217 lines
6.8 KiB
Diff
217 lines
6.8 KiB
Diff
From 10653a171bc0ca145236d2c75e5c5422caeb8b55 Mon Sep 17 00:00:00 2001
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From: Vishal Verma <vishal.l.verma@intel.com>
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Date: Wed, 23 Feb 2022 22:28:05 -0700
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Subject: [PATCH 140/217] util/size.h: fix build for older compilers
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Add a fallback for older compilers that lack __builtin_add_overflow()
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and friends. Commit 7aa7c7be6e80 ("util: add the struct_size() helper from the
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kernel") which added these helpers from the kernel neglected to copy
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over the fallback code.
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Link: https://lore.kernel.org/r/20220224052805.2462449-1-vishal.l.verma@intel.com
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Fixes: 7aa7c7be6e80 ("util: add the struct_size() helper from the kernel")
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Reported-by: Joao Martins <joao.m.martins@oracle.com>
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Reviewed-by: Joao Martins <joao.m.martins@oracle.com>
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Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>
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---
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util/size.h | 163 ++++++++++++++++++++++++++++++++++++++++++++++++++--
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1 file changed, 159 insertions(+), 4 deletions(-)
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diff --git a/util/size.h b/util/size.h
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index e72467f..1cb0669 100644
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--- a/util/size.h
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+++ b/util/size.h
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@@ -6,6 +6,7 @@
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#include <stdbool.h>
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#include <stdint.h>
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#include <util/util.h>
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+#include <ccan/short_types/short_types.h>
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#define SZ_1K 0x00000400
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#define SZ_4K 0x00001000
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@@ -43,23 +44,177 @@ static inline bool is_power_of_2(unsigned long long v)
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* alias for __builtin_add_overflow, but add type checks similar to
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* below.
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*/
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-#define check_add_overflow(a, b, d) (({ \
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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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+#if GCC_VERSION >= 50100
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+#define COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW 1
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+#endif
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+
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+#if __clang__ && \
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+ __has_builtin(__builtin_mul_overflow) && \
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+ __has_builtin(__builtin_add_overflow)
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+#define COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW 1
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+#endif
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+
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+#if COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW
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+
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+#define check_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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__builtin_add_overflow(__a, __b, __d); \
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-}))
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+})
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+
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+#define check_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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+ __builtin_sub_overflow(__a, __b, __d); \
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+})
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-#define check_mul_overflow(a, b, d) (({ \
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+#define check_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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__builtin_mul_overflow(__a, __b, __d); \
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-}))
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+})
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+
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+
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+#else /* !COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW */
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+
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+/* Checking for unsigned overflow is relatively easy without causing UB. */
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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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+/*
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+ * If one of a or b is a compile-time constant, this avoids a division.
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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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+/*
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+ * For signed types, detecting overflow is much harder, especially if
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+ * we want to avoid UB. But the interface of these macros is such that
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+ * we must provide a result in *d, and in fact we must produce the
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+ * result promised by gcc's builtins, which is simply the possibly
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+ * wrapped-around value. Fortunately, we can just formally do the
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+ * operations in the widest relevant unsigned type (u64) and then
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+ * truncate the result - gcc is smart enough to generate the same code
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+ * with and without the (u64) casts.
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+ */
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+
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+/*
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+ * Adding two signed integers can overflow only if they have the same
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+ * sign, and overflow has happened iff the result has the opposite
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+ * sign.
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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 = (u64)__a + (u64)__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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+/*
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+ * Subtraction is similar, except that overflow can now happen only
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+ * when the signs are opposite. In this case, overflow has happened if
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+ * the result has the opposite sign of a.
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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 = (u64)__a - (u64)__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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+/*
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+ * Signed multiplication is rather hard. gcc always follows C99, so
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+ * division is truncated towards 0. This means that we can write the
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+ * overflow check like this:
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+ *
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+ * (a > 0 && (b > MAX/a || b < MIN/a)) ||
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+ * (a < -1 && (b > MIN/a || b < MAX/a) ||
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+ * (a == -1 && b == MIN)
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+ *
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+ * The redundant casts of -1 are to silence an annoying -Wtype-limits
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+ * (included in -Wextra) warning: When the type is u8 or u16, the
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+ * __b_c_e in check_mul_overflow obviously selects
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+ * __unsigned_mul_overflow, but unfortunately gcc still parses this
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+ * code and warns about the limited range of __b.
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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 = (u64)__a * (u64)__b; \
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+ (__b > 0 && (__a > __tmax/__b || __a < __tmin/__b)) || \
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+ (__b < (typeof(__b))-1 && (__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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+
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+#define check_add_overflow(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 check_sub_overflow(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 check_mul_overflow(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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/*
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* Compute a*b+c, returning SIZE_MAX on overflow. Internal helper for
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--
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2.27.0
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