Impact: corrects a bug which made the non-dyn function tracer not functional
With latest git, the non-dynamic function tracer didn't get any trace.
The problem was the fact that ftrace_enabled wasn't initialized to 1
because ftrace hasn't any init function when DYNAMIC_FTRACE is disabled.
So when a tracer tries to register an ftrace_ops struct,
__register_ftrace_function failed to set the hook.
This patch corrects it by setting an init function to initialize
ftrace during the boot.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
this warning:
kernel/trace/ftrace.c:189: warning: ‘frozen_record_count’ defined but not used
triggers because frozen_record_count is only used in the KCONFIG_MARKERS
case. Move the variable it there.
Alas, this frozen-record facility seems to have little use. The
frozen_record_count variable is not used by anything, nor the flags.
So this section might need a bit of dead-code-removal care as well.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
fix:
kernel/trace/ftrace.c: In function 'ftrace_release':
kernel/trace/ftrace.c:271: error: implicit declaration of function 'ftrace_release_hash'
release_hash is not needed without dftraced.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
The ftrace hash was used by the ftrace_daemon code. The record ip function
would place the calling address (ip) into the hash. The daemon would later
read the hash and modify that code.
The hash complicates the code. This patch removes it.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
The arch dependent function ftrace_mcount_set was only used by the daemon
start up code. This patch removes it.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
The ftrace daemon is complex and error prone. This patch strips it out
of the code.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Add ftrace warn on to disable ftrace as well as report a warning.
[ Thanks to Andrew Morton for suggesting using the WARN_ON return value ]
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
When an anomaly is detected, we need a way to completely disable
ftrace. Right now we have two functions: ftrace_kill and ftrace_kill_atomic.
The ftrace_kill tries to do it in a "nice" way by converting everything
back to a nop.
The "nice" way is dangerous itself, so this patch removes it and only
has the "atomic" version, which is all that is needed.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Have the ftrace_modify_code return error values:
-EFAULT on error of reading the address
-EINVAL if what is read does not match what it expected
-EPERM if the write fails to update after a successful match.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
The x86 architecture uses a static recording of mcount caller locations
and is not affected by this patch.
For architectures still using the dynamic ftrace daemon, this patch is
critical. It removes the race between the recording of a function that
calls mcount, the unloading of a module, and the ftrace daemon updating
the call sites.
This patch adds the releasing of the hash functions that the daemon uses
to update the mcount call sites. When a module is unloaded, not only
are the replaced call site table update, but now so is the hash recorded
functions that the ftrace daemon will use.
Again, architectures that implement MCOUNT_RECORD are not affected by
this (which currently only x86 has).
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
With the recent updates to ftrace, there should not be any failures when
modifying the code. If there is, then we need to warn about it.
This patch has a cleaned up version of the code that I used to discover
that the weak symbols were causing failures.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
When CONFIG_DYNAMIC_FTRACE isn't used, neither is mcount_addr. This
patch eliminates that warning.
Signed-off-by: Steven Noonan <steven@uplinklabs.net>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This must be brown paper bag week for Steven Rostedt!
While working on ftrace for PPC, I discovered that the hash locking done
when CONFIG_FTRACE_MCOUNT_RECORD is not set, is totally incorrect.
With a cut and paste error, I had the hash lock macro to lock for both
hash_lock _and_ hash_unlock!
This bug did not affect x86 since this bug was introduced when
CONFIG_FTRACE_MCOUNT_RECORD was added to x86.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
The mcount record method of ftrace scans objdump for references to mcount.
Using mcount as the reference to test if the calls to mcount being replaced
are indeed calls to mcount, this use of mcount was also caught as a
location to change. Using a variable that points to the mcount address
moves this reference into the data section that is not scanned, and
we do not use a false location to try and modify.
The warn on code was what was used to detect this bug.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
After disabling FTRACE_MCOUNT_RECORD via a patch, a dormant build
failure surfaced:
kernel/trace/ftrace.c: In function 'ftrace_record_ip':
kernel/trace/ftrace.c:416: error: incompatible type for argument 1 of '_spin_lock_irqsave'
kernel/trace/ftrace.c:433: error: incompatible type for argument 1 of '_spin_lock_irqsave'
Introduced by commit 6dad8e07f4c10b17b038e84d29f3ca41c2e55cd0 ("ftrace:
add necessary locking for ftrace records").
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
The new design of pre-recorded mcounts and updating the code outside of
kstop_machine has changed the way the records themselves are protected.
This patch uses the ftrace_lock to protect the records. Note, the lock
still does not need to be taken within calls that are only called via
kstop_machine, since the that code can not run while the spin lock is held.
Also removed the hash_lock needed for the daemon when MCOUNT_RECORD is
configured. Also did a slight cleanup of an unused variable.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
If one of the self tests of ftrace has disabled the function tracer,
do not run the code to convert the mcount calls in modules.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
When a mcount pointer is recorded into a table, it is used to add or
remove calls to mcount (replacing them with nops). If the code is removed
via removing a module, the pointers still exist. At modifying the code
a check is always made to make sure the code being replaced is the code
expected. In-other-words, the code being replaced is compared to what
it is expected to be before being replaced.
