tracing: arm64: Avoid missing-prototype warnings

These are all tracing W=1 warnings in arm64 allmodconfig about missing
prototypes:

kernel/trace/trace_kprobe_selftest.c:7:5: error: no previous prototype for 'kprobe_trace_selftest_target' [-Werror=missing-pro
totypes]
kernel/trace/ftrace.c:329:5: error: no previous prototype for '__register_ftrace_function' [-Werror=missing-prototypes]
kernel/trace/ftrace.c:372:5: error: no previous prototype for '__unregister_ftrace_function' [-Werror=missing-prototypes]
kernel/trace/ftrace.c:4130:15: error: no previous prototype for 'arch_ftrace_match_adjust' [-Werror=missing-prototypes]
kernel/trace/fgraph.c:243:15: error: no previous prototype for 'ftrace_return_to_handler' [-Werror=missing-prototypes]
kernel/trace/fgraph.c:358:6: error: no previous prototype for 'ftrace_graph_sleep_time_control' [-Werror=missing-prototypes]
arch/arm64/kernel/ftrace.c:460:6: error: no previous prototype for 'prepare_ftrace_return' [-Werror=missing-prototypes]
arch/arm64/kernel/ptrace.c:2172:5: error: no previous prototype for 'syscall_trace_enter' [-Werror=missing-prototypes]
arch/arm64/kernel/ptrace.c:2195:6: error: no previous prototype for 'syscall_trace_exit' [-Werror=missing-prototypes]

Move the declarations to an appropriate header where they can be seen
by the caller and callee, and make sure the headers are included where
needed.

Link: https://lore.kernel.org/linux-trace-kernel/20230517125215.930689-1-arnd@kernel.org

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Florent Revest <revest@chromium.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
[ Fixed ftrace_return_to_handler() to handle CONFIG_HAVE_FUNCTION_GRAPH_RETVAL case ]
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

function_graph: Support recording and printing the return value of function

Analyzing system call failures with the function_graph tracer can be a
time-consuming process, particularly when locating the kernel function
that first returns an error in the trace logs. This change aims to
simplify the process by recording the function return value to the
'retval' member of 'ftrace_graph_ret' and printing it when outputting
the trace log.

We have introduced new trace options: funcgraph-retval and
funcgraph-retval-hex. The former controls whether to display the return
value, while the latter controls the display format.

Please note that even if a function's return type is void, a return
value will still be printed. You can simply ignore it.

This patch only establishes the fundamental infrastructure. Subsequent
patches will make this feature available on some commonly used processor
architectures.

Here is an example:

I attempted to attach the demo process to a cpu cgroup, but it failed:

echo `pidof demo` > /sys/fs/cgroup/cpu/test/tasks
-bash: echo: write error: Invalid argument

The strace logs indicate that the write system call returned -EINVAL(-22):
...
write(1, "273\n", 4) = -1 EINVAL (Invalid argument)
...

To capture trace logs during a write system call, use the following
commands:

cd /sys/kernel/debug/tracing/
echo 0 > tracing_on
echo > trace
echo *sys_write > set_graph_function
echo *spin* > set_graph_notrace
echo *rcu* >> set_graph_notrace
echo *alloc* >> set_graph_notrace
echo preempt* >> set_graph_notrace
echo kfree* >> set_graph_notrace
echo $$ > set_ftrace_pid
echo function_graph > current_tracer
echo 1 > options/funcgraph-retval
echo 0 > options/funcgraph-retval-hex
echo 1 > tracing_on
echo `pidof demo` > /sys/fs/cgroup/cpu/test/tasks
echo 0 > tracing_on
cat trace > ~/trace.log

To locate the root cause, search for error code -22 directly in the file
trace.log and identify the first function that returned -22. Once you
have identified this function, examine its code to determine the root
cause.

For example, in the trace log below, cpu_cgroup_can_attach
returned -22 first, so we can focus our analysis on this function to
identify the root cause.

...

