There is a regular need in the kernel to provide a way to declare having a
dynamically sized set of trailing elements in a structure. Kernel code should
always use “flexible array members”[1] for these cases. The older style of
one-element or zero-length arrays should no longer be used[2].
[1] https://en.wikipedia.org/wiki/Flexible_array_member
[2] https://github.com/KSPP/linux/issues/21
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Reject exactly same probe events as existing probes.
Multiprobe allows user to define multiple probes on same
event. If user appends a probe which exactly same definition
(same probe address and same arguments) on existing event,
the event will record same probe information twice.
That can be confusing users, so reject it.
Link: http://lkml.kernel.org/r/156879694602.31056.5533024778165036763.stgit@devnote2
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Add immediate string parameter (\"string") support to
probe events. This allows you to specify an immediate
(or dummy) parameter instead of fetching a string from
memory.
This feature looks odd, but imagine that you put a probe
on a code to trace some string data. If the code is
compiled into 2 instructions and 1 instruction has a
string on memory but other has no string since it is
optimized out. In that case, you can not fold those into
one event, even if ftrace supported multiple probes on
one event. With this feature, you can set a dummy string
like foo=\"(optimized)":string instead of something
like foo=+0(+0(%bp)):string.
Link: http://lkml.kernel.org/r/156095691687.28024.13372712423865047991.stgit@devnote2
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Add immediate value parameter (\1234) support to
probe events. This allows you to specify an immediate
(or dummy) parameter instead of fetching from memory
or register.
This feature looks odd, but imagine when you put a probe
on a code to trace some data. If the code is compiled into
2 instructions and 1 instruction has a value but other has
nothing since it is optimized out.
In that case, you can not fold those into one event, even
if ftrace supported multiple probes on one event.
With this feature, you can set a dummy value like
foo=\deadbeef instead of something like foo=%di.
Link: http://lkml.kernel.org/r/156095690733.28024.13258186548822649469.stgit@devnote2
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Allow user to delete a probe from event. This is done by head
match. For example, if we have 2 probes on an event
$ cat kprobe_events
p:kprobes/testprobe _do_fork r1=%ax r2=%dx
p:kprobes/testprobe idle_fork r1=%ax r2=%cx
Then you can remove one of them by passing the head of definition
which identify the probe.
$ echo "-:kprobes/testprobe idle_fork" >> kprobe_events
Link: http://lkml.kernel.org/r/156095688848.28024.15798690082378432435.stgit@devnote2
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Add multi-probe per one event support to kprobe events.
User can define several different probes on one trace event
if those events have same "event signature",
e.g.
# echo p:testevent _do_fork > kprobe_events
# echo p:testevent fork_idle >> kprobe_events
# kprobe_events
p:kprobes/testevent _do_fork
p:kprobes/testevent fork_idle
The event signature is defined by kprobe type (retprobe or not),
the number of args, argument names, and argument types.
Note that this only support appending method. Delete event
operation will delete all probes on the event.
Link: http://lkml.kernel.org/r/156095686913.28024.9357292202316540742.stgit@devnote2
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Add trace_event_file access APIs for trace_probe data structure.
This simplifies enabling/disabling operations in uprobe and kprobe
events so that those don't touch deep inside the trace_probe.
This also removing a redundant synchronization when the
kprobe event is used from perf, since the perf itself uses
tracepoint_synchronize_unregister() after disabling (ftrace-
defined) event, thus we don't have to synchronize in that
path. Also we don't need to identify local trace_kprobe too
anymore.
Link: http://lkml.kernel.org/r/155931584587.28323.372301976283354629.stgit@devnote2
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Support user-space dereference syntax for probe event arguments
to dereference the data-structure or array in user-space.
The syntax is just adding 'u' before an offset value.
+|-u<OFFSET>(<FETCHARG>)
e.g. +u8(%ax), +u0(+0(%si))
For example, if you probe do_sched_setscheduler(pid, policy,
param) and record param->sched_priority, you can add new
probe as below;
p do_sched_setscheduler priority=+u0($arg3)
Note that kprobe event provides this and it doesn't change the
dereference method automatically because we do not know whether
the given address is in userspace or kernel on some archs.
So as same as "ustring", this is an option for user, who has to
carefully choose the dereference method.
Link: http://lkml.kernel.org/r/155789872187.26965.4468456816590888687.stgit@devnote2
Acked-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Add "ustring" type for fetching user-space string from kprobe event.
User can specify ustring type at uprobe event, and it is same as
"string" for uprobe.
Note that probe-event provides this option but it doesn't choose the
correct type automatically since we have not way to decide the address
is in user-space or not on some arch (and on some other arch, you can
fetch the string by "string" type). So user must carefully check the
target code (e.g. if you see __user on the target variable) and
use this new type.
Link: http://lkml.kernel.org/r/155789871009.26965.14167558859557329331.stgit@devnote2
Acked-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Since commit 533059281e ("tracing: probeevent: Introduce new
argument fetching code") dropped the $comm support from uprobe
events, this re-enables it.
For $comm support, uses strlcpy() instead of strncpy_from_user()
to copy current task's comm. Because it is in the kernel space,
strncpy_from_user() always fails to copy the comm.
This also uses strlen() instead of strnlen_user() to measure the
length of the comm.
Note that this uses -ECOMM as a token value to fetch the comm
string. If the user-space pointer points -ECOMM, it will be
translated to task->comm.
Link: http://lkml.kernel.org/r/155723734162.9149.4042756162201097965.stgit@devnote2
Fixes: 533059281e ("tracing: probeevent: Introduce new argument fetching code")
Reported-by: Andreas Ziegler <andreas.ziegler@fau.de>
Acked-by: Andreas Ziegler <andreas.ziegler@fau.de>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Allow kprobe-events to record module symbols.
Since data symbols in a non-loaded module doesn't exist, it fails to
define such symbol as an argument of kprobe-event. But if the kprobe
event is defined on that module, we can defer to resolve the symbol
address.
Note that if given symbol is not found, the event is kept unavailable.
User can enable it but the event is not recorded.
Link: http://lkml.kernel.org/r/153547312336.26502.11432902826345374463.stgit@devbox
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Add $argN special fetch variable for accessing function
arguments. This allows user to trace the Nth argument easily
at the function entry.
Note that this returns most probably assignment of registers
and stacks. In some case, it may not work well. If you need
to access correct registers or stacks you should use perf-probe.
Link: http://lkml.kernel.org/r/152465888632.26224.3412465701570253696.stgit@devbox
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
