Now that there's pretty much a one to one mapping between the struct
event_trigger_ops and struct event_command, there's no reason to have two
different structures. Merge the function pointers of event_trigger_ops
into event_command.
There's one exception in trace_events_hist.c for the
event_hist_trigger_named_ops. This has special logic for the init and free
function pointers for "named histograms". In this case, allocate the
cmd_ops of the event_trigger_data and set it to the proper init and free
functions, which are used to initialize and free the event_trigger_data
respectively. Have the free function and the init function (on failure)
free the cmd_ops of the data element.
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: https://patch.msgid.link/20251125200932.446322765@kernel.org
Reviewed-by: Tom Zanussi <zanussi@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
The struct event_command has a callback function called get_trigger_ops().
This callback returns the "trigger_ops" to use for the trigger. These ops
define the trigger function, how to init the trigger, how to print the
trigger and how to free it.
The only reason there's a callback function to get these ops is because
some triggers have two types of operations. One is an "always on"
operation, and the other is a "count down" operation. If a user passes in
a parameter to say how many times the trigger should execute. For example:
echo stacktrace:5 > events/kmem/kmem_cache_alloc/trigger
It will trigger the stacktrace for the first 5 times the kmem_cache_alloc
event is hit.
Instead of having two different trigger_ops since the only difference
between them is the tigger itself (the print, init and free functions are
all the same), just use a single ops that the event_command points to and
add a function field to the trigger_ops to have a count_func.
When a trigger is added to an event, if there's a count attached to it and
the trigger ops has the count_func field, the data allocated to represent
this trigger will have a new flag set called COUNT.
Then when the trigger executes, it will check if the COUNT data flag is
set, and if so, it will call the ops count_func(). If that returns false,
it returns without executing the trigger.
This removes the need for duplicate event_trigger_ops structures.
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: https://patch.msgid.link/20251125200932.274566147@kernel.org
Reviewed-by: Tom Zanussi <zanussi@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
The option "graph-time" affects the function profiler when it is using the
function graph infrastructure. It has nothing to do with the function
graph tracer itself. The option only affects the global function profiler
and does nothing to the function graph tracer.
Move it out of the function graph tracer options and make it a global
option that is only available at the top level instance.
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: https://patch.msgid.link/20251114192318.781711154@kernel.org
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
When the system has many cores and task switching is frequent,
setting set_ftrace_pid can cause frequent pid_list->lock contention
and high system sys usage.
For example, in a 288-core VM environment, we observed 267 CPUs
experiencing contention on pid_list->lock, with stack traces showing:
#4 [ffffa6226fb4bc70] native_queued_spin_lock_slowpath at ffffffff99cd4b7e
#5 [ffffa6226fb4bc90] _raw_spin_lock_irqsave at ffffffff99cd3e36
#6 [ffffa6226fb4bca0] trace_pid_list_is_set at ffffffff99267554
#7 [ffffa6226fb4bcc0] trace_ignore_this_task at ffffffff9925c288
#8 [ffffa6226fb4bcd8] ftrace_filter_pid_sched_switch_probe at ffffffff99246efe
#9 [ffffa6226fb4bcf0] __schedule at ffffffff99ccd161
Replaces the existing spinlock with a seqlock to allow concurrent readers,
while maintaining write exclusivity.
Link: https://patch.msgid.link/20251113000252.1058144-1-leonylgao@gmail.com
Reviewed-by: Huang Cun <cunhuang@tencent.com>
Signed-off-by: Yongliang Gao <leonylgao@tencent.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Currently the function graph tracer's options are saved via a global mask
when it should be per instance. Use the new infrastructure to define a
"default_flags" field in the tracer structure that is used for the top
level instance as well as new ones.
Currently the global mask causes confusion:
# cd /sys/kernel/tracing
# mkdir instances/foo
# echo function_graph > instances/foo/current_tracer
# echo 1 > options/funcgraph-args
# echo function_graph > current_tracer
# cat trace
[..]
2) | _raw_spin_lock_irq(lock=0xffff96b97dea16c0) {
2) 0.422 us | do_raw_spin_lock(lock=0xffff96b97dea16c0);
7) | rcu_sched_clock_irq(user=0) {
2) 1.478 us | }
7) 0.758 us | rcu_is_cpu_rrupt_from_idle();
2) 0.647 us | enqueue_hrtimer(timer=0xffff96b97dea2058, base=0xffff96b97dea1740, mode=0);
# cat instances/foo/options/funcgraph-args
1
# cat instances/foo/trace
[..]
