Building with W=2 prints a number of warnings for one function that
has a pointer type mismatch:

linux/seq_buf.h: In function 'seq_buf_init':
linux/seq_buf.h:35:12: warning: pointer targets in assignment from 'unsigned char *' to 'char *' differ in signedness [-Wpointer-sign]

Change the type in the function prototype according to the type in
the structure.

Link: https://lkml.kernel.org/r/20201026161108.3707783-1-arnd@kernel.org

Fixes: 9a777793 ("tracing: Convert seq_buf fields to be like seq_file fields")
Reviewed-by: Cezary Rojewski <cezary.rojewski@intel.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

s/ring_buffer_commit_discard/ring_buffer_discard_commit/

Link: https://lkml.kernel.org/r/20201112151800.14382-1-hqjagain@gmail.comSigned-off-by: Qiujun Huang <hqjagain@gmail.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

Commit a389d86f ("ring-buffer: Have nested events still record running
time stamp") removed the only uses of rb_event_is_commit() in
rb_update_event() and rb_update_write_stamp().

Hence, since then, make CC=clang W=1 warns:

  kernel/trace/ring_buffer.c:2763:1:
    warning: unused function 'rb_event_is_commit' [-Wunused-function]

Remove this obsolete function.

Link: https://lkml.kernel.org/r/20201117053703.11275-1-lukas.bulwahn@gmail.comReviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

While debugging a situation where a delta for an event was calucalted wrong,
I realize there was nothing making sure that the delta of events are
correct. If a single event has an incorrect delta, then all events after it
will also have one. If the discrepency gets large enough, it could cause
the time stamps to go backwards when crossing sub buffers, that record a
full 64 bit time stamp, and the new deltas are added to that.

Add a way to validate the events at most events and when crossing a buffer
page. This will help make sure that the deltas are always correct. This test
will detect if they are ever corrupted.

The test adds a high overhead to the ring buffer recording, as it does the
audit for almost every event, and should only be used for testing the ring
buffer.

This will catch the bug that is fixed by commit 55ea4cf4 ("ring-buffer:
Update write stamp with the correct ts"), which is not applied when this
commit is applied.
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

Some C code in the ftrace-users.rst document is missing RST C block
annotation, which has to be added.

Link: https://lore.kernel.org/r/20201116173502.392a769c@canb.auug.org.auAcked-by: Jonathan Corbet <corbet@lwn.net>
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

The functions event_{set,clear,}_no_set_filter_flag were only used in
replace_system_preds() [now, renamed to process_system_preds()].

Commit 80765597 ("tracing: Rewrite filter logic to be simpler and
faster") removed the use of those functions in replace_system_preds().

Since then, the functions event_{set,clear,}_no_set_filter_flag were
unused. Fortunately, make CC=clang W=1 indicates this with
-Wunused-function warnings on those three functions.

So, clean up these obsolete unused functions.

Link: https://lkml.kernel.org/r/20201115155336.20248-1-lukas.bulwahn@gmail.comSigned-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

The value of variable ret is overwritten on the delete branch in the
test_create_synth_event() and we care more about the above error than
this delete portion. Remove it.

Link: https://lkml.kernel.org/r/1605283360-6804-1-git-send-email-kaixuxia@tencent.comReported-by: Tosk Robot <tencent_os_robot@tencent.com>
Signed-off-by: Kaixu Xia <kaixuxia@tencent.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

When CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS is available, the ftrace call
will be able to set the ip of the calling function. This will improve the
performance of live kernel patching where it does not need all the regs to
be stored just to change the instruction pointer.

If all archs that support live kernel patching also support
HAVE_DYNAMIC_FTRACE_WITH_ARGS, then the architecture specific function
klp_arch_set_pc() could be made generic.

It is possible that an arch can support HAVE_DYNAMIC_FTRACE_WITH_ARGS but
not HAVE_DYNAMIC_FTRACE_WITH_REGS and then have access to live patching.

Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Jiri Kosina <jikos@kernel.org>
Cc: live-patching@vger.kernel.org
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Miroslav Benes <mbenes@suse.cz>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

Currently, the only way to get access to the registers of a function via a
ftrace callback is to set the "FL_SAVE_REGS" bit in the ftrace_ops. But as this
saves all regs as if a breakpoint were to trigger (for use with kprobes), it
is expensive.

