linux-kernel - [PATCH RESEND] x86/boot: #undef memcpy etc in string.c

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Date:   Mon, 24 Jul 2017 16:51:55 -0700
From:   Matthias Kaehlcke <mka@...omium.org>
To:     Ingo Molnar <mingo@...hat.com>, "H . Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Michael Davidson <md@...gle.com>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org,
        Greg Hackmann <ghackmann@...gle.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        Arnd Bergmann <arnd@...db.de>,
        Bernhard.Rosenkranzer@...aro.org,
        Matthias Kaehlcke <mka@...omium.org>
Subject: [PATCH RESEND] x86/boot: #undef memcpy etc in string.c

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

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>
Acked-by: H. Peter Anvin <hpa@...or.com>
Signed-off-by: Matthias Kaehlcke <mka@...omium.org>
---
Original post: https://lkml.org/lkml/2017/3/16/1035

 arch/x86/boot/string.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/arch/x86/boot/string.c b/arch/x86/boot/string.c
index 630e3664906b..16f49123d747 100644
--- 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;
-- 
2.14.0.rc0.284.gd933b75aa4-goog