4) | __x64_sys_read() {
4) | ksys_read() {
4) 0.755 us | fdget_pos();
4) | vfs_read() {
4) | rw_verify_area() {
4) | security_file_permission() {
4) | apparmor_file_permission() {
4) | common_file_perm() {
4) | aa_file_perm() {
4) | rcu_read_lock_held() {
[..]
The above shows that updating the "funcgraph-args" option at the top level
instance also updates the "funcgraph-args" option in the instance but
because the update is only done by the instance that gets changed (as it
should), it's confusing to see that the option is already set in the other
instance.
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: https://patch.msgid.link/20251111232429.641030027@kernel.org
Fixes: c132be2c4f ("function_graph: Have the instances use their own ftrace_ops for filtering")
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Currently the function tracer's options are saved via a global mask when
it should be per instance. Use the new infrastructure to define a
"default_flags" field in the tracer structure that is used for the top
level instance as well as new ones.
Currently the global mask causes confusion:
# cd /sys/kernel/tracing
# mkdir instances/foo
# echo function > instances/foo/current_tracer
# echo 1 > options/func-args
# echo function > current_tracer
# cat trace
[..]
<idle>-0 [005] d..3. 1050.656187: rcu_needs_cpu() <-tick_nohz_next_event
<idle>-0 [005] d..3. 1050.656188: get_next_timer_interrupt(basej=0x10002dbad, basem=0xf45fd7d300) <-tick_nohz_next_event
<idle>-0 [005] d..3. 1050.656189: _raw_spin_lock(lock=0xffff8944bdf5de80) <-__get_next_timer_interrupt
<idle>-0 [005] d..4. 1050.656190: do_raw_spin_lock(lock=0xffff8944bdf5de80) <-__get_next_timer_interrupt
<idle>-0 [005] d..4. 1050.656191: _raw_spin_lock_nested(lock=0xffff8944bdf5f140, subclass=1) <-__get_next_timer_interrupt
# cat instances/foo/options/func-args
1
# cat instances/foo/trace
[..]
kworker/4:1-88 [004] ...1. 298.127735: next_zone <-refresh_cpu_vm_stats
kworker/4:1-88 [004] ...1. 298.127736: first_online_pgdat <-refresh_cpu_vm_stats
kworker/4:1-88 [004] ...1. 298.127738: next_online_pgdat <-refresh_cpu_vm_stats
kworker/4:1-88 [004] ...1. 298.127739: fold_diff <-refresh_cpu_vm_stats
kworker/4:1-88 [004] ...1. 298.127741: round_jiffies_relative <-vmstat_update
[..]
The above shows that updating the "func-args" option at the top level
instance also updates the "func-args" option in the instance but because
the update is only done by the instance that gets changed (as it should),
it's confusing to see that the option is already set in the other instance.
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: https://patch.msgid.link/20251111232429.470883736@kernel.org
Fixes: f20a580627 ("ftrace: Allow instances to use function tracing")
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Tracers can add specify options to modify them. This logic was added
before instances were created and the tracer flags were global variables.
After instances were created where a tracer may exist in more than one
instance, the flags were not updated from being global into instance
specific. This causes confusion with these options. For example, the
function tracer has an option to enable function arguments:
# cd /sys/kernel/tracing
# mkdir instances/foo
# echo function > instances/foo/current_tracer
# echo 1 > options/func-args
# echo function > current_tracer
# cat trace
[..]
