACING
>> +/*
>> + * The trace export - an export of Ftrace. The trace_export can process
>> + * traces and export them to a registered destination as an addition to
>> + * the current only output of Ftrace - i.e. ring buffer.
>> + *
>> + * If you want traces to be sent to some other place rather than
>> + * ring buffer only, just need to register a new trace_export and
>> + * implement its own .commit() callback or just directly use
>> + * 'trace_generic_commit()' and hooks up its own .write() function
>> + * for writing traces to the storage.
>> + *
>> + * next  - pointer to the next trace_export
>> + * commit- commit the traces to the destination
>> + * write - copy traces which have been delt with ->commit() to
>> + * the destination
>> + */
>> +struct trace_export {
>> + struct trace_export __rcu   *next;
>> + void (*commit)(struct trace_array *, struct ring_buffer_event *);
>> + void (*write)(const char *, unsigned int);
>> +};
>> +
>> +int register_ftrace_export(struct trace_export *export);
>> +int unregister_ftrace_export(struct trace_export *export);
>> +
>> +#endif   /* CONFIG_TRACING */
>> +
>> +#endif   /* _LINUX_TRACE_H */
>> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
>> index dade4c9..3163fa6 100644
>> --- a/kernel/trace/trace.c
>> +++ b/kernel/trace/trace.c
>> @@ -40,6 +40,7 @@
>>  #include 
>>  #include 
>>  #include 
>> +#include 
>>  #include 
>>
>>  #include "trace.h"
>> @@ -2128,6 +2129,155 @@ void trace_buffer_unlock_commit_regs(struct 
>> trace_array *tr,
>>   ftrace_trace_userstack(buffer, flags, pc);
>>  }
>>
>> +static DEFINE_STATIC_KEY_FALSE(ftrace_exports_enabled);
>> +
>> +static void ftrace_exports_enable(void)
>> +{
>> + static_branch_enable(_exports_enabled);
>> +}
>> +
>> +static void ftrace_exports_disable(void)
>> +{
>> + static_branch_disable(_exports_enabled);
>> +}
>> +
>> +static size_t trace_size[] = {
>> + [TRACE_FN]  = sizeof(struct ftrace_entry),
>> + [TRACE_CTX] = sizeof(struct ctx_switch_entry),
>> + [TRACE_WAKE]= sizeof(struct ctx_switch_entry),
>> + [TRACE_STACK]   = sizeof(struct stack_entry),
>> + [TRACE_PRINT]   = sizeof(struct print_entry),
>> + [TRACE_BPRINT]  = sizeof(struct bprint_entry),
>> + [TRACE_MMIO_RW] = sizeof(struct trace_mmiotrace_rw),
>> + [TRACE_MMIO_MAP]= sizeof(struct trace_mmiotrace_map),
>> + [TRACE_BRANCH]  = sizeof(struct trace_branch),
>> + [TRACE_GRAPH_RET]   = sizeof(struct ftrace_graph_ret_entry),
>> + [TRACE_GRAPH_ENT]   = sizeof(struct ftrace_graph_ent_entry),
>> + [TRACE_USER_STACK]  = sizeof(struct userstack_entry),
>> + [TRACE_BPUTS]   = sizeof(struct bputs_entry),
>> +};
>> +
>> +static void
>> +trace_generic_commit(struct trace_array *tr,
>> +struct ring_buffer_event *event)
>> +{
>> + struct trace_entry *entry;
>> + struct trace_export *export = tr->export;
>
> Why not just pass in the export directly?
>
>> + unsigned int size = 0;
>> +
>> + entry = ring_buffer_event_data(event);
>> +
>> + size = trace_size[entry->type];
>
> BTW, it would make much more sense if you just did:
>
> size = ring_buffer_event_length(event);
>
> and get rid of that silly array, as that is prone to bugs if you add a
> new type.
>
>> + if (!size)
>> + return;
>> +
>> + if (export && export->write)
>> +