The regs are already saved on the stack for the default ftrace callbacks, as
that is required otherwise a function being traced will get the wrong
arguments and possibly crash. And on x86, the arguments are already stored
where they would be on a pt_regs structure to use that code for both the
regs version of a callback, it makes sense to pass that information always
to all functions.

If an architecture does this (as x86_64 now does), it is to set
HAVE_DYNAMIC_FTRACE_WITH_ARGS, and this will let the generic code that it
could have access to arguments without having to set the flags.

This also includes having the stack pointer being saved, which could be used
for accessing arguments on the stack, as well as having the function graph
tracer not require its own trampoline!
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

In preparation to have arguments of a function passed to callbacks attached
to functions as default, change the default callback prototype to receive a
struct ftrace_regs as the forth parameter instead of a pt_regs.

For callbacks that set the FL_SAVE_REGS flag in their ftrace_ops flags, they
will now need to get the pt_regs via a ftrace_get_regs() helper call. If
this is called by a callback that their ftrace_ops did not have a
FL_SAVE_REGS flag set, it that helper function will return NULL.

This will allow the ftrace_regs to hold enough just to get the parameters
and stack pointer, but without the worry that callbacks may have a pt_regs
that is not completely filled.
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

A check with ./scripts/get_maintainer.pl --letters -f fs/tracefs/ shows
that the tracefs is not assigned to the TRACING section in MAINTAINERS.

Add the file pattern for the TRACING section to rectify that.

Link: https://lkml.kernel.org/r/20201109122250.31915-1-lukas.bulwahn@gmail.comSigned-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

s/detetector/detector/
s/enfoced/enforced/
s/writen/written/
s/actualy/actually/
s/bascially/basically/
s/Regarldess/Regardless/
s/zeroes/zeros/
s/followd/followed/
s/incrememented/incremented/
s/separatelly/separately/
s/accesible/accessible/
s/sythetic/synthetic/
s/enabed/enabled/
s/heurisitc/heuristic/
s/assocated/associated/
s/otherwides/otherwise/
s/specfied/specified/
s/seaching/searching/
s/hierachry/hierarchy/
s/internel/internal/
s/Thise/This/

Link: https://lkml.kernel.org/r/20201029150554.3354-1-hqjagain@gmail.comSigned-off-by: Qiujun Huang <hqjagain@gmail.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

'ret' in 2 functions are not used. and one of them is a void function.
So remove them to avoid gcc warning:
kernel/trace/ftrace.c:4166:6: warning: variable ‘ret’ set but not used
[-Wunused-but-set-variable]
kernel/trace/ftrace.c:5571:6: warning: variable ‘ret’ set but not used
[-Wunused-but-set-variable]

Link: https://lkml.kernel.org/r/1604674486-52350-1-git-send-email-alex.shi@linux.alibaba.comSigned-off-by: Alex Shi <alex.shi@linux.alibaba.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

Add a new config RING_BUFFER_RECORD_RECURSION that will place functions that
recurse from the ring buffer into the ftrace recused_functions file.
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

In trace_test_and_set_recursion(), current->trace_recursion is placed into a
variable, and that variable should be used for the processing, as there's no
reason to dereference current multiple times.

On trace_clear_recursion(), current->trace_recursion is modified and there's
no reason to copy it over to a variable.
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

Inspecting the data structures of the function graph tracer, I found that
the overrun value is unsigned long, which is 8 bytes on a 64 bit machine,
and not only that, the depth is an int (4 bytes). The overrun can be simply
an unsigned int (4 bytes) and pack the ftrace_graph_ret structure better.

The depth is moved up next to the func, as it is used more often with func,
and improves cache locality.
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

This adds CONFIG_FTRACE_RECORD_RECURSION that will record to a file
"recursed_functions" all the functions that caused recursion while a
callback to the function tracer was running.

Link: https://lkml.kernel.org/r/20201106023548.102375687@goodmis.org

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Guo Ren <guoren@kernel.org>
Cc: "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>
Cc: Helge Deller <deller@gmx.de>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: x86@kernel.org
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Anton Vorontsov <anton@enomsg.org>
Cc: Colin Cross <ccross@android.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Jiri Kosina <jikos@kernel.org>
Cc: Miroslav Benes <mbenes@suse.cz>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Joe Lawrence <joe.lawrence@redhat.com>
Cc: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>
Cc: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: linux-doc@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-csky@vger.kernel.org
Cc: linux-parisc@vger.kernel.org
Cc: linuxppc-dev@lists.ozlabs.org
Cc: linux-s390@vger.kernel.org
Cc: live-patching@vger.kernel.org
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

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>

If a ftrace callback requires "rcu_is_watching", then it adds the
FTRACE_OPS_FL_RCU flag and it will not be called if RCU is not "watching".
But this means that it will use a trampoline when called, and this slows
down the function tracing a tad. By checking rcu_is_watching() from within
the callback, it no longer needs the RCU flag set in the ftrace_ops and it
can be safely called directly.