There is a very small chance that the code being replaced just happens
to look like code that calls mcount (very small since the call to mcount
is relative). To remove this chance, this patch adds ftrace_release to
allow module unloading to remove the pointers to mcount within the module.
Another change for init calls is made to not trace calls marked with
__init. The tracing can not be started until after init is done anyway.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Seems that freed records can appear in the available_filter_functions list.
This patch fixes that.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This patch enables the loading of the __mcount_section of modules and
changing all the callers of mcount into nops.
The modification is done before the init_module function is called, so
again, we do not need to use kstop_machine to make these changes.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This is the infrastructure to the converting the mcount call sites
recorded by the __mcount_loc section into nops on boot. It also allows
for using these sites to enable tracing as normal. When the __mcount_loc
section is used, the "ftraced" kernel thread is disabled.
This uses the current infrastructure to record the mcount call sites
as well as convert them to nops. The mcount function is kept as a stub
on boot up and not converted to the ftrace_record_ip function. We use the
ftrace_record_ip to only record from the table.
This patch does not handle modules. That comes with a later patch.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
fix:
kernel/trace/ftrace.c:1615: error: 'ftraced_suspend' undeclared (first use in this function)
kernel/trace/ftrace.c:1615: error: (Each undeclared identifier is reported only once
kernel/trace/ftrace.c:1615: error: for each function it appears in.)
Signed-off-by: Ingo Molnar <mingo@elte.hu>
It has been suggested that I add a way to disable the function tracer
on an oops. This code adds a ftrace_kill_atomic. It is not meant to be
used in normal situations. It will disable the ftrace tracer, but will
not perform the nice shutdown that requires scheduling.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Cc: Steven Rostedt <srostedt@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Avoid modifying the mcount call-site if there is a kprobe installed on it.
These records are not marked as failed however. This allowed the filter
rules on them to remain up-to-date. Whenever the kprobe on the corresponding
record is removed, the record gets updated as normal.
Signed-off-by: Abhishek Sagar <sagar.abhishek@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Let records identified as being kprobe'd be marked as "frozen". The trouble
with records which have a kprobe installed on their mcount call-site is
that they don't get updated. So if such a function which is currently being
traced gets its tracing disabled due to a new filter rule (or because it
was added to the notrace list) then it won't be updated and continue being
traced. This patch allows scanning of all frozen records during tracing to
check if they should be traced.
Signed-off-by: Abhishek Sagar <sagar.abhishek@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Record the address of the mcount call-site. Currently all archs except sparc64
record the address of the instruction following the mcount call-site. Some
general cleanups are entailed. Storing mcount addresses in rec->ip enables
looking them up in the kprobe hash table later on to check if they're kprobe'd.
Signed-off-by: Abhishek Sagar <sagar.abhishek@gmail.com>
Cc: davem@davemloft.net
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This is a fix to give notrace filter rules priority over "set_ftrace_filter"
rules.
This fix ensures that functions which are set to be filtered and are
concurrently marked as "notrace" don't get recorded. As of now, if
a record is marked as FTRACE_FL_FILTER and is enabled, then the notrace
flag is not checked. Tested on x86-32.
Signed-off-by: Abhishek Sagar <sagar.abhishek@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Steven Rostedt wrote:
> If we unload a module and reload it, will it ever get converted again?
The intent was always to filter core kernel functions to prevent their freeing.
Here's a fix which should allow re-recording of module call-sites.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Identify functions which had their mcount call-site updates failed. This can
help us track functions which ftrace shouldn't fiddle with, and are thus not
being traced. If there is no race with any external agent which is modifying
the mcount call-site, then this file displays no entries (normal case).
Signed-off-by: Abhishek Sagar <sagar.abhishek@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Prevent freeing of records which cause problems and correspond to function from
core kernel text. A new flag, FTRACE_FL_CONVERTED is used to mark a record
as "converted". All other records are patched lazily to NOPs. Failed records
now also remain on frace_hash table. Each invocation of ftrace_record_ip now
checks whether the traced function has ever been recorded (including past
failures) and doesn't re-record it again.
Signed-off-by: Abhishek Sagar <sagar.abhishek@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
In dynamic ftrace, the mcount function starts off pointing to a stub
function that just returns.
On start up, the call to the stub is modified to point to a "record_ip"
function. The job of the record_ip function is to add the function to
a pre-allocated hash list. If the function is already there, it simply is
ignored, otherwise it is added to the list.
Later, a ftraced daemon wakes up and calls kstop_machine if any functions
have been recorded, and changes the calls to the recorded functions to
a simple nop. If no functions were recorded, the daemon goes back to sleep.
The daemon wakes up once a second to see if it needs to update any newly
recorded functions into nops. Usually it does not, but if a lot of code
has been executed for the first time in the kernel, the ftraced daemon
will call kstop_machine to update those into nops.