<idle>-0 [005] d..3. 1050.656187: rcu_needs_cpu() <-tick_nohz_next_event
<idle>-0 [005] d..3. 1050.656188: get_next_timer_interrupt(basej=0x10002dbad, basem=0xf45fd7d300) <-tick_nohz_next_event
<idle>-0 [005] d..3. 1050.656189: _raw_spin_lock(lock=0xffff8944bdf5de80) <-__get_next_timer_interrupt
<idle>-0 [005] d..4. 1050.656190: do_raw_spin_lock(lock=0xffff8944bdf5de80) <-__get_next_timer_interrupt
<idle>-0 [005] d..4. 1050.656191: _raw_spin_lock_nested(lock=0xffff8944bdf5f140, subclass=1) <-__get_next_timer_interrupt
# cat instances/foo/options/func-args
1
# cat instances/foo/trace
[..]
kworker/4:1-88 [004] ...1. 298.127735: next_zone <-refresh_cpu_vm_stats
kworker/4:1-88 [004] ...1. 298.127736: first_online_pgdat <-refresh_cpu_vm_stats
kworker/4:1-88 [004] ...1. 298.127738: next_online_pgdat <-refresh_cpu_vm_stats
kworker/4:1-88 [004] ...1. 298.127739: fold_diff <-refresh_cpu_vm_stats
kworker/4:1-88 [004] ...1. 298.127741: round_jiffies_relative <-vmstat_update
[..]
The above shows that setting "func-args" in the top level instance also
set it in the instance "foo", but since the interface of the trace flags
are per instance, the update didn't take affect in the "foo" instance.
Update the infrastructure to allow tracers to add a "default_flags" field
in the tracer structure that can be set instead of "flags" which will make
the flags per instance. If a tracer needs to keep the flags global (like
blktrace), keeping the "flags" field set will keep the old behavior.
This does not update function or the function graph tracers. That will be
handled later.
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: https://patch.msgid.link/20251111232429.305317942@kernel.org
Fixes: f20a580627 ("ftrace: Allow instances to use function tracing")
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Updates to the function profiler adds new options to tracefs. The options
are currently defined by an enum as flags. The added options brings the
number of options over 32, which means they can no longer be held in a 32
bit enum. The TRACE_ITER_* flags are converted to a macro TRACE_ITER(*) to
allow the creation of options to still be done by macros.
This change is intrusive, as it affects all TRACE_ITER* options throughout
the trace code. Merge the branch that added these options and converted
the TRACE_ITER_* enum into a TRACE_ITER(*) macro, to allow the topic
branches to still be developed without conflict.
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Function profiler shows the hit count of each function using its symbol
name. However, there are some same-name local symbols, which we can not
distinguish.
To solve this issue, this introduces an option to show the symbols
in "_text+OFFSET" format. This can avoid exposing the random shift of
KASLR. The functions in modules are shown as "MODNAME+OFFSET" where the
offset is from ".text".
E.g. for the kernel text symbols, specify vmlinux and the output to
addr2line, you can find the actual function and source info;
$ addr2line -fie vmlinux _text+3078208
__balance_callbacks
kernel/sched/core.c:5064
for modules, specify the module file and .text+OFFSET;
$ addr2line -fie samples/trace_events/trace-events-sample.ko .text+8224
do_simple_thread_func
samples/trace_events/trace-events-sample.c:23
Link: https://lore.kernel.org/all/176187878064.994619.8878296550240416558.stgit@devnote2/
Suggested-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Add some logic to give the openat system call trace event a bit more human
readable information:
syscalls:sys_enter_openat: dfd: 0xffffff9c, filename: 0x7f0053dc121c "/etc/ld.so.cache", flags: O_RDONLY|O_CLOEXEC, mode: 0000
The above is output from "perf script" and now shows the flags used by the
openat system call.
Since the output from tracing is in the kernel, it can also remove the
mode field when not used (when flags does not contain O_CREATE|O_TMPFILE)
touch-1185 [002] ...1. 1291.690154: sys_openat(dfd: 4294967196, filename: 139785545139344 "/usr/lib/locale/locale-archive", flags: O_RDONLY|O_CLOEXEC)
touch-1185 [002] ...1. 1291.690504: sys_openat(dfd: 18446744073709551516, filename: 140733603151330 "/tmp/x", flags: O_WRONLY|O_CREAT|O_NOCTTY|O_NONBLOCK, mode: 0666)
As system calls have a fixed ABI, their trace events can be extended. This
currently only updates the openat system call, but others may be extended
in the future.
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Takaya Saeki <takayas@google.com>
Cc: Tom Zanussi <zanussi@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ian Rogers <irogers@google.com>
Cc: Douglas Raillard <douglas.raillard@arm.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Link: https://lore.kernel.org/20251028231148.763161484@kernel.org
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
When a system call that can copy user space addresses into the ring
buffer, it can copy up to 511 bytes of data. This can waste precious ring
buffer space if the user isn't interested in the output. Add a new file
"syscall_user_buf_size" that gets initialized to a new config
CONFIG_SYSCALL_BUF_SIZE_DEFAULT that defaults to 63.