Link: https://lkml.kernel.org/r/20201028115613.591878956@goodmis.org
Link: https://lkml.kernel.org/r/20201106023547.711035826@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: Miroslav Benes <mbenes@suse.cz>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

If a ftrace callback does not supply its own recursion protection and
does not set the RECURSION_SAFE flag in its ftrace_ops, then ftrace will
make a helper trampoline to do so before calling the callback instead of
just calling the callback directly.

The default for ftrace_ops is going to change. It will expect that handlers
provide their own recursion protection, unless its ftrace_ops states
otherwise.

Link: https://lkml.kernel.org/r/20201028115613.444477858@goodmis.org
Link: https://lkml.kernel.org/r/20201106023547.466892083@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: Miroslav Benes <mbenes@suse.cz>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

If for some reason a function is called that triggers the recursion
detection of live patching, trigger a warning. By not executing the live
patch code, it is possible that the old unpatched function will be called
placing the system into an unknown state.

Link: https://lore.kernel.org/r/20201029145709.GD16774@alley
Link: https://lkml.kernel.org/r/20201106023547.312639435@goodmis.org

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.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: Joe Lawrence <joe.lawrence@redhat.com>
Cc: live-patching@vger.kernel.org
Suggested-by: Miroslav Benes <mbenes@suse.cz>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Acked-by: Miroslav Benes <mbenes@suse.cz>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

If a ftrace callback does not supply its own recursion protection and
does not set the RECURSION_SAFE flag in its ftrace_ops, then ftrace will
make a helper trampoline to do so before calling the callback instead of
just calling the callback directly.

The default for ftrace_ops is going to change. It will expect that handlers
provide their own recursion protection, unless its ftrace_ops states
otherwise.

Link: https://lkml.kernel.org/r/20201028115613.291169246@goodmis.org
Link: https://lkml.kernel.org/r/20201106023547.122802424@goodmis.org

Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Jiri Kosina <jikos@kernel.org>
Cc: Joe Lawrence <joe.lawrence@redhat.com>
Cc: live-patching@vger.kernel.org
Reviewed-by: Petr Mladek <pmladek@suse.com>
Acked-by: Miroslav Benes <mbenes@suse.cz>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

If a ftrace callback does not supply its own recursion protection and
does not set the RECURSION_SAFE flag in its ftrace_ops, then ftrace will
make a helper trampoline to do so before calling the callback instead of
just calling the callback directly.

The default for ftrace_ops is going to change. It will expect that handlers
provide their own recursion protection, unless its ftrace_ops states
otherwise.

Link: https://lkml.kernel.org/r/20201028115613.140212174@goodmis.org
Link: https://lkml.kernel.org/r/20201106023546.944907560@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: Miroslav Benes <mbenes@suse.cz>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Guo Ren <guoren@kernel.org>
Cc: "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>
Cc: Helge Deller <deller@gmx.de>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: x86@kernel.org
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: "Naveen N. Rao" <naveen.n.rao@linux.ibm.com>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: linux-csky@vger.kernel.org
Cc: linux-parisc@vger.kernel.org
Cc: linuxppc-dev@lists.ozlabs.org
Cc: linux-s390@vger.kernel.org
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

If a ftrace callback does not supply its own recursion protection and
does not set the RECURSION_SAFE flag in its ftrace_ops, then ftrace will
make a helper trampoline to do so before calling the callback instead of
just calling the callback directly.

The default for ftrace_ops is going to change. It will expect that handlers
provide their own recursion protection, unless its ftrace_ops states
otherwise.

Link: https://lkml.kernel.org/r/20201028115612.990886844@goodmis.org
Link: https://lkml.kernel.org/r/20201106023546.720372267@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: Miroslav Benes <mbenes@suse.cz>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Thomas Meyer <thomas@m3y3r.de>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

The preempt_count() is not a simple location in memory, it could be part of
per_cpu code or more. Each access to preempt_count(), or one of its accessor
functions (like in_interrupt()) takes several cycles. By reading
preempt_count() once, and then doing tests to find the context against the
value return is slightly faster than using in_nmi() and in_interrupt().

