linux-kernel - [PATCH 4.9 27/59] x86/boot: #undef memcpy() et al in string.c

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Date:   Wed, 21 Nov 2018 20:06:42 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Michael Davidson <md@...gle.com>,
        Matthias Kaehlcke <mka@...omium.org>,
        "H. Peter Anvin" <hpa@...or.com>, Arnd Bergmann <arnd@...db.de>,
        Bernhard.Rosenkranzer@...aro.org,
        Greg Hackmann <ghackmann@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>
Subject: [PATCH 4.9 27/59] x86/boot: #undef memcpy() et al in string.c

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Michael Davidson <md@...gle.com>

commit 18d5e6c34a8eda438d5ad8b3b15f42dab01bf05d upstream.

undef memcpy() and friends in boot/string.c so that the functions
defined here will have the correct names, otherwise we end up
up trying to redefine __builtin_memcpy() etc.

Surprisingly, GCC allows this (and, helpfully, discards the
__builtin_ prefix from the function name when compiling it),
but clang does not.

Adding these #undef's appears to preserve what I assume was
the original intent of the code.

Signed-off-by: Michael Davidson <md@...gle.com>
Signed-off-by: Matthias Kaehlcke <mka@...omium.org>
Acked-by: H. Peter Anvin <hpa@...or.com>
Cc: Arnd Bergmann <arnd@...db.de>
Cc: Bernhard.Rosenkranzer@...aro.org
Cc: Greg Hackmann <ghackmann@...gle.com>
Cc: Kees Cook <keescook@...omium.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Nick Desaulniers <ndesaulniers@...gle.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Link: http://lkml.kernel.org/r/20170724235155.79255-1-mka@chromium.org
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Signed-off-by: Nick Desaulniers <ndesaulniers@...gle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 arch/x86/boot/string.c |    9 +++++++++
 1 file changed, 9 insertions(+)

--- a/arch/x86/boot/string.c
+++ b/arch/x86/boot/string.c
@@ -16,6 +16,15 @@
 #include "ctype.h"
 #include "string.h"
 
+/*
+ * Undef these macros so that the functions that we provide
+ * here will have the correct names regardless of how string.h
+ * may have chosen to #define them.
+ */
+#undef memcpy
+#undef memset
+#undef memcmp
+
 int memcmp(const void *s1, const void *s2, size_t len)
 {
 	bool diff;