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>

14 files changed, 179 insertions, 0 deletions

diff --git a/tools/build/tests/ex/Build b/tools/build/tests/ex/Build
new file mode 100644
index 000000000..4d502f9b1
--- /dev/null
+++ b/tools/build/tests/ex/Build
@@ -0,0 +1,11 @@
+ex-y += ex.o
+ex-y += a.o
+ex-y += b.o
+ex-y += b.o
+ex-y += empty/
+ex-y += empty2/
+ex-y += inc.o
+
+libex-y += c.o
+libex-y += d.o
+libex-y += arch/
diff --git a/tools/build/tests/ex/Makefile b/tools/build/tests/ex/Makefile
new file mode 100644
index 000000000..fee032e06
--- /dev/null
+++ b/tools/build/tests/ex/Makefile
@@ -0,0 +1,27 @@
+# SPDX-License-Identifier: GPL-2.0
+export srctree := $(abspath ../../../..)
+export CC      := gcc
+export LD      := ld
+export AR      := ar
+
+ex:
+
+include $(srctree)/tools/build/Makefile.include
+
+ex: ex-in.o libex-in.o
+	$(CC) -o $@ $^
+
+ex.%: fixdep FORCE
+	make -f $(srctree)/tools/build/Makefile.build dir=. $@
+
+ex-in.o: fixdep FORCE
+	make $(build)=ex
+
+libex-in.o: fixdep FORCE
+	make $(build)=libex
+
+clean:
+	find . -name '*.o' -delete -o -name '\.*.cmd' -delete -o -name '\.*.d' -delete
+	rm -f ex ex.i ex.s
+
+.PHONY: FORCE
diff --git a/tools/build/tests/ex/a.c b/tools/build/tests/ex/a.c
new file mode 100644
index 000000000..66017a9f4
--- /dev/null
+++ b/tools/build/tests/ex/a.c
@@ -0,0 +1,6 @@
+// SPDX-License-Identifier: GPL-2.0
+
+int a(void)
+{
+	return 0;
+}
diff --git a/tools/build/tests/ex/arch/Build b/tools/build/tests/ex/arch/Build
new file mode 100644
index 000000000..55506189e
--- /dev/null
+++ b/tools/build/tests/ex/arch/Build
@@ -0,0 +1,2 @@
+libex-y += e.o
+libex-y += f.o
diff --git a/tools/build/tests/ex/arch/e.c b/tools/build/tests/ex/arch/e.c
new file mode 100644
index 000000000..f6ef585b5
--- /dev/null
+++ b/tools/build/tests/ex/arch/e.c
@@ -0,0 +1,6 @@
+// SPDX-License-Identifier: GPL-2.0
+
+int e(void)
+{
+	return 0;
+}
diff --git a/tools/build/tests/ex/arch/f.c b/tools/build/tests/ex/arch/f.c
new file mode 100644
index 000000000..bffd9c67e
--- /dev/null
+++ b/tools/build/tests/ex/arch/f.c
@@ -0,0 +1,6 @@
+// SPDX-License-Identifier: GPL-2.0
+
+int f(void)
+{
+	return 0;
+}
diff --git a/tools/build/tests/ex/b.c b/tools/build/tests/ex/b.c
new file mode 100644
index 000000000..2b29fb4d3
--- /dev/null
+++ b/tools/build/tests/ex/b.c
@@ -0,0 +1,6 @@
+// SPDX-License-Identifier: GPL-2.0
+
+int b(void)
+{
+	return 0;
+}
diff --git a/tools/build/tests/ex/c.c b/tools/build/tests/ex/c.c
new file mode 100644
index 000000000..a63b20ab8
--- /dev/null
+++ b/tools/build/tests/ex/c.c
@@ -0,0 +1,6 @@
+// SPDX-License-Identifier: GPL-2.0
+
+int c(void)
+{
+	return 0;
+}
diff --git a/tools/build/tests/ex/d.c b/tools/build/tests/ex/d.c
new file mode 100644
index 000000000..e114e8dca
--- /dev/null
+++ b/tools/build/tests/ex/d.c
@@ -0,0 +1,6 @@
+// SPDX-License-Identifier: GPL-2.0
+
+int d(void)
+{
+	return 0;
+}
diff --git a/tools/build/tests/ex/empty/Build b/tools/build/tests/ex/empty/Build
new file mode 100644
index 000000000..e69de29bb
--- /dev/null
+++ b/tools/build/tests/ex/empty/Build
diff --git a/tools/build/tests/ex/empty2/README b/tools/build/tests/ex/empty2/README
new file mode 100644
index 000000000..2107cc5bf
--- /dev/null
+++ b/tools/build/tests/ex/empty2/README
@@ -0,0 +1,2 @@
+This directory is left intentionally without Build file
+to test proper nesting into Build-less directories.