Re: [PATCHV5 1/3] tracing: add a possibility of exporting function trace to other places instead of ring buffer only

2016-08-30 Thread Chunyan Zhang 
On 30 August 2016 at 22:30, Steven Rostedt  wrote:
> On Tue, 30 Aug 2016 16:07:28 +0800
> Chunyan Zhang  wrote:
>
>> Currently Function traces can be only exported to ring buffer, this
>> patch added trace_export concept which can process traces and export
>> them to a registered destination as an addition to the current only
>> output of Ftrace - i.e. ring buffer.
>>
>> In this way, if we want Function traces to be sent to other destination
>> rather than ring buffer only, we just need to register a new
>> trace_export and implement its own .commit() callback or just use
>> 'trace_generic_commit()' which this patch also added and hooks up its
>> own .write() function for writing traces to the storage.
>>
>> With this patch, only Function trace (trace type is TRACE_FN)
>> is supported.
>>
>> Signed-off-by: Chunyan Zhang 
>> ---
>>  include/linux/trace.h |  35 
>>  kernel/trace/trace.c  | 155 
>> +-
>>  kernel/trace/trace.h  |   1 +
>>  3 files changed, 190 insertions(+), 1 deletion(-)
>>  create mode 100644 include/linux/trace.h
>>
>> diff --git a/include/linux/trace.h b/include/linux/trace.h
>> new file mode 100644
>> index 000..30ded92
>> --- /dev/null
>> +++ b/include/linux/trace.h
>> @@ -0,0 +1,35 @@
>> +#ifndef _LINUX_TRACE_H
>> +#define _LINUX_TRACE_H
>> +
>> +#include 
>> +struct trace_array;
>> +
>> +#ifdef CONFIG_TRACING
>> +/*
>> + * The trace export - an export of Ftrace. The trace_export can process
>> + * traces and export them to a registered destination as an addition to
>> + * the current only output of Ftrace - i.e. ring buffer.
>> + *
>> + * If you want traces to be sent to some other place rather than
>> + * ring buffer only, just need to register a new trace_export and
>> + * implement its own .commit() callback or just directly use
>> + * 'trace_generic_commit()' and hooks up its own .write() function
>> + * for writing traces to the storage.
>> + *
>> + * next  - pointer to the next trace_export
>> + * commit- commit the traces to the destination
>> + * write - copy traces which have been delt with ->commit() to
>> + * the destination
>> + */
>> +struct trace_export {
>> + struct trace_export __rcu   *next;
>> + void (*commit)(struct trace_array *, struct ring_buffer_event *);
