[PATCH 5.4 55/68] compiler.h: Introduce absolute_pointer macro

From: Greg Kroah-Hartman
Date: Mon Sep 27 2021 - 13:07:06 EST

From: Guenter Roeck <linux@xxxxxxxxxxxx>

[ Upstream commit f6b5f1a56987de837f8e25cd560847106b8632a8 ]

absolute_pointer() disassociates a pointer from its originating symbol
type and context. Use it to prevent compiler warnings/errors such as

drivers/net/ethernet/i825xx/82596.c: In function 'i82596_probe':
arch/m68k/include/asm/string.h:72:25: error:
'__builtin_memcpy' reading 6 bytes from a region of size 0 [-Werror=stringop-overread]

Such warnings may be reported by gcc 11.x for string and memory
operations on fixed addresses.

Suggested-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx>
Reviewed-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
include/linux/compiler.h | 2 ++
1 file changed, 2 insertions(+)

diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index 9446e8fbe55c..bce983406aaf 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -233,6 +233,8 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val,
(typeof(ptr)) (__ptr + (off)); })

+#define absolute_pointer(val) RELOC_HIDE((void *)(val), 0)
/* Make the optimizer believe the variable can be manipulated arbitrarily. */
#define OPTIMIZER_HIDE_VAR(var) \