| Message ID | 20220224052805.2462449-1-vishal.l.verma@intel.com |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [ndctl] util/size.h: fix build for older compilers | expand |
On 2/24/22 05:28, Vishal Verma wrote: > Add a fallback for older compilers that lack __builtin_add_overflow() > and friends. Commit 7aa7c7be6e80 ("util: add the struct_size() helper from the > kernel") which added these helpers from the kernel neglected to copy > over the fallback code. > > Fixes: 7aa7c7be6e80 ("util: add the struct_size() helper from the kernel") > Reported-by: Joao Martins <joao.m.martins@oracle.com> > Signed-off-by: Vishal Verma <vishal.l.verma@intel.com> Reviewed-by: Joao Martins <joao.m.martins@oracle.com> You might wanna want this to get to v72.y branch considering the breakage exists there. Thanks for the followup! > --- > util/size.h | 163 ++++++++++++++++++++++++++++++++++++++++++++++++++-- > 1 file changed, 159 insertions(+), 4 deletions(-) > > diff --git a/util/size.h b/util/size.h > index e72467f..1cb0669 100644 > --- a/util/size.h > +++ b/util/size.h > @@ -6,6 +6,7 @@ > #include <stdbool.h> > #include <stdint.h> > #include <util/util.h> > +#include <ccan/short_types/short_types.h> > > #define SZ_1K 0x00000400 > #define SZ_4K 0x00001000 > @@ -43,23 +44,177 @@ static inline bool is_power_of_2(unsigned long long v) > * alias for __builtin_add_overflow, but add type checks similar to > * below. > */ > -#define check_add_overflow(a, b, d) (({ \ > +#define is_signed_type(type) (((type)(-1)) < (type)1) > +#define __type_half_max(type) ((type)1 << (8*sizeof(type) - 1 - is_signed_type(type))) > +#define type_max(T) ((T)((__type_half_max(T) - 1) + __type_half_max(T))) > +#define type_min(T) ((T)((T)-type_max(T)-(T)1)) > + > +#if GCC_VERSION >= 50100 > +#define COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW 1 > +#endif > + > +#if __clang__ && \ > + __has_builtin(__builtin_mul_overflow) && \ > + __has_builtin(__builtin_add_overflow) > +#define COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW 1 > +#endif > + > +#if COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW > + > +#define check_add_overflow(a, b, d) ({ \ > typeof(a) __a = (a); \ > typeof(b) __b = (b); \ > typeof(d) __d = (d); \ > (void) (&__a == &__b); \ > (void) (&__a == __d); \ > __builtin_add_overflow(__a, __b, __d); \ > -})) > +}) > > -#define check_mul_overflow(a, b, d) (({ \ > +#define check_sub_overflow(a, b, d) ({ \ > + typeof(a) __a = (a); \ > + typeof(b) __b = (b); \ > + typeof(d) __d = (d); \ > + (void) (&__a == &__b); \ > + (void) (&__a == __d); \ > + __builtin_sub_overflow(__a, __b, __d); \ > +}) > + > +#define check_mul_overflow(a, b, d) ({ \ > typeof(a) __a = (a); \ > typeof(b) __b = (b); \ > typeof(d) __d = (d); \ > (void) (&__a == &__b); \ > (void) (&__a == __d); \ > __builtin_mul_overflow(__a, __b, __d); \ > -})) > +}) > + > + > +#else /* !COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW */ > + > +/* Checking for unsigned overflow is relatively easy without causing UB. */ > +#define __unsigned_add_overflow(a, b, d) ({ \ > + typeof(a) __a = (a); \ > + typeof(b) __b = (b); \ > + typeof(d) __d = (d); \ > + (void) (&__a == &__b); \ > + (void) (&__a == __d); \ > + *__d = __a + __b; \ > + *__d < __a; \ > +}) > +#define __unsigned_sub_overflow(a, b, d) ({ \ > + typeof(a) __a = (a); \ > + typeof(b) __b = (b); \ > + typeof(d) __d = (d); \ > + (void) (&__a == &__b); \ > + (void) (&__a == __d); \ > + *__d = __a - __b; \ > + __a < __b; \ > +}) > +/* > + * If one of a or b is a compile-time constant, this avoids a division. > + */ > +#define __unsigned_mul_overflow(a, b, d) ({ \ > + typeof(a) __a = (a); \ > + typeof(b) __b = (b); \ > + typeof(d) __d = (d); \ > + (void) (&__a == &__b); \ > + (void) (&__a == __d); \ > + *__d = __a * __b; \ > + __builtin_constant_p(__b) ? \ > + __b > 0 && __a > type_max(typeof(__a)) / __b : \ > + __a > 0 && __b > type_max(typeof(__b)) / __a; \ > +}) > + > +/* > + * For signed types, detecting overflow is much harder, especially if > + * we want to avoid UB. But the interface of these macros is such that > + * we must provide a result in *d, and in fact we must produce the > + * result promised by gcc's builtins, which is simply the possibly > + * wrapped-around value. Fortunately, we can just formally do the > + * operations in the widest relevant unsigned type (u64) and then > + * truncate the result - gcc is smart enough to generate the same code > + * with and without the (u64) casts. > + */ > + > +/* > + * Adding two signed integers can overflow only if they have the same > + * sign, and overflow has happened iff the result has the opposite > + * sign. > + */ > +#define __signed_add_overflow(a, b, d) ({ \ > + typeof(a) __a = (a); \ > + typeof(b) __b = (b); \ > + typeof(d) __d = (d); \ > + (void) (&__a == &__b); \ > + (void) (&__a == __d); \ > + *__d = (u64)__a + (u64)__b; \ > + (((~(__a ^ __b)) & (*__d ^ __a)) \ > + & type_min(typeof(__a))) != 0; \ > +}) > + > +/* > + * Subtraction is similar, except that overflow can now happen only > + * when the signs are opposite. In this case, overflow has happened if > + * the result has the opposite sign of a. > + */ > +#define __signed_sub_overflow(a, b, d) ({ \ > + typeof(a) __a = (a); \ > + typeof(b) __b = (b); \ > + typeof(d) __d = (d); \ > + (void) (&__a == &__b); \ > + (void) (&__a == __d); \ > + *__d = (u64)__a - (u64)__b; \ > + ((((__a ^ __b)) & (*__d ^ __a)) \ > + & type_min(typeof(__a))) != 0; \ > +}) > + > +/* > + * Signed multiplication is rather hard. gcc always follows C99, so > + * division is truncated towards 0. This means that we can write the > + * overflow check like this: > + * > + * (a > 0 && (b > MAX/a || b < MIN/a)) || > + * (a < -1 && (b > MIN/a || b < MAX/a) || > + * (a == -1 && b == MIN) > + * > + * The redundant casts of -1 are to silence an annoying -Wtype-limits > + * (included in -Wextra) warning: When the type is u8 or u16, the > + * __b_c_e in check_mul_overflow obviously selects > + * __unsigned_mul_overflow, but unfortunately gcc still parses this > + * code and warns about the limited range of __b. > + */ > + > +#define __signed_mul_overflow(a, b, d) ({ \ > + typeof(a) __a = (a); \ > + typeof(b) __b = (b); \ > + typeof(d) __d = (d); \ > + typeof(a) __tmax = type_max(typeof(a)); \ > + typeof(a) __tmin = type_min(typeof(a)); \ > + (void) (&__a == &__b); \ > + (void) (&__a == __d); \ > + *__d = (u64)__a * (u64)__b; \ > + (__b > 0 && (__a > __tmax/__b || __a < __tmin/__b)) || \ > + (__b < (typeof(__b))-1 && (__a > __tmin/__b || __a < __tmax/__b)) || \ > + (__b == (typeof(__b))-1 && __a == __tmin); \ > +}) > + > + > +#define check_add_overflow(a, b, d) \ > + __builtin_choose_expr(is_signed_type(typeof(a)), \ > + __signed_add_overflow(a, b, d), \ > + __unsigned_add_overflow(a, b, d)) > + > +#define check_sub_overflow(a, b, d) \ > + __builtin_choose_expr(is_signed_type(typeof(a)), \ > + __signed_sub_overflow(a, b, d), \ > + __unsigned_sub_overflow(a, b, d)) > + > +#define check_mul_overflow(a, b, d) \ > + __builtin_choose_expr(is_signed_type(typeof(a)), \ > + __signed_mul_overflow(a, b, d), \ > + __unsigned_mul_overflow(a, b, d)) > + > +#endif > > /* > * Compute a*b+c, returning SIZE_MAX on overflow. Internal helper for > > base-commit: 3e4a66f0dfb02046f6d3375d637840b6da9c71d1