>> + void (*write)(const char *, unsigned int);
>> +};
>> +
>> +int register_ftrace_export(struct trace_export *export);
>> +int unregister_ftrace_export(struct trace_export *export);
>> +
>> +#endif   /* CONFIG_TRACING */
>> +
>> +#endif   /* _LINUX_TRACE_H */
>> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
>> index dade4c9..3163fa6 100644
>> --- a/kernel/trace/trace.c
>> +++ b/kernel/trace/trace.c
>> @@ -40,6 +40,7 @@
>>  #include 
>>  #include 
>>  #include 
>> +#include 
>>  #include 
>>
>>  #include "trace.h"
>> @@ -2128,6 +2129,155 @@ void trace_buffer_unlock_commit_regs(struct 
>> trace_array *tr,
>>   ftrace_trace_userstack(buffer, flags, pc);
>>  }
>>
>> +static DEFINE_STATIC_KEY_FALSE(ftrace_exports_enabled);
>> +
>> +static void ftrace_exports_enable(void)
>> +{
>> + static_branch_enable(_exports_enabled);
>> +}
>> +
>> +static void ftrace_exports_disable(void)
>> +{
>> + static_branch_disable(_exports_enabled);
>> +}
>> +
>> +static size_t trace_size[] = {
>> + [TRACE_FN]  = sizeof(struct ftrace_entry),
>> + [TRACE_CTX] = sizeof(struct ctx_switch_entry),
>> + [TRACE_WAKE]= sizeof(struct ctx_switch_entry),
>> + [TRACE_STACK]   = sizeof(struct stack_entry),
>> + [TRACE_PRINT]   = sizeof(struct print_entry),
>> + [TRACE_BPRINT]  = sizeof(struct bprint_entry),
>> + [TRACE_MMIO_RW] = sizeof(struct trace_mmiotrace_rw),
>> + [TRACE_MMIO_MAP]= sizeof(struct trace_mmiotrace_map),
>> + [TRACE_BRANCH]  = sizeof(struct trace_branch),
>> + [TRACE_GRAPH_RET]   = sizeof(struct ftrace_graph_ret_entry),
>> + [TRACE_GRAPH_ENT]   = sizeof(struct ftrace_graph_ent_entry),
>> + [TRACE_USER_STACK]  = sizeof(struct userstack_entry),
>> + [TRACE_BPUTS]   = sizeof(struct bputs_entry),
>> +};
>> +
>> +static void
>> +trace_generic_commit(struct trace_array *tr,
>> +struct ring_buffer_event *event)
>> +{
>> + struct trace_entry *entry;
>> + struct trace_export *export = tr->export;
>
> Why not just pass in the export directly?
>
>> + unsigned int size = 0;
>> +
>> + entry = ring_buffer_event_data(event);
>> +
>> + size = trace_size[entry->type];
>
> BTW, it would make much more sense if you just did:
>
> size = ring_buffer_event_length(event);
>
> and get rid of that silly array, as that is prone to bugs if you add a
> new type.
>
>> + if (!size)
>> + return;
>> +
>> + if (export && export->write)
>> + export->write((char *)entry, size);
>> +}
>> +
>> +static

