ftrace: Synchronize the initialization of ftrace_opsgrafted

There's some internal state that ftrace_ops needs to have set, but since
it can be declared outside of the ftrace.c code, it calls
ftrace_ops_init() on the ops in every global function. The issue is that
if two tasks call it on the same ops at the same time it is possible to
have the initialization of one corrupt the initialization of the other
call.

Create a ops_mutex to use to synchronize every initialization of the
ftrace_ops. The mutex is taken within checking the ftrace_ops flag that
states it was initializied but the flag is checked again after the mutex
has been taken. Checking first outside the mutex allows it to shortcut
having to take the mutex. But then the check needs to be done again after
the mute is taken in case of races.

Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260902095501.6b59af20@gandalf.local.home
Fixes: f04f24fb7e48d ("ftrace, kprobes: Fix a deadlock on ftrace_regex_lock")
Reported-by: sashiko-bot@kernel.org
Close: https://lore.kernel.org/all/20260829025528.49A831F000E9@smtp.kernel.org/
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 323 insertions, 0 deletions

diff --git a/Documentation/admin-guide/kdump/gdbmacros.txt b/Documentation/admin-guide/kdump/gdbmacros.txt
new file mode 100644
index 000000000..030de95e3
--- /dev/null
+++ b/Documentation/admin-guide/kdump/gdbmacros.txt
@@ -0,0 +1,323 @@
+#
+# This file contains a few gdb macros (user defined commands) to extract
+# useful information from kernel crashdump (kdump) like stack traces of
+# all the processes or a particular process and trapinfo.
+#
+# These macros can be used by copying this file in .gdbinit (put in home
+# directory or current directory) or by invoking gdb command with
+# --command=<command-file-name> option
+#
+# Credits:
+# Alexander Nyberg <alexn@telia.com>
+# V Srivatsa <vatsa@in.ibm.com>
+# Maneesh Soni <maneesh@in.ibm.com>
+#
+
+define bttnobp
+	set $tasks_off=((size_t)&((struct task_struct *)0)->tasks)
+	set $pid_off=((size_t)&((struct task_struct *)0)->thread_group.next)
+	set $init_t=&init_task
+	set $next_t=(((char *)($init_t->tasks).next) - $tasks_off)
+	set var $stacksize = sizeof(union thread_union)
+	while ($next_t != $init_t)
+		set $next_t=(struct task_struct *)$next_t
+		printf "\npid %d; comm %s:\n", $next_t.pid, $next_t.comm
+		printf "===================\n"
+		set var $stackp = $next_t.thread.sp
+		set var $stack_top = ($stackp & ~($stacksize - 1)) + $stacksize
+
+		while ($stackp < $stack_top)
+			if (*($stackp) > _stext && *($stackp) < _sinittext)
+				info symbol *($stackp)
+			end
+			set $stackp += 4
+		end
+		set $next_th=(((char *)$next_t->thread_group.next) - $pid_off)
+		while ($next_th != $next_t)
+			set $next_th=(struct task_struct *)$next_th
+			printf "\npid %d; comm %s:\n", $next_t.pid, $next_t.comm
+			printf "===================\n"
+			set var $stackp = $next_t.thread.sp
+			set var $stack_top = ($stackp & ~($stacksize - 1)) + stacksize
+
+			while ($stackp < $stack_top)
+				if (*($stackp) > _stext && *($stackp) < _sinittext)
+					info symbol *($stackp)
+				end
+				set $stackp += 4
+			end
+			set $next_th=(((char *)$next_th->thread_group.next) - $pid_off)
+		end
+		set $next_t=(char *)($next_t->tasks.next) - $tasks_off
+	end
+end
+document bttnobp
+	dump all thread stack traces on a kernel compiled with !CONFIG_FRAME_POINTER
+end