The config also is used to limit how much perf can read from user space.
Also lower the max down to 165, as this isn't to record everything that a
system call may be passing through to the kernel. 165 is more than enough.
The reason for 165 is because adding one for the nul terminating byte, as
well as possibly needing to append the "..." string turns it into 170
bytes. As this needs to save up to 3 arguments and 3 * 170 is 510 which
fits nicely in 512 bytes (a power of 2).
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Takaya Saeki <takayas@google.com>
Cc: Tom Zanussi <zanussi@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ian Rogers <irogers@google.com>
Cc: Douglas Raillard <douglas.raillard@arm.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Link: https://lore.kernel.org/20251028231148.260068913@kernel.org
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Allow more than one field of a syscall trace event to read user space.
Build on top of the user_mask by allowing more than one bit to be set that
corresponds to the @args array of the syscall metadata. For each argument
in the @args array that is to be read, it will have a dynamic array/string
field associated to it.
Note that multiple fields to be read from user space is not supported if
the user_arg_size field is set in the syscall metada. That field can only
be used if only one field is being read from user space as that field is a
number representing the size field of the syscall event that holds the
size of the data to read from user space. It becomes ambiguous if the
system call reads more than one field. Currently this is not an issue.
If a syscall event happens to enable two events to read user space and
sets the user_arg_size field, it will trigger a warning at boot and the
user_arg_size field will be cleared.
The per CPU buffer that is used to read the user space addresses is now
broken up into 3 sections, each of 168 bytes. The reason for 168 is that
it is the biggest portion of 512 bytes divided by 3 that is 8 byte aligned.
The max amount copied into the ring buffer from user space is now only 128
bytes, which is plenty. When reading user space, it still reads 167
(168-1) bytes and uses the remaining to know if it should append the extra
"..." to the end or not.
This will allow the event to look like this:
sys_renameat2(olddfd: 0xffffff9c, oldname: 0x7ffe02facdff "/tmp/x", newdfd: 0xffffff9c, newname: 0x7ffe02face06 "/tmp/y", flags: 1)
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Takaya Saeki <takayas@google.com>
Cc: Tom Zanussi <zanussi@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ian Rogers <irogers@google.com>
Cc: Douglas Raillard <douglas.raillard@arm.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Link: https://lore.kernel.org/20251028231148.095789277@kernel.org
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
As of commit 654ced4a13 ("tracing: Introduce tracepoint_is_faultable()")
system call trace events allow faulting in user space memory. Have some of
the system call trace events take advantage of this.
Use the trace_user_fault_read() logic to read the user space buffer from
user space and instead of just saving the pointer to the buffer in the
system call event, also save the string that is passed in.
The syscall event has its nb_args shorten from an int to a short (where
even u8 is plenty big enough) and the freed two bytes are used for
"user_mask". The new "user_mask" field is used to store the index of the
"args" field array that has the address to read from user space. This
value is set to 0 if the system call event does not need to read user
space for a field. This mask can be used to know if the event may fault or
not. Only one bit set in user_mask is supported at this time.
This allows the output to look like this:
sys_access(filename: 0x7f8c55368470 "/etc/ld.so.preload", mode: 4)
sys_execve(filename: 0x564ebcf5a6b8 "/usr/bin/emacs", argv: 0x7fff357c0300, envp: 0x564ebc4a4820)
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Takaya Saeki <takayas@google.com>
Cc: Tom Zanussi <zanussi@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ian Rogers <irogers@google.com>
Cc: Douglas Raillard <douglas.raillard@arm.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Link: https://lore.kernel.org/20251028231147.261867956@kernel.org
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
The write to the trace_marker file is a critical section where it cannot
take locks nor allocate memory. To read from user space, it allocates a per
CPU buffer when the trace_marker file is opened, and then when the write
system call is performed, it uses the following method to read from user
space:
preempt_disable();
buffer = per_cpu_ptr(cpu_buffers, cpu);
do {
cnt = nr_context_switches_cpu();
migrate_disable();
preempt_enable();
ret = copy_from_user(buffer, ptr, len);
preempt_disable();
migrate_enable();
} while (!ret && cnt != nr_context_switches_cpu());
if (!ret)
ring_buffer_write(buffer);
preempt_enable();
It records the number of context switches for the current CPU, enables
preemption, copies from user space, disable preemption and then checks if
the number of context switches changed. If it did not, then the buffer is
valid, otherwise the buffer may have been corrupted and the read from user
space must be tried again.