1) | cgroup_migrate() {
1) 0.651 us | cgroup_migrate_add_task(); /* = 0xffff93fcfd346c00 */
1) | cgroup_migrate_execute() {
1) | cpu_cgroup_can_attach() {
1) | cgroup_taskset_first() {
1) 0.732 us | cgroup_taskset_next(); /* = 0xffff93fc8fb20000 */
1) 1.232 us | } /* cgroup_taskset_first = 0xffff93fc8fb20000 */
1) 0.380 us | sched_rt_can_attach(); /* = 0x0 */
1) 2.335 us | } /* cpu_cgroup_can_attach = -22 */
1) 4.369 us | } /* cgroup_migrate_execute = -22 */
1) 7.143 us | } /* cgroup_migrate = -22 */

...

Link: https://lkml.kernel.org/r/1fc502712c981e0e6742185ba242992170ac9da8.1680954589.git.pengdonglin@sangfor.com.cn

Tested-by: Florian Kauer <florian.kauer@linutronix.de>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Donglin Peng <pengdonglin@sangfor.com.cn>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

fgraph: Add declaration of "struct fgraph_ret_regs"

In final testing of:

https://patchwork.kernel.org/project/linux-trace-kernel/patch/1fc502712c981e0e6742185ba242992170ac9da8.1680954589.git.pengdonglin@sangfor.com.cn/
"function_graph: Support recording and printing the return value of function"

The test failed due to a new warning found in the build:

kernel/trace/fgraph.c:243:56: warning: ‘struct fgraph_ret_regs’ declared inside parameter list will not be visible outside of this definition or declaration

Instead of asking to send another patch series, just add it and then apply
the updates.

Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

ftrace/fgraph: fix increased missing-prototypes warnings

After commit e999995c84c3 ("ftrace: cleanup ftrace_graph_caller enable
and disable") merged into the linux-next tree, the kernel test robot
(lkp@intel.com) has send out report that there are increased missing-prototypes
warnings caused by that commit.

COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.3.0 make.cross W=1 \
O=build_dir ARCH=sh SHELL=/bin/bash kernel/trace/
warning: no previous prototype for 'ftrace_enable_ftrace_graph_caller' [-Wmissing-prototypes]
warning: no previous prototype for 'ftrace_disable_ftrace_graph_caller' [-Wmissing-prototypes]
warning: no previous prototype for 'ftrace_return_to_handler' [-Wmissing-prototypes]
warning: no previous prototype for 'ftrace_graph_sleep_time_control' [-Wmissing-prototypes]

BTW there are so many missing-prototypes warnings if build kernel with "W=1".

The increased warnings for 'ftrace_[enable,disable]_ftrace_graph_caller'
is caused by CONFIG_FUNCTION_GRAPH_TRACER && !CONFIG_DYNAMIC_FTRACE,
so the declarations in <linux/ftrace.h> can't be seen in fgraph.c.

And this warning can't reproduce on x86_64 since x86_64 select
HAVE_FUNCTION_GRAPH_TRACER only when DYNAMIC_FTRACE, so fgraph.c will
always see the declarations in <linux/ftrace.h>.

This patch fix the increased warnings by put the definitions in
CONFIG_DYNAMIC_FTRACE although there are no real problems exist.

Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Acked-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Link: https://lore.kernel.org/r/20220506032737.23375-1-zhouchengming@bytedance.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

sched/tracing: Append prev_state to tp args instead

Commit fa2c3254d7cf (sched/tracing: Don't re-read p->state when emitting
sched_switch event, 2022-01-20) added a new prev_state argument to the
sched_switch tracepoint, before the prev task_struct pointer.

This reordering of arguments broke BPF programs that use the raw
tracepoint (e.g. tp_btf programs). The type of the second argument has
changed and existing programs that assume a task_struct* argument
(e.g. for bpf_task_storage access) will now fail to verify.

If we instead append the new argument to the end, all existing programs
would continue to work and can conditionally extract the prev_state
argument on supported kernel versions.

Fixes: fa2c3254d7cf (sched/tracing: Don't re-read p->state when emitting sched_switch event, 2022-01-20)
Signed-off-by: Delyan Kratunov <delyank@fb.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Link: https://lkml.kernel.org/r/c8a6930dfdd58a4a5755fc01732675472979732b.camel@fb.com

ftrace: cleanup ftrace_graph_caller enable and disable

The ftrace_[enable,disable]_ftrace_graph_caller() are used to do
special hooks for graph tracer, which are not needed on some ARCHs
that use graph_ops:func function to install return_hooker.