Re: [PATCHV5 1/3] tracing: add a possibility of exporting function trace to other places instead of ring buffer only

2016-08-30 Thread Steven Rostedt 
On Tue, 30 Aug 2016 16:07:28 +0800
Chunyan Zhang  wrote:

> Currently Function traces can be only exported to ring buffer, this
> patch added trace_export concept which can process traces and export
> them to a registered destination as an addition to the current only
> output of Ftrace - i.e. ring buffer.
> 
> In this way, if we want Function traces to be sent to other destination
> rather than ring buffer only, we just need to register a new
> trace_export and implement its own .commit() callback or just use
> 'trace_generic_commit()' which this patch also added and hooks up its
> own .write() function for writing traces to the storage.
> 
> With this patch, only Function trace (trace type is TRACE_FN)
> is supported.
> 
> Signed-off-by: Chunyan Zhang 
> ---
>  include/linux/trace.h |  35 
>  kernel/trace/trace.c  | 155 
> +-
>  kernel/trace/trace.h  |   1 +
>  3 files changed, 190 insertions(+), 1 deletion(-)
>  create mode 100644 include/linux/trace.h
> 
> diff --git a/include/linux/trace.h b/include/linux/trace.h
> new file mode 100644
> index 000..30ded92
> --- /dev/null
> +++ b/include/linux/trace.h
> @@ -0,0 +1,35 @@
> +#ifndef _LINUX_TRACE_H
> +#define _LINUX_TRACE_H
> +
> +#include 
> +struct trace_array;
> +
> +#ifdef CONFIG_TRACING
> +/*
> + * The trace export - an export of Ftrace. The trace_export can process
> + * traces and export them to a registered destination as an addition to
> + * the current only output of Ftrace - i.e. ring buffer.
> + *
> + * If you want traces to be sent to some other place rather than
> + * ring buffer only, just need to register a new trace_export and
> + * implement its own .commit() callback or just directly use
> + * 'trace_generic_commit()' and hooks up its own .write() function
> + * for writing traces to the storage.
> + *
> + * next  - pointer to the next trace_export
> + * commit- commit the traces to the destination
> + * write - copy traces which have been delt with ->commit() to
> + * the destination
> + */
> +struct trace_export {
> + struct trace_export __rcu   *next;
> + void (*commit)(struct trace_array *, struct ring_buffer_event *);
> + void (*write)(const char *, unsigned int);
> +};
> +
> +int register_ftrace_export(struct trace_export *export);
> +int unregister_ftrace_export(struct trace_export *export);
> +
> +#endif   /* CONFIG_TRACING */
> +
> +#endif   /* _LINUX_TRACE_H */
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index dade4c9..3163fa6 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -40,6 +40,7 @@
>  #include 
>  #include 
>  #include 
> +#include 
>  #include 
>  
>  #include "trace.h"
> @@ -2128,6 +2129,155 @@ void trace_buffer_unlock_commit_regs(struct 
> trace_array *tr,
>   ftrace_trace_userstack(buffer, flags, pc);
>  }
>  
> +static DEFINE_STATIC_KEY_FALSE(ftrace_exports_enabled);
> +
> +static void ftrace_exports_enable(void)
> +{
> + static_branch_enable(_exports_enabled);
> +}
> +
> +static void ftrace_exports_disable(void)
> +{
> + static_branch_disable(_exports_enabled);
> +}
> +
> +static size_t trace_size[] = {
> + [TRACE_FN]  = sizeof(struct ftrace_entry),
> + [TRACE_CTX] = sizeof(struct ctx_switch_entry),
> + [TRACE_WAKE]= sizeof(struct ctx_switch_entry),
> + [TRACE_STACK]   = sizeof(struct stack_entry),
> + [TRACE_PRINT]   = sizeof(struct print_entry),
> + [TRACE_BPRINT]  = sizeof(struct bprint_entry),
> + [TRACE_MMIO_RW] = sizeof(struct trace_mmiotrace_rw),
> + [TRACE_MMIO_MAP]= sizeof(struct trace_mmiotrace_map),
> + [TRACE_BRANCH]  = sizeof(struct trace_branch),
> + [TRACE_GRAPH_RET]   = sizeof(struct ftrace_graph_ret_entry),
> + [TRACE_GRAPH_ENT]   = sizeof(struct ftrace_graph_ent_entry),
> + [TRACE_USER_STACK]  = sizeof(struct userstack_entry),
> + [TRACE_BPUTS]   = sizeof(struct bputs_entry),
> +};
> +
> +static void
> +trace_generic_commit(struct trace_array *tr,
> +struct ring_buffer_event *event)
> +{
> + struct trace_entry *entry;
> + struct trace_export *export = tr->export;

Why not just pass in the export directly?

> + unsigned int size = 0;
> +
> + entry = ring_buffer_event_data(event);
> +
> + size = trace_size[entry->type];

BTW, it would make much more sense if you just did:

size = ring_buffer_event_length(event);

and get rid of that silly array, as that is prone to bugs if you add a
new type.

> + if (!size)
> + return;
> +
> + if (export && export->write)
> + export->write((char *)entry, size);
> +}
> +
> +static DEFINE_MUTEX(ftrace_export_lock);
> +
> +static struct trace_export __rcu *ftrace_exports_list __read_mostly;
> +
> +static inline void
>

Re: [PATCHV5 1/3] tracing: add a possibility of exporting function trace to other places instead of ring buffer only

2016-08-30 Thread Steven Rostedt 
On Tue, 30 Aug 2016 16:07:28 +0800
Chunyan Zhang  wrote:

