On Wed, Oct 01, 2025 at 08:57:02PM +0200, Morten Brørup wrote: > > From: Kai Ji [mailto:[email protected]] > > Sent: Wednesday, 1 October 2025 17.33 > > > > Bugzilla ID: 1773 > > https://bugs.dpdk.org/show_bug.cgi?id=1773 > > > > Signed-off-by: Kai Ji <[email protected]> > > --- > > lib/eal/include/rte_memory.h | 38 ++++++++++++++++++++++++++++++++++++ > > 1 file changed, 38 insertions(+) > > > > diff --git a/lib/eal/include/rte_memory.h > > b/lib/eal/include/rte_memory.h > > index dcc0e69cfe..6939c1caad 100644 > > --- a/lib/eal/include/rte_memory.h > > +++ b/lib/eal/include/rte_memory.h > > @@ -746,6 +746,44 @@ __rte_experimental > > void > > rte_memzero_explicit(void *dst, size_t sz); > > > > +/** > > + * @warning > > + * @b EXPERIMENTAL: this API may change without prior notice. > > + * > > + * Constant-time memory comparison. > > + * > > + * This function compares two memory regions in constant time, making > > it > > + * resistant to timing side-channel attacks. The execution time > > depends only > > + * on the length parameter, not on the actual data values being > > compared. > > + * > > + * This is particularly important for cryptographic operations where > > timing > > + * differences could leak information about secret keys, passwords, or > > other > > + * sensitive data. > > + * > > + * @param a > > + * Pointer to the first memory region to compare > > + * @param b > > + * Pointer to the second memory region to compare > > + * @param n > > + * Number of bytes to compare > > + * @return > > + * 0 if the memory regions are identical, non-zero if they differ > > + */ > > +__rte_experimental > > +static inline int > > +rte_timingsafe_memcmp(const void *a, const void *b, size_t n) > > +{ > > + const volatile uint8_t *pa = (const volatile uint8_t *)a; > > + const volatile uint8_t *pb = (const volatile uint8_t *)b; > > + uint8_t result = 0; > > + size_t i; > > + > > + for (i = 0; i < n; i++) > > + result |= pa[i] ^ pb[i]; > > + > > + return result; > > +} > > + > > #ifdef __cplusplus > > } > > #endif > > -- > > 2.34.1 > > NAK. > This returns (binary) non-equality only. It does not return (tri-state) <0, > 0, or >0, so it's not like memcmp or FreeBSD timingsafe_memcmp. > > Also, please put the function ("memeq") first in the name, and then the extra > property ("timingsafe") last, like rte_memzero_explicit. > Like this: > __rte_experimental > static inline bool > rte_memeq_timingsafe(const void *a, const void *b, size_t n) > { > const volatile uint8_t *pa = (const volatile uint8_t *)a; > const volatile uint8_t *pb = (const volatile uint8_t *)b; > uint8_t result = 0; > size_t i; > > for (i = 0; i < n; i++) > result |= pa[i] ^ pb[i]; > > return result == UINT8_C(0); > } > > Stephen, agree? >
Not sure I agree with you on the naming. I'd rather see us adopt the BSD function (present on multiple BSDs) rather than rolling our own completely new function with new behaviour. /Bruce