Link: https://lkml.kernel.org/r/20201028115612.780796355@goodmis.org
Link: https://lkml.kernel.org/r/20201106023546.558881845@goodmis.orgSigned-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

To make it easier for ftrace callbacks to have recursion protection, provide
a ftrace_test_recursion_trylock() and ftrace_test_recursion_unlock() helper
that tests for recursion.

Link: https://lkml.kernel.org/r/20201028115612.634927593@goodmis.org
Link: https://lkml.kernel.org/r/20201106023546.378584067@goodmis.orgSigned-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

Currently, if a callback is registered to a ftrace function and its
ftrace_ops does not have the RECURSION flag set, it is encapsulated in a
helper function that does the recursion for it.

Really, all the callbacks should have their own recursion protection for
performance reasons. But they should not all implement their own. Move the
recursion helpers to global headers, so that all callbacks can use them.

Link: https://lkml.kernel.org/r/20201028115612.460535535@goodmis.org
Link: https://lkml.kernel.org/r/20201106023546.166456258@goodmis.orgSigned-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

Since the kprobe handlers have protection that prohibits other handlers from
executing in other contexts (like if an NMI comes in while processing a
kprobe, and executes the same kprobe, it will get fail with a "busy"
return). Lockdep is unaware of this protection. Use lockdep's nesting api to
differentiate between locks taken in INT3 context and other context to
suppress the false warnings.

Link: https://lore.kernel.org/r/20201102160234.fa0ae70915ad9e2b21c08b85@kernel.org

Cc: Peter Zijlstra <peterz@infradead.org>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

parse_synth_field() returns a pointer and requires that errors get
surrounded by ERR_PTR(). The ret variable is initialized to zero, but should
never be used as zero, and if it is, it could cause a false return code and
produce a NULL pointer dereference. It makes no sense to set ret to zero.

Set ret to -ENOMEM (the most common error case), and have any other errors
set it to something else. This removes the need to initialize ret on *every*
error branch.

Fixes: 761a8c58 ("tracing, synthetic events: Replace buggy strcat() with seq_buf operations")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

The recursion protection of the ring buffer depends on preempt_count() to be
correct. But it is possible that the ring buffer gets called after an
interrupt comes in but before it updates the preempt_count(). This will
trigger a false positive in the recursion code.

Use the same trick from the ftrace function callback recursion code which
uses a "transition" bit that gets set, to allow for a single recursion for
to handle transitions between contexts.

Cc: stable@vger.kernel.org
Fixes: 567cd4da ("ring-buffer: User context bit recursion checking")
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

The array size is FTRACE_KSTACK_NESTING, so the index FTRACE_KSTACK_NESTING
is illegal too. And fix two typos by the way.

Link: https://lkml.kernel.org/r/20201031085714.2147-1-hqjagain@gmail.comSigned-off-by: Qiujun Huang <hqjagain@gmail.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

When an interrupt or NMI comes in and switches the context, there's a delay
from when the preempt_count() shows the update. As the preempt_count() is
used to detect recursion having each context have its own bit get set when
tracing starts, and if that bit is already set, it is considered a recursion
and the function exits. But if this happens in that section where context
has changed but preempt_count() has not been updated, this will be
incorrectly flagged as a recursion.

To handle this case, create another bit call TRANSITION and test it if the
current context bit is already set. Flag the call as a recursion if the
TRANSITION bit is already set, and if not, set it and continue. The
TRANSITION bit will be cleared normally on the return of the function that
set it, or if the current context bit is clear, set it and clear the
TRANSITION bit to allow for another transition between the current context
and an even higher one.

Cc: stable@vger.kernel.org
Fixes: edc15caf ("tracing: Avoid unnecessary multiple recursion checks")
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

The code that checks recursion will work to only do the recursion check once
if there's nested checks. The top one will do the check, the other nested
checks will see recursion was already checked and return zero for its "bit".
On the return side, nothing will be done if the "bit" is zero.

The problem is that zero is returned for the "good" bit when in NMI context.
This will set the bit for NMIs making it look like *all* NMI tracing is
recursing, and prevent tracing of anything in NMI context!

The simple fix is to return "bit + 1" and subtract that bit on the end to
get the real bit.

Cc: stable@vger.kernel.org
Fixes: edc15caf ("tracing: Avoid unnecessary multiple recursion checks")
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

The nesting count of trace_printk allows for 4 levels of nesting. The
nesting counter starts at zero and is incremented before being used to
retrieve the current context's buffer. But the index to the buffer uses the
nesting counter after it was incremented, and not its original number,
which in needs to do.