> Currently Function traces can be only exported to ring buffer, this
> patch added trace_export concept which can process traces and export
> them to a registered destination as an addition to the current only
> output of Ftrace - i.e. ring buffer.
> 
> In this way, if we want Function traces to be sent to other destination
> rather than ring buffer only, we just need to register a new
> trace_export and implement its own .commit() callback or just use
> 'trace_generic_commit()' which this patch also added and hooks up its
> own .write() function for writing traces to the storage.
> 
> With this patch, only Function trace (trace type is TRACE_FN)
> is supported.
> 
> Signed-off-by: Chunyan Zhang 
> ---
>  include/linux/trace.h |  35 
>  kernel/trace/trace.c  | 155 
> +-
>  kernel/trace/trace.h  |   1 +
>  3 files changed, 190 insertions(+), 1 deletion(-)
>  create mode 100644 include/linux/trace.h
> 
> diff --git a/include/linux/trace.h b/include/linux/trace.h
> new file mode 100644
> index 000..30ded92
> --- /dev/null
> +++ b/include/linux/trace.h
> @@ -0,0 +1,35 @@
> +#ifndef _LINUX_TRACE_H
> +#define _LINUX_TRACE_H
> +
> +#include 
> +struct trace_array;
> +
> +#ifdef CONFIG_TRACING
> +/*
> + * The trace export - an export of Ftrace. The trace_export can process
> + * traces and export them to a registered destination as an addition to
> + * the current only output of Ftrace - i.e. ring buffer.
> + *
> + * If you want traces to be sent to some other place rather than
> + * ring buffer only, just need to register a new trace_export and
> + * implement its own .commit() callback or just directly use
> + * 'trace_generic_commit()' and hooks up its own .write() function
> + * for writing traces to the storage.
> + *
> + * next  - pointer to the next trace_export
> + * commit- commit the traces to the destination
> + * write - copy traces which have been delt with ->commit() to
> + * the destination
> + */
> +struct trace_export {
> + struct trace_export __rcu   *next;
> + void (*commit)(struct trace_array *, struct ring_buffer_event *);
> + void (*write)(const char *, unsigned int);
> +};
> +
> +int register_ftrace_export(struct trace_export *export);
> +int unregister_ftrace_export(struct trace_export *export);
> +
> +#endif   /* CONFIG_TRACING */
> +
> +#endif   /* _LINUX_TRACE_H */
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index dade4c9..3163fa6 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -40,6 +40,7 @@
>  #include 
>  #include 
>  #include 
> +#include 
>  #include 
>  
>  #include "trace.h"
> @@ -2128,6 +2129,155 @@ void trace_buffer_unlock_commit_regs(struct 
> trace_array *tr,
>   ftrace_trace_userstack(buffer, flags, pc);
>  }
>  
> +static DEFINE_STATIC_KEY_FALSE(ftrace_exports_enabled);
> +
> +static void ftrace_exports_enable(void)
> +{
> + static_branch_enable(_exports_enabled);
> +}
> +
> +static void ftrace_exports_disable(void)
> +{
> + static_branch_disable(_exports_enabled);
> +}
> +
> +static size_t trace_size[] = {
> + [TRACE_FN]  = sizeof(struct ftrace_entry),
> + [TRACE_CTX] = sizeof(struct ctx_switch_entry),
> + [TRACE_WAKE]= sizeof(struct ctx_switch_entry),
> + [TRACE_STACK]   = sizeof(struct stack_entry),
> + [TRACE_PRINT]   = sizeof(struct print_entry),
> + [TRACE_BPRINT]  = sizeof(struct bprint_entry),
> + [TRACE_MMIO_RW] = sizeof(struct trace_mmiotrace_rw),
> + [TRACE_MMIO_MAP]= sizeof(struct trace_mmiotrace_map),
> + [TRACE_BRANCH]  = sizeof(struct trace_branch),
> + [TRACE_GRAPH_RET]   = sizeof(struct ftrace_graph_ret_entry),
> + [TRACE_GRAPH_ENT]   = sizeof(struct ftrace_graph_ent_entry),
> + [TRACE_USER_STACK]  = sizeof(struct userstack_entry),
> + [TRACE_BPUTS]   = sizeof(struct bputs_entry),
> +};
> +
> +static void
> +trace_generic_commit(struct trace_array *tr,
> +struct ring_buffer_event *event)
> +{
> + struct trace_entry *entry;
> + struct trace_export *export = tr->export;

Why not just pass in the export directly?