diff --git a/util/size.h b/util/size.h index e72467f..1cb0669 100644 --- a/util/size.h +++ b/util/size.h @@ -6,6 +6,7 @@ #include <stdbool.h> #include <stdint.h> #include <util/util.h> +#include <ccan/short_types/short_types.h> #define SZ_1K 0x00000400 #define SZ_4K 0x00001000 @@ -43,23 +44,177 @@ static inline bool is_power_of_2(unsigned long long v) * alias for __builtin_add_overflow, but add type checks similar to * below. */ -#define check_add_overflow(a, b, d) (({ \ +#define is_signed_type(type) (((type)(-1)) < (type)1) +#define __type_half_max(type) ((type)1 << (8*sizeof(type) - 1 - is_signed_type(type))) +#define type_max(T) ((T)((__type_half_max(T) - 1) + __type_half_max(T))) +#define type_min(T) ((T)((T)-type_max(T)-(T)1)) + +#if GCC_VERSION >= 50100 +#define COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW 1 +#endif + +#if __clang__ && \ + __has_builtin(__builtin_mul_overflow) && \ + __has_builtin(__builtin_add_overflow) +#define COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW 1 +#endif + +#if COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW + +#define check_add_overflow(a, b, d) ({ \ typeof(a) __a = (a); \ typeof(b) __b = (b); \ typeof(d) __d = (d); \ (void) (&__a == &__b); \ (void) (&__a == __d); \ __builtin_add_overflow(__a, __b, __d); \ -})) +}) -#define check_mul_overflow(a, b, d) (({ \ +#define check_sub_overflow(a, b, d) ({ \ + typeof(a) __a = (a); \ + typeof(b) __b = (b); \ + typeof(d) __d = (d); \ + (void) (&__a == &__b); \ + (void) (&__a == __d); \ + __builtin_sub_overflow(__a, __b, __d); \ +}) + +#define check_mul_overflow(a, b, d) ({ \ typeof(a) __a = (a); \ typeof(b) __b = (b); \ typeof(d) __d = (d); \ (void) (&__a == &__b); \ (void) (&__a == __d); \ __builtin_mul_overflow(__a, __b, __d); \ -})) +}) + + +#else /* !COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW */ + +/* Checking for unsigned overflow is relatively easy without causing UB. */ +#define __unsigned_add_overflow(a, b, d) ({ \ + typeof(a) __a = (a); \ + typeof(b) __b = (b); \ + typeof(d) __d = (d); \ + (void) (&__a == &__b); \ + (void) (&__a == __d); \ + *__d = __a + __b; \ + *__d < __a; \ +}) +#define __unsigned_sub_overflow(a, b, d) ({ \ + typeof(a) __a = (a); \ + typeof(b) __b = (b); \ + typeof(d) __d = (d); \ + (void) (&__a == &__b); \ + (void) (&__a == __d); \ + *__d = __a - __b; \ + __a < __b; \ +}) +/* + * If one of a or b is a compile-time constant, this avoids a division. + */ +#define __unsigned_mul_overflow(a, b, d) ({ \ + typeof(a) __a = (a); \ + typeof(b) __b = (b); \ + typeof(d) __d = (d); \ + (void) (&__a == &__b); \ + (void) (&__a == __d); \ + *__d = __a * __b; \ + __builtin_constant_p(__b) ? \ + __b > 0 && __a > type_max(typeof(__a)) / __b : \ + __a > 0 && __b > type_max(typeof(__b)) / __a; \ +}) + +/* + * For signed types, detecting overflow is much harder, especially if + * we want to avoid UB. But the interface of these macros is such that + * we must provide a result in *d, and in fact we must produce the + * result promised by gcc's builtins, which is