Link: https://lkml.kernel.org/r/20201029161905.4269-1-hqjagain@gmail.com

Cc: stable@vger.kernel.org
Fixes: 3d9622c1 ("tracing: Add barrier to trace_printk() buffer nesting modification")
Signed-off-by: Qiujun Huang <hqjagain@gmail.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

Pull x86 fixes from Thomas Gleixner:
 "Three fixes all related to #DB:

   - Handle the BTF bit correctly so it doesn't get lost due to a kernel
     #DB

   - Only clear and set the virtual DR6 value used by ptrace on user
     space triggered #DB. A kernel #DB must leave it alone to ensure
     data consistency for ptrace.

   - Make the bitmasking of the virtual DR6 storage correct so it does
     not lose DR_STEP"

* tag 'x86-urgent-2020-11-01' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/debug: Fix DR_STEP vs ptrace_get_debugreg(6)
  x86/debug: Only clear/set ->virtual_dr6 for userspace #DB
  x86/debug: Fix BTF handling

Pull timer fixes from Thomas Gleixner:
 "A few fixes for timers/timekeeping:

   - Prevent undefined behaviour in the timespec64_to_ns() conversion
     which is used for converting user supplied time input to
     nanoseconds. It lacked overflow protection.

   - Mark sched_clock_read_begin/retry() to prevent recursion in the
     tracer

   - Remove unused debug functions in the hrtimer and timerlist code"

* tag 'timers-urgent-2020-11-01' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  time: Prevent undefined behaviour in timespec64_to_ns()
  timers: Remove unused inline funtion debug_timer_free()
  hrtimer: Remove unused inline function debug_hrtimer_free()
  time/sched_clock: Mark sched_clock_read_begin/retry() as notrace

Pull smp fix from Thomas Gleixner:
 "A single fix for stop machine.

  Mark functions no trace to prevent a crash caused by recursion when
  enabling or disabling a tracer on RISC-V (probably all architectures
  which patch through stop machine)"

* tag 'smp-urgent-2020-11-01' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  stop_machine, rcu: Mark functions as notrace

Pull locking fixes from Thomas Gleixner:
 "A couple of locking fixes:

   - Fix incorrect failure injection handling in the fuxtex code

   - Prevent a preemption warning in lockdep when tracking
     local_irq_enable() and interrupts are already enabled

   - Remove more raw_cpu_read() usage from lockdep which causes state
     corruption on !X86 architectures.

   - Make the nr_unused_locks accounting in lockdep correct again"

* tag 'locking-urgent-2020-11-01' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  lockdep: Fix nr_unused_locks accounting
  locking/lockdep: Remove more raw_cpu_read() usage
  futex: Fix incorrect should_fail_futex() handling
  lockdep: Fix preemption WARN for spurious IRQ-enable

Pull char/misc fixes/removals from Greg KH:
 "Here's some small fixes for 5.10-rc2 and a big driver removal.

  The fixes are for some reported issues in the interconnect and
  coresight drivers, nothing major.

  The "big" driver removal is the MIC drivers have been asked to be
  removed as the hardware never shipped and Intel no longer wants to
  maintain something that no one can use. This is welcomed by many as
  the DMA usage of these drivers was "interesting" and the security
  people were starting to question some issues that were starting to be
  found in the codebase.

  Note, one of the subsystems for this driver, the "VOP" code, will
  probably come back in future kernel versions as it was looking to
  potentially solve some PCIe virtualization issues that a number of
  other vendors were wanting to solve. But as-is, this codebase didn't
  work for anyone else so no actual functionality is being removed.

  All of these have been in linux-next with no reported issues"

* tag 'char-misc-5.10-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc:
  coresight: cti: Initialize dynamic sysfs attributes
  coresight: Fix uninitialised pointer bug in etm_setup_aux()
  coresight: add module license
  misc: mic: remove the MIC drivers
  interconnect: qcom: use icc_sync state for sm8[12]50
  interconnect: qcom: Ensure that the floor bandwidth value is enforced
  interconnect: qcom: sc7180: Init BCMs before creating the nodes
  interconnect: qcom: sdm845: Init BCMs before creating the nodes
  interconnect: Aggregate before setting initial bandwidth
  interconnect: qcom: sdm845: Enable keepalive for the MM1 BCM