> + unsigned int size = 0;
> +
> + entry = ring_buffer_event_data(event);
> +
> + size = trace_size[entry->type];

BTW, it would make much more sense if you just did:

size = ring_buffer_event_length(event);

and get rid of that silly array, as that is prone to bugs if you add a
new type.

> + if (!size)
> + return;
> +
> + if (export && export->write)
> + export->write((char *)entry, size);
> +}
> +
> +static DEFINE_MUTEX(ftrace_export_lock);
> +
> +static struct trace_export __rcu *ftrace_exports_list __read_mostly;
> +
> +static inline void
> +ftrace_exports(struct trace_array *tr, struct

[PATCHV5 1/3] tracing: add a possibility of exporting function trace to other places instead of ring buffer only

2016-08-30 Thread Chunyan Zhang 
Currently Function traces can be only exported to ring buffer, this
patch added trace_export concept which can process traces and export
them to a registered destination as an addition to the current only
output of Ftrace - i.e. ring buffer.

In this way, if we want Function traces to be sent to other destination
rather than ring buffer only, we just need to register a new
trace_export and implement its own .commit() callback or just use
'trace_generic_commit()' which this patch also added and hooks up its
own .write() function for writing traces to the storage.

With this patch, only Function trace (trace type is TRACE_FN)
is supported.

Signed-off-by: Chunyan Zhang 
---
 include/linux/trace.h |  35 
 kernel/trace/trace.c  | 155 +-
 kernel/trace/trace.h  |   1 +
 3 files changed, 190 insertions(+), 1 deletion(-)
 create mode 100644 include/linux/trace.h

diff --git a/include/linux/trace.h b/include/linux/trace.h
new file mode 100644
index 000..30ded92
--- /dev/null
+++ b/include/linux/trace.h
@@ -0,0 +1,35 @@
+#ifndef _LINUX_TRACE_H
+#define _LINUX_TRACE_H
+
+#include 
+struct trace_array;
+
+#ifdef CONFIG_TRACING
+/*
+ * The trace export - an export of Ftrace. The trace_export can process
+ * traces and export them to a registered destination as an addition to
+ * the current only output of Ftrace - i.e. ring buffer.
+ *
+ * If you want traces to be sent to some other place rather than
+ * ring buffer only, just need to register a new trace_export and
+ * implement its own .commit() callback or just directly use
+ * 'trace_generic_commit()' and hooks up its own .write() function
+ * for writing traces to the storage.
+ *
+ * next- pointer to the next trace_export
+ * commit  - commit the traces to the destination
+ * write   - copy traces which have been delt with ->commit() to
+ *   the destination
+ */
+struct trace_export {
+   struct trace_export __rcu   *next;
+   void (*commit)(struct trace_array *, struct ring_buffer_event *);
+   void (*write)(const char *, unsigned int);
+};
+
+int register_ftrace_export(struct trace_export *export);
+int unregister_ftrace_export(struct trace_export *export);
+
+#endif /* CONFIG_TRACING */
+
+#endif /* _LINUX_TRACE_H */
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index dade4c9..3163fa6 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -40,6 +40,7 @@
 #include 
 #include 
 #include 
+#include 
 #include 
 
 #include "trace.h"
@@ -2128,6 +2129,155 @@ void trace_buffer_unlock_commit_regs(struct trace_array 
*tr,
ftrace_trace_userstack(buffer, flags, pc);
 }
 