diff --git a/tools/build/tests/ex/ex.c b/tools/build/tests/ex/ex.c
new file mode 100644
index 000000000..3c02756ef
--- /dev/null
+++ b/tools/build/tests/ex/ex.c
@@ -0,0 +1,22 @@
+// SPDX-License-Identifier: GPL-2.0
+
+int a(void);
+int b(void);
+int c(void);
+int d(void);
+int e(void);
+int f(void);
+int inc(void);
+
+int main(void)
+{
+	a();
+	b();
+	c();
+	d();
+	e();
+	f();
+	inc();
+
+	return 0;
+}
diff --git a/tools/build/tests/ex/inc.c b/tools/build/tests/ex/inc.c
new file mode 100644
index 000000000..3636ab5bf
--- /dev/null
+++ b/tools/build/tests/ex/inc.c
@@ -0,0 +1,9 @@
+// SPDX-License-Identifier: GPL-2.0
+#ifdef INCLUDE
+#include "krava.h"
+#endif
+
+int inc(void)
+{
+	return 0;
+}
diff --git a/tools/build/tests/run.sh b/tools/build/tests/run.sh
new file mode 100755
index 000000000..2c54e4d43
--- /dev/null
+++ b/tools/build/tests/run.sh
@@ -0,0 +1,70 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+
+function test_ex {
+	make -C ex V=1 clean > ex.out 2>&1
+	make -C ex V=1 >> ex.out 2>&1
+
+	if [ ! -x ./ex/ex ]; then
+	  echo FAILED
+	  exit -1
+	fi
+
+	make -C ex V=1 clean > /dev/null 2>&1
+	rm -f ex.out
+}
+
+function test_ex_suffix {
+	make -C ex V=1 clean > ex.out 2>&1
+
+	# use -rR to disable make's builtin rules
+	make -rR -C ex V=1 ex.o >> ex.out 2>&1
+	make -rR -C ex V=1 ex.i >> ex.out 2>&1
+	make -rR -C ex V=1 ex.s >> ex.out 2>&1
+
+	if [ -x ./ex/ex ]; then
+	  echo FAILED
+	  exit -1
+	fi
+
+	if [ ! -f ./ex/ex.o -o ! -f ./ex/ex.i -o ! -f ./ex/ex.s ]; then
+	  echo FAILED
+	  exit -1
+	fi
+
+	make -C ex V=1 clean > /dev/null 2>&1
+	rm -f ex.out
+}
+
+function test_ex_include {
+	make -C ex V=1 clean > ex.out 2>&1
+
+	# build with krava.h include
+	touch ex/krava.h
+	make -C ex V=1 CFLAGS=-DINCLUDE >> ex.out 2>&1
+
+	if [ ! -x ./ex/ex ]; then
+	  echo FAILED
+	  exit -1
+	fi
+
+	# build without the include
+	rm -f ex/krava.h ex/ex
+	make -C ex V=1 >> ex.out 2>&1
+
+	if [ ! -x ./ex/ex ]; then
+	  echo FAILED
+	  exit -1
+	fi
+
+	make -C ex V=1 clean > /dev/null 2>&1
+	rm -f ex.out
+}
+
+echo -n Testing..
+
+test_ex
+test_ex_suffix
+test_ex_include
+
+echo OK