ftrace: Add sample with custom ops

When reworking core ftrace code or architectural ftrace code, it's often
necessary to test/analyse/benchmark a number of ftrace_ops
configurations. This patch adds

ftrace: Add sample with custom ops

When reworking core ftrace code or architectural ftrace code, it's often
necessary to test/analyse/benchmark a number of ftrace_ops
configurations. This patch adds a module which can be used to explore
some of those configurations.

I'm using this to benchmark various options for changing the way
trampolines and handling of ftrace_ops work on arm64, and ensuring other
architectures aren't adversely affected.

For example, in a QEMU+KVM VM running on a 2GHz Xeon E5-2660
workstation, loading the module in various configurations produces:

| # insmod ftrace-ops.ko
| ftrace_ops: registering:
| relevant ops: 1
| tracee: tracee_relevant [ftrace_ops]
| tracer: ops_func_nop [ftrace_ops]
| irrelevant ops: 0
| tracee: tracee_irrelevant [ftrace_ops]
| tracer: ops_func_nop [ftrace_ops]
| saving registers: NO
| assist recursion: NO
| assist RCU: NO
| ftrace_ops: Attempted 100000 calls to tracee_relevant [ftrace_ops] in 1681558ns (16ns / call)

| # insmod ftrace-ops.ko nr_ops_irrelevant=5
| ftrace_ops: registering:
| relevant ops: 1
| tracee: tracee_relevant [ftrace_ops]
| tracer: ops_func_nop [ftrace_ops]
| irrelevant ops: 5
| tracee: tracee_irrelevant [ftrace_ops]
| tracer: ops_func_nop [ftrace_ops]
| saving registers: NO
| assist recursion: NO
| assist RCU: NO
| ftrace_ops: Attempted 100000 calls to tracee_relevant [ftrace_ops] in 1693042ns (16ns / call)

| # insmod ftrace-ops.ko nr_ops_relevant=2
| ftrace_ops: registering:
| relevant ops: 2
| tracee: tracee_relevant [ftrace_ops]
| tracer: ops_func_nop [ftrace_ops]
| irrelevant ops: 0
| tracee: tracee_irrelevant [ftrace_ops]
| tracer: ops_func_nop [ftrace_ops]
| saving registers: NO
| assist recursion: NO
| assist RCU: NO
| ftrace_ops: Attempted 100000 calls to tracee_relevant [ftrace_ops] in 11965582ns (119ns / call)

| # insmod ftrace-ops.ko save_regs=true
| ftrace_ops: registering:
| relevant ops: 1
| tracee: tracee_relevant [ftrace_ops]
| tracer: ops_func_nop [ftrace_ops]
| irrelevant ops: 0
| tracee: tracee_irrelevant [ftrace_ops]
| tracer: ops_func_nop [ftrace_ops]
| saving registers: YES
| assist recursion: NO
| assist RCU: NO
| ftrace_ops: Attempted 100000 calls to tracee_relevant [ftrace_ops] in 4459624ns (44ns / call)

Link: https://lkml.kernel.org/r/[email protected]

Cc: Florent Revest <[email protected]>
Acked-by: Masami Hiramatsu (Google) <[email protected]>
Signed-off-by: Mark Rutland <[email protected]>
Signed-off-by: Steven Rostedt (Google) <[email protected]>

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ftrace/samples: Add module to test multi direct modify interface

Adding ftrace-direct-multi-modify.ko kernel module that uses
modify_ftrace_direct_multi API. The core functionality is taken
from ftr

ftrace/samples: Add module to test multi direct modify interface

Adding ftrace-direct-multi-modify.ko kernel module that uses
modify_ftrace_direct_multi API. The core functionality is taken
from ftrace-direct-modify.ko kernel module and changed to fit
multi direct interface.

The init function creates kthread that periodically calls
modify_ftrace_direct_multi to change the trampoline address
for the direct ftrace_ops. The ftrace trace_pipe then shows
trace from both trampolines.

Link: https://lkml.kernel.org/r/[email protected]

Cc: Ingo Molnar <[email protected]>
Reviewed-by: Heiko Carstens <[email protected]>
Tested-by: Heiko Carstens <[email protected]>
Signed-off-by: Jiri Olsa <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>

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ftrace/samples: add missing Kconfig option for ftrace direct multi sample

Currently it is not possible to build the ftrace direct multi example
anymore due to broken config dependencies. Fix this by

ftrace/samples: add missing Kconfig option for ftrace direct multi sample

Currently it is not possible to build the ftrace direct multi example
anymore due to broken config dependencies. Fix this by adding
SAMPLE_FTRACE_DIRECT_MULTI config option.

This broke when merging s390-5.16-1 due to an incorrect merge conflict
resolution proposed by me.

Also rename SAMPLE_FTRACE_MULTI_DIRECT to SAMPLE_FTRACE_DIRECT_MULTI
so it matches the module name.

Fixes: 0b707e572a19 ("Merge tag 's390-5.16-1' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux")
Acked-by: Steven Rostedt (VMware) <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Heiko Carstens <[email protected]>

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ftrace/samples: Add multi direct interface test module

Adding simple module that uses multi direct interface:

register_ftrace_direct_multi
unregister_ftrace_direct_multi

The init function regi

ftrace/samples: Add multi direct interface test module

Adding simple module that uses multi direct interface:

register_ftrace_direct_multi
unregister_ftrace_direct_multi

The init function registers trampoline for 2 functions,
and exit function unregisters them.

Link: https://lkml.kernel.org/r/[email protected]

Signed-off-by: Jiri Olsa <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>

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tracing: Sample module to demonstrate kernel access to Ftrace instances.

This is a sample module to demonstrate the use of the newly introduced and
exported APIs to access Ftrace instances from with

tracing: Sample module to demonstrate kernel access to Ftrace instances.

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/[email protected]

Reviewed-by: Aruna Ramakrishna <[email protected]>
Signed-off-by: Divya Indi <[email protected]>
[ Moved to samples/ftrace ]
Signed-off-by: Steven Rostedt (VMware) <[email protected]>

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ftrace/samples: Add a sample module that implements modify_ftrace_direct()

Add a sample module that tests modify_ftrace_direct(), and this can be used
by the selftests as well.

Signed-off-by: Steve

ftrace/samples: Add a sample module that implements modify_ftrace_direct()

Add a sample module that tests modify_ftrace_direct(), and this can be used
by the selftests as well.

Signed-off-by: Steven Rostedt (VMware) <[email protected]>

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ftrace: Add another example of register_ftrace_direct() use case

Add another module sample that registers a direct trampoline to a function
via register_ftrace_direct(). Having another module that d

ftrace: Add another example of register_ftrace_direct() use case

Add another module sample that registers a direct trampoline to a function
via register_ftrace_direct(). Having another module that does this allows to
test the use case of multiple direct callers registered, as more than one
direct caller goes into another path, and is needed to perform proper
testing of the register_ftrace_direct() call.

Signed-off-by: Steven Rostedt (VMware) <[email protected]>

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ftrace: Add sample module that uses register_ftrace_direct()

Add a sample module that shows a simple use case for
regsiter_ftrace_direct(), and how to use it.

Signed-off-by: Steven Rostedt (VMware)

ftrace: Add sample module that uses register_ftrace_direct()

Add a sample module that shows a simple use case for
regsiter_ftrace_direct(), and how to use it.

Signed-off-by: Steven Rostedt (VMware) <[email protected]>

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