+static DEFINE_STATIC_KEY_FALSE(ftrace_exports_enabled);
+
+static void ftrace_exports_enable(void)
+{
+   static_branch_enable(_exports_enabled);
+}
+
+static void ftrace_exports_disable(void)
+{
+   static_branch_disable(_exports_enabled);
+}
+
+static size_t trace_size[] = {
+   [TRACE_FN]  = sizeof(struct ftrace_entry),
+   [TRACE_CTX] = sizeof(struct ctx_switch_entry),
+   [TRACE_WAKE]= sizeof(struct ctx_switch_entry),
+   [TRACE_STACK]   = sizeof(struct stack_entry),
+   [TRACE_PRINT]   = sizeof(struct print_entry),
+   [TRACE_BPRINT]  = sizeof(struct bprint_entry),
+   [TRACE_MMIO_RW] = sizeof(struct trace_mmiotrace_rw),
+   [TRACE_MMIO_MAP]= sizeof(struct trace_mmiotrace_map),
+   [TRACE_BRANCH]  = sizeof(struct trace_branch),
+   [TRACE_GRAPH_RET]   = sizeof(struct ftrace_graph_ret_entry),
+   [TRACE_GRAPH_ENT]   = sizeof(struct ftrace_graph_ent_entry),
+   [TRACE_USER_STACK]  = sizeof(struct userstack_entry),
+   [TRACE_BPUTS]   = sizeof(struct bputs_entry),
+};
+
+static void
+trace_generic_commit(struct trace_array *tr,
+  struct ring_buffer_event *event)
+{
+   struct trace_entry *entry;
+   struct trace_export *export = tr->export;
+   unsigned int size = 0;
+
+   entry = ring_buffer_event_data(event);
+
+   size = trace_size[entry->type];
+   if (!size)
+   return;
+
+   if (export && export->write)
+   export->write((char *)entry, size);
+}
+
+static DEFINE_MUTEX(ftrace_export_lock);
+
+static struct trace_export __rcu *ftrace_exports_list __read_mostly;
+
+static inline void
+ftrace_exports(struct trace_array *tr, struct ring_buffer_event *event)
+{
+   struct trace_export *export;
+
+   preempt_disable_notrace();
+
+   for (export = rcu_dereference_raw_notrace(ftrace_exports_list);
+export && export->commit;
+export = rcu_dereference_raw_notrace(export->next)) {
+   tr->export = export;
+   export->commit(tr, event);
+   }
+
+   preempt_enable_notrace();
+}
+
+static inline void
+add_trace_export(struct trace_export **list,

[PATCHV5 1/3] tracing: add a possibility of exporting function trace to other places instead of ring buffer only

2016-08-30 Thread Chunyan Zhang 
Currently Function traces can be only exported to ring buffer, this
patch added trace_export concept which can process traces and export
them to a registered destination as an addition to the current only
output of Ftrace - i.e. ring buffer.

In this way, if we want Function traces to be sent to other destination
rather than ring buffer only, we just need to register a new
trace_export and implement its own .commit() callback or just use
'trace_generic_commit()' which this patch also added and hooks up its
own .write() function for writing traces to the storage.

With this patch, only Function trace (trace type is TRACE_FN)
is supported.

Signed-off-by: Chunyan Zhang 
---
 include/linux/trace.h |  35 
 kernel/trace/trace.c  | 155 +-
 kernel/trace/trace.h  |   1 +
 3 files changed, 190 insertions(+), 1 deletion(-)
 create mode 100644 include/linux/trace.h

