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From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Alexander Burmashev <alexander.burmashev@oracle.com>
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Date: Wed, 22 Jul 2020 06:04:38 -0700
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Subject: [PATCH] update safemath with fallback code for gcc older than 5.1
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The code used in the header was taken from linux kernel commit
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f0907827a8a9152aedac2833ed1b674a7b2a44f2. Rasmus Villemoes
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<linux@rasmusvillemoes.dk>, the original author of the patch, was
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contacted directly, confirmed his authorship of the code, and gave his
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permission on treating that dual license as MIT and including into GRUB2
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sources
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Signed-off-by: Alex Burmashev <alexander.burmashev@oracle.com>
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---
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include/grub/safemath.h | 119 +++++++++++++++++++++++++++++++++++++++++++++++-
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1 file changed, 118 insertions(+), 1 deletion(-)
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diff --git a/include/grub/safemath.h b/include/grub/safemath.h
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index c17b89bba17..1ccac276b59 100644
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--- a/include/grub/safemath.h
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+++ b/include/grub/safemath.h
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@@ -31,7 +31,124 @@
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#define grub_mul(a, b, res) __builtin_mul_overflow(a, b, res)
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#else
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-#error gcc 5.1 or newer or clang 3.8 or newer is required
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+/*
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+ * Copyright 2020 Rasmus Villemoes
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+ *
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+ * Permission is hereby granted, free of charge, to any person obtaining a copy
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+ * of this software and associated documentation files (the "Software"), to
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+ * deal in the Software without restriction, including without limitation the
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+ * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
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+ * sell copies of the Software, and to permit persons to whom the Software is
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+ * furnished to do so, subject to the following conditions:
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+ *
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+ * The above copyright notice and this permission notice shall be included in
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+ * all copies or substantial portions of the Software.
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+
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+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
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+ * IN THE SOFTWARE.
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+ */
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+/*
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+ * The code used in this header was taken from linux kernel commit
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+ * f0907827a8a9152aedac2833ed1b674a7b2a44f2
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+ * Rasmus Villemoes <linux@rasmusvillemoes.dk>, the original author of the
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+ * patch, was contacted directly, confirmed his authorship of the code, and
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+ * gave his permission on treating that dual license as MIT and including into
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+ * GRUB2 sources
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+ */
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+
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+#include <grub/types.h>
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+#define is_signed_type(type) (((type)(-1)) < (type)1)
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+#define __type_half_max(type) ((type)1 << (8*sizeof(type) - 1 - is_signed_type(type)))
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+#define type_max(T) ((T)((__type_half_max(T) - 1) + __type_half_max(T)))
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+#define type_min(T) ((T)((T)-type_max(T)-(T)1))
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+
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+#define __unsigned_add_overflow(a, b, d) ({ \
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+ typeof(+(a)) __a = (a); \
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+ typeof(+(b)) __b = (b); \
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+ typeof(d) __d = (d); \
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+ (void) (&__a == &__b); \
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+ (void) (&__a == __d); \
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+ *__d = __a + __b; \
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+ *__d < __a; \
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+})
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+#define __unsigned_sub_overflow(a, b, d) ({ \
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+ typeof(+(a)) __a = (a); \
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+ typeof(+(b)) __b = (b); \
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+ typeof(d) __d = (d); \
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+ (void) (&__a == &__b); \
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+ (void) (&__a == __d); \
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+ *__d = __a - __b; \
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+ __a < __b; \
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+})
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+#define __unsigned_mul_overflow(a, b, d) ({ \
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+ typeof(+(a)) __a = (a); \
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+ typeof(+(b)) __b = (b); \
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+ typeof(d) __d = (d); \
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+ (void) (&__a == &__b); \
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+ (void) (&__a == __d); \
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+ *__d = __a * __b; \
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+ __builtin_constant_p(__b) ? \
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+ __b > 0 && __a > type_max(typeof(__a)) / __b :\
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+ __a > 0 && __b > type_max(typeof(__b)) / __a; \
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+})
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+
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+#define __signed_add_overflow(a, b, d) ({ \
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+ typeof(+(a)) __a = (a); \
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+ typeof(+(b)) __b = (b); \
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+ typeof(d) __d = (d); \
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+ (void) (&__a == &__b); \
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+ (void) (&__a == __d); \
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+ *__d = (grub_uint64_t)__a + (grub_uint64_t)__b; \
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+ (((~(__a ^ __b)) & (*__d ^ __a)) \
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+ & type_min(typeof(__a))) != 0; \
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+})
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+
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+#define __signed_sub_overflow(a, b, d) ({ \
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+ typeof(+(a)) __a = (a); \
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+ typeof(+(b)) __b = (b); \
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+ typeof(d) __d = (d); \
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+ (void) (&__a == &__b); \
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+ (void) (&__a == __d); \
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+ *__d = (grub_uint64_t)__a - (grub_uint64_t)__b; \
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+ ((((__a ^ __b)) & (*__d ^ __a)) \
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+ & type_min(typeof(__a))) != 0; \
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+})
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+
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+#define __signed_mul_overflow(a, b, d) ({ \
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+ typeof(+(a)) __a = (a); \
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+ typeof(+(b)) __b = (b); \
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+ typeof(d) __d = (d); \
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+ typeof(+(a)) __tmax = type_max(typeof(+(a))); \
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+ typeof(+(a)) __tmin = type_min(typeof(+(a))); \
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+ (void) (&__a == &__b); \
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+ (void) (&__a == __d); \
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+ *__d = (grub_uint64_t)__a * (grub_uint64_t)__b; \
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+ (__b > 0 && (__a > __tmax/__b || __a < __tmin/__b)) ||\
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+ (__b < (typeof(__b))-1 && \
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+ (__a > __tmin/__b || __a < __tmax/__b)) || \
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+ (__b == (typeof(__b))-1 && __a == __tmin); \
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+})
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+
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+#define grub_add(a, b, d) \
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+ __builtin_choose_expr(is_signed_type(typeof(+(a))), \
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+ __signed_add_overflow(a, b, d), \
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+ __unsigned_add_overflow(a, b, d))
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+
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+#define grub_sub(a, b, d) \
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+ __builtin_choose_expr(is_signed_type(typeof(+(a))), \
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+ __signed_sub_overflow(a, b, d), \
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+ __unsigned_sub_overflow(a, b, d))
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+
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+#define grub_mul(a, b, d) \
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+ __builtin_choose_expr(is_signed_type(typeof(+(a))), \
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+ __signed_mul_overflow(a, b, d), \
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+ __unsigned_mul_overflow(a, b, d))
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+
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#endif
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#endif /* GRUB_SAFEMATH_H */
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