1 files changed, 36 insertions, 30 deletions

diff --git a/include/linux/init.h b/include/linux/init.h
index 3561ea30ed8c..0e274bb51709 100644
--- a/include/linux/init.h
+++ b/include/linux/init.h
@@ -163,24 +163,8 @@ extern bool initcall_debug;
 
 #ifndef __ASSEMBLY__
 
-#ifdef CONFIG_LTO
-/* Work around a LTO gcc problem: when there is no reference to a variable
- * in a module it will be moved to the end of the program. This causes
- * reordering of initcalls which the kernel does not like.
- * Add a dummy reference function to avoid this. The function is
- * deleted by the linker.
- */
-#define LTO_REFERENCE_INITCALL(x) \
-	; /* yes this is needed */			\
-	static __used __exit void *reference_##x(void)	\
-	{						\
-		return &x;				\
-	}
-#else
-#define LTO_REFERENCE_INITCALL(x)
-#endif
-
-/* initcalls are now grouped by functionality into separate 
+/*
+ * initcalls are now grouped by functionality into separate
  * subsections. Ordering inside the subsections is determined
  * by link order. 
  * For backwards compatibility, initcall() puts the call in 
@@ -188,12 +172,39 @@ extern bool initcall_debug;
  *
  * The `id' arg to __define_initcall() is needed so that multiple initcalls
  * can point at the same handler without causing duplicate-symbol build errors.
+ *
+ * Initcalls are run by placing pointers in initcall sections that the
+ * kernel iterates at runtime. The linker can do dead code / data elimination
+ * and remove that completely, so the initcall sections have to be marked
+ * as KEEP() in the linker script.
  */
-
-#define __define_initcall(fn, id) \
+#ifdef CONFIG_LTO_CLANG
+  /*
+   * With LTO, the compiler doesn't necessarily obey link order for
+   * initcalls, and the initcall variable needs to be globally unique
+   * to avoid naming collisions.  In order to preserve the correct
+   * order, we add each variable into its own section and generate a
+   * linker script (in scripts/link-vmlinux.sh) to ensure the order
+   * remains correct.  We also add a __COUNTER__ prefix to the name,
+   * so we can retain the order of initcalls within each compilation
+   * unit, and __LINE__ to make the names more unique.
+   */
+  #define ___lto_initcall(c, l, fn, id, __sec) \
+	static initcall_t __initcall_##c##_##l##_##fn##id __used \
+		__attribute__((__section__( #__sec \
+			__stringify(.init..##c##_##l##_##fn)))) = fn;
+  #define __lto_initcall(c, l, fn, id, __sec) \
+	___lto_initcall(c, l, fn, id, __sec)
+
+  #define ___define_initcall(fn, id, __sec) \
+	__lto_initcall(__COUNTER__, __LINE__, fn, id, __sec)
+#else
+  #define ___define_initcall(fn, id, __sec) \
 	static initcall_t __initcall_##fn##id __used \
-	__attribute__((__section__(".initcall" #id ".init"))) = fn; \
-	LTO_REFERENCE_INITCALL(__initcall_##fn##id)
+		__attribute__((__section__(#__sec ".init"))) = fn;
+#endif
+
+#define __define_initcall(fn, id) ___define_initcall(fn, id, .initcall##id)
 
 /*
  * Early initcalls run before initializing SMP.
@@ -229,16 +240,11 @@ extern bool initcall_debug;
 
 #define __initcall(fn) device_initcall(fn)
 
-#define __exitcall(fn) \
+#define __exitcall(fn)						\
 	static exitcall_t __exitcall_##fn __exit_call = fn
 
-#define console_initcall(fn) \
-	static initcall_t __initcall_##fn \
-	__used __section(.con_initcall.init) = fn
-
-#define security_initcall(fn) \
-	static initcall_t __initcall_##fn \
-	__used __section(.security_initcall.init) = fn
+#define console_initcall(fn)	___define_initcall(fn, con, .con_initcall)
+#define security_initcall(fn)	___define_initcall(fn, security, .security_initcall)
 
 struct obs_kernel_param {
 	const char *str;