The problem currently is that there's no way to stop the daemon from doing
this, and it can cause unneeded latencies (800us which for some is bothersome).
This patch adds a new file /debugfs/tracing/ftraced_enabled. If the daemon
is active, reading this will return "enabled\n" and "disabled\n" when the
daemon is not running. To disable the daemon, the user can echo "0" or
"disable" into this file, and "1" or "enable" to re-enable the daemon.
Since the daemon is used to convert the functions into nops to increase
the performance of the system, I also added that anytime something is
written into the ftraced_enabled file, kstop_machine will run if there
are new functions that have been detected that need to be converted.
This way the user can disable the daemon but still be able to control the
conversion of the mcount calls to nops by simply,
"echo 0 > /debugfs/tracing/ftraced_enabled"
when they need to do more conversions.
To see the number of converted functions:
"cat /debugfs/tracing/dyn_ftrace_total_info"
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Hi Ingo/Steven,
Ftrace currently maintains an update count which includes false updates,
i.e, updates which failed. If anything, such failures should be tracked
by some separate variable, but this patch provides a minimal fix.
Signed-off-by: Abhishek Sagar <sagar.abhishek@gmail.com>
Cc: rostedt@goodmis.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Hi Steven,
I noticed that concurrent instances of ftrace_record_ip()
have a race between ftrace_hash list traversal during
ftrace_ip_in_hash() (before acquiring ftrace_shutdown_lock)
and ftrace_add_hash(). If it's so then this should fix it.
Signed-off-by: Abhishek Sagar <sagar.abhishek@gmail.com>
Cc: rostedt@goodmis.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
While debugging latencies in the RT kernel, I found that it would be nice
to be able to filter away functions from the trace than just to filter
on functions.
I added a new interface to the debugfs tracing directory called
set_ftrace_notrace
When dynamic frace is enabled, this lets you filter away functions that will
not be recorded in the trace. It is similar to adding 'notrace' to those
functions but by doing it without recompiling the kernel.
Here's how set_ftrace_filter and set_ftrace_notrace interact. Remember, if
set_ftrace_filter is set, it removes all functions from the trace execpt for
those listed in the set_ftrace_filter. set_ftrace_notrace will prevent those
functions from being traced.
If you were to set one function in both set_ftrace_filter and
set_ftrace_notrace and that function was the same, then you would end up
with an empty trace.
the set of functions to trace is:
set_ftrace_filter == empty then
all functions not in set_ftrace_notrace
else
set of the set_ftrace_filter and not in set of set_ftrace_notrace.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
David S. Miller noticed the following bug: the -pg instrumentation
function callback is named differently on each platform. On x86 it
is mcount, on sparc it is _mcount. So the export does not make sense
in kernel/trace/ftrace.c - move it to x86.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
It causes unaligned access traps on platforms like sparc
(ftrace_page may be marked packed, but once we return
a dyn_ftrace sub-object from this array to another piece
of code, the "packed" part of the typing information doesn't
propagate).
But also, it didn't serve any purpose either. Even if packed,
on 64-bit or 32-bit, it didn't give us any more dyn_ftrace
entries per-page.
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Due to debug hooks in the kernel that can change the way smp_processor_id
works, use raw_smp_processor_id in mcount called functions (namely
ftrace_record_ip). Currently we annotate most debug functions from calling
mcount, but we should not rely on that to prevent kernel lockups.
This patch uses the raw_smp_processor_id to prevent a recusive crash
that can happen if a debug hook in smp_processor_id calls mcount.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
When dynamic ftrace fails and sets itself disabled, the ftraced daemon
will go back to sleep everytime it wakes up. The setting of the
ftraced state to UNINTERRUPTIBLE is skipped in this process, and the
daemon takes up 100% of the CPU. This patch makes sure the ftraced daemon
sets itself to UNINTERRUPTIBLE in that loop.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
now that we have a kbuild method for notrace, no need to pollute the
C code with the annotations.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
PowerPC is very fragile when it comes to use of function names
and function addresses. ftrace needs to either use all function
addresses or function names (i.e. my_func as suppose to &my_func).
This patch chooses to use the names and not the addresses, and
makes ftrace consistent.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Since ftrace touches practically every function. If we detect any
anomaly, we want to fully disable ftrace. This patch adds code
to try shutdown ftrace as much as possible without doing any more
harm is something is detected not quite correct.
This only kills ftrace, this patch does have checks for other parts of
the tracer (irqsoff, wakeup, etc.).
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
The ftrace dynamic function update allocates a record to store the
instruction pointers that are being modified. If the modified
instruction pointer fails to update, then the record is marked as
failed and nothing more is done.
Worse, if the modification fails, but the record ip function is still
called, it will allocate a new record and try again. In just a matter
of time, will this cause a serious memory leak and crash the system.
This patch plugs this memory leak. When a record fails, it is
included back into the pool of records to be used. Now a record may
fail over and over again, but the number of allocated records will
not increase.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