diff --git a/include/linux/trace.h b/include/linux/trace.h
new file mode 100644
index 000..30ded92
--- /dev/null
+++ b/include/linux/trace.h
@@ -0,0 +1,35 @@
+#ifndef _LINUX_TRACE_H
+#define _LINUX_TRACE_H
+
+#include 
+struct trace_array;
+
+#ifdef CONFIG_TRACING
+/*
+ * The trace export - an export of Ftrace. The trace_export can process
+ * traces and export them to a registered destination as an addition to
+ * the current only output of Ftrace - i.e. ring buffer.
+ *
+ * If you want traces to be sent to some other place rather than
+ * ring buffer only, just need to register a new trace_export and
+ * implement its own .commit() callback or just directly use
+ * 'trace_generic_commit()' and hooks up its own .write() function
+ * for writing traces to the storage.
+ *
+ * next- pointer to the next trace_export
+ * commit  - commit the traces to the destination
+ * write   - copy traces which have been delt with ->commit() to
+ *   the destination
+ */
+struct trace_export {
+   struct trace_export __rcu   *next;
+   void (*commit)(struct trace_array *, struct ring_buffer_event *);
+   void (*write)(const char *, unsigned int);
+};
+
+int register_ftrace_export(struct trace_export *export);
+int unregister_ftrace_export(struct trace_export *export);
+
+#endif /* CONFIG_TRACING */
+
+#endif /* _LINUX_TRACE_H */
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index dade4c9..3163fa6 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -40,6 +40,7 @@
 #include 
 #include 
 #include 
+#include 
 #include 
 
 #include "trace.h"
@@ -2128,6 +2129,155 @@ void trace_buffer_unlock_commit_regs(struct trace_array 
*tr,
ftrace_trace_userstack(buffer, flags, pc);
 }
 
+static DEFINE_STATIC_KEY_FALSE(ftrace_exports_enabled);
+
+static void ftrace_exports_enable(void)
+{
+   static_branch_enable(_exports_enabled);
+}
+
+static void ftrace_exports_disable(void)
+{
+   static_branch_disable(_exports_enabled);
+}
+
+static size_t trace_size[] = {
+   [TRACE_FN]  = sizeof(struct ftrace_entry),
+   [TRACE_CTX] = sizeof(struct ctx_switch_entry),
+   [TRACE_WAKE]= sizeof(struct ctx_switch_entry),
+   [TRACE_STACK]   = sizeof(struct stack_entry),
+   [TRACE_PRINT]   = sizeof(struct print_entry),
+   [TRACE_BPRINT]  = sizeof(struct bprint_entry),
+   [TRACE_MMIO_RW] = sizeof(struct trace_mmiotrace_rw),
+   [TRACE_MMIO_MAP]= sizeof(struct trace_mmiotrace_map),
+   [TRACE_BRANCH]  = sizeof(struct trace_branch),
+   [TRACE_GRAPH_RET]   = sizeof(struct ftrace_graph_ret_entry),
+   [TRACE_GRAPH_ENT]   = sizeof(struct ftrace_graph_ent_entry),
+   [TRACE_USER_STACK]  = sizeof(struct userstack_entry),
+   [TRACE_BPUTS]   = sizeof(struct bputs_entry),
+};
+
+static void
+trace_generic_commit(struct trace_array *tr,
+  struct ring_buffer_event *event)
+{
+   struct trace_entry *entry;
+   struct trace_export *export = tr->export;
+   unsigned int size = 0;
+
+   entry = ring_buffer_event_data(event);
+
+   size = trace_size[entry->type];
+   if (!size)
+   return;
+
+   if (export && export->write)
+   export->write((char *)entry, size);
+}
+
+static DEFINE_MUTEX(ftrace_export_lock);
+
+static struct trace_export __rcu *ftrace_exports_list __read_mostly;
+
+static inline void
+ftrace_exports(struct trace_array *tr, struct ring_buffer_event *event)
+{
+   struct trace_export *export;
+
+   preempt_disable_notrace();
+
+   for (export = rcu_dereference_raw_notrace(ftrace_exports_list);
+export && export->commit;
+export = rcu_dereference_raw_notrace(export->next)) {
+   tr->export = export;
+   export->commit(tr, event);
+   }
+
+   preempt_enable_notrace();
+}
+
+static inline void
+add_trace_export(struct trace_export **list, struct trace_export *export)