The system call trace events are now faultable and have the same
restrictions as the trace_marker write. For system calls to read the user
space buffer (for example to read the file of the openat system call), it
needs the same logic. Instead of copying the code over to the system call
trace events, make the code generic to allow the system call trace events to
use the same code. The following API is added internally to the tracing sub
system (these are only exposed within the tracing subsystem and not to be
used outside of it):
trace_user_fault_init() - initializes a trace_user_buf_info descriptor
that will allocate the per CPU buffers to copy from user space into.
trace_user_fault_destroy() - used to free the allocations made by
trace_user_fault_init().
trace_user_fault_get() - update the ref count of the info descriptor to
allow more than one user to use the same descriptor.
trace_user_fault_put() - decrement the ref count.
trace_user_fault_read() - performs the above action to read user space
into the per CPU buffer. The preempt_disable() is expected before
calling this function and preemption must remain disabled while the
buffer returned is in use.
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Takaya Saeki <takayas@google.com>
Cc: Tom Zanussi <zanussi@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ian Rogers <irogers@google.com>
Cc: Douglas Raillard <douglas.raillard@arm.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Link: https://lore.kernel.org/20251028231147.096570057@kernel.org
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Pull tracing fixes from Steven Rostedt:
"The previous fix to trace_marker required updating trace_marker_raw as
well. The difference between trace_marker_raw from trace_marker is
that the raw version is for applications to write binary structures
directly into the ring buffer instead of writing ASCII strings. This
is for applications that will read the raw data from the ring buffer
and get the data structures directly. It's a bit quicker than using
the ASCII version.
Unfortunately, it appears that our test suite has several tests that
test writes to the trace_marker file, but lacks any tests to the
trace_marker_raw file (this needs to be remedied). Two issues came
about the update to the trace_marker_raw file that syzbot found:
- Fix tracing_mark_raw_write() to use per CPU buffer
The fix to use the per CPU buffer to copy from user space was
needed for both the trace_maker and trace_maker_raw file.
The fix for reading from user space into per CPU buffers properly
fixed the trace_marker write function, but the trace_marker_raw
file wasn't fixed properly. The user space data was correctly
written into the per CPU buffer, but the code that wrote into the
ring buffer still used the user space pointer and not the per CPU
buffer that had the user space data already written.
- Stop the fortify string warning from writing into trace_marker_raw
After converting the copy_from_user_nofault() into a memcpy(),
another issue appeared. As writes to the trace_marker_raw expects
binary data, the first entry is a 4 byte identifier. The entry
structure is defined as:
struct {
struct trace_entry ent;
int id;
char buf[];
};
The size of this structure is reserved on the ring buffer with:
size = sizeof(*entry) + cnt;
Then it is copied from the buffer into the ring buffer with:
memcpy(&entry->id, buf, cnt);
This use to be a copy_from_user_nofault(), but now converting it to
a memcpy() triggers the fortify-string code, and causes a warning.
The allocated space is actually more than what is copied, as the
cnt used also includes the entry->id portion. Allocating
sizeof(*entry) plus cnt is actually allocating 4 bytes more than
what is needed.
Change the size function to:
size = struct_size(entry, buf, cnt - sizeof(entry->id));
And update the memcpy() to unsafe_memcpy()"
* tag 'trace-v6.18-3' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
tracing: Stop fortify-string from warning in tracing_mark_raw_write()
tracing: Fix tracing_mark_raw_write() to use buf and not ubuf
The fix to use a per CPU buffer to read user space tested only the writes
to trace_marker. But it appears that the selftests are missing tests to
the trace_maker_raw file. The trace_maker_raw file is used by applications
that writes data structures and not strings into the file, and the tools
read the raw ring buffer to process the structures it writes.