So introduce the weak version in ftrace core code to cleanup
in x86.

Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Acked-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/r/20220420160006.17880-1-zhouchengming@bytedance.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

ftrace: Make ftrace_graph_is_dead() a static branch

ftrace_graph_is_dead() is used on hot paths, it just reads a variable
in memory and is not worth suffering function call constraints.

For instance, at entry of prepare_ftrace_return(), inlining it avoids
saving prepare_ftrace_return() parameters to stack and restoring them
after calling ftrace_graph_is_dead().

While at it using a static branch is even more performant and is
rather well adapted considering that the returned value will almost
never change.

Inline ftrace_graph_is_dead() and replace 'kill_ftrace_graph' bool
by a static branch.

The performance improvement is noticeable.

Link: https://lkml.kernel.org/r/e0411a6a0ed3eafff0ad2bc9cd4b0e202b4617df.1648623570.git.christophe.leroy@csgroup.eu

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

sched/tracing: Don't re-read p->state when emitting sched_switch event

As of commit

c6e7bd7afaeb ("sched/core: Optimize ttwu() spinning on p->on_cpu")

the following sequence becomes possible:

p->__state = TASK_INTERRUPTIBLE;
__schedule()
deactivate_task(p);
ttwu()
READ !p->on_rq
p->__state=TASK_WAKING
trace_sched_switch()
__trace_sched_switch_state()
task_state_index()
return 0;

TASK_WAKING isn't in TASK_REPORT, so the task appears as TASK_RUNNING in
the trace event.

Prevent this by pushing the value read from __schedule() down the trace
event.

Reported-by: Abhijeet Dharmapurikar <adharmap@quicinc.com>
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Link: https://lore.kernel.org/r/20220120162520.570782-2-valentin.schneider@arm.com

x86/ftrace: Make function graph use ftrace directly

We don't need special hook for graph tracer entry point,
but instead we can use graph_ops::func function to install
the return_hooker.

This moves the graph tracing setup _before_ the direct
trampoline prepares the stack, so the return_hooker will
be called when the direct trampoline is finished.

This simplifies the code, because we don't need to take into
account the direct trampoline setup when preparing the graph
tracer hooker and we can allow function graph tracer on entries
registered with direct trampoline.

Link: https://lkml.kernel.org/r/20211008091336.33616-4-jolsa@kernel.org

[fixed compile error reported by kernel test robot <lkp@intel.com>]
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

tracing: Fix various typos in comments

Fix ~59 single-word typos in the tracing code comments, and fix
the grammar in a handful of places.

Link: https://lore.kernel.org/r/20210322224546.GA1981273@gmail.com
Link: https://lkml.kernel.org/r/20210323174935.GA4176821@gmail.com

Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

fgraph: Initialize tracing_graph_pause at task creation

On some archs, the idle task can call into cpu_suspend(). The cpu_suspend()
will disable or pause function graph tracing, as there's some paths in
bringing down the CPU that can have issues with its return address being
modified. The task_struct structure has a "tracing_graph_pause" atomic
counter, that when set to something other than zero, the function graph
tracer will not modify the return address.

The problem is that the tracing_graph_pause counter is initialized when the
function graph tracer is enabled. This can corrupt the counter for the idle
task if it is suspended in these architectures.

CPU 1 CPU 2
----- -----
do_idle()
cpu_suspend()
pause_graph_tracing()
task_struct->tracing_graph_pause++ (0 -> 1)

start_graph_tracing()
for_each_online_cpu(cpu) {
ftrace_graph_init_idle_task(cpu)
task-struct->tracing_graph_pause = 0 (1 -> 0)

unpause_graph_tracing()
task_struct->tracing_graph_pause-- (0 -> -1)

The above should have gone from 1 to zero, and enabled function graph
tracing again. But instead, it is set to -1, which keeps it disabled.

There's no reason that the field tracing_graph_pause on the task_struct can
not be initialized at boot up.

Cc: stable@vger.kernel.org
Fixes: 380c4b1411ccd ("tracing/function-graph-tracer: append the tracing_graph_flag")
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=211339
Reported-by: pierre.gondois@arm.com
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

ftrace: Reverse what the RECURSION flag means in the ftrace_ops

Now that all callbacks are recursion safe, reverse the meaning of the
RECURSION flag and rename it from RECURSION_SAFE to simply RECURSION.
Now only callbacks that request to have recursion protecting it will
have the added trampoline to do so.

