linux-kernel - [PATCH AUTOSEL 4.19 07/15] compiler.h: Introduce absolute

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Date:   Wed, 22 Sep 2021 23:39:21 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Guenter Roeck <linux@...ck-us.net>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Sasha Levin <sashal@...nel.org>, luc.vanoostenryck@...il.com,
        linux-sparse@...r.kernel.org
Subject: [PATCH AUTOSEL 4.19 07/15] compiler.h: Introduce absolute_pointer macro

From: Guenter Roeck <linux@...ck-us.net>

[ 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@...ux-foundation.org>
Signed-off-by: Guenter Roeck <linux@...ck-us.net>
Reviewed-by: Geert Uytterhoeven <geert@...ux-m68k.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 include/linux/compiler.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index 6a53300cbd1e..ab9dfb14f486 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -228,6 +228,8 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val,
     (typeof(ptr)) (__ptr + (off)); })
 #endif
 
+#define absolute_pointer(val)	RELOC_HIDE((void *)(val), 0)
+
 #ifndef OPTIMIZER_HIDE_VAR
 /* Make the optimizer believe the variable can be manipulated arbitrarily. */
 #define OPTIMIZER_HIDE_VAR(var)						\
-- 
2.30.2