The fix that reads the per CPU buffers passes the new per CPU buffer to
the trace_marker file writes, but the update to the trace_marker_raw write
read the data from user space into the per CPU buffer, but then still used
then passed the user space address to the function that records the data.
Pass in the per CPU buffer and not the user space address.
TODO: Add a test to better test trace_marker_raw.
Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: https://lore.kernel.org/20251011035243.386098147@kernel.org
Fixes: 64cf7d058a ("tracing: Have trace_marker use per-cpu data to read user space")
Reported-by: syzbot+9a2ede1643175f350105@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/68e973f5.050a0220.1186a4.0010.GAE@google.com/
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Pull tracing clean up and fixes from Steven Rostedt:
- Have osnoise tracer use memdup_user_nul()
The function osnoise_cpus_write() open codes a kmalloc() and then a
copy_from_user() and then adds a nul byte at the end which is the
same as simply using memdup_user_nul().
- Fix wakeup and irq tracers when failing to acquire calltime
When the wakeup and irq tracers use the function graph tracer for
tracing function times, it saves a timestamp into the fgraph shadow
stack. It is possible that this could fail to be stored. If that
happens, it exits the routine early. These functions also disable
nesting of the operations by incremeting the data "disable" counter.
But if the calltime exits out early, it never increments the counter
back to what it needs to be.
Since there's only a couple of lines of code that does work after
acquiring the calltime, instead of exiting out early, reverse the if
statement to be true if calltime is acquired, and place the code that
is to be done within that if block. The clean up will always be done
after that.
- Fix ring_buffer_map() return value on failure of __rb_map_vma()
If __rb_map_vma() fails in ring_buffer_map(), it does not return an
error. This means the caller will be working against a bad vma
mapping. Have ring_buffer_map() return an error when __rb_map_vma()
fails.
- Fix regression of writing to the trace_marker file
A bug fix was made to change __copy_from_user_inatomic() to
copy_from_user_nofault() in the trace_marker write function. The
trace_marker file is used by applications to write into it (usually
with a file descriptor opened at the start of the program) to record
into the tracing system. It's usually used in critical sections so
the write to trace_marker is highly optimized.
The reason for copying in an atomic section is that the write
reserves space on the ring buffer and then writes directly into it.
After it writes, it commits the event. The time between reserve and
commit must have preemption disabled.
The trace marker write does not have any locking nor can it allocate
due to the nature of it being a critical path.
Unfortunately, converting __copy_from_user_inatomic() to
copy_from_user_nofault() caused a regression in Android. Now all the
writes from its applications trigger the fault that is rejected by
the _nofault() version that wasn't rejected by the _inatomic()
version. Instead of getting data, it now just gets a trace buffer
filled with:
tracing_mark_write: <faulted>
To fix this, on opening of the trace_marker file, allocate per CPU
buffers that can be used by the write call. Then when entering the
write call, do the following:
preempt_disable();
cpu = smp_processor_id();
buffer = per_cpu_ptr(cpu_buffers, cpu);
do {
cnt = nr_context_switches_cpu(cpu);
migrate_disable();
preempt_enable();
ret = copy_from_user(buffer, ptr, size);
preempt_disable();
migrate_enable();
} while (!ret && cnt != nr_context_switches_cpu(cpu));
if (!ret)
ring_buffer_write(buffer);
preempt_enable();
This works similarly to seqcount. As it must enabled preemption to do
a copy_from_user() into a per CPU buffer, if it gets preempted, the
buffer could be corrupted by another task.
To handle this, read the number of context switches of the current
CPU, disable migration, enable preemption, copy the data from user
space, then immediately disable preemption again. If the number of
context switches is the same, the buffer is still valid. Otherwise it
must be assumed that the buffer may have been corrupted and it needs
to try again.
Now the trace_marker write can get the user data even if it has to
fault it in, and still not grab any locks of its own.
* tag 'trace-v6.18-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
tracing: Have trace_marker use per-cpu data to read user space
ring buffer: Propagate __rb_map_vma return value to caller
tracing: Fix irqoff tracers on failure of acquiring calltime
tracing: Fix wakeup tracers on failure of acquiring calltime
tracing/osnoise: Replace kmalloc + copy_from_user with memdup_user_nul
It was reported that using __copy_from_user_inatomic() can actually
schedule. Which is bad when preemption is disabled. Even though there's
logic to check in_atomic() is set, but this is a nop when the kernel is
configured with PREEMPT_NONE. This is due to page faulting and the code
could schedule with preemption disabled.