Also remove the outdated comment about "PER_CPU" when determining to
use the ftrace_ops_assist_func.

Link: https://lkml.kernel.org/r/20201028115613.742454631@goodmis.org
Link: https://lkml.kernel.org/r/20201106023547.904270143@goodmis.org

Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Jiri Kosina <jikos@kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Miroslav Benes <mbenes@suse.cz>
Cc: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>
Cc: Petr Mladek <pmladek@suse.com>
Cc: linux-doc@vger.kernel.org
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

fgraph: Convert ret_stack tasklist scanning to rcu

It seems that alloc_retstack_tasklist() can also take a lockless
approach for scanning the tasklist, instead of using the big global
tasklist_lock. For this we also kill another deprecated and rcu-unsafe
tsk->thread_group user replacing it with for_each_process_thread(),
maintaining semantics.

Here tasklist_lock does not protect anything other than the list
against concurrent fork/exit. And considering that the whole thing
is capped by FTRACE_RETSTACK_ALLOC_SIZE (32), it should not be a
problem to have a pontentially stale, yet stable, list. The task cannot
go away either, so we don't risk racing with ftrace_graph_exit_task()
which clears the retstack.

The tsk->ret_stack management is not protected by tasklist_lock, being
serialized with the corresponding publish/subscribe barriers against
concurrent ftrace_push_return_trace(). In addition this plays nicer
with cachelines by avoiding two atomic ops in the uncontended case.

Link: https://lkml.kernel.org/r/20200907013326.9870-1-dave@stgolabs.net

Acked-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

tracing: Define MCOUNT_INSN_SIZE when not defined without direct calls

In order to handle direct calls along side of function graph tracer, a check
is made to see if the address being traced by the function graph tracer is a
direct call or not. To get the address used by direct callers, the return
address is subtracted by MCOUNT_INSN_SIZE.

For some archs with certain configurations, MCOUNT_INSN_SIZE is undefined
here. But these should not be using direct calls anyway. Just define
MCOUNT_INSN_SIZE to zero in this case.

Link: https://lore.kernel.org/r/202001020219.zvE3vsty%lkp@intel.com

Reported-by: kbuild test robot <lkp@intel.com>
Fixes: ff205766dbbee ("ftrace: Fix function_graph tracer interaction with BPF trampoline")
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

ftrace: Fix function_graph tracer interaction with BPF trampoline

Depending on type of BPF programs served by BPF trampoline it can call original
function. In such case the trampoline will skip one stack frame while
returning. That will confuse function_graph tracer and will cause crashes with
bad RIP. Teach graph tracer to skip functions that have BPF trampoline attached.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

ftrace: Rename ftrace_graph_stub to ftrace_stub_graph

The ftrace_graph_stub was created and points to ftrace_stub as a way to
assign the functon graph tracer function pointer to a stub function with a
different prototype than what ftrace_stub has and not trigger the C
verifier. The ftrace_graph_stub was created via the linker script
vmlinux.lds.h. Unfortunately, powerpc already uses the name
ftrace_graph_stub for its internal implementation of the function graph
tracer, and even though powerpc would still build, the change via the linker
script broke function tracer on powerpc from working.

By using the name ftrace_stub_graph, which does not exist anywhere else in
the kernel, this should not be a problem.

Link: https://lore.kernel.org/r/1573849732.5937.136.camel@lca.pw

Fixes: b83b43ffc6e4 ("fgraph: Fix function type mismatches of ftrace_graph_return using ftrace_stub")
Reorted-by: Qian Cai <cai@lca.pw>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

fgraph: Fix function type mismatches of ftrace_graph_return using ftrace_stub

The C compiler is allowing more checks to make sure that function pointers
are assigned to the correct prototype function. Unfortunately, the function
graph tracer uses a special name with its assigned ftrace_graph_return
function pointer that maps to a stub function used by the function tracer
(ftrace_stub). The ftrace_graph_return variable is compared to the
ftrace_stub in some archs to know if the function graph tracer is enabled or
not. This means we can not just simply create a new function stub that
compares it without modifying all the archs.