+
+define btthreadstack
+	set var $pid_task = $arg0
+
+	printf "\npid %d; comm %s:\n", $pid_task.pid, $pid_task.comm
+	printf "task struct: "
+	print $pid_task
+	printf "===================\n"
+	set var $stackp = $pid_task.thread.sp
+	set var $stacksize = sizeof(union thread_union)
+	set var $stack_top = ($stackp & ~($stacksize - 1)) + $stacksize
+	set var $stack_bot = ($stackp & ~($stacksize - 1))
+
+	set $stackp = *((unsigned long *) $stackp)
+	while (($stackp < $stack_top) && ($stackp > $stack_bot))
+		set var $addr = *(((unsigned long *) $stackp) + 1)
+		info symbol $addr
+		set $stackp = *((unsigned long *) $stackp)
+	end
+end
+document btthreadstack
+	 dump a thread stack using the given task structure pointer
+end
+
+
+define btt
+	set $tasks_off=((size_t)&((struct task_struct *)0)->tasks)
+	set $pid_off=((size_t)&((struct task_struct *)0)->thread_group.next)
+	set $init_t=&init_task
+	set $next_t=(((char *)($init_t->tasks).next) - $tasks_off)
+	while ($next_t != $init_t)
+		set $next_t=(struct task_struct *)$next_t
+		btthreadstack $next_t
+
+		set $next_th=(((char *)$next_t->thread_group.next) - $pid_off)
+		while ($next_th != $next_t)
+			set $next_th=(struct task_struct *)$next_th
+			btthreadstack $next_th
+			set $next_th=(((char *)$next_th->thread_group.next) - $pid_off)
+		end
+		set $next_t=(char *)($next_t->tasks.next) - $tasks_off
+	end
+end
+document btt
+	dump all thread stack traces on a kernel compiled with CONFIG_FRAME_POINTER
+end
+
+define btpid
+	set var $pid = $arg0
+	set $tasks_off=((size_t)&((struct task_struct *)0)->tasks)
+	set $pid_off=((size_t)&((struct task_struct *)0)->thread_group.next)
+	set $init_t=&init_task
+	set $next_t=(((char *)($init_t->tasks).next) - $tasks_off)
+	set var $pid_task = 0
+
+	while ($next_t != $init_t)
+		set $next_t=(struct task_struct *)$next_t
+
+		if ($next_t.pid == $pid)
+			set $pid_task = $next_t
+		end
+
+		set $next_th=(((char *)$next_t->thread_group.next) - $pid_off)
+		while ($next_th != $next_t)
+			set $next_th=(struct task_struct *)$next_th
+			if ($next_th.pid == $pid)
+				set $pid_task = $next_th
+			end
+			set $next_th=(((char *)$next_th->thread_group.next) - $pid_off)
+		end
+		set $next_t=(char *)($next_t->tasks.next) - $tasks_off
+	end
+
+	btthreadstack $pid_task
+end
+document btpid
+	backtrace of pid
+end
+
+
+define trapinfo
+	set var $pid = $arg0
+	set $tasks_off=((size_t)&((struct task_struct *)0)->tasks)
+	set $pid_off=((size_t)&((struct task_struct *)0)->thread_group.next)
+	set $init_t=&init_task
+	set $next_t=(((char *)($init_t->tasks).next) - $tasks_off)
+	set var $pid_task = 0
+
+	while ($next_t != $init_t)
+		set $next_t=(struct task_struct *)$next_t
+
+		if ($next_t.pid == $pid)
+			set $pid_task = $next_t
+		end
+
+		set $next_th=(((char *)$next_t->thread_group.next) - $pid_off)
+		while ($next_th != $next_t)
+			set $next_th=(struct task_struct *)$next_th
+			if ($next_th.pid == $pid)
+				set $pid_task = $next_th
+			end
+			set $next_th=(((char *)$next_th->thread_group.next) - $pid_off)
+		end
+		set $next_t=(char *)($next_t->tasks.next) - $tasks_off
+	end
+
+	printf "Trapno %ld, cr2 0x%lx, error_code %ld\n", $pid_task.thread.trap_no, \
+				$pid_task.thread.cr2, $pid_task.thread.error_code
+
+end
+document trapinfo
+	Run info threads and lookup pid of thread #1
+	'trapinfo <pid>' will tell you by which trap & possibly
+	address the kernel panicked.