Link: https://lore.kernel.org/all/20250819105152.2766363-1-luogengkun@huaweicloud.com/
The solution was to change the __copy_from_user_inatomic() to
copy_from_user_nofault(). But then it was reported that this caused a
regression in Android. There's several applications writing into
trace_marker() in Android, but now instead of showing the expected data,
it is showing:
tracing_mark_write: <faulted>
After reverting the conversion to copy_from_user_nofault(), Android was
able to get the data again.
Writes to the trace_marker is a way to efficiently and quickly enter data
into the Linux tracing buffer. It takes no locks and was designed to be as
non-intrusive as possible. This means it cannot allocate memory, and must
use pre-allocated data.
A method that is actively being worked on to have faultable system call
tracepoints read user space data is to allocate per CPU buffers, and use
them in the callback. The method uses a technique similar to seqcount.
That is something like this:
preempt_disable();
cpu = smp_processor_id();
buffer = this_cpu_ptr(&pre_allocated_cpu_buffers, cpu);
do {
cnt = nr_context_switches_cpu(cpu);
migrate_disable();
preempt_enable();
ret = copy_from_user(buffer, ptr, size);
preempt_disable();
migrate_enable();
} while (!ret && cnt != nr_context_switches_cpu(cpu));
if (!ret)
ring_buffer_write(buffer);
preempt_enable();
It's a little more involved than that, but the above is the basic logic.
The idea is to acquire the current CPU buffer, disable migration, and then
enable preemption. At this moment, it can safely use copy_from_user().
After reading the data from user space, it disables preemption again. It
then checks to see if there was any new scheduling on this CPU. If there
was, it must assume that the buffer was corrupted by another task. If
there wasn't, then the buffer is still valid as only tasks in preemptable
context can write to this buffer and only those that are running on the
CPU.
By using this method, where trace_marker open allocates the per CPU
buffers, trace_marker writes can access user space and even fault it in,
without having to allocate or take any locks of its own.
Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Luo Gengkun <luogengkun@huaweicloud.com>
Cc: Wattson CI <wattson-external@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/20251008124510.6dba541a@gandalf.local.home
Fixes: 3d62ab32df ("tracing: Fix tracing_marker may trigger page fault during preempt_disable")
Reported-by: Runping Lai <runpinglai@google.com>
Tested-by: Runping Lai <runpinglai@google.com>
Closes: https://lore.kernel.org/linux-trace-kernel/20251007003417.3470979-2-runpinglai@google.com/
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Pull tracing updates from Steven Rostedt:
- Use READ_ONCE() and WRITE_ONCE() instead of RCU for syscall
tracepoints
Individual system call trace events are pseudo events attached to the
raw_syscall trace events that just trace the entry and exit of all
system calls. When any of these individual system call trace events
get enabled, an element in an array indexed by the system call number
is assigned to the trace file that defines how to trace it. When the
trace event triggers, it reads this array and if the array has an
element, it uses that trace file to know what to write it (the trace
file defines the output format of the corresponding system call).
The issue is that it uses rcu_dereference_ptr() and marks the
elements of the array as using RCU. This is incorrect. There is no
RCU synchronization here. The event file that is pointed to has a
completely different way to make sure its freed properly. The reading
of the array during the system call trace event is only to know if
there is a value or not. If not, it does nothing (it means this
system call isn't being traced). If it does, it uses the information
to store the system call data.
The RCU usage here can simply be replaced by READ_ONCE() and
WRITE_ONCE() macros.
- Have the system call trace events use "0x" for hex values
Some system call trace events display hex values but do not have "0x"
in front of it. Seeing "count: 44" can be assumed that it is 44
decimal when in actuality it is 44 hex (68 decimal). Display "0x44"
instead.
- Use vmalloc_array() in tracing_map_sort_entries()
The function tracing_map_sort_entries() used array_size() and
vmalloc() when it could have simply used vmalloc_array().
- Use for_each_online_cpu() in trace_osnoise.c()
Instead of open coding for_each_cpu(cpu, cpu_online_mask), use
for_each_online_cpu().