Instead, have the linker script create a function_graph_stub that maps to
ftrace_stub, and this way we can define the prototype for it to match the
prototype of ftrace_graph_return, and make the compiler checks all happy!

Link: http://lkml.kernel.org/r/20191015090055.789a0aed@gandalf.local.home

Cc: linux-sh@vger.kernel.org
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: Rich Felker <dalias@libc.org>
Reported-by: Sami Tolvanen <samitolvanen@google.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

ftrace: Look up the address of return_to_handler() using helpers

This ensures that we use the right address on architectures that use
function descriptors.

Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/8f6f14d192a994008ac370ce14036bbe67224c7d.1567707399.git.naveen.n.rao@linux.vnet.ibm.com

tracing: Fix ftrace_graph_get_ret_stack() to use task and not current

The function ftrace_graph_get_ret_stack() takes a task struct descriptor but
uses current as the task to perform the operations on. In pretty much all
cases the task decriptor is the same as current, so this wasn't an issue.
But there is a case in the ARM architecture that passes in a task that is
not current, and expects a result from that task, and this code breaks it.

Fixes: 51584396cff5 ("arm64: Use ftrace_graph_get_ret_stack() instead of curr_ret_stack")
Reported-by: James Morse <james.morse@arm.com>
Tested-by: James Morse <james.morse@arm.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

fgraph: Add comment to describe ftrace_graph_get_ret_stack

The ret_stack should not be accessed directly via the curr_ret_stack
variable on the task_struct. This is because the ret_stack is going to be
converted into a series of longs and not an array of ret_stack structures.
The way that a ret_stack should be retrieved is via the
ftrace_graph_get_ret_stack structure, but it needs to be documented on how
to use it.

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

function_graph: Have profiler use new helper ftrace_graph_get_ret_stack()

The ret_stack processing is going to change, and that is going
to break anything that is accessing the ret_stack directly. One user is the
function graph profiler. By using the ftrace_graph_get_ret_stack() helper
function, the profiler can access the ret_stack entry without relying on the
implementation details of the stack itself.

Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

function_graph: Move ftrace_graph_ret_addr() to fgraph.c

Move the function function_graph_ret_addr() to fgraph.c, as the management
of the curr_ret_stack is going to change, and all the accesses to ret_stack
needs to be done in fgraph.c.

Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

fgraph: Add new fgraph_ops structure to enable function graph hooks

Currently the registering of function graph is to pass in a entry and return
function. We need to have a way to associate those functions together where
the entry can determine to run the return hook. Having a structure that
contains both functions will facilitate the process of converting the code
to be able to do such.

This is similar to the way function hooks are enabled (it passes in
ftrace_ops). Instead of passing in the functions to use, a single structure
is passed in to the registering function.

The unregister function is now passed in the fgraph_ops handle. When we
allow more than one callback to the function graph hooks, this will let the
system know which one to remove.

Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

fgraph: Move function graph specific code into fgraph.c

To make the function graph infrastructure more managable, the code needs to
be in its own file (fgraph.c). Move the code that is specific for managing
the function graph infrastructure out of ftrace.c and into fgraph.c

Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

function_graph: Remove the use of FTRACE_NOTRACE_DEPTH

The curr_ret_stack is no longer set to a negative value when a function is
not to be traced by the function graph tracer. Remove the usage of
FTRACE_NOTRACE_DEPTH, as it is no longer needed.

Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

fgraph: Have set_graph_notrace only affect function_graph tracer

In order to make the function graph infrastructure more generic, there can
not be code specific for the function_graph tracer in the generic code. This
includes the set_graph_notrace logic, that stops all graph calls when a
function in the set_graph_notrace is hit.

By using the trace_recursion mask, we can use a bit in the current
task_struct to implement the notrace code, and move the logic out of
fgraph.c and into trace_functions_graph.c and keeps it affecting only the
tracer and not all call graph callbacks.

Acked-by: Namhyung Kim <namhyung@kernel.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

fgraph: Create a fgraph.c file to store function graph infrastructure

As the function graph infrastructure can be used by thing other than
tracing, moving the code to its own file out of the trace_functions_graph.c
code makes more sense.

The fgraph.c file will only contain the infrastructure required to hook into
functions and their return code.

Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>