simply the possibly + * wrapped-around value. Fortunately, we can just formally do the + * operations in the widest relevant unsigned type (u64) and then + * truncate the result - gcc is smart enough to generate the same code + * with and without the (u64) casts. + */ + +/* + * Adding two signed integers can overflow only if they have the same + * sign, and overflow has happened iff the result has the opposite + * sign. + */ +#define __signed_add_overflow(a, b, d) ({ \ + typeof(a) __a = (a); \ + typeof(b) __b = (b); \ + typeof(d) __d = (d); \ + (void) (&__a == &__b); \ + (void) (&__a == __d); \ + *__d = (u64)__a + (u64)__b; \ + (((~(__a ^ __b)) & (*__d ^ __a)) \ + & type_min(typeof(__a))) != 0; \ +}) + +/* + * Subtraction is similar, except that overflow can now happen only + * when the signs are opposite. In this case, overflow has happened if + * the result has the opposite sign of a. + */ +#define __signed_sub_overflow(a, b, d) ({ \ + typeof(a) __a = (a); \ + typeof(b) __b = (b); \ + typeof(d) __d = (d); \ + (void) (&__a == &__b); \ + (void) (&__a == __d); \ + *__d = (u64)__a - (u64)__b; \ + ((((__a ^ __b)) & (*__d ^ __a)) \ + & type_min(typeof(__a))) != 0; \ +}) + +/* + * Signed multiplication is rather hard. gcc always follows C99, so + * division is truncated towards 0. This means that we can write the + * overflow check like this: + * + * (a > 0 && (b > MAX/a || b < MIN/a)) || + * (a < -1 && (b > MIN/a || b < MAX/a) || + * (a == -1 && b == MIN) + * + * The redundant casts of -1 are to silence an annoying -Wtype-limits + * (included in -Wextra) warning: When the type is u8 or u16, the + * __b_c_e in check_mul_overflow obviously selects + * __unsigned_mul_overflow, but unfortunately gcc still parses this + * code and warns about the limited range of __b. + */ + +#define __signed_mul_overflow(a, b, d) ({ \ + typeof(a) __a = (a); \ + typeof(b) __b = (b); \ + typeof(d) __d = (d); \ + typeof(a) __tmax = type_max(typeof(a)); \ + typeof(a) __tmin = type_min(typeof(a)); \ + (void) (&__a == &__b); \ + (void) (&__a == __d); \ + *__d = (u64)__a * (u64)__b; \ + (__b > 0 && (__a > __tmax/__b || __a < __tmin/__b)) || \ + (__b < (typeof(__b))-1 && (__a > __tmin/__b || __a < __tmax/__b)) || \ + (__b == (typeof(__b))-1 && __a == __tmin); \ +}) + + +#define check_add_overflow(a, b, d) \ + __builtin_choose_expr(is_signed_type(typeof(a)), \ + __signed_add_overflow(a, b, d), \ + __unsigned_add_overflow(a, b, d)) + +#define check_sub_overflow(a, b, d) \ + __builtin_choose_expr(is_signed_type(typeof(a)), \ + __signed_sub_overflow(a, b, d), \ + __unsigned_sub_overflow(a, b, d)) + +#define check_mul_overflow(a, b, d) \ + __builtin_choose_expr(is_signed_type(typeof(a)), \ + __signed_mul_overflow(a, b, d), \ + __unsigned_mul_overflow(a, b, d)) + +#endif /* * Compute a*b+c, returning SIZE_MAX on overflow. Internal helper for
Add a fallback for older compilers that lack __builtin_add_overflow() and friends. Commit 7aa7c7be6e80 ("util: add the struct_size() helper from the kernel") which added these helpers from the kernel neglected to copy over the fallback code. Fixes: 7aa7c7be6e80 ("util: add the struct_size() helper from the kernel") Reported-by: Joao Martins <joao.m.martins@oracle.com> Signed-off-by: Vishal Verma <vishal.l.verma@intel.com> --- util/size.h | 163 ++++++++++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 159 insertions(+), 4 deletions(-) base-commit: 3e4a66f0dfb02046f6d3375d637840b6da9c71d1