- Move the buffer field in struct trace_seq to the end
The buffer field in struct trace_seq is architecture dependent in
size, and caused padding for the fields after it. By moving the
buffer to the end of the structure, it compacts the trace_seq
structure better.
- Remove redundant zeroing of cmdline_idx field in
saved_cmdlines_buffer()
The structure that contains cmdline_idx is zeroed by memset(), no
need to explicitly zero any of its fields after that.
- Use system_percpu_wq instead of system_wq in user_event_mm_remove()
As system_wq is being deprecated, use the new wq.
- Add cond_resched() is ftrace_module_enable()
Some modules have a lot of functions (thousands of them), and the
enabling of those functions can take some time. On non preemtable
kernels, it was triggering a watchdog timeout. Add a cond_resched()
to prevent that.
- Add a BUILD_BUG_ON() to make sure PID_MAX_DEFAULT is always a power
of 2
There's code that depends on PID_MAX_DEFAULT being a power of 2 or it
will break. If in the future that changes, make sure the build fails
to ensure that the code is fixed that depends on this.
- Grab mutex_lock() before ever exiting s_start()
The s_start() function is a seq_file start routine. As s_stop() is
always called even if s_start() fails, and s_stop() expects the
event_mutex to be held as it will always release it. That mutex must
always be taken in s_start() even if that function fails.
* tag 'trace-v6.18' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
tracing: Fix lock imbalance in s_start() memory allocation failure path
tracing: Ensure optimized hashing works
ftrace: Fix softlockup in ftrace_module_enable
tracing: replace use of system_wq with system_percpu_wq
tracing: Remove redundant 0 value initialization
tracing: Move buffer in trace_seq to end of struct
tracing/osnoise: Use for_each_online_cpu() instead of for_each_cpu()
tracing: Use vmalloc_array() to improve code
tracing: Have syscall trace events show "0x" for values greater than 10
tracing: Replace syscall RCU pointer assignment with READ/WRITE_ONCE()
Pull probe fix from Masami Hiramatsu:
- Fix race condition in kprobe initialization causing NULL pointer
dereference. This happens on weak memory model, which does not
correctly manage the flags access with appropriate memory barriers.
Use RELEASE-ACQUIRE to fix it.
* tag 'probes-fixes-v6.17' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
tracing: Fix race condition in kprobe initialization causing NULL pointer dereference
Pull file->f_path constification from Al Viro:
"Only one thing was modifying ->f_path of an opened file - acct(2).
Massaging that away and constifying a bunch of struct path * arguments
in functions that might be given &file->f_path ends up with the
situation where we can turn ->f_path into an anon union of const
struct path f_path and struct path __f_path, the latter modified only
in a few places in fs/{file_table,open,namei}.c, all for struct file
instances that are yet to be opened"
* tag 'pull-f_path' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (23 commits)
Have cc(1) catch attempts to modify ->f_path
kernel/acct.c: saner struct file treatment
configfs:get_target() - release path as soon as we grab configfs_item reference
apparmor/af_unix: constify struct path * arguments
ovl_is_real_file: constify realpath argument
ovl_sync_file(): constify path argument
ovl_lower_dir(): constify path argument
ovl_get_verity_digest(): constify path argument
ovl_validate_verity(): constify {meta,data}path arguments
ovl_ensure_verity_loaded(): constify datapath argument
ksmbd_vfs_set_init_posix_acl(): constify path argument
ksmbd_vfs_inherit_posix_acl(): constify path argument
ksmbd_vfs_kern_path_unlock(): constify path argument
ksmbd_vfs_path_lookup_locked(): root_share_path can be const struct path *
check_export(): constify path argument
export_operations->open(): constify path argument
rqst_exp_get_by_name(): constify path argument
nfs: constify path argument of __vfs_getattr()
bpf...d_path(): constify path argument
done_path_create(): constify path argument
...
Pull fs_context updates from Al Viro:
"Change vfs_parse_fs_string() calling conventions
Get rid of the length argument (almost all callers pass strlen() of
the string argument there), add vfs_parse_fs_qstr() for the cases that
do want separate length"
* tag 'pull-fs_context' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
do_nfs4_mount(): switch to vfs_parse_fs_string()
change the calling conventions for vfs_parse_fs_string()
