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This is a sample module to demonstrate the use of the newly introduced and
exported APIs to access Ftrace instances from within the kernel.
Newly introduced APIs used here -
1. Create/Lookup a trace array with the given name.
struct trace_array *trace_array_get_by_name(const char *name)
2. Destroy/Remove a trace array.
int trace_array_destroy(struct trace_array *tr)
4. Enable/Disable trace events:
int trace_array_set_clr_event(struct trace_array *tr, const char *system,
const char *event, bool enable);
Exported APIs -
1. trace_printk equivalent for instances.
int trace_array_printk(struct trace_array *tr,
unsigned long ip, const char *fmt, ...);
2. Helper function.
void trace_printk_init_buffers(void);
3. To decrement the reference counter.
void trace_array_put(struct trace_array *tr)
Sample output(contents of /sys/kernel/tracing/instances/sample-instance)
NOTE: Tracing disabled after ~5 sec)
_-----=> irqs-off
/ _----=> need-resched
| / _---=> hardirq/softirq
|| / _--=> preempt-depth
||| / delay
TASK-PID CPU# |||| TIMESTAMP FUNCTION
| | | |||| | |
sample-instance-1452 [002] .... 49.430948: simple_thread: trace_array_printk: count=0
sample-instance-1452 [002] .... 49.430951: sample_event: count value=0 at jiffies=4294716608
sample-instance-1452 [002] .... 50.454847: simple_thread: trace_array_printk: count=1
sample-instance-1452 [002] .... 50.454849: sample_event: count value=1 at jiffies=4294717632
sample-instance-1452 [002] .... 51.478748: simple_thread: trace_array_printk: count=2
sample-instance-1452 [002] .... 51.478750: sample_event: count value=2 at jiffies=4294718656
sample-instance-1452 [002] .... 52.502652: simple_thread: trace_array_printk: count=3
sample-instance-1452 [002] .... 52.502655: sample_event: count value=3 at jiffies=4294719680
sample-instance-1452 [002] .... 53.526533: simple_thread: trace_array_printk: count=4
sample-instance-1452 [002] .... 53.526535: sample_event: count value=4 at jiffies=4294720704
sample-instance-1452 [002] .... 54.550438: simple_thread: trace_array_printk: count=5
sample-instance-1452 [002] .... 55.574336: simple_thread: trace_array_printk: count=6
Link: http://lkml.kernel.org/r/1574276919-11119-3-git-send-email-divya.indi@oracle.com
Reviewed-by: Aruna Ramakrishna <aruna.ramakrishna@oracle.com>
Signed-off-by: Divya Indi <divya.indi@oracle.com>
[ Moved to samples/ftrace ]
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
85 lines
2.4 KiB
C
85 lines
2.4 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* If TRACE_SYSTEM is defined, that will be the directory created
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* in the ftrace directory under /sys/kernel/tracing/events/<system>
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*
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* The define_trace.h below will also look for a file name of
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* TRACE_SYSTEM.h where TRACE_SYSTEM is what is defined here.
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* In this case, it would look for sample-trace.h
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*
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* If the header name will be different than the system name
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* (as in this case), then you can override the header name that
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* define_trace.h will look up by defining TRACE_INCLUDE_FILE
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*
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* This file is called sample-trace-array.h but we want the system
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* to be called "sample-subsystem". Therefore we must define the name of this
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* file:
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*
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* #define TRACE_INCLUDE_FILE sample-trace-array
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*
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* As we do in the bottom of this file.
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*
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* Notice that TRACE_SYSTEM should be defined outside of #if
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* protection, just like TRACE_INCLUDE_FILE.
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*/
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#undef TRACE_SYSTEM
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#define TRACE_SYSTEM sample-subsystem
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/*
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* TRACE_SYSTEM is expected to be a C valid variable (alpha-numeric
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* and underscore), although it may start with numbers. If for some
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* reason it is not, you need to add the following lines:
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*/
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#undef TRACE_SYSTEM_VAR
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#define TRACE_SYSTEM_VAR sample_subsystem
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/*
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* But the above is only needed if TRACE_SYSTEM is not alpha-numeric
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* and underscored. By default, TRACE_SYSTEM_VAR will be equal to
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* TRACE_SYSTEM. As TRACE_SYSTEM_VAR must be alpha-numeric, if
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* TRACE_SYSTEM is not, then TRACE_SYSTEM_VAR must be defined with
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* only alpha-numeric and underscores.
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*
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* The TRACE_SYSTEM_VAR is only used internally and not visible to
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* user space.
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*/
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/*
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* Notice that this file is not protected like a normal header.
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* We also must allow for rereading of this file. The
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*
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* || defined(TRACE_HEADER_MULTI_READ)
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*
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* serves this purpose.
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*/
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#if !defined(_SAMPLE_TRACE_ARRAY_H) || defined(TRACE_HEADER_MULTI_READ)
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#define _SAMPLE_TRACE_ARRAY_H
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#include <linux/tracepoint.h>
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TRACE_EVENT(sample_event,
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TP_PROTO(int count, unsigned long time),
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TP_ARGS(count, time),
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TP_STRUCT__entry(
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__field(int, count)
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__field(unsigned long, time)
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),
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TP_fast_assign(
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__entry->count = count;
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__entry->time = time;
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),
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TP_printk("count value=%d at jiffies=%lu", __entry->count,
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__entry->time)
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);
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#endif
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#undef TRACE_INCLUDE_PATH
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#define TRACE_INCLUDE_PATH .
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#define TRACE_INCLUDE_FILE sample-trace-array
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#include <trace/define_trace.h>
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