+end
+
+define dump_record
+	set var $desc = $arg0
+	set var $info = $arg1
+	if ($argc > 2)
+		set var $prev_flags = $arg2
+	else
+		set var $prev_flags = 0
+	end
+
+	set var $prefix = 1
+	set var $newline = 1
+
+	set var $begin = $desc->text_blk_lpos.begin % (1U << prb->text_data_ring.size_bits)
+	set var $next = $desc->text_blk_lpos.next % (1U << prb->text_data_ring.size_bits)
+
+	# handle data-less record
+	if ($begin & 1)
+		set var $text_len = 0
+		set var $log = ""
+	else
+		# handle wrapping data block
+		if ($begin > $next)
+			set var $begin = 0
+		end
+
+		# skip over descriptor id
+		set var $begin = $begin + sizeof(long)
+
+		# handle truncated message
+		if ($next - $begin < $info->text_len)
+			set var $text_len = $next - $begin
+		else
+			set var $text_len = $info->text_len
+		end
+
+		set var $log = &prb->text_data_ring.data[$begin]
+	end
+
+	# prev & LOG_CONT && !(info->flags & LOG_PREIX)
+	if (($prev_flags & 8) && !($info->flags & 4))
+		set var $prefix = 0
+	end
+
+	# info->flags & LOG_CONT
+	if ($info->flags & 8)
+		# (prev & LOG_CONT && !(prev & LOG_NEWLINE))
+		if (($prev_flags & 8) && !($prev_flags & 2))
+			set var $prefix = 0
+		end
+		# (!(info->flags & LOG_NEWLINE))
+		if (!($info->flags & 2))
+			set var $newline = 0
+		end
+	end
+
+	if ($prefix)
+		printf "[%5lu.%06lu] ", $info->ts_nsec / 1000000000, $info->ts_nsec % 1000000000
+	end
+	if ($text_len)
+		eval "printf \"%%%d.%ds\", $log", $text_len, $text_len
+	end
+	if ($newline)
+		printf "\n"
+	end
+
+	# handle dictionary data
+
+	set var $dict = &$info->dev_info.subsystem[0]
+	set var $dict_len = sizeof($info->dev_info.subsystem)
+	if ($dict[0] != '\0')
+		printf " SUBSYSTEM="
+		set var $idx = 0
+		while ($idx < $dict_len)
+			set var $c = $dict[$idx]
+			if ($c == '\0')
+				loop_break
+			else
+				if ($c < ' ' || $c >= 127 || $c == '\\')
+					printf "\\x%02x", $c
+				else
+					printf "%c", $c
+				end
+			end
+			set var $idx = $idx + 1
+		end
+		printf "\n"
+	end
+
+	set var $dict = &$info->dev_info.device[0]
+	set var $dict_len = sizeof($info->dev_info.device)
+	if ($dict[0] != '\0')
+		printf " DEVICE="
+		set var $idx = 0
+		while ($idx < $dict_len)
+			set var $c = $dict[$idx]
+			if ($c == '\0')
+				loop_break
+			else
+				if ($c < ' ' || $c >= 127 || $c == '\\')
+					printf "\\x%02x", $c
+				else
+					printf "%c", $c
+				end
+			end
+			set var $idx = $idx + 1
+		end
+		printf "\n"
+	end
+end
+document dump_record
+	Dump a single record. The first parameter is the descriptor,
+	the second parameter is the info, the third parameter is
+	optional and specifies the previous record's flags, used for
+	properly formatting continued lines.
+end
+
+define dmesg
+	# definitions from kernel/printk/printk_ringbuffer.h
+	set var $desc_committed = 1
+	set var $desc_finalized = 2
+	set var $desc_sv_bits = sizeof(long) * 8
+	set var $desc_flags_shift = $desc_sv_bits - 2
+	set var $desc_flags_mask = 3 << $desc_flags_shift
+	set var $id_mask = ~$desc_flags_mask
+
+	set var $desc_count = 1U << prb->desc_ring.count_bits
+	set var $prev_flags = 0
+
+	set var $id = prb->desc_ring.tail_id.counter
+	set var $end_id = prb->desc_ring.head_id.counter
+
+	while (1)
+		set var $desc = &prb->desc_ring.descs[$id % $desc_count]
+		set var $info = &prb->desc_ring.infos[$id % $desc_count]
+
+		# skip non-committed record
+		set var $state = 3 & ($desc->state_var.counter >> $desc_flags_shift)
+		if ($state == $desc_committed || $state == $desc_finalized)
+			dump_record $desc $info $prev_flags
+			set var $prev_flags = $info->flags
+		end
+
+		if ($id == $end_id)
+			loop_break
+		end
+		set var $id = ($id + 1) & $id_mask
+	end
+end
+document dmesg
+	print the kernel ring buffer
+end