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, 60 insertions, 0 deletions

diff --git a/scripts/stackdelta b/scripts/stackdelta
new file mode 100755
index 000000000..44d2dfd62
--- /dev/null
+++ b/scripts/stackdelta
@@ -0,0 +1,60 @@
+#!/usr/bin/env perl
+# SPDX-License-Identifier: GPL-2.0
+
+# Read two files produced by the stackusage script, and show the
+# delta between them.
+#
+# Currently, only shows changes for functions listed in both files. We
+# could add an option to show also functions which have vanished or
+# appeared (which would often be due to gcc making other inlining
+# decisions).
+#
+# Another possible option would be a minimum absolute value for the
+# delta.
+#
+# A third possibility is for sorting by delta, but that can be
+# achieved by piping to sort -k5,5g.
+
+sub read_stack_usage_file {
+    my %su;
+    my $f = shift;
+    open(my $fh, '<', $f)
+	or die "cannot open $f: $!";
+    while (<$fh>) {
+	chomp;
+	my ($file, $func, $size, $type) = split;
+	# Old versions of gcc (at least 4.7) have an annoying quirk in
+	# that a (static) function whose name has been changed into
+	# for example ext4_find_unwritten_pgoff.isra.11 will show up
+	# in the .su file with a name of just "11". Since such a
+	# numeric suffix is likely to change across different
+	# commits/compilers/.configs or whatever else we're trying to
+	# tweak, we can't really track those functions, so we just
+	# silently skip them.
+	#
+	# Newer gcc (at least 5.0) report the full name, so again,
+	# since the suffix is likely to change, we strip it.
+	next if $func =~ m/^[0-9]+$/;
+	$func =~ s/\..*$//;
+	# Line numbers are likely to change; strip those.
+	$file =~ s/:[0-9]+$//;
+	$su{"${file}\t${func}"} = {size => $size, type => $type};
+    }
+    close($fh);
+    return \%su;
+}
+
+@ARGV == 2
+    or die "usage: $0 <old> <new>";
+
+my $old = read_stack_usage_file($ARGV[0]);
+my $new = read_stack_usage_file($ARGV[1]);
+my @common = sort grep {exists $new->{$_}} keys %$old;
+for (@common) {
+    my $x = $old->{$_}{size};
+    my $y = $new->{$_}{size};
+    my $delta = $y - $x;
+    if ($delta) {
+	printf "%s\t%d\t%d\t%+d\n", $_, $x, $y, $delta;
+    }
+}