FAILED: patch "[PATCH] static_call: Don't make __static_call_return0 static" failed to apply to 5.16-stable tree

The patch below does not apply to the 5.16-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 8fd4ddda2f49a66bf5dd3d0c01966c4b1971308b Mon Sep 17 00:00:00 2001
From: Christophe Leroy <[email protected]>
Date: Mon, 14 Mar 2022 12:49:36 +0100
Subject: [PATCH] static_call: Don't make __static_call_return0 static

System.map shows that vmlinux contains several instances of __static_call_return0():

	c0004fc0 t __static_call_return0
	c0011518 t __static_call_return0
	c00d8160 t __static_call_return0

arch_static_call_transform() uses the middle one to check whether we are setting a call to __static_call_return0 or not:

	c0011520 <arch_static_call_transform>:
	c0011520:       3d 20 c0 01     lis     r9,-16383	<== r9 =  0xc001 << 16
	c0011524:       39 29 15 18     addi    r9,r9,5400	<== r9 += 0x1518
	c0011528:       7c 05 48 00     cmpw    r5,r9		<== r9 has value 0xc0011518 here

So if static_call_update() is called with one of the other instances of __static_call_return0(), arch_static_call_transform() won't recognise it.

In order to work properly, global single instance of __static_call_return0() is required.

index 3e56a9751c06..fcc5b48989b3 100644
@@ -248,10 +248,7 @@ static inline int static_call_text_reserved(void *start, void *end)
 	return 0;
 }
 
-static inline long __static_call_return0(void)
-{
-	return 0;
-}
+extern long __static_call_return0(void);
 
 #define EXPORT_STATIC_CALL(name)					\
 	EXPORT_SYMBOL(STATIC_CALL_KEY(name));				\

index 471d71935e90..847a82bfe0e3 100644
@@ -114,7 +114,8 @@ obj-$(CONFIG_CPU_PM) += cpu_pm.o
 obj-$(CONFIG_BPF) += bpf/
 obj-$(CONFIG_KCSAN) += kcsan/
 obj-$(CONFIG_SHADOW_CALL_STACK) += scs.o
-obj-$(CONFIG_HAVE_STATIC_CALL_INLINE) += static_call.o
+obj-$(CONFIG_HAVE_STATIC_CALL) += static_call.o
+obj-$(CONFIG_HAVE_STATIC_CALL_INLINE) += static_call_inline.o
 obj-$(CONFIG_CFI_CLANG) += cfi.o
 
 obj-$(CONFIG_PERF_EVENTS) += events/