From: Tom Rini <trini@konsulko.com>
Date: Tue, 28 Mar 2023 18:54:51 +0000 (-0400)
Subject: linker_lists: Rework start/end macros to not rely on undefined behavior
X-Git-Url: http://git.dujemihanovic.xyz/%22/img/sics.gif/%22/static/git-favicon.png?a=commitdiff_plain;h=d0e3378ad73ed80d4baab95e2c3aaa0a18ae7747;p=u-boot.git

linker_lists: Rework start/end macros to not rely on undefined behavior

Per the GCC bug listed below, the way we do linker lists is relying on
undefined behavior that seems to work in gcc, but doesn't always work in
clang. Andrew suggests rewriting our start/end macros in a different way
(as implemented here, from what he said in comment 1) to avoid these
problems.

Reported-by: AdityaK <appujee@google.com>
Suggested-by: Andrew Pinski <apinski@marvell.com>
Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108915
Signed-off-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Andrew Pinski <apinski@marvell.com>
---

diff --git a/include/linker_lists.h b/include/linker_lists.h
index d3da9d44e8..f9a2ee0c76 100644
--- a/include/linker_lists.h
+++ b/include/linker_lists.h
@@ -127,7 +127,9 @@
 	static char start[0] __aligned(CONFIG_LINKER_LIST_ALIGN)	\
 		__attribute__((unused))					\
 		__section("__u_boot_list_2_"#_list"_1");			\
-	(_type *)&start;						\
+	_type * tmp = (_type *)&start;					\
+	asm("":"+r"(tmp));						\
+	tmp;								\
 })
 
 /**
@@ -153,7 +155,9 @@
 ({									\
 	static char end[0] __aligned(4) __attribute__((unused))		\
 		__section("__u_boot_list_2_"#_list"_3");			\
-	(_type *)&end;							\
+	_type * tmp = (_type *)&end;					\
+	asm("":"+r"(tmp));						\
+	tmp;								\
 })
 /**
  * ll_entry_count() - Return the number of elements in linker-generated array
@@ -247,7 +251,9 @@
 ({									\
 	static char start[0] __aligned(4) __attribute__((unused))	\
 		__section("__u_boot_list_1");				\
-	(_type *)&start;						\
+	_type * tmp = (_type *)&start;					\
+	asm("":"+r"(tmp));						\
+	tmp;								\
 })
 
 /**
@@ -270,7 +276,9 @@
 ({									\
 	static char end[0] __aligned(4) __attribute__((unused))		\
 		__section("__u_boot_list_3");				\
-	(_type *)&end;							\
+	_type * tmp = (_type *)&end;					\
+	asm("":"+r"(tmp));						\
+	tmp;								\
 })
 
 #endif /* __ASSEMBLY__ */